Commission of the European Communities

t i ■ I JL I I

echnical steel research

Properties and Service Performance

STUDY ON DESIGN OF STEEL BUILDING IN EARTHQUAKE ZONES

Report EUR 12091 EN

Blow-up from microfiche original

Commission of the European Communities

technical steel research

Properties and Service Performance

STUDY ON DESIGN OF STEEL BUILDING IN EARTHQUAKE ZONES

EUROPEAN CONVENTION FOR CONSTRUCTIONAL STEELWORK Avenue des Ombrages, 32/36

B-1200 BRUSSELS

Contract No 7210.ZZ/437 (15.3.1984-15.9.1985)

FINAL REPORT

1989

Directorate-General Science, Research and Development

PA

: .c CL'

n 7 EUR 12091 EN

Published by the COMMISSION OF THE EUROPEAN COMMUNITIES

Directorate-General Telecommunications, Information Industries and Innovation

L-2920 Luxembourg

LEGAL NOTICE Neither the Commission of the European Communities nor any person acting on behalf of the Commission is responsible for the use which might be made of

the following information.

Catalogue number: CD - NA - 12091-EN-C

ECSC-EEC-EAEC, Brussels • Luxembourg, 1989

STUDY ON DESIGN OF STEEL BUILDING IN EARTHQUAKE ZONES

SUMMARY

The present study is attempted to give a contribution to the knowledge of the behaviour of steel structures in seismic zones, and of enhancing the competitiveness of steel in the European and exported markets. It presents all the available data and indicates which studies are necessary in the future in order to push the possibilities of steel structures.

The presentation of the results is articulated in the following chapters:

Chapter 1, "INTRODUCTION", presents the general index and briefly describes some researches on the behaviour of steel structures under severe conditions promoted by ECSC.

Chapter 2, "SYNTHESIS OF SEISMIC DATA FOR STEEL BUILDINGS", collects references on the subject together with a short comment on each paper. Before each comment the name of the author, title of the work, year of publication and number of pages of the paper are presented. These references are followed by five key words which include in all cases the words: seismic design and steel structures. The papers are collected in subchapters concerning the principal aspects of the seismic behaviour of steel structures. Designers and researchers will take profit of this list in order to easly find an up to date state of art of the most interesting problems.

Chapter 3, "THE EXPERIMENTAL ASSESSEMENT OF SEISMIC STRENGTH AND DUCTILITY OF STRUCTURAL ELEMENTS AND CONNECTIONS", mainly reflects the studies performed in the last 3 years by the members of the ECCS Technical Committee 13 dealing with Seismic Design of Steel Structures (at present Working Group 1.3 of T.C.I). The ECCS recommended testing procedure for assessing the behaviour of structural steel elements under cyclic loads is presented. In order to check the validity of the ECCS recommendations and to win some basic information on the hysteretic behaviour of steel bracing frames some studies were realized and the obtained results are discussed. The behaviour of beam-to-column connections and some considerations on the b/t ratios are also presented.

Chapter 4, "THE ASSESSEMENT OF q FACTORS", propose a method for state the behaviour factor of structures which can be modelled as systems with one degree of freedom. Then, it is used to determine the behaviour factor q of some one floor cantilevers. Numerical analysis have been performed on HEA series columns, which were deflected both in the plane of maximum and minimum rigidity. The obtained q factors are compared with those suggested by the Eurocode No 8 outlined that for this type of structures the value suggested is conservative. Of course this item is the more important and useful to the designers, but exthensive studies leave still to be performed in order to study in a meaninful way the behaviour factors q to adopt in a reliable and economic design of steel structures.

IV­

ETUDE SUR LA CONCEPTION DES CONSTRUCTIONS EN ACIER EN ZONE SISMIQUE

.RESUME

Cette étude est destinée à contribuer à la connaissance du comportement des constructions en acier en zone sismique et à accroître la compétitivité de l'acier en Europe et à l'exportation. Elle présente toutes les données dis­ponibles et indique les études à entreprendre pour mieux valoriser les ca­pacités des structures en acier.

La présentation est découpée de la façon suivante :

Le chapitre 1, INTRODUCTION, présente la table des références et décrit brièvement quelques recherches financées par la CECA sur l'étude du com­portement de structures en acier soumises à des sollicitations sévères.

Le chapitre 2, SYNTHESE DES DONNEES RELATIVES AUX CONSTRUCTIONS EN ACIER EN ZONE SISMIQUE, rassemble des références sur ce sujet, avec, pour chacune, un bref commentaire. Chaque référence est définie par le nom de son auteur, le titre du travail, l'année de publication et le nombre de pages. De plus, le contenu de ces références est défini par cinq mots clés, dont deux sont toujours : conception parasismique, construction en acier. Les articles de référence sont regroupés en sous­chapitres relatifs aux principaux aspects du comportement des structures en acier en zone sismique. Les projeteurs et les chercheurs bénéficient ainsi d'une liste de références permettant de trouver rapidement un état de la question récent sur les sujets les plus intéressants. ■•;

Le chapitre 3, EVALUATION EXPERIMENTALE DE LA RESISTANCE ET DE LA DUCTILITE D'ELEMENTS DE STRUCTURE ET D'ASSEMBLAGES SOUS ACTION SISMIQUE, reprend essentiellement les études et développements accomplis au cours des trois dernières années par les membres du Comité Technique 13, actuellement re­baptisé Groupe de Travail 1.3 "Construction en zone sismique" du Comité Technique 1 de la CE.CM. La procédure expérimentale d'étude du comportement d'éléments structurels en acier sous des actions cycliques développée dans ce groupe est pré­sentée. Certaines études effectuées pour tester la validité de la procédure CECM et définir des données fondamentales du comportement des contrevente­ments sous action alternée sont présentées et les résultats sont discutés. On présente également des résultats relatifs au comportement d'asemblages poutre­colonne et des considérations sur l'influence des rapports b/t.

Le chapitre 4, EVALUATION DES FACTEURS q, contient une proposition de mé­thode d'établissement du facteur q de structures qui peuvent être modéli­sées comme des systèmes à un degré de liberté. Cette méthode est utilisée pour déterminer le facteur de comportement structural q de portiques à un niveau dont les colonnes sont des profils HEA, sollicités dans leur plan faible ou fort. Les valeurs de q ainsi obtenues sont comparées aux valeurs suggérées dans 1'EUROCODE 8, dont on constate qu'elles sont toujours con­servatives. Ce résultat est évidemment important pour les auteurs de projet, mais on constate aussi que des études exhaustives sont encore né­cessaires pour définir les facteurs q à adopter dans un dimensionnement à la fois réaliste et économique des structures en acier en zone sismique.

V-

.STUDIE - STAHLKONSTRUKTION IN ERDBEBENGEBIETEN

KURZFASSUNG

Die vorliegende Studie hatte das Ziel, zur Verbesserung der Kenntnisse über das Verhalten von Stahlkonstruktionen in Erdbebengebieten beizutragen und die Wettbewerbsfähigkeit von Stahl auf dem Europäischen und dem Export-Markt zu fördern. In' dem Studienbericht werden die bisher verfügbaren Informationen und Daten zu diesem Thema vorgelegt und es wird auf weitere erforderliche Untersuchungen hingewiesen, die die Möglichkeiten für Stahlkonstruktionen ver­bessern würden.

Die Ergebnisse der Untersuchungen werden in vier Kapitel vorgestellt :

Das Kapitel 1 "Einleitung" enthält das Inhaltsverzeichnis und fasst die Ergeb­nisse einiger Forschungsvorhaben zusammen, die bisher zum Thema "Stahlkonstruk­tionen unter Extrembedingungen", von der EGKS gefördert wurden.

Das Kapitel 2 "Zusammenfassung von Informationen und Daten zu Stahlbauten in Erdbebengebieten" liefert einen Literaturüberblick mit kurzer Kommentierung jeder Veröffentlichung, die mit Autorennamen, Titel, Erscheinungsjahr, Seiten­zahl ausgewiesen wird. Die Literaturhinweise werden durch 5 Stichworte in Ergän­zung zu "Erdbeben Entwurf" und "Stahlkonstruktionen" erweitert. Die Literatur­zusammenstellung ist nach den für das seismische Verhalten von Stahlkonstruk­tionen wesentlichen Gesichtspunkten in Unterkapitel gegliedert.

Anwender und Forscher können sich aufgrund der Zusammenstellung leicht ein Bild vom derzeitigen Stand der Technik zu den wichtigsten Problemen machen.

Das Kapitel 3 "Experimenteller Nachweis der Festigkeit und Duktilität von Bau­teilen und Verbindungen unter seismischen Beanspruchungen" gibt hauptsächlich einen Überblick über die Untersuchungen, die in den letzten 3 Jahren von Mit­gliedern des Technischen Kommitees 13 (Erdbebenbemessung von Stahlbauten) der EKS (jetzt Arbeitsgruppe 1.3 der Technischen Kommission 1) durchgeführt wurden. Dabei wird die von der EKS empfohlene Versuchsdurchführung zur Bestimmung des Verhaltens von Stahlbauteilen unter zyklischen Lasten vorgestellt. Die zum Zwecke der Überprüfung dieser Empfehlungen und zur Bestimmung erster Grundinfor­mationen zum hysteretischen Verhalten von Stahlverbänden durchgeführten Unter­suchungen werden beschrieben und die Ergebnisse diskutiert. Es werden auch einige Resultate zum Verhalten von Stützen-Riegel-Verbindungen und Schlussfolge­rungen für die b/t-Verhältnisse für zyklische Belastung angegeben.

Im Kapitel 4 "Bestimmung von q-Faktoren" wird eine Methode zur Bestimmung von Verhaltensfaktoren q für Systeme angegeben, die als Schwinger mit einem Frei­heitsgrad abgebildet werden können. Die q-Faktoren für einige eingeschossige Konstruktionen werden mit dieser Methode bestimmt. Für HEA Profilstützen werden für Biegung um die starke und schwache Achse numerische Ergebnisse für q angege­ben und mit den Angaben im Entwurf des Eurocode 8 verglichen. Die dort vorge­schlagenen q-Werte erweisen sich als konservativ. Gerade dieses Thema ist natür­lich für den Entwurf besonders wichtig, es müssen aber noch weitere ausführliche Untersuchungen durchgeführt werden, um q-Werte für einen sicheren und Wirtschaft liehen Entwurf von Stahlkonstruktionen zu ermitteln.

VII

ABSTRACT

This study is attempted to give a contribution to the knowledge of the behaviour of steel structures in seismic zones. It presents all the available data and indicates which studies are necessary in the future in order to push the possibilities of steel structures. The study is divided into three main parts. The first one, collects references on the subject together with a short comment on each paper. The second concerns the assessement of strength and ductility of steel members and connections under cyclic loads. In the last part a method for state the behaviour factor q is proposed, and some results for simple structures are presented.

KEY WORDS: steel structures; seismic design; behaviour factor; ductility; cyclic loads.

SOMMAIRE

Cette étude est destinée à contribuer à la connaissance du comportement des constructions en acier en zone sismique. Elle présente toutes'les données disponibles et indique quelles études sont nécessaires dans le futur pour valoriser encore les capacités des structures en acier. L'étude est divisée en trois parties. La première consiste en un recueil de références avec, pour chacune, un bref commentaire. La seconde concerne l'évaluation 'de la résistance et de la ductilité des éléments de structure en acier et de leurs assemblages sous des actions cycliques.

Dans la dernière partie, on propose une méthode d'évaluation du facteur q de comportement structurel et on montre quelques exemples d'application de cette méthode à des structures simples.

Mots clés : construction métallique, conception parasismique, facteur de comportement structural, ductilité, action cyclique.

ZUSAMMENFASSUNG Die Studie hat das Ziel, zur Verbesserung der Kenntnisse über das Verhalten von Stahlkonstruktionen in Erdbebengebieten beizutragen. Es werden alle verfügbaren Informationen und Daten zu diesem Thema vorgelegt, und es wird auf weitere not­wendige Untersuchungen hingewiesen, die die Möglichkeiten von Stahlkonstruk­tionen verbessern würden. Der Bericht ist in 3 Hauptteile gegliedert : Der erste Teil gibt eine Literaturübersicht mit Kommentierung jeder Veröffentli­chung. Der zweite Teil betrifft die experimentelle Bestimmung der Festigkeit und Duktilität von Stahlbauteilen und Verbindungen unter zyklischer Last. Der letzte Teil liefert eine Methode zur Bestimmung der Verhaltensfaktoren q sowie einige numerische Ergebnisse für einfache Tragwerke. Stichworte : Stahlbauten, Erdbebenentwurf, Verhaltensfaktor, Duktilität,

zyklische Belastung.

IX-

G E N E R A L I N D E X

Page

CHAPTER 1 - INTRODUCTION 1

CHAPTER 2 - SYNTHESIS OF SEISMIC DATA FOR STEEL IN BUILDINGS 13

2 . 1 - DAMAGES 19 2. 2 - BEHAVIOUR OF COMPRESSION MEMBERS AND THEIR CONNECTIONS .. 20 2 . 3 - CALCULATION METHODS 25 2 . 4 - JOINTS 30 2 . 5 - DESIGN CRITERIA 36 2 . 6 - RECOMMENDATIONS 41 2 . 7 - MULTI-STORY BUILDINGS 45 2 . 8 - LOW-RISE BUILDINGS 49 2 . 9 - FRAME BEHAVIOUR 52 2.10- BRACING BEHAVIOUR 62 2.11- ECCENTRIC BRACING BEHAVIOUR 70 2.12 - INTERACTION BETWEEN FRAMES AND BRACINGS 74 2.13- STRUCTURAL SYSTEMS 78

CHAPTER 3 - THE EXPERIMENTAL ASSESSMENT OF SEISMIC STRENGTH AND DUCTILITY OF STRUCTURAL ELEMENTS AND CONNECTIONS 89

3 . 1 - INTRODUCTION 92 3 . 2 - THE ECCS RECOMMENDED TESTING PROCEDURE FOR ASSESSING THE

BEHAVIOUR OF STRUCTURAL STEEL ELEMENTS UNDER CYCLIC LOADS 99

3.2.1 - INTRODUCTION 102 3.2.2 - ASPECTS OF THE TESTING PROCEDURE FOR ASSESSING

THE BEHAVIOUR OF STRUCTURAL STEEL ELEMENTS 103 3.2.3 - COMPLETE TESTING PROCEDURE 103 3.2.4 - SHORT TESTING PROCEDURE Ill 3.2.5 - END OF TEST 112 3.2.6 - COMBINATION OF LOADS 113 3.2.7 - COMMENTARY ON POSSIBLE DEFINITIONS OF F .- 113

Page

3.3 - TESTS FOLLOWING THE ECCS RECOMMENDATIONS 115

3.3.1 - BEHAVIOUR OF BRACINGS 117 3.3.2 - BEHAVIOUR OF BEAM-TO-COLUMNS CONNECTIONS 124

3.4 - VALIDITY OF THE ECCS RECOMMENDATIONS 130 3.5 - CONSIDERATIONS ON b/t RATIOS 153 3.6- REFERENCES 159

CHAPTER 4 - THE ASSESSMENT OF q FACTORS 163

4.1- INTRODUCTION 166 4.2- METHOD FOR STATE THE BEHAVIOUR FACTOR q 168 4.3 - ONE FLOOR CANTILEVERS 171 4.4- FURTHER INVESTIGATIONS AND CODE APPROACH 180 4.5- REFERENCES 188

- 1

. C H A P T E R - l

INTRODUCTION

3 -

PRODUCTION

Even if steel, thanks to its ductility, is the more appropriate material

to employ for construction in seismic areas, many national authorities and

many owners prefer nevertheless concrete structures in spite of their

heaviness.

The interest of designers on the specific problems of steel structures in

seismic areas is quite joung, that is about no more than 20 years. In that

period, a certain amount of experimental as well as theoretical investiga­

tions has been made. Most of these investigations have been sponsored by

the European Coal and Steel Community research programme in the field of the

utilization of steel structures in seismic regions, involving the recent

following contracts : 7210 SA 111/SA 305/SA 306/SA 202/ SA 403/ SB 403/

SA 407/ SA 814/ SA 401/ SA 109/ SA 606. Of particular interest for the beha­

viour of steel structures under severe conditions, are the ECSC researches

summarized at the end of this introduction.

Other investigations have been performed recently in the U.S. and in Japan. t

All indicate a comparatively good behaviour of steel structures under seismic

action when compared to other materials.

In order to contribute to the promotion of steel construction, an

analysis and a synthesis of data were performed with the aim of improving

the methods for the design of steel structures in seismic zones, and of

enhancing the competitiveness of steel in the European and exports markets.

The data accumulated on ECSC research form a valuable complement to the

work that has been undertaken in the field of design codes and in particu­

lar of Eurocode 8, the European Code for Structures in Seismic Regions,

which is concerned with the design of concrete, masonry and steel construc­

tions. Eurocode 8 project has enabled q factors to be specified which define

the capability of the a structural system to resist seismic loads in the

post-elastic range and take into account the energy dissipation capacity of a

ductile response of the constructions.

The q factors specified for steel structures in the first draft of the

Eurocode are very conservative and, thus, not to the advantage of steel cons­

truction. This mainly due to the lack of knowledge on the performances of

steel structures subjected to cyclic loads.

The present study is first attempt to give a contribution to the knowlegde of

the behaviour of steel structures in seismic zones. It presents all the avail­

able data and indicates which studies are necessary in the future in order to

push the possibilities of steel structures.

The presentation of the results will be articulated in the following chapters :

Chapter 2 collects about references on the subject together with a short comment

on each paper. Designers and researchers will take profit of this list in order

to easily find an up to date state of art of the most interesting problems.

Chapter 3 concerns the assessment of strength and ductility of steel

members and connections subjected to cyclic loads, lhe chapter mainly

reflects the studies performed in the last 3 years by the members of the

ECCS Technical Committee 13 dealing with Seismic Design of Steel Struck

tures (at present Working Group 1.3 of T.C.I.) .

The study of an experimental procedure, tests on bracings and local stabi­

lity of compressed parts, and the assessment of numerical models are foun-

damental contributions to the knowledge of the behaviour of steel structu­

res.

Chapter 4 deals with the assessment of the q factor. A method is proposed

and some results for simple structures are presented. Of course this item

is the more important and useful to the designers, but extensive studies

leave still to be performed. It is our hope that in the next 2-3 years,

many numerical calibrations on typical steel structures will be carried on.

Thus, it will be possible to state correct, safe and economical values for

q factors in order to push the use of steel structures in european market.

At the end of this introduction it must be remembered that during the meeting

of Napoli (November 1984) the Technical Committee 13 gave the task of collec­

ting the material of this report to Ing. Luis Manuel Calado de Oliviera Martins

under my responsability. For his competence and intelligence this work was

possible and to him I wish to present my most warm thanks.

This presentation is followed by the list of ECCS W3 1.3 - Seismic Design

members. They will have, in the next future, the responsability and the task

to continue the studies on argument in order to give an always more important

role to steel structures in seismic zones.

ECSC RESEARCHES REFERRED TO IN PAGE 1

INFLUENCE OF STRESS-STRAIN DIAGRAM CHARACTERISTICS ON THE REDISTRIBUTION OF

BENDING MDMENTS AFTER PLASTIC HINGES HAVE BEEN FORMED, by A. Bernard, M. Darin.

The purpose of the research is to examine how far the new concepts of the

plastic design of the frameworks can be applied to high-strength steels, which

have usually a higher yield strength Re to tensile strength Rm ratio than mild

steel and to determine the influence of stress-strain diagram characteristics on

the redistribution capacity of bending stresses at plastic hinges.

The research covers four steel types with Rm/Re ratios between 1.10 and 1.53

and a yield plateau between 5.4 and 21.9 times the yield strain.

The laboratory tests concern overall buckling, local buckling, lateral

buckling and the structural ductility up to the collapse of HE 120 B and IPE 140

rolled sections. The tests are on continuous beams and on frames. The

quantitative effects of the main parameters describing the stress-strain diagram

are also studied by computer simulation of laboratory tests.

It appears that the design with standards based only on yield stress gives

ample security to plastic collapse for all the Rm/Re ratios taken into account.

The plastic design concepts can be applied as well.

Of course the widening of permissible Rm/Re ratios and of plastic elongation

for plastic design are of direct interest for earthquake resistant design,

because its concepts are so close to those of plastic design.

OVERALL AND LOCAL BUCKLING OF THIN-WALLED HOLLOW FOR AXIAL LOADING, by J.

Rondai, M. Braham, J. P. Grimault and OVERALL AND LOCAL BUCKLING OF THIN-WALLED

HOLLOW FOR EXCENTRIC LOADING, by J. P. Grimault, A. Plunder, J. Rondai.

The aim of the first research is to study the interaction between local plate

buckling and overall buckling of centrically loaded thin-walled tubular members.

The study is limited to cold-formed members with rectangular hollow sections.

7 -

In a first part, the test results are described. Nine different sections have

been selected. The experimental program is concerned with stub column test and

long column tests. It also contains measurements on yield stress, residual

stresses in the profile and in the original plate, and geometrical

imperfections.

In a second part, the results obtained f rem several existing methods of

calculation are compared with tests results. A new method of calculation is

developed and it gives good results. A preliminary study shows that this last

method could be extended to the case of beam-columns.

The second research is aimed to investigate the interaction between local

plate buckling and overall buckling of eccentrically compressed thin-walled

tubular members. It is restricted to cold-formed members with rectangular hollow

cross sections.

The first part of the report is devoted to experimental results that are

drawn from tests on two types of sections: the first one is hot finished whilst

the second one is cold finished. The experimental program is concerned with i)

stub column tests, ii) long column tests in combined compression and bending and

iii) beam tests in pure bending. Measurements of yield stress, residual stresses

and geometrical imperfections of the profiles are reported.

In the second part of the report, a design method is suggested for

beam-columns with thin-walled rectangular hollow cross sections. The procedure

allows for a complete continuity between columns and beam-columns, thick-walled

and thin-walled profiles. Theoretical and experimental results are shown in good

agreement with respect to the semi-probabilistic concept adopted by the European

Convention for Constructional Steelwork.

HYBRID BEAMS - VOIDABILITY, STATIC AND FATIGUE BEHAVIOUR, by W. Chapeau, R.

Maguoi, A. Piron, A. Plumier.

Several specific problems of hybrid girders are analyzed in this report.

Tests results are presented together with references on state of knowledges in

the studied fields. The shopwork problems, mainly those of high strength steel

welding are dealt with in the first part of the report. As regards the cold

craking phenomenon, the short transverse properties and the residual ductility

of the heat affected zone. The second part deals with the statical behaviour of

hybrid girders: it contains a short study of pure bending, which was interrupted

by an accident; the causes of the accident are explained; a study on the problem

of lateral buckling and web crippling under concentrated loads is then given;,

the second part ends with a thorough study of shear buckling of unstiffened and

stiffened girders. The third part contains a study of the fatigue behaviour of

stiffned hybrid girders.

The report concludes to an interest of hybrid girders and high strength

steels in some specific fields of bridges and structures; that interest will

bring practical use only for high strength steels with a good weldability and a

carbon percentage less than 0.1%, in countries where the up to date computation

methods for web buckling are allowed by national standards.

COMPOSITE HYBRID BEAMS, by A. Bruls, A. Piron, Bo, Caparro, Augusti, Buti.

This research has allowed to define the conditions in which cased beams of

high strength steel can be made. The realization of three prestressed beams and

one cased beam not prestressed and their static tests have proved the

reliability of the calculation of the method proposed, and the usefulness of the

prestressing in respect to cracking and stiffness. In addition, due to

prestressing, the hybrid beams behave elastically in the normal service

conditions.

The comparison between the experimental results and the theoretical

calculations based on the creep coefficients of the European Recommendations has

show the need of using quite sophisticated calculation criteria so as to

interpret, with an acceptable approximation, the real behaviour of the

structure.

The fatigue test has shown a good performance of the prestressed structure in

comparison with a steel homogeneous beam having equal resistance, even though

forecasts made at theoretical level proved a little too optimistic.

The experimental research also include bonding tests like the "beam-test" on

smooth steel samples and on steel samples treated with adhesives. Whilst on the

smooth samples the joint proved to be perfect, the samples treated with

adhesives showed an excesive slipping gradient in the long run. This would

suggest not to rely on such a bonding method.

RIGID FRAME CONNECTIONS TO œNCRETE FILLED TUBULAR STEEL COLUMNS, by P. Ansourian.

Rigid frame connections between I beams of normal and wide flange section,

and square steel tubes were examined experimentally in tests of nine structural

units. Both welded and high strength friction bolted joints were examined. The

axial load on the columns varied from 0.15 to 0.75 of their squash load. Failure

in the connection occurred in three of the units. The deformation of the column

were analyzed in a second order elasto-plastic numerical analysis including the

effects of the axial load and the bending moment distribution existing in the

tests. Where failure occurred in the column, agreement in column deformation

between theory and expriment was excellent, while the calculated collapse loads

were always conservative. Premature weld failure occurred in connections to the

front face of the tube. The best connections were these which transmitted the

beam tension flange force to the back of the filled tube.

Though considering only monotonicai ly increased loading, the report contains

a lot of valuable test data on several types of joints, a theoretical method for

computation of load displacement curve and indications on the best type of rigid

joints. The report is thus a fundamental basis for test on computation of

behaviour of these kinds of joint under cyclic loading.

10-

BEAM-CDLUMN CONNECTIONS BASED ON THE USE OF STUDS, by R. Maquoi, X. Naveau,

J. Rondai.

Stud shear connectors are widely used as connectors between steel and

concrete in composite construction. The aim of the present research is to

examine the feasibility of a similar technique for framing connections between

beams and columns by means of treaded connectors, specially for hollow section

columns, for which connections set problems.

In the experimental part of the research, several sections and stud diameters

are investigated and the following tests are performed:

- determination of the welding parameters for the threaded connectors;

- tensile and shear tests on welded studs and on simple connection models;

- tests on beam-column assemblages with a square hollow section for the column

and an IPE section for the beam. For these tests, end plates are welded on the

IPE section or the assemblage uses angles connecting either the beam web or

beam flanges to the wall of the column. In any case, only threaded connectors

are used.

On base of experimental results, a design method is suggested, which appears

quite similar to that used for bolted connections.

Though tests are performed under monotonicaily increased loading, the load displacement curve recorded gives information on the relative rigidity of various types of joints and is a good basis for research work under cyclic loading.

EXPERIMENTAL STUDIES ON RESISTANCE AND DUCTILITY OF STRUCTURAL CONNECTIONS,

by L. Sanpaolesi, L. Biolzi, S. Caramelli, R. Tacchi.

The research presents a serie of tests on bracings and beam-to-columns joints

subjected to cyclic loads. Different types of bolted connections were examined

in order to study the plastic behaviour of subassemblages.

It was demonstrated that only a full resistance bolted joints may be assumed

as effective in bracing connections.

11

EXPERIMENTAL ANALYSIS ON RESISTANCE AND DUCTILITY OF CORRUGATED SHEET PANELS,

by L. Sanpaolesi, L. Biolzi, R. Tacchi.

The research considers the possibility of taking into account the facades to

seismic resistance of the buildings.

Some tests on corrugated sheet panel subjected to in-plane shear cyclic

forces vere performed.

Unfortunately, the local instability of the sheet panels cause poor resourses

of ductility of such structural arrangements.

Prof. Dr. Ing. Giulio Bailio

12-

EOCS WG 1.3 - Seismic Design members

Prof. Dr. Ing. F. M. Mazzolarli (Chairman) I

Prof. J. M. Aribert F

Prof. Dr. Ing. Giulio Bailio I

Mr. R. Pepin L

Dr. Ing. A. Plumier B

Dipl.-Ing. ETH R. Sagesser CH

Prof. Dr. Ing. G. Sedlacek D

Mr. K. Tohmsen DK

Mr. H. D. Walker GB

Prof. Dr. Ing. A. Giuffre I

Prof. B. Kaţo J

Prof. Dr. Ing. A. Lamas P

Dr. F. Nahler A

Prof. Dr. T. Naka J

Mr. R. Siirila SF

Prof. C. Thomas GB Dr. D. Tordoff GB

-13

C H A P T E R - 2

SYNTHESIS OF SEISMIC DATA FOR STEEL IN BUILDINGS

15

TABLE OF CONTENTS

Page

GENERALITIES 16

2. 1 - DAMAGES 19

2. 2 - BEHAVIOUR OF COMPRESSION MEMBERS AND THEIR CONNECTIONS 20

2 . 3 - CALCULATION METHODS 25

2 . 4 - JOINTS 30

2 . 5 - DESIGN CRITERIA 36

2 . 6 - RECOMMENDATIONS 41

2 . 7 - MULTI-STORY BUILDINGS 45

2 . 8 - LOW-RISE BUILDINGS 49

2 . 9 - FRAME BEHAVIOUR 52

2.10- BRACING BEHAVIOUR 62

2.11- ECCENTRIC BRACING BEHAVIOUR 70

2.12 - INTERACTION BETWEEN FRAMES AND BRACINGS ■ 74

2.13- STRUCTURAL SYSTEMS 78

16

GENERALITIES

A brief canment to each paper dealing with seismic design of steel structures is presented. Before each comment the name of the author, title of the work, year of publication and number of pages of the paper are presented. These references are followed by five key words which include in all cases the main subjects of the report: seismic design and steel structures. The papers are collected in subchapters concerning the principal aspects of

the seismic behaviour of steel structures.

The list of the key words used is:

B

acceleration

beams beam-columns behaviour factor bolts braces buckling building construction

calculation methods collapse columns compression members connections

damages damping design criteria design rules detailing drift ductility

17 -

earthquakes eccentric braces

fasteners fatigue foundations fracture frames frequency friction

H high-rise buildings histeretic behaviour

impact

joints

loads low-rise buildings

M multy-storey buildings

offshore structures

panels planning

?¿/V<*

18

R recommendations repairing rolling systems

seismic design shear slip spectrum stability steel structures structural safety structural systems subassemblages

typology torsion toværs

U

uplift

V vessels vibration

W warping welding

19

2.1 - DAMAGES

BERTERO, V., BRESLER, B., SELNA, L., CHOPRA, A. and KORETSKY, A. (1973) DESIGN IMPLICATIONS OF DAMAGES OBSERVED IN THE OLIVE VIEW MEDICAL CENTER BUILDINGS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 51-65. *1*

This article examines the possible causes and design implications of the observed damages in the Olive View Medical Center produced by the San Fernando earthquake. The buildings under study are of reinforced concrete. Special attention is given on the aspects involved in the seismic design, ground motion, material characteristics and structural features of individual buildings. Some recommendations with a view to minimize earthquake damage are also presented.

KEY WORDS: steel structures; seismic design; damages; ductility; detailing.

BUBNOV, S. (1972) DAMAGE EVALUATION. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 247-253. *2*

This state of art is concerned with the problem of planning and design of structures in seismic regions. Four topics are examined: the first one regards the pre-earthquake preparation; the second is concerned to the performance of buildings during earthquakes, specially tall buildings; the third topic is related to the inspections after the earthquake. Finally, the fourth is related to the teaching taked out from damages caused by the earthquake.

KEY WORDS: steel structures; seismic design; damages; ductility; planning.

PINKHAM, C.W. (1972) EVALUATION OF THE EARTHQUAKE DAMAGE. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 229-245. *3*

The aim of this paper is the evaluation of the damage in buildings caused by earthquakes. The damage occasioned specially in reinforced concrete tall buildings by two levels (high and weak intensity) of the earthquake motions are described. Some photos are presented to accompany the description. The errors and mistakes namely of design and construction, which have been in the origin of those damages are examined. Some design recommendations and general rules of construction are suggested.

KEY WORDS: steel structures; seismic design; damages; ductility; detailing.

TANAKA, A., MORITA, K. and YAMANOUCHI, H. ( ? ) DAMAGE OF BRACED STEEL FRAMES DUE TO THE 1978 MIYAGIKEN-OKI EARTHQUAKE. ( ? ),.page 49-56. *4*

In this paper are described the results of a research study carried out on damage of several braced steel frames due to the 1978 Miyagiken-Oki earthquake. Among the reasons for the large damage examined in the structures are pointed out: inadequate detailing of the joints; insufficient strength of the connections; misevaluation of the lateral resistance of the frames and unbalanced arrangement of braces. To accompany the description, seme photos are presented.

KEY WORDS: steel structures; seismic design; damages; braces; connections.

20

2.2 - BEHAVIOUR OF COMPRESSION MEMBERS AND THEIR CONNECTIONS

FISHER, J. and GURNEY, T. (1972) HIGH-CYCLIC FATIGUE OF CONNECTIONS AND DETAILS. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 757-769. *1*

This general paper deals with the major factors that influence the fatigue strength of members and their connections subjected to cyclic loads, and suggests how they should be considered in design. In particular, the detail of the joints and their initial flaw conditions are examined, as well as the crack propagation and the residual stresses. Furthermore, brief comments ' about design conditions that provide high cycle strength are presented.

KEY WORDS: steel structures; seismic design; fatigue; connections; fracture.

JAIN, A. and GOEL, S. (1979) CYCLIC END MOMENTS AND BUCKLING IN STEEL MEMBERS. Proc. of the 2nd U. S. Nat. Conf. on Earthquake Engineering, EERI, Standford University, page 413-422. *2*

A hysteresis model for steel members which accounts the interaction between axial load and bending moment is presented. Reduction in the axial compression load after the first cycle and the residual elongation is considered. Neverthless, to take account of these effects it is necessary to do experimental tests to calibrate the model. Finally, some comments are presented about the use of the model in the prediction of the dynamic behaviour of braced frames.

KEY WORDS: steel structures; seismic design; buckling; hysteretic behaviour; compression members.

KATO, B. and LU, LE-WU (1972) INSTABILITY EFFECTS UNDER DYNAMIC AND REPEATED LOAD. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 463-481. *3*

The paper presents and discusses some instability problems of columns and frames subjected to dynamic and cyclic loadings. The influence of the dynamic axial loads due to earthquake on the stability of the columns is described. For members and cantilever beam-columns subjected to axial loads and cyclic bending moments, a technique is developed for the construction of the load-deflection curve, which is based on the monotonie load curve. This technique is also applied to frames under cyclic deflections. Emphasis is placed on the aspects that are important in earthquake-resistant design of building frames.

KEY WORDS: steel structures; seismic design; stability; columns; frames.

21

KRAWINKLER, H., JOINTS. *4*

BERTERO, V. and POPOV, E. (1975) SHEAR BEHAVIOR OF STEEL FRAME ASCE Journal of the Structural Division, STll, page 2317-2336.

This paper presents the results of a series of experiments investigating the strength, stiffness, ductility, and hysteretic shear behaviour of beam-column joints in frames with strong columns weak girders subjected to s'evere lateral loading. Mathematical models of joint behaviour and design recommendations derived f rem these experimental investigations and from analytical studies are presented. Only joints of beam-to-column subassemblages made of standard rolled sections subjected to strong axis bending are investigated.

KEY WORDS: steel structures; seismic design; joints; ductility; shear.

POPOV, E. (1972) LOW-CYCLE FATIGUE OF œNNECTIONS AND DETAILS. Proc. of the Int. Conf. on Planning and Design on Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 741-755. *5*

The article examines the results of experimentation carried out on steel members and connections subjected to low-cycle fatigue. In particular, the good correlation with the results obtained with cantilevers of small size and full size is pointed out. An empirical expression for the energy dissipation is proposed. The mode of failure of specimens submited to low-cycle fatigue is analogous to the high-cycle one, allowing to conclude that design recommendations for high-cycle fatigue are also applicable to low-cycle fatigue.

KEY WORDS: fracture.

steel structures; seismic design; fatigue; connections;

POPOV, E. and PINKNEY, R. (1971) CYCLIC YIELD REVERSAL IN STEEL BUILDING CONNECTIONS. AISC The Engineering Journal, July, page 67-79. *6*

Described herein are tests of 24 connection specimens subjected to various cyclic, quasi-static loading sequencies. Five different basic connection types are investigated. In three of these, the beam is connected to the flange of the column. In the remaining two, the beam is connected indirectly to the web of the column. All of the connection details are chosen on the basis of their practibility and their widespread use. In addition to the behaviour and the manner of failure of the beams and their connections to the columns, the hysteretic response of the beams under repeated and reversed loadings received particular attention.

KEY WORDS: columns.

steel structures; seismic design; 'connections; ductility;

POPOV, E., BERTERO, V. and KRAWINKLER, H. (1973) MOMENT-RESISTING STEEL SUBASSEMBLAGES UNDER SEISMIC LOADINGS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 1481-1490. *7*

The paper summarizes the results of an experimental research regarding the hysteretic behaviour of structural systems and their components under cyclic loads. The subassemblages are idealized by two horizontal beams attached to a vertical column. The P-delta effect and the behaviour of plastic hinges in columns under cyclic loads are also discussed.

KEY WORDS: steel structures; seismic design; subassemblages; hysteretic behaviour; connections.

-22

TAKANASHI, K. (1973) INELASTIC LATERAL BUCKLING OF STEEL BEAMS SUBJECTED TO REPEATED AND REVERSED LOADINGS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 795-798. *8*

This general paper is concerned with the problem of the interaction in steel beams between lateral buckling and cyclic loads. The results of the experimental investigation carred out on rolled H-shaped sections under repeated and reversed loading at constant deflection amplitudes are summarized.

KEY WORDS: steel structures; seismic design; buckling; hysteretic behaviour; beams.

VANN, W., THOMPSON, L., WHALLEY, L. and OZIER, L. (1973) CYCLIC BEHAVIOR OF ROLLED STEEL MEMBERS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 1187-1193. *9*

The scope of this experimental work is to analyse some aspects of the behaviour and failure characteristics of rolled steel members subjected to cyclic loadings. Three différents cases have been examined: unbraced beam, braced beam and unbraced beam-column. Emphasis is placed on the effects of cross-sectional dimensions, span length, and intermediate lateral bracing.

KEY WORDS: steel structures; seismic design; buckling; hysteretic behaviour; beams.

YAMADA, M., SAKAE, K., TADOKORO, T. and SHIRAKAWA, K. (1970/1971) . ELASTO--PLASTISCHE BIEGEFORMANDERUNGEN VON STAHLSTUTZEN MIT I-QUERSCHNITT, Teil I and Teil II, Der Stahlbau, n.12/1970, n.3/1971, n.5/1971. *10*

In order to analyse the elasto-plastic bending deformation of wide flange steel columns subjected to constant axial compression load, the cross sectional form of the wide flange profile is modelled by several assumption and a bilinear stress-strain relationship with a strain hardening coefficient is assumed. With these assumptions the bending moment-axial force interaction curves and bending moment-curvature relationships are derived for the wide flange cross section. The alternately repeated elasto-plastic cyclic bending of wide flange steel beam-columns subjected to constant axial compression load is also studied. Finally, the results are compared with the experimental tests.

KEY WORDS: steel structures; seismic design; beam-columns; hysteretic behaviour; stability.

-23

TANABASHI, R., YOKOO, Y., WAKABAYASHI, M., NAKAMURA, T. and KUNIEDA, M. (1971) DEFORMATION HISTORY DEPENDENT INELASTIC STABILITY OF COLUMNS SUBJECTED TO COMBINED ALTERNATING LOADING. Colloque International RILEM, Buenos Aires, page 275-295. *11*

In this paper the behaviour of short columns of a hysteretic strain hardening material is studied, under a constant axial compressive load and repeated constant displacements amplitude at midspan. An experimental investigation, with a large description of the testing machine, and a theoretical study are done. Some curves and conclusions are presented where is pointed out that a regular variation process of the initial hysteresis loops toward more oblong loops with greater elastic regions and with portions of the same negative slope can be observed. This negative slope is consequence of the P-delta effects, while the increasing of the elastic regions is justified by the constitutive law of the material.

KEY WORDS: steel structures; seismic design; columns; hysteretic behaviour; stability.

TAKANASHI, K., TANIGUCHI, H. and TANAKA, H. (1980) INELASTIC RESPONSE OF H-SHAPED COLUMNS TO TWO DIMENSIONAL EARTHQUAKE MOTIONS. Bull. ERS, n.13, Institute of Industrial Science, University of Tokyo, page 15-27. *12*

The work deals with the study of H-shaped steel columns subjected to two components of earthquake ground motions. Two analysis are performed: a theoretical and an experimental one. The model used in the theoretical analysis is a single column built into the rigid floors. The experimental analysis is based on the bi-axial bending theory of the beam-column. In both analysis is assumed that the principal axis of the H-shaped column section are initially parallel to the two components of the earthquake. Some figures of displacements and restoring forces obtained from the experimental tests are shown.

KEY WORDS: steel structures; seismic design; columns; earthquakes; stability.

FAELLA, C. and RAMASCO, R. (1981) DUTTILITÀ" TRASLAZIONALE DELLE COLONNE IN ACCIAIO. Giornate C.T.A., Palermo, page 285-301. *13*

A finite element model for the elastic-plastic analysis of beam-columns subjected to constante axial compressive load and variable shear force is proposed. The beam-column is modelled by a bar subdivided in several elements and the section is divided in a finite number of strips. Both extremities of the bar are connected by elasto-plastic springs. The material is considered to be elasto-plastic and the strain hardening may be taken into account. To avoid local instability, limitation of the maximum deformation is performed. Some examples to show the influence of some parameters on the shear force-displacement curve are presented.

KEY WORDS: steel structures; seismic design; columns; ductility; compression members.

24

CALADO, L. (1985) SIMULAÇÃO NUMERICA DO COMPORTAMENTO SISMICO DE ESTRUTURAS METÁLICAS CONTRAVENTADAS. Dissertation submitted of the requirements for the degree of Master of Science in the Technical University of Lisbon, January, 82 pages. *14*

The work deals with a finite element able to describe the behaviour of cyclic axially loaded members taking into account the geometrical and physical nonlinear effects. Its formulation is developed and the results obtained with this model are compared with experimental studies allowing to check the model. A numerical study is then developed to investigate the influence of some parameters which affect the bearing capacity of compressed members. The work also shows how the element can be used to simulate the braces in order to predict the seismic behaviour of plane braced pin-end structures, and the evaluation of the behaviour factor of this type of structures.

KEY WORDS: steel structures; seismic design; stability; braces; compression members.

Toma, S. and Chen, W. (1982) INELASTIC CYCLIC ANALYSIS OF PIN-ENDED TUBES. ASCE Journal of the Structural Division, ST10, page 2278-2294. *15*

An analytical study of the inelastic cyclic load-deflection behaviour and load-shortening behaviour of axially loaded steel tubular bracing members subjected to cyclic loading is presented. Expressions are first derived for the moment and axial strain expressed explicitly in terms of curvature and thrust for tubular sections with geometric imperfections and residual stresses. For the case of reversed loading, several approximations of the moment-thrust-curvature curves and moment-thrust-axial strain curves are made. Using these relations, cyclic solutions of pin-ended columns subjected to one cycle of axial loading are obtained and compared with some available experimental tests.

KEY WORDS: steel structures; seismic design; stability; braces; compression members.

Fukumoto, Y. and Kusarna, H. (1985) LOCAL INSTABILITY TESTS OF PLATE ELEMENTS UNDER CYCLIC UNIAXIAL LOADING. Journal of Structural Engineering, vol.111 , No 5, page 1051-1066. *16*

An experimental study of the inelastic cyclic load-deformation behaviour of welded built-up square box-section short columns subjected to cyclic axial loading is presented. A total of 10 test specimens were fabricated . from mild and Mgh strength steels, having plate elements with the width-thichness ratios of 40, 60 and 80 for mild steel, and 40 and 60 for high strength steel. Furthermore, monotonicaily increased loading tests were carried out for comparison with deformation behaviour of cyclic loading tests. This paper emphasizes the development of alternating local instability of plate elements associated with cyclic loading sequences.

KEY WORDS: steel structures; seismic design; stability; columns; compression members.

-25-

2.3 - CALCULATION METHODS

ARIBERT, J. and EDJTEMAI, N. (1981) PRISE EN COMETE DE DUCTILITE" DANS LA RESPONSE SPECTRALE A UN SEISME. Construction Métallique, n.4, page 3-23.

This work shows the basic concepts which allow to take into account the ductility of the structure in the spectral response of one earthquake. A review on the elastic response spectra and the influence of the ductility in the earthquake strength of the structure is presented. The concept of elastic response spectra is afterwards generalized to the elasto-plastic response spectra. Two criteria to consider the correiativeness between the elastic and elasto-plastic response spectra are analyzed. A numerical model to obtain the elasto-plastic spectra is presented. In the end an approximative method to obtain the elasto-plastic response spectra from the elastic response spectra is suggested.

KEY WORDS: steel structures; seismic design; ductility; spectrum; calculation methods.

BEA, R. (1979) EARTHQUAKE AND WAVE DESIGN CRITERIA FOR OFFSHORE PLATFORMS. ASCE Journal of the Structural Division, ST2, page 401-419. *2*

In this work a process for development of earthquake design criteria for offshore platforms is presented. The process considers: 1) Projected environmental conditions; 2) Platform system characteristics; 3) Environmental loadings and forces on the platform systems; 4) Uncertainties in projected environmental conditions, forces, and platform response; 5) Platform system performance, particulary inelastic behaviour during extreme overload conditions; 6) Reliability quantified as the ability of the platform system to perform satisfactorily in the full range of projected environmental conditions; 7) Decisions on what constitues acceptable performance and reliability.

KEY WORDS: steel structures; seismic design; offshore structures; calculation methods; planning.

FIESENHEISER, E. and RONAN, J. (1976) RAPID SELECTION OF BEAM-COLUMNS FOR WIND OR EARTHQUAKE EFFECTS. AISC Engineering Journal, n.4, page 97-102. *3*

This technical paper present four design charts to expedite selection of beam-columns subjected to axial force and bending moment about the X-axis. Those charts are based on the AISC formulas (Specification Section 1.6 - Combined stresses). The charts are elaborated for two possibilities of the yield stress (36 and 50 Ksi) and for two possibilities of the end conditions of the members (restrained Cm=0.85 and unrestrained Cm=l. 00 ). To understand how to use the charts some examples are given-

KEY WORDS: steel structures; seismic design; calculation methods; beam-columns; loads.

26-

FLEISCHER, W. (1974) SIMPLIFIED SEISMIC DRIFT ANALYSIS OF HIGH-RISE STEEL FRAMES. AISC Engineering Journal, n.3, page 53-64. *4*

This paper presents a simplified method to obtain drift statements for high rise steel frames under the application of seismic loads. The equations of this method are developed for two cases: planar rigid and planar braced frames. The method is demonstrated step by step by an example of a typical drift analysis in a planar rigid high-rise steel bent, including a description of the procedure for both rigid and braced frames. In the last section, the development of the method and the derivations of the working equations are explained.

KEY WORDS: steel structures; seismic design; drift; high-rise buildings; calculation methods.

KAR, A. (1979) SEISMIC SUPPORT: SPEEDY DETERMINATION OF FREQUENCY. ASCE Journal of the Structural Division, ST7, page 1289-1306. *5*

In this paper, formulas for expedite determination of the natural frequency of the most commons steel braced structures used as support for subsystems are presented. All the structures are assumed as systems of a single degree of freedom. The formulas and recommendations allow the determination of the transverse and longitudinal natural frequencies for the structures showed in the figures, and are valid for pin or rigid connection between horizontal and vertical members. Finally, an example of application is presented to demonstrate the use of the formulas.

KEY WORDS: steel structures; seismic design; frequency; calculation methods; frames.

MONTGOMERY, C. and HALL, W. (1979) SEISMIC DESIGN OF LOW-RISE STEEL BUILDINGS ASCE Journal of the Structural Division, ST10, page 1917-1933. *6*

This paper presents some methods and recommendations for design procedures of low-rise steel buildings. The paper begins with a brief description of the building system for purposes of illustration. The second portion of the paper contains a review of the behaviour of low-rise steel buildings when subjected to seismic ground motion. With a view to a practical procedure two methods of analysis are refered: response spectra and modal method. These two methods are compared with the time history analysis. In the concluding sections of the paper, recommended design procedures are presented and certain suggested guidelines for improved practice are examined. •

KEY WORDS: steel structures; seismic design; frames; low-rise buildings; calculation methods.

SMILOWITZ, R. and NEWMARK, N. (1979) DESIGN SISMIC ACCELERATION IN BUILDINGS ASCE Journal of the Structural Division, ST12, page 2487-2496. *7*

In this paper, is suggested an expedite procedure for determining design story shears and overturning moments distributions over the.heigth of a structure to resist the effects of strong ground motions. Four factors are taken into account: 1) The mode of the deformation of the structure; 2) The percentage of structural setback; 3) The fundamental frequency of the structure; and 4) The interaction soil-structure. Some tables and design charts are given to calculate these distributions.

KEY WORDS: steel structures; seismic design; calculation methods; frequency; acceleration.

27 -

IGARASHI, S., INOUE, K., ASANO, M. and OGAWA, K. (1973) RESTORING FORCE CHARACTERISTICS OF STEEL DIAGONAL BRACINGS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 2162-2171. *8*

In this work is studied the load-deformation relationship and the dynamic response characteristics of steel X-bracing structures under earthquake ground motions. An axial load-deformation relationship of the bracing members is suggested and employed to calculate the dynamic response of a X-braced structure with one degree-of-freedom. The influence of the slenderness ratio on the dynamic response of X-braced structures is also analysed.

KEY WORDS: steel structures; seismic design; columns; stability; hysteretic behaviour.

TEAL, E. (1978) SEISMIC DRIFT CONTROL AND BUILDING PERIODS. AISC Engineering Journal, n.2, page 30-38. *9*

General parameters of seismic drift control and building periods are discussed in this paper. It begins with a description of the forces formulas used in the drift control and proposed by the 1976 Uniform Building Code (UBC). That description is followed from several considerations and figures showing the most important factores influence. It is explained how should be applied in design all the considerations done. A design example is presented, to a better understanding of the drift control and how to use the UBC.

KEY WORDS: steel structures; seismic design; drift; frequency; calculation methods.

VASQUES, J., POPOV, E. and BERTERO, V. (1973) EARTHQUAKE ANALYSIS OF STEEL FRAMES WITH NON-RIGID JOINTS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 1752-1755. *10*

In this paper, a model of the non-rigidity of the panel zone existing in the joints of a frame is present. The formulation is based on two assumptions: 1) The single component of a panel zone distortion is a shear deformation, and 2) The constitutive relationship is a bilinear model. It is also explained how the model can be assembled into the structure's stiffness matrix considering the deformable joint. Some results of the application of the model to a structure subjected to earthquakes are included.

KEY WORDS: steel structures; seismic design; ductility; joints; frames.

BALLIO, G. and MAZZOLANI, F. (1980) I COLLEGAMENTI NELLE STRUTTURE SISMO-RESISTENTI DI ACCIAIO. Ed. Italsider, Quaderno Tecnico n.ll, 47 pages. *11*

The objective of this monography is to present some practical and theoretical elements on the seismic design of steel structures and their connections. In order to achieve this objective, the work is divided In three parts: (1) In the first chapter, basic principles on limit states, structural steel systems and the behaviour of their connections are presented. (2) The second chapter, deals with the design of the connections referring particulary its ductility. (3) In the last chapter, some elucidatory examples are shown.

KEY WORDS: steel structures; seismic design; joints; detailing; ductility.

-28

CASCIATT, F., FARAVELLI, L. and ZANON, P. (1978) CRITERI DI COMBINAZIONE DEI CARICHI ACCIDENTALI DI STRUTTURE METALLICHE IN ZONA SISMICA. Costruzioni Metalliche, n.3, 8 pages. *12*

A new criterion for combination of accidental loads considering its variability in time is proposed. The paper begins with a brief review of the existing methods seting off that in all methods the loads are described as a continuous process in time. A new formulation on a probabilistic way of the structural safety which takes account the variability of the accidental loads in time, and describe the loads as a filtered Poisson processes is developed. That methodology is applied on the design of an industrial steel structure to a better understand of the proposed formulation.

KEY WORDS: steel structures; seismic design; structural safety; collapse; loads.

FUJIWARA, T. (1978) AN APPROACH TO THE ASEISMIC DESIGN OF THE STRUCTURAL MEMBERS. Proc. of the 5th Japan Earthquake Engineering Symoosium, page 825-832. *13*

The work deals with dynamic response analysis of plane and space frame structures. A brief description of the method to use on the nonlinear earthquake response analyses is briefly mentioned. A study of the behaviour of plane frame, braced frame and space frame structures with local restoring force characteristics in the elasto-plastic joints subjected to ground motion is shown. In the last section, a method of design of structural members based on the distribution of the shear force is proposed.

KEY WORDS: steel structures; seismic design; frames; ductility; calculation methods.

FUJIWARA, T. (1979) EARTHQUAKE RESPONSE OF FRAME STRUCTURES HAVING ASEISMIC ELEMENTS. Trans, of the Achitectural Institute of Japan, n.285, November, page 101-108 and n.286, December, page 65-74. *14*

A method of earthquake response analysis of braced frame structures is proposed. An analytical formulation of the hysterectic characteristics of the brace with elasto-plastic joints is presented. The equation of motion of a braced frame using the method previously exposed are established and applied to a structure to predict the earthquake response. The results are later compared with the elastic response, and some conclusions are appointed.

KEY WORDS: steel structures; seismic design; braces; calculation methods; hysteretic behaviour.

-29-

FUJIWARA, T. (1980) SEISMIC BEHAVIOR OF INELASTIC MEMBERS OF BRACED FRAME STRUCTURE. Proc. of the 7th World Conference on Earthquake Engineering, Istanbul, Turkey, page 241-248. *15*

A formulation of the seismic behaviour of inelastic members of braced frame structures is presented in this work. An analytical representation of the brace which takes account of (1) the relation between the bending moment and the rotation of the member with axial force and (2) elasto-plastic joints is exposed. In the last section, is compared the elasto-plastic dynamic response of braced frame using the method previously exposed with a structure without braced members.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; ductility.

KATO, B. and AKIYAMA, H. (1982) SEISMIC DESIGN OF STEEL BUILDINGS. ASCE ' Journal of the Structural Division, ST8, page 1709-1721. *16*

An approach for the ultimate limit state' design of steel buildings againts the credible severest earthquake is presented on the basis of energy concept. The safety of the structure is judged by comparing structure's energy dissipating capacity with earthquake input energy to the structure. A general safety criterion is first developed for a simple elasto-plastic shear-type system, and then a procedure is analyzed in detail to relate the strength and deformation capacity of steel members to those of the dynamically equivalent elasto-plastic system.

KEY WORDS: steel structures; seismic design; braces; structural safety; ductility.

KATO, B. and AKIYAMA, H. (1981) DUCTILITY OF MEMBERS AND FRAMES SUBJECTED TO BUCKLING. Presented at the May, 1981 International Convention and Exhibition, ASCE, held at, New York, N.Y. (Preprint 81-100), 14 pages. *17*

Criteria to evaluate the eventual good behaviour of steel structures and their members subjected to strong ground motion are presented. Firstly, the moment-rotation relationships which take account of the buckling of structural members based on test results are developed. The tests are performed on members subjected to bending moment with and without axial compression load. An analytical model of moment frames is developed and related with the moment-rotation relationship of the members. In the last section, the ductility ratio of the frame is evaluated and related with the ductility ratio of the members.

KEY WORDS: steel structures; seismic design; ductility; buckling; frames.

ARIBERT, J. and BROZZETTI, J. (1984) COMPORTEMENT ET CONCEPTS DE DIMENSIONNEMENT DES CONSTRUCTIONS METALLIQUES EN ZONE SISMIQUE. Construction Métallique, n.l, page 5-23. *18*

The purpose of this work is to present some practical and theoretical elements on the behaviour and seismic design of steel structures and their connections. In order to achieve this objective, the work is divided in three parts. In the first part, special attention is paid to the strengh, stability and hysteretic behaviour of steel members. The second part deals with the nonlinear dynamic methods of structures. In the last part, some numerical values to use in the checking of the limit states according to the CE.CM. are presented.

KEY WORDS: steel structures; seismic design; ductility; stability; calculation methods.

30 2.4 - JOINTS

KATO, B. and McGUIRE, W. (1973) ANALYSIS OF T-STUB FLANGE-TO-COLUMN CONNECTIONS. ASCE Journal of the Structural Division, ST5, page 865-888. *1*

An analytic and experimental study on the behaviour of high strength bolted connections is presented. Four cases are considered: (1) Separation does not occur before ultimate strength of the member is reached; (2) Separation occurs in range from yield strength to ultimate strength of the member; (3) Separation occurs in range from elastic limit to yield strength of the member; (4) Separation occurs before the member reaches it elastic limit. The test results are compared with the theoretical ones, and a design method using the theoretical formulas is suggested.

KEY WORDS: fasteners.

steel structures; seismic design; joints; ductility;

MICALI, A. (1981) OYSTER - ROLLING ANTI-SEISMIC SYSTEM. Aldo Micali, 47100 Porli, Italy, 6 pages. *2*

This technical report presents a rolling anti-seismic system to absorb horizontal displacement derive from the ground motion. This mechanical gear is composed by two concavous elements inserted by a sphere whose diameter is lightly higher in relation to the total heigth of the two concavous elements. It is possible to superpose two of these systems in order to absorb great horizontal displacements. To follow the explanation some figures are shown.

KEY WORDS: steel structures; seismic design; joints; rolling systems; detailing.

POPOV, E. and PINKNEY, R. (1971) CYCLIC YIELD REVERSAL IN STEEL BUILDING CONNECTIONS. AISC The Engineering Journal, July, page 66-79. *4*

Described herein are tests of 24 connection specimens subjected to various cyclic, quasi-static loading sequencies. Five different basic connection types are investigated. In three of these, the beam is connected to the flange of the column. In the remaining two, the beam is connected indirectly to the web of the column. All of the connection details are chosen on the basis of their practibility and their widespread use. In additon to the behaviour and the manner of failure of the beams and their connections to the columns, the hysterectic response of the beams under repeated and reversed loadings received particular attention.

KEY WORDS: steel structures; seismic design; joints; ductility; columns.

ROEDER, C. and HAWKINS, N. (1981) CONNECTIONS BETWEEN STEEL FRAMES AND WALLS. AISC The Engineering Journal, n.l, page 22-29. *5*

CONCRETE

This work describes an analytical and experimental study on the behaviour of the connections between steel frames and concrete walls. This connection combine a steel plate, which is embedded into the concrete with headed metal studs, with a typical steel frame connection between the plate and the beam. A brief analyses of the deflection of mixed structures for some connection conditions is presented. A design procedure to obtain strength, stiffeness and ductility for the connections is suggested. In the concluding sections, the results of a series of experiments are decribed and compared with the design procedure.

KEY WORDS: steel structures; seismic design; frames; bolts; connections.

31

RU-LIANG WANG, L. and CARRLE, G. (1978) END RESTRAINTS ON STEEL JOIST FLOOR VIBRATIONS. AISC The Engineering Journal, n.2, page 54-58. *6*

This general article deals with the vibration of steel joist floors and presents a method of controlling the floor vibrations. Some concepts on the vibration of floors are exposed and it is suggested that varying the rotational end restraints of the floor it is possible to control the vibration. In the last part, some figures are presented, showing the influence of the end restraints on the frequency, static deflection and amplitude of the floor.

KEY WORDS: steel structures; seismic design; connections; vibration; frequency.

ZANON, P. (1979) RESISTENZA E DUTTILITÀ" DI ANGOLARI TESI BULLONATI. Costruzioni Metalliche, n.4, 19 pages. *7*

Described herein are the results of an experimental research program regarding the collapse behaviour of some typical joints for tensioned bars formed by angles. The study is carried out on sixty-nine elements to see the influence of some parameters: connection geometry; type of connection - welded or bolted; number of bolts; class of bolts; joint ductility. A great number of photos of mechanism of collapse and load-displacement curves are shown for several connections. Some comments regarding the experimental research are done in the end.

KEY WORDS: steel structures; seismic design; detailing; joints; ductility.

KRAWINKLER, H. and POPOV, E. (1982) SEISMIC BEHAVIOR OF MOMENT CONNECTIONS AND JOINTS. ASCE Journal of the Sructural Division, ST2, page 373-391. *8*

The behaviour of moment connections and beam-column joints in moment resisting steel frames subjected to severe earthquakes is studied. The cyclic inelastic deformation capacities of different types of connections are discussed and design recommendations are presented. A conceptual approach to the prediction of the low cyclic fatigue life of welded connections under random loading is outlined, utilizing concepts of elastic-plastic fracture mechanics. The shear behaviour of beam-column joints subjected to large cyclic beam moment reversals is summarized. Based on experimental evidence and in a simplified mathematical model for shear strength, a method for the shear design of joints is suggested.

KEY WORDS: steel structures; seismic design; joints; hysteretic behaviour; fatigue.

KATO, B. (1982) BEAM TO COLUMN CONNECTION RESEARCH IN JAPAN. ASCE, Journal of the Sructural Division, ST2, page 343-360. *9*

The study of the behaviour on the beam-to-column connection is analysed. Special attention is given to the behaviour of joint panels. For some beam to column connection types is suggested design formulas. Based on an experimental research a semi-empirical moment-shear deformation relationship for the panel zone is proposed. The influence of the shear deformation and local buckling of joint panels on frame behaviour is commented and formulas for the local strength of diaphragm to column joints are suggested.

KEY WORDS: steel structures; seismic design; frames; connections; shear.

-32

NISSFOLK, B. (1979) FATIGUE STRENGTH OF JOINTS IN SHEET METAL PANELS. 2. Screwed and Riveted Connections, Swedish Council for Building Research, Stockholm, Sweden, Document D15: 1979, 196 pages. *10*

This report is part of a research program regarding the structural use of sheet metal panels. The work begins with an analyses of the fatigue phencmenom and the crack propagation. The results of experimental studies on the strength of sheet metal structures and their connections under different static and fatigue loading conditions are presented. The performance requirements for fasteners in sheet panels is also investigated. The great number of photos, tables and curves concerning the tests performed provides data for design of sheet metal structures. KEY WORDS: steel structures; seismic design; fatigue; panels; fasteners.

STRNAD, M. (1981) FATIGUE STRENGTH OF SCREWED FASTENINGS IN THIN SHEET COMPONENTS. The Structural Engineer, vol. 59B, No. 3, September, page 33-40. *11*

The paper is concerned with the analysis of the behaviour of screwed fastenings subjected to repeated loading that can lead to fatigue and also provide data on which some practical calculations can be based. It begins with an analyses of the influence of the time variation of loading in the fatigue strength of fastenings. For the elasto-plastic design strength of fastenings is suggested two ways of the determination of the design load. Some experimental results to a better understanding of the behaviour of the fastenings subjected to cyclic loadings are presented, outlined that in the limite state design of screwed fastenings the elasto-plastic behaviour must not be ignored.

KEY WORDS: steel structures; seismic design; fatigue; joints; fasteners.

KLEE, S. and SEEGER, T. (1973) SCHWINGFF^IGKEITSUNTERSUCHUNGEN AN PROFILBLECH­BEFESTIGUNGEN MIT SETZBOLZEN. Der Stahlbau n. 10, page 309-318. *12*

The resistance of corrugated steel sheet fastenings with drive pins under longitudinal, transverse static and cyclic loading is investigated. For longitudinal loading of 5 10E3 cycles, the fatigue strength, characterized mostly by sheet failure, are 35% to 60% of the static strength depending on the steet thickness. For transverse loading of 5 10E4 cycles the fatigue strength characterized here by pin failure, is about 30% of the static strength. In addition, fatigue strength values are determined under combined transverse and longitudinal loading.

KEY WORDS: steel structures; seismic design; fatigue; joints; fasteners.

STRNAD, M. ( ? ) FATIGUE STRENGTH OF SCREWED FASTENINGS. Proceeding of IABSE Colloquium on Fatigue of Steel and Concrete Structures, page 683-690. *13*

This state of art is concerned with the problem of the behaviour of screwed fastenings subjected to cyclic loadings that can lead to fatigue. A brief summary concerned with the past experimental research and a description on the response of a fastening subjected to cyclic loading and the parameters that influences the fatigue strength are presented. Based on statical evaluation of experimental results emperical design formulas for fatigue strength of screwed fastenings are suggested.

KEY WORDS: steel structures; seismic design; fatigue; joints; fasteners.

33 -

MARSH, C. and PALL, A. ( ? ) FRICTION DEVICES TO CONTROL SEISMIC RESPONSE. Interna Report, Concordia University, Montreal, page 809-818. *14*

This report presents a technique for kinetic energy dissipation in structures based on friction joints, during strong earthquakes. Some systems for concrete and steel structures are suggested. The idea of these systems is to reduce the earthquake damages in buildings by using friction joints which acts as fuses. The explanation is followed by some figures.

KEY WORDS: steel structures; seismic design; joints; friction; detailing.

PALL, A. , MARSH, C. and FAZIO, P. (1980) FRICTION JOINTS FOR SEISMIC CONTROL OF LARGE PANEL STRUCTURES. PCI Journal, vol. 25, n. 6, page 38-61. *15*

A technique for energy dissipation in concrete panel structures based in friction joints during strong earthquakes is suggested in this paper. The behaviour of these joints and selection of its location is explained. Some results of experimental tests realized on différents joints are shown. In order to investigate the influence of these joints on the seismic response of panel structures a simple idealization of these joints are suggested, and some seismic analyses with parametric study are performed for the optimization of seismic response.

KEY WORDS: steel structures; seismic design; joints; friction; detailing.

TAKANASHI, K., TANAKA, H. and TANAGUCHI ( ? ) INFLUENCE OF SLIPPING AT HIGH STRENGTH BOLT CONNECTIONS ON DYNAMIC BEHAVIOUR OF FRAMES. Report of the Institute of Industrial Science, University of Tokyo, 19 pages. *16*

In this work the influence of slipping at high strength bolt connections on seismic response of frames is investigated. Some repeated and reversed load tests on high strength bolt connections are performed in order to establish the analitical load-deformation relationship of the connection. A numerical model of bolted connections is suggested and a mathematical formulation of the dynamic behaviour of frames with these connections is developed. The analitical results using the previous formulation are compared with experimental tests carried on steel frames and are used for discussion of the slip on the seismic response of frames.

KEY WORDS: steel structures; seismic design; frames; slip; bolts.

BALLIO, G. and MAZZOLANI, F.M. (1980) I COLLEGAMENTI NELLE STRUTTURE SISMO-RESISTENTI DI ACCIAIO. Ed. Italsider, Quaderno Tecnico n.ll, 47 pages. *17*

The objective of this moncgraphy is to present some practical and theoretical elements on the seismic design of steel structures and their connections. In order to achieve this objective, the work is divided in three parts: (1) In the first chapter, basic principles on limit states, structural steel systems and the behaviour of their connections are presented. (2) The second chapter, deals with the design of the connections referring particulary its ductility. (3) In the last chapter, seme elucidatory examples are shown.

KEY WORDS: steel structures; seismic design; joints; detailing, ductility.

34

RENTSCHLER, G., CHEN, W. and DRISCOLL, G. (1980) TESTS OF BEAM-TO-COLUMN WEB MOMENT CONNECTIONS. ASCE Journal of the Structural Division, ST5, page 1005-1022. *18*

Described herein are the results of a series of four full-scale beam to column moment resisting web connection assemblages under static loading. Each assemblage consists of an 5.50m long column and a beam approximativ 1.50m long connected at midheight of the column. Four different geometries of welding and bolting the beam to the column are tested. These connections simulate building connections with the beam transmitting shear and moment to the column and the column being acted upon by an axial load. Special attention is paid to the strength, stiffness and ductility of those connections.

KEY WORDS: steel structures; seismic design; connections; detailing, ductility.

CHEN, W. and PATEL, K. (1981) STATIC BEHAVIOR OF BEAM-TO-COLUMN MOMENT CONNECTIONS. ASCE Journal of the Structural Division, ST9, page 1815-1838. *19*

Described herein are tests of 12 full-size symmetrically-loaded moment resisting beam-to-column connections, subjected to monotonicaily increasing static loading to failure. All specimens are designed incorporating all possible limiting cases in practical connection design. The discussion of the tests is diveded into four parts: 1) Fully welded connections; 2) Flange welded, web bolted connections; 3) Flange welded connections with various means of carrying a shear; 4) Fully-bolted connections. The results show the general behaviour of moment connections and peculiar change in behaviour when the connection detailings are changed from fully welded to bolted and to fully bolted.

KEY WORDS: steel structures; seismic design; connections; detailing, ductility.

RENTSCHLER, G., CHEN, W. and DRISCOLL, G. (1982) BEAM-TO-COLUMN WEB CONNECTION details. ASCE Journal of the Structural Division, ST2, page 393-409. *20*

The results of eight simulated tests on web connection details are presented. In the simulations, pairs of steel plates are welded to column sections using different attachment ' details. These plates represent the tension and compression flanges of the beam attached to the column. The pair of flange plates are loaded by tension and compression forces to simulate the bending moment of a beam acting upon the column. Observations are made of stresses and deformations as well as phenomena that prevented the connections from obtaining the theoretical maximum_load level.

KEY WORDS: steel structures; seismic design; connections; detailing; ductility.

35

BERTERO, V., POPOV, E. and KRAWINKLER, H. (1972) BEAM-COLUMN SUBASSEMBLAGES. UNDER REPEATED LOADING. ASCE Journal of the Structural Division, ST5, page 1137-1159. *21*

An experimental study on the behaviour of two types of structural steel half-scale subassemblages of a multistory unbraced frame subjected to simulated gravity and cyclic seismic loads is presented in this paper. The two types of specimens are typical of an upper story and a lower story of a building. One of the simulated seismic loading patterns applied to the specimens is of the low cyclic fatigue type with progressively increasing displacement amplitudes. The other is of the incremental displacement type. The lateral loads are applied in a quasistatic manner. Special attention is given to the behaviour of the column panel zone and the 2nd order effects.

KEY WORDS: steel structures; seismic design; subassemblages; hysteretic behaviour; ductility.

MONCARZ, P. and GERSTLE, K. (1981) STEEL FRAMES WITH NONLINEAR CONNECTIONS. ASCE Journal of the Structural Division, ST8, page 1427-1441. *24*

In this paper is outlined a method of analysis which accounts for nonlinear connection behaviour and variable load histories. The analytical approach is briefly described and applyed to some frames to document the consequences of approximations on the prediction of sway, force distribution among girders and columns, deflection stability, and response to load histories. Finally, some conclusions based on the numerical evidence are presented.

KEY WORDS: steel structures; seismic design; frames; hysteretic behaviour; connections.

BOUWMAN, L. (1982) BOLTED CONNECTIONS DYNAMICALLY LOADED IN TENSION. ASCE Journal of the Structural Division, ST9, page 2117-2129. *28*

A report of fatigue tests on tensile loaded bolted connections is presented. The object of these dynamic tests is to determine the fatigue strength of the connections for various locations of the contact pressures, various preloads and bolts distances. Some typical examples of structural connections design are presented, being outlined that, by a judiciously selection of the location of the contact faces, in connections with bolts loaded dynamically in tension, a good structural design can be obtained.

KEY WORDS: steel structures; seismic design; bolts; fatigue; connections.

BUTLER, L., PAL, S. and KULAK, G. (1972) ECCENTRICALLY LOADED WELDED CONNECTIONS. ASCE Journal of the Structural Division, ST5, page 989-1005. *29*

\x The behaviour of eccentrically loaded welded connections is investigated in this paper. With this purpose a theoretical method is developed for predicting the ultimate loads of eccentrically loaded fillet welded connections. The method is based upon the load deformation response of elemental fillet welded. The method takes into account the variation in fillet weld strength with respect to the direction of the applied load. An experimental program is done and the results are compared with the predicted by the analytical method.

KEY WORDS: steel structures; seismic design; welding; ductility; connections.

36

2.5 - DESIGN CRITERIA

ARNOLD, C. (1979) CONFIGURATION AND SEISMIC DESIGN: A GENERAL REVIEW. Proc. of the II U.S. National Conference on Earthquake Engineering, EERI, Standford University, page 22-36. *1*

The relationship between building configuration (size and shape) and seimic design is explained in this paper. After a short analysis of the Uniforme Building Code (USA), which gives some rational rules for building configurations, it identifies some configuration problems namely: general building form; size; nature and location of resisting elements. It is possible to conclude that the final configuration choice is the result of a decision process which involves architects and structural engineers in a way to reach a good configuration and a safe building.

KEY WORDS: steel structures; seismic design; planning; typology; design criteria.

BERG, V. and HANSON, R. (1973) ENGINEERING LESSONS TAUGHT BY EARTHQUAKES. Proc. of the V World Conference on Earthquake Enguneering, Rome, page 82-93. *2*

This general article describes the results of a research study carried on earthquake damages of some reinforced concrete structures. The errors and mistakes which have been in the origin of those damages are examined. Some photos are shown to accompany the description. Evaluation of damages caused by earthquakes gives us the opportunity to check the assumptions made in the planning and design of structures.

KEY WORDS: steel structures; seismic design; planning; damages; design criteria.

FUJIMOTO, M. and NAKA, T. ( ? ) EXPERIMENTAL STUDIES CONCERNING STEEL STRUCTURES, THEIR ELEMENTS AND THEIR CONNECTIONS. ( ? ) , page 47-65. *3*

This state of art presents some mechanical characteristics of steel structures, their elements and their connections under cyclic loadings obtained through experimental investigation. The topics considered are: (1) Materials; (2) Local buckling of plate elements; (3) Compression members; (4) Beam and columns; (5) Mechanical fasteners and welding; (6) Connections; (7) Unbraced frames; (8) Braced frames. Based on these topics, is suggested a summary for a symposium discussion.

KEY WORDS: steel structures; seismic design; connections; frames; hysteretic behaviour.

-37

FUJIMOTO, M. (1970) DESIGN ESSENTIALS IN EARTHQUAKE RESISTANT BUILDINGS. Architectural Institute of Japan, Tokyo, page 91-114. *4*

The 5th chapter of the book "Design essentials in earthquake resistant buildings" is dedicated to the steel structures. This chapter is divided in three parts. In the first part, "General", some considerations on steel structures and mechanical characteristics of the steel are presented. The second part, "Structural design", deals with the structural typology and the use of the diferents types of steel members, hot rolled steel shapes and steel pipes. The last part "Structural precautions", examines the seismic design of steel members and their connections, bolted and welded.

KEY WORDS: steel structures; seismic design; connections; design criteria; detailing.

GIANGRECO, E. (1971) TENDANCES ACTUELLES DANS LE CALCUL ANTISISMIQUE DES CONSTRUCTIONS METALLIQUES. Construction Métallique, n.3, pagell-21. *5*

The fundamental criteria for planning of steel multi-story buildings in seismic zones are examined in this work. The dynamic response based on the response spectra is reviewed. The estimation of the seismic coefficient and the parameters that influence its value, such as: seismici ty zone; type of soil foundation; dynamic behaviour of the structure; masses distribution along the heigth of the building is consedered. The influence of the braces on the spacial earthquake response of multi-story buildings of diferents shapes is analysed and some remarks on seismic design of industrial buildings are outlined.

KEY WORDS: steel structures; seismic design; frames; design criteria; braces.

GIANGRECO, E. (1969) ORIENTAMENTI SULLA PROGETTAZIONE DI COSTRUZIONI IN ACCIAIO IN ZONA SISMICA. Costruzioni tetaniche, n. 5, 7 pages. *6*

The fundamental criteria for planning of steel multi-story buildings in seismic zones are examined in this note. Special attention is given on the estimation of the seismic coefficient and the parameters that influence its value, such as: seismici ty zone; type of soil foundation; dynamic behaviour of the structure; masses distribution along the heigth of the building. The influence of the braces on the earthquake response of multi-story buildings is also considered through the analysis of an example of a frame structure with and without braces.

KEY WORDS: steel structures; seismic design; frames; design criteria; braces.

KATO, B. and AKIYAMA, H. (1982) SEISMIC DESIGN OF STEEL BUILDINGS. ASCE Journal of the Structural Division, ST8, page 1709-1721. *7*

An approach for the ultimate limite state design of steel buildings againts the credible severest earthquake is presented on the basis of energy concept. The safety of the structure is judged by comparing structure's energy dissipating capacity with earthquake input energy to the structure. A general safety criterion is first developed for a simple elasto-plastic shear-type system, and then a procedure is analyzed in detail to relate the strength and deformation-capacity of steel members to those of the dynamically equivalent elasto-plastic system.

KEY WORDS: steel structures; seismic design; braces; structural safety; ductility.

38

RAMASCO, R. (1979) PROBLEMI DI INGEGNERIA SISMICA. Palermo, Corso sulle strutture in acciaio; Le strutture in acciaio nella edilizia, ACAI, CESIA, CTA, Aprile-Giugno, 40 pages. *8*

In this note, the dynamic analyses fundaments of steel structures are reviewed. The dynamic equations of a system with one degree of freedom are deduced for a later generalization to systems with many degrees of freedom. To predict the natural frequences of structures, the Holzer's method is deduced. In the seismic design, a simplified method to estimate the forces acting on multi-story frames is presented. The concluding sections have some references on stiff elements and braces.

KEY WORDS: steel structures; seismic design; frames; calculation methods; braces.

TEAL, J. (1975) SEISMIC DRIFT CONTROL CRITERIA. AISC Engineering Journal, n.2, page 56-67. *9*

In this work, the seismic drift control is analyzed. It is defined as the product of two variables: building flexibility and seismic force. As the seismic force is not known, it is suggested to define the drift by one index, "Dynamic Flexibility Index", in order to compare the performance of different buildings. Tables giving the values of this index for buildings of different types, height and occupancy are presented allowing a vision of the practical limits of the index. In appendix, it is given a vocabulary of some terms used in seismic design.

KEY WORDS: steel structures; seismic design; drift; structural safety; design criteria.

PLUMIER, A. (1981) ELEMENTS DE CONCEPTION DES STRUCTURES EN ACIER EN ZONE SISMIQUE. Note Technique NT20, Septembre, Centre de Recherches Scientifiques et Techniques de l'Industrie des Fabrications Métalliques, Bruxelles, 52 pages. *10*

The fundamental principles concerning with the planning and seismic design of steel structures and their connections are exposed in this technical report. The work is divided in four chapters. In the first chapter, a brief review of seismic action, behaviour of structures and seismic design methods is presented. The second chapter deals with the fundamental rules of planning of earthquake resistent buildings. In the third chapter seme design recommendations regarding with connections, instability, type of steel and braced frames are suggested. In the last chapter, are exposed a few remarks relating to the behaviour of bridges and its seismic detailing. In annex, a design example of the type "Static Equivalence Force" using the New Zealand Code is examined.

KEY WORDS: steel structures; seismic design; planning; design criteria; connections.

-39

BALLIO, G. (1980) CONSIDERAZIONI SUL PROGETTO DI STRUTTURE INACCIAIO IN ZONA SISMICA. Costruzioni Metalliche, n.2, page 61-67. *11*

The article examines some problems regarding seismic design of steel structures and their connections. The study of the structural safety based on limite states approach is presented. The behaviour of structural members is analyzed in particular the influence of the slenderness and local instability on the ductility of the struts. The performance of the connections (bolted and welded) is also investigated, specially its ductility. Some criteria for evaluation and control of ductility of struts and their connections are presented. A numerical example of simple bracing truss is solved to a better understand of the concepts presented.

KEY WORDS: steel structurés; seismic design; ductility; design criteria; connections.

DECLERCK, R. and HISETTE, J. (1978) L'INDUSTRIE DE LA CONSTRUCTION EN JAPON. C.S.T.C. - Revue, n.4, Decembre, page 8-15. *12*

This general paper presents an economical study on the building construction in Japan. The topics examined are: The Japanese building companies; The wages and the social loads; The professional organic structures in the building constructions; The research in the building sector; The building dockyard. In the last topic are presented seme data on the planning, safety and building technic of a new town - Ashiyahama.

KEY WORDS: steel structures; seismic design; building construction; planning; structural safety.

ENGLEBERT, J. (1978) TENDANCE DE L'INDUSTRIALISATION DU BATIMENT EN JAPON. C.S.T.C. - Revue, n.4, Decembre, page 35-44. *13*

In this paper, it is concisely presented two governamental operations realized in Japan in 1970 and 1976 with a view to find new building formulas in the face of the increase of the costs of the lands and the constructions. The two operations were called "Pilot-House" (1970) and "Housing 55" (1976). For the two operations are succintly described the winner projects (the preconized systems and the materials used (steel, concrete and wood)). Some photos are shown to accompany this description, and some conclusions on these two governamental operations are exposed.

KEY WORDS: steel structures; seismic design; building construction; planning; design criteria.

POPOV, E. and BLACK, R. (1981) STEEL STRUTS UNDER SEVERE CYCLIC LOADINGS. ASCE Journal of the Structural Division, ST9, page 1857-1881. *14*

The results of cyclic experiments on 24 struts of different steel shapes of sizes employed in practice are reported in this paper. The geometries of some of the specimens are so selected that they also-simulate some frequently used sections of larger members. The reported hysteric loops provide a wide range of data on the inelastic behaviour of struts under severe reversing loads. An approach for predicting analytically the deteriorating capacity of struts under extreme load reversals is suggested. Sane practical implications resulting from this work are summarized at the end of the paper.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; stability; columns.

40

COMO, M. and IANNI, G. (1981) DUTTILITÀ" E CALCOLO ALLO STATO LIMITE DELLE STRUCTTURE ANTISISMICHE. Università" degli Studi di Napoli, Quaderni di Teoria e Tecnica delle Strutture n.487, 12 pages. *15*

A seismic design methodology for structures with control of ductility is suggested in this work. It is based on a optimum condition of ductility, that is: the collapse mechanism should be the global type; the ductility of the structure should not be excessively high in order to give rise to an economical seismic design; the local safety of the sections should be compatible with the verifications by admissible stresses. The theoretical bases are developed, allowing to estimate the elasto-plastic dissipation capacity of the structure during a strong earthquake. Special emphasis is given to reinforced concrete structures and in final part a illustrative example using the proposed methodology is presented.

KEY WORDS: steel structures; seismic design; ductility; frames; calculation methods.

COMO, M. and IANNI, G. (1981) RESISTENZA E DUTTILITÀ" NECESSARIE ALLE COSTRUZIONI PER L'ASSORBIMENTO DEI TERREMOTI DISTRUTTIVI. Industria Italiana delle Costruzioni, n.120, 7 pages. *17*

Through the observation of the difference of level between the Italian Seismic Code spectrum and the acceleration spectra of some recent italian strong earthquakes is suggested a method based on the ultimate kinetic energy that the structure can absorve, to evaluate the ductility and strength demand of structures to resist to strong earthquakes. A simplified scheme of the energy dissipation is assumed and the equations for the ultimate kinetic energy are deduced. The concept of "aseismic toughness" is introduced. To evaluate the seismic ductility requirements are presented seme curves of the "aseismic toughness". The paper ends with a proposal of an improvement of the Italian Seismic Code.

KEY WORDS: steel structures; seismic design; ductility; frames; design criteria.

SANTORELLI, S. (1976) LA COSTRUZIONE DI TERREMOTI ARTIFICIALI: LO SPETTRO DI PROGETTO. Università" degli Studi di Napoli, Quaderni di Teoria e Tecnica delle Strutture n.400, 8 pages. *18*

In this work, it is suggested a method to define a more suitable spectrum of project related to the structure and based on the available data of real earthquakes. Seme contents on the principal parameters which influence the earthquake intensity are presented. To evaluate the maximum ground acceleration in the building zone, some formulas and curves are given, being function of the magnitude and the epicentrum distance selected for the building zone. The paper ends with an illustrative example showing how can these values be used with a dynamic analyses of the structure to evaluate the spectrum of project.

KEY WORDS: steel structures; seismic design; spectrum; earthquakes; calculation methods.

41 -

2.6 - RECOMMEM)ATIONS

ALONGI, C. (1981) SINTESI DELLA NORMATIVA INTERNAZIONALE PER QUANTO CONCERNE IL COEFICIENTE DI STRUTTURA. Istituto di Scienza e Tecnica delle Costruzioni, Politecnico di Milano, Technical Report n. 1/81, 36 pages.

In this research are compared the values of the behavior factor ( q ) considered in some international codes. The codes considered are: Algeria, Argentine, Canada, Chile, China, Cuba, France, Japan, Mexico, New Zealand, Peru, Portugal, Rumania, Turkey, U.S.A., U.R.S.S.. In the end, a summarizing table for different structural types and for the codes considered is presented together with some remarks.

KEY WORDS: steel structures; seismic design; behaviour factor; ductility; recommendations.

CECM - ECCS (1971) CONCEPTION ET CALCUL DES BATIMENTS A ETAGES DANS LES ZONES SISMIQUES. Recommandations de la CE.CM., CECM-XIII-71-1F, Construction Métallique, n.3, page 50-57. *2*

Design rules and recommendations of structures in seismic regions are presented herein. In the first part, design concepts and safety verifications are presented together with discussion of the choice of the braces and foundations to use in the structure. The seismic loads, specially the horizontal forces are examined in the second part, as well as the influence of the building shape in the torsional behaviour of the structure. In the concluding sections a few remarks on ductility are presented.

KEY WORDS: steel structures; seismic design; recommendations; torsion; structural safety.

GAVARINI, C (1980) AGGIORNAMENTO DELLA NORMATIVA ANTISÍSMICA. Consiglio Nazionale delle Ricerche, Progetto Finalizzato Geodinamica, Convegno Annuale, Roma, 6/8.5.80, 10 pages. *3*

The purpose of this general work is to bring up-to-date the italian rules for design of structures in seismic . regions. A summary on technical rules since 1909 until 1980 are presented in the first part. The philosophy of the actual technical rules (1975) is examided and commented. In the last section, seme research future lines in this field are drawn.

KEY WORDS: steel structures; seismic design; structural safety; recommendations; design rules.

42

GRECO, C. (1972) ORIENTAMENTI NELLA MODERNA NORMATIVA SISMICA. Seminario di Ingegneria Sismica, Instituto Universitario Statale di Architettura di Reggio Calabria, 22/24.6.72, 47 pages. *4*

In this paper, remarks on some international codes for structures in seismic zones as well as their seismic behaviour are presented. The topics examined are: 1) Hypotesis on seismic behaviour of structures; 2) Seismic response; 3) Fundamental parameters in the seismic response; 4) Seismic intensity; 5) Response of structures with multy degree of freedom; 6) The elasto-plastic behaviour and the ductility factor; 7) The three-dimensional behaviour of framed structures; 8) Generalities on seismic international codes; 9) Discussion of some seismic international codes; 10) Dicussion of the draft for the new italian seismic code.

KEY WORDS: steel structures; seismic design; structural safety; recommendations ; design rules.

GIANGRECO, E. ( ? ) SPECIFICATIONS ON MULTI-STORY BUILDINGS AND IN PARTICULAR ON STEEL STRUCTURES IN SEISMIC. ( ? ) , page 625-635. *5*

It is briefly reported on the works of the Commission XIII of the Convention of European Constructional Steelwork Associations concerning the recommendations for designing steel structures in seismic area. The results of a study on the dynamic behaviour of plane and space framed structures are also shown. Finally, some simplified formulae obtained through a large numerical investigation are suggested.

KEY WORDS: steel structures; seismic design; vibration; frames; recommendations.

WATABE, M., ISHIYAMA, Y. and FUKUTA, T. (1983) EARTHQUAKE RESISTANT REGULATIONS FOR BUILDING STRUCTURES IN JAPAN. Original of this document is Building Standard Law in Japan, page 493-501. *6*

The purpose of these general article is to present some topics of the Japanese recommendations for buildings in seismic zone. The topics are refered with the design procedure and the lateral seismic shear. For the first topic, remarks on eccentricity, stiffness and ultimate lateral shear strengh are presented. In the second one, lateral seismic shear above the ground level, lateral seismic shear of appendages and of the basement are considered.

KEY WORDS: steel structures; seismic design; shear; recommendations; calculation methods.

MINISTERO DEI LAVORI PUBBLICI (1980) NORME TECNICHE PER LE COSTRUZIONI IN ZONE SISMICHE, Roma, 30 Guigno 1980, 43 pages. *7*

These italian rules contain specific design information concerning structures in seismic zones. The chapters are: 1) General principles and design methods; 2) Seismic action; 3) Load combinations; 4) Structure performance; 5) Soil foundation performance; 6) Design rules; 7) Design criteria; 8) Structural analysis; 9) Safety verification. To a better understanding of the rules some comments are presented.

KEY WORDS: steel structures; seismic design; structural safety; recommendations; design rules.

43-

MINISTERO DEI LAVORI PUBBLICI (1981) NORMATIVA PER LE RIPARAZIONI ED IL RAFFORZAMENTO DEGLI DANNEGGIATI DAL SISMA NELLE REGIONI BASILICATA, CAMPANIA E PUGLIA. Supplemento ordinario alla "Gazzeta Ufficiale" n. 198, Roma, 21 Luglio, 10 pages. *8*

The purpose of these recommendations is to provide the rules necessary for buildings strengthening and their repairing due to earthquake damages. The rules are applicable to concrete structures, steel structures and masonry structures. Design procedures and construction techniques for strengthening and repairing these buildings are described.

KEY WORDS: steel structures; seismic design; damages; repairing; recommendations.

MINISTERO DEI LAVORI PUBBLICI, PRESIDENZA DEL CONSIGLIO SUPERIORE, SERVIZIO TECNICO CENTRALE (1981) ISTRUZIONI PER L'APPLICAZIONE DELLA NORMATIVA TECNICA PER LA RIPARAZIONE ED IL RAFFORZAMENTO DEGLI EDIFICI DANNEGGIATI DAL SISMA. Legge 14.5.1981 N.219, art.10, 68 pages. *9*

The purpose of these recommendations is to clarify the rules given in the "Supplemento ordinario alla "Gazzeta Ufficiale" n. 198, Roma, 21 Luglio" (Ni *8*) on the strengthening and repairing of buildings due to earthquake damages. General design procedures and construction techniques specialy for masonry structures are presented. In appendix, some numerical examples concerning the verification of the structural safety are presented.

KEY WORDS: steel structures; seismic design; damages; repairing; recommendations.

TEAL, E. (1975) SEISMIC DESIGN PRACTICE FOR STEEL BUILDINGS. AISC Engineering Journal, n.4, page 101-151. *10*

The work provides a treatment on seismic theory and design, particulary as it applies to structural steel. Much of the theory is condensed into simple terms more readily applied to the typical problems faced by busy design engineers. Specific seismic code provisions are discussed, to aid in their interpretation. The work is divided in six sections: 1) Seismic design Terminology (Part 1); 2) Basis for 1974 SEAOC Seismic Code; 3) Seismic design of a 7-story office building; 4) Building code variations from the 1974 SEAOC Seismic Code; 5) Seismic design Terminology (Part 2); 6) Drift control analysis for steel moment frames; Appendix: SEAOC Code.

KEY WORDS: steel structures; seismic design; drift; design rules; calculation methods.

44

ZSUTTY, T. and SHAH, H. (1979) FINAL DRAFT OF SEISMIC RESISTANT DESIGN RULES FOR BUILDING STRUCTURES. The John A. Blume Eathquake Engineering Center, Department of Civil Engineering, Stanford University, August, 63 pages. *12*

These Algerian provisions are applicable to all building structures. They are, however, not directly applicable to important non-building structures such as bridges, dams, pipelines or electrical distribution equipment. These recommendations are expressed in terms of two levels of ground shaking: 1) Maximum capable ground shaking; 2) Maximum probable ground shaking. They are divided in four chapters: 1) Generalities; 2) General Principles; 3) Design Rules; 4) Structures with Different Materials, (alike with Nl *15*)

KEY WORDS: steel structures; seismic design; design rules; recommendations; structural safety.

ZSUTTY, T. and SHAH, H. (1978) A COMMENTARY FOR THE RECOMMENDED DESIGN PROCEDURE FOR ALGERIA. The John A. Blume Eathquake Engineering Center, Department of Civil Engineering, Stanford University, June, 176 pages. *13*

This interesting rational explanation on seismic theory and design is divided in ten chapters: 1) Introduction; 2) Introduction to the Proposed Seismic Design Procedure; 3) Design Philosophy and Acceptable Risk; 4) Development of the Dynamic Amplification Factor Shape Statistics; 5) The Effective Structural Response Spectrum; 6) Types and Behaviour of Lateral Force Resisting Systems; 7) Reliability of Design Objectives; 8) Construction of Design Spectra, Design Procedure and Calibration of Strength Design Load Levels; 9) Examples on the Use of the Proposed Method; 10) Conclusion.

KEY WORDS: steel structures; seismic design; recommendations;, design rules; structural safety.

CONSIGLIO NAZIONALE DELLE RICERCHE, GRUPPO NAZIONALE DIFESA TERREMOTI (1981) RELAZIONE INTRODUTTIVA, Roma, 26.11.81, 10 pages. *14*

In this report, it is presented the purposes of the "Gruppo Nazionale per la Difesa dai Terremoti" (GNDT) established by the italian law n.874 of 22/12/80. The purposes are to address, to co-ordinate, to promote and to develop the study and earthquake operations for the earthquake protection, and to give technique and science advices to the Ministries and Local Entities.

KEY WORDS: steel structures; seismic design; recommendations; damages; structural safety.

REGLES PARASISMIQUES ALGERIENNES (1981), Republique Algérienne Démocratique et Populaire, Ministere de l'Habitat et de l'Urbanisme, Juillet, 86 pages. *15*

These Algerian recommendations are applicable to all building structures. They are, however, not directly applicable to important non-building structures such as bridges, dams, pipelines or electrical distribution equipment. These design rules are expressed in terms of two levels of ground shaking: 1) Maximum capable ground shaking; 2) Maximum probable ground shaking. They are divided in four chapters: 1) Generalities; 2) General Principles; 3) Design Rules; 4) Design Procedures for Braces, (alike with Nl *12*)

KEY WORDS: steel structures; seismic design; safety; recommendations.

design rules; structural

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2.7 - MULTI-STORY BUILDINGS

EDISHERASHVILI, N. and SHAISHMELASHVILI, V. (1973) EXPERIMENTAL STUDIES OF DYNAMIC CHARACTERISTICS OF MULTY-STOREY STEEL FRAME BUILDING LARGE-SCALE MODELS WITH DIFFERENT VERTICAL BRACINGS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 299-303. *1*

Herein are presented results of experimental studies of large scale models (1/6 of natural size) of steel carcass buildings with frame and frame bracing systems. The carcass models are tested for: free, forced (resonance) vibrations and static very intensive horizontal loads permitting to cause destruction of model constructions. Special attention is paid to variation of vibration frequencies and to the damping decrement of models when plastic deformations are developed in them.

KEY WORDS: steel structures; seismic design; braces; frames; multy-storey buildings.

FLEISCHER, W. (1974) SIMPLIFIED SEISMIC DRIFT ANALYSIS OF HIGH-RISE STEEL FRAMES. AISC Engineering Journal, n.3, page 53-64. *2*

This paper presents a simplified method to obtain drift statements for high-rise steel frames under the application of seismic loads. The equations of this method are developed for two cases: planar rigid and planar braced frames. The method is demonstrated step by step by an example of a typical drift analysis in a planar rigid high rise steel bent, including a description of the procedure for both rigid and braced frames. In the end, the development of the method and the derivations of the working equations are explained.

KEY WORDS: steel structures; seismic design; drift; high-rise buildings; calculation methods.

GIANGRECO, E. ( ? ) SPECIFICATIONS ON MULTI-STORY BUILDINGS AND IN PARTICULAR 'ON STEEL STRUCTURES IN SEISMIC. ( ? ) , page 625-635. *3*

It is briefly reported on the works of the Commission XIII of the Convention of European Constructional Steelwork Associations concerning the recommendations for designing steel structures in seismic area. The results of a study on the dynamic behavior of plane and space framed structures are also shown. Finally, some simplified formulae obtained through a large numerical investigation are suggested.

KEY WORDS: steel structures; seismic design; vibration; frames; recommendations.

46 -

GOEL, S. and HANSON, R. (1973) SEISMIC BEHAVIOR OF MULTISTORY BRACED STEEL FRAMES. Proc. of the V World Conf. on Earthquake Engineering, Reme, page 2934-2943. *4*

This paper presents and discusses the results of a numerical study on the influence of the method of design and different arrangements of the bracing members (fully braced, bottom story open, alternate stories open and completely unbraced) in the seismic response of multistory steel frames. The dynamic response is computed by assuming an elasto-plastic type hysteresis behaviour in tension only for the diagonal bracing members, in bending for the girders, and the 2nd order effects for the columns. In the end, some curves for different response parameters are shown.

KEY WORDS: steel structures; seismic design; calculation methods; braces; ductility.

KONNO, T. and KIMURA, E. (1973) EARHQUAKE EFFECTES ON STEEL TOWER STRUCTURES ATOP BUILDINGS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 184-194. *5*

This article presents the results of the full scale measurements and earthquake response analysis carried out on some steel towers for microwave antennes in Japan, as well as the results of vibration tests performed by using steel tower and building models. It is outlined that the steel tower atop building may be affected by the vibrational characteristics of the building and consequently generate high seismic forces at the time of a strong earthquake since the damping of tower is very small. Finally, some remarks on the seismic forces acting on the steel towers are presented.

KEY WORDS: steel structures; seismic design; towers; vibration; multy-storey buildings.

LORD, J. (1972) INELASTIC DYNAMIC BEHAVIOR OF TALL BUILDINGS. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 291-297. *6*

In this general article, it is presented some energy and drift considerations involved in determining the inelastic dynamic behaviour of tall buildings. The energy considerations are related with the stability of the structure and the distribution of energy dissipation during an earthquake event, while drift considerations are refered to the drift control and the inelastic drift predictions.

KEY WORDS: steel structures; seismic design; multy-storey buildings; stability; drift.

SANDHU, B. (1974) DYNAMIC ANALYSIS OF MULTISTORY BUILDINGS. AISC Engineering Journal, n.3, page 67-72. *7*

Some simplified methods for determining natural periods in first, second and third modes of vibrations of multistory buildings are presented in this paper. The simplified methods are developed using the concept of an elastic wave equation in solid uniforme bars. For the horizontal deflection of the building, it is taken into account the contribution of the shear deformation, flexural deformation and the deformation due to joint rotations. Some remarks on the influence of the foundation rotation and translation in the use of the formulas are presented. The paper ends with an illustrative example for a six story shear building.

KEY WORDS: steel structures; seismic design; design rules; vibration; multy-storey buildings.

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TEAL, E. (1975) SEISMIC DESIGN PRACTICE FOR STEEL BUILDINGS. AISC Engineering Journal, n.4, page 101-151. *8*

The work provides a treatment on seismic theory and design, particulary as it applies to structural steel. Much of the theory is condensed into simple terms more readily applied to the typical problems faced by busy design engineers. Specific seismic code provisions are discussed, to aid in their interpretation. The work is divided in six sections: 1) Seismic design terminology (Part 1); 2) Basis for 1974 SEAOC Seismic Code; 3) Seismic design of a 7-story office building; 4) Building code variations from the 1974 SEAOC Seismic Code; 5) Seismic design terminology (Part 2); 6) Drift control analysis for steel moment frames; Appendix: SEAOC Code.

KEY WORDS: steel structures; seismic design; drift; design rules; calculation methods.

YAMADA, M. (1972) EFFECT OF CYCLIC LOADING ON BUILDINGS. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. II, page 725-739. *9*

In this article are presented some recommendations that provide fatigue and fracture criteria for cyclic loading. These recommendations are refered to: 1) Loading related to fatigue and fracture of tall steel buildings; 2) Low cyclic fatigue characteristics of structural steels; 3) Low cycle fatigue fracture limits of structural members as the evaluation basis or design criteria for aseismic capacity.

KEY TORDS: steel structures; seismic design; fatigue; fracture; design criteria.

MUTO, K. and NAGATA, M. (1981) CALCUL ANTISISMIQUE D'UN IMMEUBLE DE GRANDE HAUTER. Construction Métallique, n.3, page 63-74. *10*

This work presents the results of. an analytic seismic study of a multistory building. Due to the unusual plan design (in V), as well as the thickness of their structural elements, the analysis performed had in attention the stresses and the strains due to the tridimensional effect under the seismic loads. The seismic study is made with support of a tridimensional frame analysis program using the feed back method. It is succintly described the building, the principles employed in the seismic design and the formulation used in the program. Finally some curves and tables describing the behaviour of the building are shown.

KEY WORDS: steel structures; seismic design; design criteria; vibration; multy-storey buildings.

D'ANURIA, P. and RAMASCO, R. (1980) L'ECCENTRICITÀ"" CONVENZIONALE DELLE AZIONI SISMICHE ORIZZONTALI NEGLI EDIFICI MULTIPIANO DISSIMMETRICI. Università* degli Studi di Napoli, Quaderno di Teoria e Tecnica delle Strutture n.471, 13 pages. *11*

This paper presents a methodology of how to find the conventional eccentricity of the horizontal seismic forces used in the seismic design of multistorey dissymetryc buildings. The method has been developped first considering a two degrees of freedom model which does not take into account thè effects of not in phase seismic horizontal acceleration. The results obtained have been verified by examining some multistorey buildings.

KEY WORDS: steel structures; seismic design; design rules; calculation methods; multy-storey buildings.

48

PAPIA, M., ZINGONE, G. and RUSSO, G. (1981) UN CRITERIO DI CALCOLO ALLO STATO LIMITE ULTIMO DEI SISTEMI INTELAIATI IN ACCIAIO IN ZONA SISMICA. Giornate Italiane della Costruzione in Acciaio, Palermo, page 485-498. *12*

This article shows a limite state design procedure for braces of steel structures in seismic zone as a function of the ductility demand of the structure in relation to a pre-established safety coefficient when subjected to strong ground motion. Some simplified hypotheses on the earthquake simulation are established in order to obtain formulas of easy use. The formulation is based on energy criteria, and it is possible to consider two distributions of the seismic loads: uniforme and triangular. The paper ends with an illustrative example of the use of those formulas.

KEY WORDS: steel structures; seismic design; ductility; calculation methods; multy-storey buildings.

MEROVICH, A., NICOLETTI, J. and HARTLE, E. (1982) ECCENTRIC BRACING IN TALL BUILDINGS. ASCE Journal of the Structural Division, ST9, page 2066-2080. *13*

The paper describes how an eccentric bracing scheme may be used to satisfy the requirements for both drift control and ductility in the design of high-rise structure located in a zone of high seismic expose. This structural system is used in the design of the 4 Embarcadero Center Building situated in downtown San Francisco. A brief description of the site and the building is done, as well as the static and dynamic analyses performed. Special attention is paid to the ductility of. beams and columns.

KEY WORDS: steel structures; seismic design; high-rise buildings; eccentric braces; drift.

49

2.8 - LOW-RISE BUILDINGS

CLOUGH, R., REA, D., TANG, D. and WATABE, M. (1973) EARTHQUAKE SIMULATOR TEST OF A THREE STORY STEEL FRAME STRUCTURE. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 308-311. *1*

This paper shows the results of experimental tests conducted on a three story steel frame structure using a square shaking table. In this structure, the panel zones are left understrength so that yielding would occur first in the panel zone. The intensity of the table motions are increased progressively until a peak acceleration of 0.5 g to cause yielding in the panel zones. The results described could be used in analytical studies to determine the accurancy of the computer programs for predicting the behaviour of steel frames under large vibrations enough to cause inelastic behaviour.

KEY WORDS: steel structures; seismic design; ductility; low-rise buildings; frames.

MONTGOMERY, C. and HALL, W. (1979) SEISMIC DESIGN OF LOW-RISE STEEL BUILDINGS. ASCE Journal of the Structural Division, ST10, page 1917-1933. *2*

This paper presents some methods and recommendations for design procedures of low-rise steel buildings. The paper begins with a brief description of the building system for purposes of illustration. The second part of the paper contains a review of the behaviour of low-rise steel buildings when subjected to seismic ground motion. With a view to a practical procedure two methods of analysis are refered: response spectra and modal method. These two methods are compared with the time history analysis. In the concluding sections of the paper, recommended design procedures are presented and certain suggested guidelines for improved practice aire examined.

KEY WORDS: steel structures; seismic design; frames; low-rise buildings; calculation methods.

TAKANASHI, K., UDAGAWA, K. and TAKANA, H. (1982) PSEUDO DYNAMIC TESTS ON A 2-STORY STEEL FRAME BY COMPUTER LOAD TEST APPARATUS HYBRID SYSTEM. Proc. of the VII World Conf. on Earthquake Engineering, Athens, 8 pages. *3*

This work presents a non-linear earthquake response analysis method by the computer load test apparatus hybrid system, where the response calculations are carried out on the basis of real restoring force characteristics. The procedure of the hybrid system is explained and applied in the non-linear response analysis of a two story steel frame. The results are compared with the "pure" computer analysis.

KEY WORDS: steel structures; seismic design; ductility; low-rise buildings; frames.

50

GRECO, C. and RAMASCO, R. (1972) LA RISPOSTA SISMICA DI STRUTTURE INTELAIATE PIANE DI FORMA QUALSIASI. Giornale del Genio Civile, n.4,5,6, 13 pages. *4*

A method of seismic design for plane framed structures of any shape which takes account the horizontal and vertical ground motions is suggested in this article. The analytical formulation is shown and the method is applied to some structural samples of industrial buildings. Some significant aspects of the seismic behaviour are emphasized namely the influence of the vertical acceleration and the roof inclination. The conclusions presented are interesting and useful for a correct planning.

KEY WORDS: steel structures; seismic design; acceleration; low-rise buildings; calculation methods.

CONTALDO, M., RAMASCO, R. and SANTORELLI, S. (1977) UN'INDAGINE TEORICA SULL'INFLUENZA DELLA CONTEMPORANEITÀ' DEI MOTI SISMICI ORIZZONTALI E VERTICALI NELLA RISPOSTA DELLE STRUTTURE. Giornale del Genio Civile, n.7,8,9, 22 pages. *5*

The paper presents an analytical study on the influence of the interation between horizontal and vertical acceleration on the seismic behaviour of steel structures. A simple model of two degrees of freedom consisting of a mass elastically restrained by two springs, one horizontal and the other inclined, is developed. A numerical research using the model for seme inclinations of the spring and some relations between the vertical and horizontal periods is realized. Afterwards the model is applied to seme structural typologies in order to obtain some coefficients which allow to predict the displacement and the efforts in those typologies.

KEY WORDS: steel structures; seismic design; acceleration; low-rise buildings; calculation methods.

KANETA, K., KOHZU, I. and MIYAKAWA, H. (1982) LOW CYCLE FATIGUE DAMAGE OF WEAK BEAM TYPE STEEL STRUCTURE DUE TO EARTHQUAKE. Proc. of the VII European Conf. on Earthquake Engineering, Athens, page 323-332. *6*

The low cycle fatigue damage at the beam of one bay, one story steel frames due to both horizontal and vertical ground acceleration, as well as gravity load, is investigated in this work. The structural frame model employed in this study is restricted to a situation in which the flexural stiffness of the beam is infinite and the axial forces at the columns are ignored. The frame has lumped masses placed at the top of the columns and at midspan of the beam. Some results showing the behaviour of the frame and seme conclusions drawn out from these results are presented in the end.

KEY WORDS: steel structures; seismic design; acceleration; low-rise buildings; fatigue.

51

JORUKOVSKI, D. and MAMUCEVSKI, D. (1982) MATHEMATICAL MODEL OF A SINGLE BAY STEEL FRAME STRUCTURE USING PARAMETRE SYSTEM IDENTIFICATION AND SHAKING TABLE EXPERIMENTS. Proc. of the VII European Conf. on Earthquake Engineering, Athens, page 333-339. *7*

In this general paper is suggested a technique for the definition of a mathematical model of a prefabricated steel frame structure using parametre system identification and shaking table experiments. The mathematical model has two degrees of freedom with two lumped masses and the load-displacement relationship is defined by the Ramberg-Osgood model. According to the authors the use of this technique offers a considerably more realistic solutions which is phisically closer to the dynamic solution and in the present case was used to define the viscous damping coefficient value.

KEY WORDS: steel structures; seismic design; low-rise buildings; frames; damping.

PETRINI, V., SETTI, P. and ZANDONINI, R. (1982) INELASTIC BEHAVIOUR OF STEEL FRAMES SUBJECTED TO STRONG EARTHQUAKES. Proc. of the VTI European Conf. on Earthquake Engineering, Athens, page 347-356. *8*

This paper presents a numerical technique for the elasto-plastic dynamic analysis of steel columns permitted to sway. Constant axial loads are considered, while the lateral loads and the ground acceleration can vary with time according to any law. This approach takes into account the real bending moment thrust curvature relationship for the given cross section, allowing for structural imperfection. The non-linear effects of the vertical load due to the lateral displacements and the initial deflected configuration are also considered. Some results are presented and discussed with reference columns of ligth industrial buildings.

KEY WORDS: steel structures; seismic design; low-rise buildings; columns; stability.

SETTI, P. and ZANDONINI, R. (1980) CONSIDERAZIONI SUL COMPORTAMENTO SISMICO DEI TELAI MONOPIANO IN ACCIAIO A COPERTURA NON SPINGENTE. Ingegneria Sismica in Italia, C.I.S.M., Udine, page 313-324..*9*

The seismic behaviour of ligth industrial buildings is discussed in this work. It begins with an analysis of the Italian Code of steel structures in a way to select the cases to study. To investigate the elasto-plastic response of those frames a numerical model of one degree of freedom is presented. This model is applied in the analysis of different frames subjected to Tolmezzo and El Centro earthquakes, being the results compared with the elastic analysis based on the response spectrum. Some conclusions drawn out from these results are presented in the end.

KEY WORDS: steel structures; seismic design; low-rise buildings; columns; stability.

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2.9 - FRAME BEHAVIOUR

CARPENTER, L. and LU, LE-WU (1973) REVERSED AND REPEATED LOAD TESTS OF FULL SCALE STEEL FRAMES. AISI Bulletin n.24 April 1973, 38 pages. *1*

In this bulletin is described the tests done in full sized single bay steel frames subjected to constant gravity loads on the beams and columns and cycles of reversed and repeated displacements. Some particular problems are investigated, namely: the effect of the local buckling of the beam in the single story frame; the behaviour of the columns in the inelastic range and of thé beam to beam-column connections; the effect of the localization of the plastic hinges in the behaviour of a two story frame. The bulletin describes the design of the steel frames, the technique developed to test those frames, the experimental behaviour of the frames and the observations drawn out from the experimental results.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; connections; frames.

FLEISCHER, W. (1974) SIMPLIFIED SEISMIC DRIFT ANALYSIS OF HIGH-RISE STEEL FRAMES. AISC Engineering Journal, n.3, page 53-64. *2*

This paper presents a simplified method to obtain drift statements for high-rise steel frames under the application of seismic loads. The equations of this method are developed for two cases: planar rigid and planar braced frames. The method is demonstrated step by step by an example of a typical drift analysis in a planar rigid high rise steel bent, including a description of the procedure for both rigid and braced frames. In the last section, the development of the method and the derivations of the working equations are explained.

KEY WORDS: steel structures; seismic design; drift; high-rise buildings; calculation methods.

GRECO, C. and RAMASCO, R. (1972) LA RISPOSTA SISMICA DI STRUTTURE INTELAIATE PIANE DI FORMA QUALSIASI. Giornale del Genio Civile, n.4,5,6, 13 pages. *3*

A method of seismic design for plane framed structures of any shape which takes account the horizontal and vertical ground motions is suggested in this article. The analytical formulation is shown and the method is applied to some structural samples of industrial buildings. Some significant aspects of the seismic behaviour are emphasized namely the influence of the vertical acceleration and the roof inclination. The conclusions presented are interesting and useful for a correct planning.

KEY WORDS: steel structures; seismic design; acceleration; low-rise buildings; calculation methods.

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HUCKELBRIDGE, A. and CLOUGH, R. (1978) SEISMIC RESPONSE OF UPLIFTING BUILDING FRAME. ASCE Journal of the Structural Division, ST8, page 1211-1229. *4*

This work shows the results of an experimental and analytical research program on seismic response of uplifting building frames. In the experimental tests a one-third scale model of a nine story steel moment frame prototype with special detail of the footing to allow column uplift on the shaking table is used. In the nonlinear analytical procedure it is employed bilinear elastic foundation elements with zero tensile capacity in the upward direction to accurate behaviour during uplift motion of the frame. The results of the two analyses are compared for two cases: fixed and uplift foundation. In the end, a discussion of the results obtained are presented with some conclusions.

KEY WORDS: steel structures; seismic design; frames; uplift; foundations.

KATO, B. , AKIYAMA, H., SUZUKI, H. and FUKAZAWA, Y. (1973) DYNAMIC COLLAPSE TESTS OF STEEL STRUCTURAL MODELDS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 1457-1460. *5*

This general article presents the results of an experimental study on the dynamic behaviour and strength of beam-columns with H-shaped cross section. The beam-columns are fixed at both ends and are tested on a shaking table which can generate simulated earthquake motions. The results of the experimental tests are compared with those of the numerical analysis which take into account the strain-hardening of the steel and the 2nd order effects.

KEY WORDS: steel structures; seismic design; columns; stability; hysteretic behaviour.

KATO, B. and LU, LE-WU (1972) INSTABILITY EFFECTS UNDER DYNAMIC AND REPEATED LOADS. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 463-481. *6*

The paper presents and discusses some instability problems of columns and frames subjected to dynamic and cyclic loadings. The influence of the dynamic axial loads due to earthquake on the stability of the columns are described. For members and cantilever beam-columns subjected to axial loads and cyclic bending moments a technique is developed for the construction of the load-deflection curve, which is based on the monotonie load diagram. This technique is also applied to frames under cyclic deflections. Emphasis is placed on the aspects that are important in earthquake-resistant design of building frames.

KEY WORDS: steel structures; seismic design; stability; columns; frames.

KOSTEM, C. and HECKMAN, D. (1979) EARTHQUAKE RESPONSE OF THREE DIMENSIONAL STEEL FRAMES STIFFENED BY OPEN TUBULAR CONCRETE SHEAR WALLS. Proc. of the 2nd U. S. Nat. Conf. on Earthquake Engineering, EERI, Standford University, page 969-977. *7*

This work shows the results of a numerical study on the dynamic behaviour of frame-shear wall systems. An open tubular concrete shear wall (U-shaped) extending through the height of the building is considered. Special attention is paid to the effect of the changes in the dimensions (length and thickness) of the open tubular concrete shear wall in the fundamental frequencies of this structural system.

KEY WORDS: steel structures; seismic design; multy-storey buildings; shear; frequency.

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OKADA, H., TAKEDA, T., YOSHIOKA, K., OMOTE, Y. and NAKAGAWA, K. (1973) EXPERIMENTAL AND RESEARCH ON THE RESPONSE OF STEEL MODEL STRUCTURES SUBJECTED TO IMPACT HORIZONTAL LOADING AND TO SIMULATED EARTHQUAKES. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 2721-2730. *8*

The behaviour of steel frames under impulsive loading and earthquake motions are reported in this article. It is divided in two parts. In the first part, experimental results of one-bay one-storied steel portal frames (four specimens) under impact loading at their base with the use of a shock table are reported and compared with the elasto-plastic analysis. In the second part, experimental results of a two-bay three-storied portal frame under simulated earthquake motion using a vibration table are presented together with the theoretical analysis.

KEY WORDS: steel structures; seismic design; impact; vibration; frames.

POPOV, E. (1980) SEISMIC BEHAVIOUR OF STRUCTURAL SUBASSEMBLAGES, the Structural Division, ST7, page 1451-1470. *9*

ASCE Journal of

In this paper, some types of hysteretic loops which can be observed in inelastic experiments with structural members and systems under cyclic loads are presented. Attention is directed to structural steel and reinforced concrete members and subassemblages. The distinction among the various ductility factors are emphasized. The relationship between the response spectrum approach and conventional code design procedure is also examined. This paper may serve as an aid for evaluating the numerous hysteretic loops which are becoming available in the literature.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; ductility;.subassemblages.

RAMASCO, R. and SANTORELLI, S. (1973) LA SCHEMATIZZAZIONE SHEAR-TYPE NELLA RISPOSTA SISMICA DI OSSATURE INTELAIATE PIANE. Estratto dal Giornale del Genio Civile, fase. 9,10,11,12, 10 pages. *10*

This paper suggests a process for the definition of shear type frames equivalent to plane frameworks and concerning the evaluation of the horizontal forces caused by seismic phenomena. Some remarks on the shear type frame are presented and a numerical investigation for some frames of different heigth using the shear type frame and the dynamic analysis is realized. The comparing of the two methods shows a good degree of approximation of the shear type frame for the first three modes of vibration. Some comments on the use of the shear type frame in the seismic design are presented in the last part.

KEY WORDS: frames.

steel structures; seismic design; shear; calculation methods;

55

RAMASCO, R. and SANTORELLI, S. (1974) L'INFLUENZA DELLO SMORZAMENTO E DEL COMPORTAMENTO ELASTO-PLASTICO SULLA RISPOSTA SISMICA DI OSSATURE INTELAIATE PIANE. Estratto dal Giornale del Genio Civile, fase. 10,11,12, 14 pages. *11*

The influence of the damping in the seismic behaviour of steel plane frames is studied in this article. A brief review of the definition of ductility is presented in the beginning. Based on a shear type frame, it is developed a formulation to evaluate the damping matrix and a numerical research to examine the influence of the damping on the different natural modes in frames of different height using the precedent formulation is done. In the end, it is presented some observations drawn out from the numerical investigation.

KEY WORDS: steel structures; seismic design; damping; ductility; frames.

TAKANASHI, K., UDAGAWA, K. and TAKANA, H. (1978) EARTHQUAKE RESPONSE ANALYSIS OF STEEL FRAMES BY COMPUTER-ACTUATOR ON-LINE SYSTEM. V Japan Earthquake Engineering Symposium, page 1321-1328. *12*

In this paper is analyzed the non-linear response of one and two story steel frames, using the instantaneous restoring forces obtained from the structural experiment and controlled by computer which is running simultaneously for the response calculation (computer actuator on-line system). Two methods of numerical integration of the equation of motion using the secant stiffness at a step of the specimen or the instantaneous restoring force of the specimen in structural experiment are explained and applied in the non-linear response of sane frames. Some results and concluding remarks are also presented.

KEY WORDS: steel structures; seismic design; ductility; hysteretic behaviour; frames.

TAKANASHI, K. and TANIGUCHI, H. (1982) PSEUDO-DYNAMIC ON FRAMES INCLUDING HIGH STRENGTH BOLTED CONNECTIONS. Proc. of the VII European Conf. on Earthquake Engineering, Athens, 4 pages. *13*

To study the influence of slippage in high strength bolted connections, a numerical model for the moment-rotation relationship in the beam is proposed in this paper. This model consists of a bi-linear type hysteresis loop which describes the behaviour before slippage and a slip type hysteresis loop which describes the behaviour after slippage. The dynamic response of some frames using this model are compared with experimental results and some conclusions are presented.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; slip; connections.

TANABASHI, R., KANETA, K. and ISHIKA, T. (1973) ON THE RIGIDITY AND DUCTILITY OF STEEL BRACING ASSEMBLAGE. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 834-840. *14*

This paper shows the results of the experiment on the strength and ductility of the Y-braced frames carried out by using column testing machine. Static tests are performed on five models of Y-braced frames and compared with the K-braced frames. A table describing the size, properties of the cross-sections of the members and mechanical properties of the material is presented, as well as the curves obtained in the experimental tests.

KEY WORDS: steel structures; seismic design; ductility; braces; connections.

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TANG, D. and CLOUGH, R. (1979) SHAKING TABLE EARTHQUAKE RESPONSE OF STEEL FRAME. ASCE Journal of the Structural Division, STI, page 221-243. *15*

This paper presents the results of an experimental and analytical investigation on the seismic behaviour of a large scale steel structure. The test structure consists of two identical 5.30m high three story frames having a bay width of 3.70m and to excite the structure a shaking table motion is used. After a brief comment of the planning of the test structure and test program, the most significant results are examined. The description of suitable analytical models for computing the seismic behaviour of the structure, the effects of various model parameters and the experimental results are presented in the last part.

KEY WORDS: steel structures; seismic design; ductility; frames; connections.

UCHIDA, N., AOYAGI, T., KAWAMURA, M. and NAKAGAWA, K. (1973) VIBRATION TEST OF STEEL FRAME HAVING PRECAST CONCRETE PANELS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 1167-1176. *16*

In this work are reported the tests conducted in a two-storey, two-bay steel frame model having full-size precast concrete panels in order to obtain seme basic data on the effects of precast concrete panels on the vibration characteristics of the high-rise buildings, and the behaviour of the panel fastening system. The tests conducted are: 1) Forced vibration test; 2) Free vibration test; 3) Dynamic load test. Special attention is paid to the modes of deflection of precast concrete panels and slabs.

KEY WORDS: steel structures; seismic design; panels; vibration; frames.

VASQUES, J., POPOV, E. and BERTERO, V. (1973) EARTHQUAKE ANALYSIS OF STEEL FRAMES WITH NON-RIGID JOINTS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 1752-1755. *17*

In this paper, a model of the non-rigidity of the panel zone existing in the joints of a frame is presented. The formulation is based on two assumptions: 1) The single component of a panel zone distortion is a shear deformation, and 2) The constitutive relationship is a bilinear model. It is also explained how the model can be assembled into the structure's stiffness matrix considering the deformable joint. Some results of the application of the model to a structure subjected to an earthquake are included.

KEY WORDS: steel structures; seismic design; ductility; joints; frames.

WAKABAYASHI, M., NONAKA, T. and MATSUI, C. (1969) AN EXPERIMENTAL STUDY ON THE HORIZONTAL RESTORING FORCES IN STEEL FRAMES UNDER LARGE VERTICAL LOADS. Proc. of the TV World Conf. on Earthquake Engineering, Santiago, vol.1, page 177-193. *18*

Herein are presented the results of an experimental study on the behaviour of single bay, one and two storyed rectangular frames and "cruciform" frames with wide flange sections under constant vertical load on the columns and varying horizontal force. A theoretical analysis is made to study the elasto-plastic behaviour of those frames and compared with the experimental results. Some curves of the horizontal force-displacement relationship are shown being outlined a redution in the restoring force due to the unstable effect of the vertical loads.

KEY WORDS: steel structures; seismic design; ductility; stability; frames.

-57 -

WAKABAYHASHI, M. (1972) FRAMES UNDER STRONG IMPULSIVE, WIND OR SEISMIC LOADING. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 343-363. *19*

This state of art presents some mechanical characteristics of steel structures, their elements and connections under strong impulsive, wind or seismic loading. The topics are: fundamental characteristics of frames; relationship between load characteristics and frame characteristics; ductility of members and connections; braced and unbraced frames; hysteretic characteristics and low cycle fatigue of steel members and their connections; hysteretic characteristics of braced and unbraced frames; progressive plastic deformation. In the end a large reference list and number of figures are presented.

KEY WORDS: steel structures; seismic design; stability; hysteretic behaviour; braces.

WAKABAYASHI, M., NONAKA, T., MINAMI, K. and SHIBATA, M. (1971) EXPERIMENTAL STUDIES ON THE LARGE PLASTIC DEFORMATION OF FRAMES DUE TO HORIZONTAL IMPACT. Bulletin of the Disaster Prevention Research Institute, Kyoto University, vol.20, Part 4, n. 181, March, page 245-266. *20*

The main objective of this paper is to measure the load and acceleration magnitudes, as well as the total impulse and the velocity change in frames due to horizontal impact. In the experimental tests, two cases are considered: 1) The portal frame speciments are subjected to impact loads in their columns tops, and 2) The portal frames are subjected to a large acceleration for a short duration at the column bases. The. applied load and the inicial velocity are measured by the barium titane ceramics accelerometer and load cell. A theoretical analysis is done in order to evaluate the final plastic deflection of the frame being the results compared with the experimental tests.

KEY WORDS: steel structures; seismic design; stability; frames; impact.

WAKABAYASHI, M., NONAKA, T. and MORINO, S. (1969) AN EXPERIMENTAL STUDY ON THE INELASTIC BEHAVIOR OF STEEL FRAMES WITH A RECTANGULAR CROSS-SECTION SUBJECTED TO VERTICAL AND HORIZONTAL LOADING. Bulletin of the Disaster Prevention Research Institute, Kyoto University, vol.18, Part 3, n. 145, February, page 65-82. *21*

This paper presents the experimental results of a study on the inelastic behaviour of single bay three-storied frames using 1/30 scale models with rectangular cross-sections. A constant vertical load is applied symmetrically on the top of the upper columns and a varying horizontal force is applied in a quasi-static manner at top floor level. Some experimental results are compared with the theoretical analysis. In the discussion of the results, the following points are considered: 1) Deformed shape of specimens; 2) Horizontal force-displacement relation; 3) The effect of the vertical load; 4) The effect of the dimensions and material; 5) The maximum horizontal force; ductility factor.

KEY WORDS: steel structures; seismic design; stability; ductility; frames.

58

WAKABAYASHI, M., NONAKA, T. and MATSUI, C. (1967) AN EXPERIMENTAL STUDY ON THE INELASTIC BEHAVIOR OF STEEL FRAMES SUBJECTED TO VERTICAL AND HORIZONTAL LOADING. Bulletin of the Disaster Prevention Research Institute, Kyoto University, vol.17, Part 1, n. 119, July, page 27-48. *22*

Herein are presented the experimental results of a study on the inelastic behaviour of single bay, one and two-storied frames using 1/4 scale models with wide flange sections. Vertical loads are applied constantly on the columns and a varying horizontal force is applied at top floor level. Special attention is paid to the effects to the axial forces existing in the columns on the behaviour of unbraced frames. The theoretical analysis is also done in order to determine the restoring force characteristics, or the horizontal force-displacement relation being the results compared with the experimental tests.

KEY WORDS: steel structures; seismic design; stability; ductility; frames.

WAKABAYASHI, M., MATSUI, C , MINAMI, K. and METANI, I. (1973) INELASTIC BEHAVIOR OF STEEL FRAMES SUBJECTED TO CONSTANT VERTICAL AND ALTERNATING HORIZONTAL LOADS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 1194-1197. *23*

This general article presents the experimental results of a study on the inelastic behaviour of both braced and unbraced frames under constant vertical and alternating horizontal loading using four full scale models. The behaviour under monotonie loading is also presented for comparison with that under alternating loading. A theoretical analysis is made to study the hysteretic behaviour of both braced and unbraced frames tested, being later on the results compared with the experimental tests. At last, seme theoretical and experimental hysteretic curves are shown.

KEY WORDS: steel structures; seismic design; stability; braces; hysteretic behaviour.

SETTI, P. and ZANDONINI, R. (1980) CONSIDERAZIONI SUL COMPORTAMENTO SISMICO DEI TELAI MONOPIANO IN ACCIAIO A COPERTURA NON SPINGENTE. Ingegneria Sismica in Italia, C.I.S.M., Udine, page 313-324. *24*

The seismic behaviour of ligth industrial buildings is discussed in this work. It begins with an analysis of the Italian Code of steel structures in a way to select the cases to study. To investigate the elasto-plastic response of those frames a numerical model of one degree of freedom is presented. This model is applied in the analysis of different frames subjected to Tolmezzo and El Centro earthquakes, being the results compared with the elastic analysis based on the response spectrum. Some conclusions drawn out from these results are presented in the end.

KEY WORDS: steel structures; seismic design; low-rise buildings; columns; stability.

59 -

PETRINI, V., SETTI, P. and ZÄNDONINI, R. (1982) INELASTIC BEHAVIOUR OF STEEL FRAMES SUBJECTED TO STRONG EARTHQUAKES. Proc. of the VII European Conf. on Earthquake Engineering, Athens, page 347-356. *25*

This paper presents a numerical technique for the elasto-plastic dynamic analysis of steel columns permitted to sway. Constant axial loads are considered, while the lateral loads and the ground acceleration can vary with time according to any law. This approach takes into account the real bending moment thrust curvature relationship for the given cross section, allowing for structural imperfection. The non-linear effects of the vertical load due to the lateral displacements and the initial deflected configuration are also considered. Some results are presented and discussed with reference columns of ligth industrial buildings.

KEY WORDS: steel structures; seismic design; low-rise buildings; columns; stability.

UDAGAWA, K., TAKANASHI, K. and KATO, B. (1984) EFFECTS OF DISPLACEMENT RATES ON THE BEHAVIOR OF STEEL BEAMS AND COMPOSITE BEAMS. Proc. of the VIII World Conf. on Earthquake Engineering, San Francisco, 8 pages. *26*

This paper deals with quasi-static and dynamic tests of steel beams and fully composite beams with steel deck subjected to monotonie and cyclic loadings, and investigates how the difference of displacement rates affects: 1) Maximum moment capacity; 2) Elastic stiffness and stiffness under unloading in plastic range and 3) Deformation capacity and shape of hysteresis loop. A viscous damping in an elastic range of steel beams is evaluated and the increase in moment capacities due to a viscous damping is examined.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; damping; ductility.

TANIGUCHI, H. and TAKANASHI, K. (1984) INELASTIC RESPONSE BEHAVIOR OF H-SHAPED STEEL COLUMN TO BI-DIRECTIONAL EARTHQUAKE MOTION. Proc. of the VIII World Conf. on Earthquake Engineering, San Francisco, 8 pages. *27*

This paper presents the response behaviour of steel H-shaped columns to two horizontal components of recorded earthquake motions analyzed by a hybrid system of a digital computer and a loading test system. Two numerical methods are presented: one uses a tri-linear type stress-strain relationship and the other is an extention of Ziegler's kinematic hardening rule with a bi-linear type shear-displacement relationship. The results computed by these numerical models are compared with the experimental tests.

KEY WORDS: steel structures; seismic design; columns; stability; hysteretic behaviour.

60

RAMASCO, R. (1971) LA RISPOSTA SISMICA DELLE STRUTTURE INTELAIATE PIANE IN CAMPO ELASTO-PLASTICO. Giornale del Genio Civile, Luglio, fase. 7, page 547-567. *28*

The main objective of this paper is to examine the seismic behaviour of framed structures in elasto-plastic range. In order to achive this objective a program of automatic calculation is developed and its formulation is presented. The program is quite general both for materials, concrete and steel, and for the shape of the framework on the hypotesis of rectangular frame. Some numerical applications on steel framed structures and concrete framed structures are shown in order to study some phenomena, such as the damping and the P-delta effect due to vertical loads on the elasto-plastic behaviour.

KEY WORDS: steel structures; seismic design; stability; frames; damping.

0N0, T. (1982) DEFORMATION CAPACITY AND ULTIMATE STRENGTH OF COLD FORMED STEEL MEMBERS AND FRAMES. Proc. of the VTI European Conf. on Earthquake Engineering, Athens, page 315-322. *29*

This article shows the experimental results on deformation capacity and ultimate strength of cold formed steel members and frames. Two testing programs are performed: one is the bending test of beams in order to understand the plastic deformation capacity of cold formed steel members and, the other is the lateral loading test of the moment frames and braced frames in order to explain the inelastic behaviour and the deformation capacity. In the moment-rotation curves of the beams special attention is paid on the influence of the slenderness ratios of members. Tables describing the dimension of test beams, test frames and material properties are presented, as well as some experimental curves.

KEY WORDS: steel structures; seismic design; stability; frames; buckling.

Mcniven, H. and Matzen, V. (1978) A MATHEMATICAL MODEL TO PREDICT THE INELASTIC RESPONSE OF A STEEL FRAME: FORMULATION OF THE MODEL. Earthequake Engineering and Structural Dynamics, vol.6, page 189-202. *30*

The purpose of this research is to use data from experiments to formulate a mathematical model that will predict the non-linear response of a single-storey steel frame to an earthquake input. The process used in this formulation is system identification. The form of the model is a second-order non-linear differential equation with linear viscous damping and Ramberg-Osgood type hysteresis. The damping coefficient and the three parameters in the hysteretic model are to be established. An integral weighted mean squared error function is used to evaluate the "goodness of fit" between the model's response and the structure's response when both are subjected to the same exitation.

KEY WORDS: steel structures; seismic design; stability; frames; structural safety.

61

Mcniven, H. and Matzen, V. (1978) A MATHEMATICAL MODEL TO PREDICT THE INELASTIC RESPONSE OF A STEEL FRAME: ESTABLISHMENT OF PARAMETERS FROM SHAKING TABLE EXPERIMENTS. Earthequake Engineering and Structural Dynamics, vol.6, page 203-219. *31*

The purpose of this research is to use data from experiments to formulate a mathematical model that will predict the non-linear response of a single-storey steel frame to an earthquake input. The process used in this formulation is system identification. In experiments performed on a shaking table, the frame was subjected to two earthquake motions at several intensities. In each case the frame underwent severe inelastic deformation. A computer program which incorporates the concepts of system identification makes use of the recorded data to establish four parameters in a non-linear mathematical model. When different amounts of data are used in the program, parameter sets are established which give the best model response for that amount of test data.

KEY WORDS: steel structures; seismic design; stability; frames; structural safety.

Popov, E. and Bertero, V. (1980) SEISMIC ANALYSIS OF SOME STEEL BUILDING FRAMES. ASCE Journal of the Engineering Mechanics Division, vol.106, EMI, page 75-92. *32*

Assurance of ductile behaviour under inelastic load reversals occurring during severe seismic disturbances is basic for earthquake-resistant design of structural frames. The principal features encountered in the analysis of this behaviour for three major types of steel building frames are considered in this paper. The widely used moment-resisting framing is considered first. This is followed by an examination of conventionally braced frames. Lastly, a novel bracing system in which the diagonal braces are made eccentric with respect to the beam-column joint are considered.

KEY WORDS: steel structures; seismic design; frame; eccentric braces; subassemblages.

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2.10 - BRACING BEHAVIOUR

ANDERSON, J. (1975) SEISMIC BEHAVIOR OF K-BRACED FRAMING SYSTEMS. ASCE Journal of the Structural Division, ST10, page 2147-2159. *1*

The purpose of this work is to evaluate the inelastic seismic response of three K-brace framing systems to strong earthquake motions. The framing systems considered in this work are ten stories high with three equal bays. In all cases, the primary K-bracing is located in the center bay with the bracing members oriented so as to form a vee. The seismic response of those frames is determined by a numerical analysis which is briefly described. The comparison of the seismic response of the three systems is evaluate in terms of the following parameters: 1) Absolute maximum lateral displacement; 2) Maximum relative displacement; 3) Ductility requirement; 4) Hysteretic behaviour; 5) Time history.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; ductility.

EDISHERASHVTLI, N. and SHAISHMELASHVILI, V. (1973) EXPERIMENTAL STUDIES OF DYNAMIC CHARACTERISTICS OF MULTY-STOREY STEEL FRAME BUILDING LARGE-SCALE MODELS WITH DIFFERENT VERTICAL BRACINGS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 299-303. *2*

Herein are presented results of experimental studies of large scale models (1/6 of natural size) of steel carcass building with frame and frame bracing systems. The carcass models are tested for: free, ' forced (resonance) vibrations and static very intensive horizontal loads permitting to cause destruction of model constructions. Special attention is paid to variation of vibration frequencies and to the damping decrement of models when plastic deformations are developed in them.

KEY WORDS: steel structures; seismic design; braces; frames; multy-storey buildings.

GOEL, S. and HANSON, R. (1973) SEISMIC BEHAVIOR OF MULTISTORY BRACED STEEL FRAMES. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 2934-2943. *3*

This paper presents and discusses the results of a numerical study on the influence of the method of design and different arrangements of the bracing members (fully braced, bottom story open, alternate stories open and completely unbraced) in the seismic response of multistory steel frames. The dynamic response is computed by assuming an elasto-plastic type hysteretic behaviour in tension only for the diagonal bracing members, in bending for the girders, and the 2nd order effects for the

"columns. In the end, some curves for different response parameters are shown.

KEY WORDS: steel structures; seismic design; calculation methods; braces; ductility.

-63 -HUCKELBRIDGE, A. and CLOUGH, R. (1978) SEISMIC RESPONSE OF UPLIFTING BUILDING

FRAME. ASCE Journal of the Structural Division, ST8, page 1211-1229. *4*

This work shows the results of an experimental and analytical research program on seismic response of uplifting building frames. In the experimental tests a one-third scale model of a nine story steel moment frame prototype with special detail of the footing to allow column uplift on the shaking table was used. In the nonlinear analytical procedure it was employed bilinear elastic foundation elements with zero tensile capacity in the upward direction to accurate behaviour during uplift motion of the frame. The results of the two analyses are compared for two cases: fixed and uplift foundation. In the end, a discussion of the results obtained are presented with some conclusions.

KEY WORDS: steel structures; seismic design; frames; uplift; foundations.

JAIN, A. and GOEL, S. (1980) SEISMIC RESPONSE OF ECCENTRICALLY BRACED FRAMES. ASCE Journal of the Structural Division, ST4, page 843-859. *5*

The purpose of this paper is to define the situation in which a bracing member can be treated as rigid-connected nonbuckling type, rigid-connected buckling type, or pin-connected buckling type so that an appropriate hysteretic model can be used in the seismic analysis of eccentrically braced frames. The seismic response of three eccentrically braced frames with different member proportions are also compared so as to study the merits of different design philosophies used to proportion the frame members.

KEY WORDS: steel structures; seismic design; eccentric braces; buckling; frames.

MURAKAMI, M., TAMURA, R., TANAKA, Y., OAMI, K., OSAWA, Y. and UMEMURA, H. (1973) EARTHQUAKE RESISTANTE OF A STEEL FRAME APARTMENT HOUSE WITH . PRECAST CONCRETE PANEL. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 2688-2697. *6*

The dynamic behaviour of a steel frame apartment house with precast concrete wall panels and its surrounding soil during actual earthquakes is investigated in this work. Sixteen sets of the electro-magnetic seismometers are installed to measure the earthquake acceleration records under, around and inside the building. With those records if is possible to establish an appropriate dynamic model for the soil-building system to study the dynamic behaviour of this kind of building under severe earthquake exitations. Seme results and concluding remarks are presented in the end.

KEY WORDS: steel structures; seismic design; multy-storey buildings; vibration; frames.

MAISON, B. and POPOV, E. (1980) CYCLIC RESPONSE PREDICTION FOR BRACED STEEL FRAMES. ASCE Journal of the Structural Division, ST7, page 1401-1416. *7*

In this paper, some experimental results on the behaviour of half-scale K braced building frames subjected to severe cyclic loading are reviewed. This is followed by a presentation of the experimentally determined hysteretic behaviour for the individual braces used in the test frames. An improved procedure for a computer simulation of brace behaviour is then described. Using this formulation, the overall inelastic cyclic response of one of the test frames is compared with the predicted results. The agreement between the experimental and analytical results are good.

KEY WORDS: steel structures; seismic design; braces; frames; hysteretic behaviour.

-64

POPOV, E. (1980) SEISMIC BEHAVIOR OF STRUCTUAL SUBASSEMBLAGES. ASCE Journal of the Structural Division, ST7, page 1451-1470. *8*

In this paper seme types of hysteretic loops which can be observed in inelastic experiments with structural members and systems under cyclic loads are presented. Attention is directed to structural steel and reinforced concrete members and subassemblages. The distinction among the various ductility factors are emphasized. The relationship between the response spectrum approach and conventional code design procedure is also examined. This paper may serve as an aid for evaluating the numerous hysteretic loops which are becoming available in the literature.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; ductility; subassemblages.

WAKABAYASHI, M. and TSUJI, B. (1967) EXPERIMENTAL INVESTIGATION ON THE BEHAVIOR OF FRAMES WITH AND WITHOUT BRACING UNDER HORIZONTAL LOADING. Bulletin of the Disaster Prevention Research Institute, Kyoto University, vol.16, Part 2, n. 112, January, page 81-94. *9*

The experimental results on the behaviour of steel frames with and without bracing under horizontal loading are shown in this paper. The test speciments are moment frames and one span two storied frames. The experiments are conducted for the moment frames under monotonous horizontal and also under repeated loading, and for the one span two storied frames under repeated horizontal loading. Special attention is paid on the influence of the local or lateral buckling of the frame and to the buckling and post-buckling behaviour of the compressive bracing on the restoring force characteristics of the whole frame. In appendix, it is given a method for calculating the axial force-displacement relationship of the compression bracing.

KEY WORDS: steel structures; seismic design; buckling; braces; hysteretic behaviour.

WAKABAYASHI, M., MATSUI, C , MINAMI, K. and MITANI, I. (1974) INELASTIC BEHAVIOR OF FULL-SCALE STEEL FRAMES WITH AND WITHOUT BRACINGS. Bulletin of the Disaster Prevention Research Institute, Kyoto University, vol.24, Part 1, n. 216, March, page 1-23. *10*

Inelastic behaviour of unbraced and braced steel frames subjected to a monotonie and alternatingly repeated horizontal load are experimentally investigated on approximately full-scale, one-bay, one-story models of mild steel H-sections. Eigth frames are tested; four braced and four unbraced. Four of them are horizontally loaded with their columns simultaneously subjected to constant vertical load. The other four frames are loaded only horizontally. A theoretical analysis of elastic-plastic behaviour of those frames are realyzed and compared with the test results. Some tables describing the properties of frames members and loading conditions of test frames are presented as well as the experimental load-displacement relationships.

KEY WORDS: steel structures; seismic design; stability; braces; hysteretic behaviour.

65 -

WAKABAYASHI, M. (1970) THE BEHAVIOR OF STEEL FRAMES WITH DIAGONAL BRACINGS UNDER REAPEATED LOADING. Japan - U.S. Seminar on Earthquake Engineering with Emphasis on the Safety of School Buildings, September 21-26, Sendai, 31 pages. *11*

This state of art is mainly concerned with the behaviour of bracing members used in steel structures. Some topics are examined, namely: 1) School buildings and steel structures in Japan; 2) The damages of steel structures due to the 1968 Tokachi Offing earthquake; 3) Current situation of diagonal bracing used in steel structures; 4) Previous studies on braced frames; 5) Pretensioning and hysteretic characteristics of steel bar bracings; 6) Buckling and hysteretic characteristics of compressed bracings; 7) Experimental study on the behaviour of steel frames with diagonal bracings. In the end, some figures and curves are presented.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; stability.

BALLIO, G. , GOBETTI, A. and ZANON, P. (1979) SIMULATION OF DYNAMIC BEHAVIOUR OF PIN JOINTED STRUCTURES WITH A NON SYMMETRICAL CONSTITUTIVE LAW. Simulation of Sistem '79, North-Holland Publishing Company, page 509-516. *12*

The seismic response of pin jointed structures is analyzed in this paper. The investigation is performed for a typical steel frame, i.g. a bracing system of industrial building. The model used for the non symmetrical constitutive law of compressed and tensioned bars is described and applied in a step-by-step algoritm to evaluate the dynamic behaviour of pin jointed structures. A numerical example is presented showing the possibilities of the proposed method. Some considerations on the ductility requested by the dynamic loads to this kind of structures are presented.

KEY WORDS: steel structures; behaviour; braces.

seismic design; ductility; hysteretic

BALLIO, G., GOBETTI, A. and ZANON, P. (1979) RESISTENZA E DUTTILITÀ" DI STRUTTURE RETICOLARI DI CONTROVENTO. Atti del Convegno 1978 Consiglio Nazionale delle Ricerche, Progetto Finalizzato "Geodinamica", Roma, Gennaio, page 291-305. *13*

In this general work, it is presented some experimental and numerical results concerning the behaviour of steel structures, their elements and connections in seismic zones. Special attention is given to the braces, namely the influence of its slenderness and the type of end connection in the strength and ductility of those members. In the end some experimental and theoretical curves are shown.

KEY WORDS: steel structures; behaviour; braces.

seismic design; ductility; hysteretic

66

BALLIO, G., CAMPANINI, G., GOBETTI, A. and ZANON, P. (1980) CONDIZIONI DI COLLASSO DI STRUTTURE METALLICHE RETICOLARI DI CONTROVENTO SOGGETTE AD AZIONI SISMICHE. Ingegneria Sismica in Italia, C.I.S.M., Udine, page 275-287. *14*

The dynamic behaviour of braced structures is the argument of this paper. The correlation between the applied load and the longitudinal displacement for compressed bars, varying according with the slenderness of the bar is briefly described and idealized constitutive laws for compressed and tensioned bars are suggested. The results of a numerical approach on the behaviour of a bracing structure during an earthquake are presented and used to find the relation between design seismic coefficient and collapse acceleration by amplifying the adopted input.

KEY WORDS: steel structures; seismic design; ductility; collapse; braces.

BALLIO, G., GOBETTI, A. and ZANON, P. (1979) ANALYTICAL COMPUTATIONS OF DYNAMIC BEHAVIOUR OF PIN JOINTED STRUCTURES. Proc. of the Int. Conf. on Environmental Forces on Engineering Structures, London, July, 14 pages. *15*

The seismic behaviour of bracings built up with angles profiles is investigated in this work. For this purpose, an experimental and numerical analysis in order to measure the ductility of tensioned and compressioned members with bolted and welded connections have been performed as well as a numerical approach for simulation with a computer the behaviour of bracing structures during an earthquake. The constitutive laws used in the model for the compressed and tensioned bars is briefly described and applied in a step-by-step algoritm to evaluate the dynamic behaviour of a pin jointed structure. A numerical example is shown as well as some considerations on the ductility requested to this kind of structures.

KEY WORDS: steel structures; seismic design; ductility; hysteretic behaviour; braces.

HIGGINBOTHAM, A. and HANSON, R. (1976) AXIAL HYSTERETIC BEHAVIOR OF STRUCTURAL MEMBERS. ASCE Journal of the Structural Division, ST7, page 1365-1380. *16*

This paper presents a procedure for modeling axially-loaded members under large inelastic cyclic deflections. Two analytical solutions for pin-ended members are formulated. Both solutions employ the plastic hinge concept, including axial force effects, to account for plastic rotation. The solutions differ in accounting for axial displacement due to lateral deflection of the members. The first solution uses the exact expression for curvature whereas the second solution assumes the internal bending moment to vary linearly along the member. The results obtained with these procedures are compared with the experimental ones.

KEY WORDS: steel structures; seismic design; braces; stability; hysteretic behaviour.

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SAMPAOLESI, L. , BIOLZI, L. and TACCHI, R. ( ? ) SUL COMPORTAMEOTXD DI STRUTTURE DI CONTROVENTO RETICOLARI IN ACCIAIO SOTTO AZIONI SISMICHE. ( ? ) , 32 pages. *17*

The report presents the results of a research program dealing with the analysis of the behaviour of steel braced structures subjected to alternate loading conditions. In the experimental tests a natural scale models of a frame with one and two braces are utilized. Experiments are performed by using a test apparatus able to impress cyclic displacements slowly variable in time. A numerical model for predicting the behaviour of the braces is presented and applied in an algoritm to evaluate the behaviour of braced structures. Some considerations on the ductility requested by these structures and its hysterectic behaviour are presented in the end.

KEY WORDS: steel behaviour; braces.

structures; seismic design; ductility; hysteretic

CALADO, L. (1985) SIMULAÇÃO NUMERICA DO COMPORTAMENTO SISMICO DE ESTRUTURAS METÁLICAS CONTRAVENTADAS. Dissertation submitted of the requirements for the degree of Master of Science in the Technical University of Lisbon, January, 82 pages. *18*

The work deals with a finite element able to describe the behaviour of cyclic axially loaded members taking into account the geometrical and physical nonlinear effects. Its formulation is developed and the results obtained with this model are compared with experimental studies allowing to check the model. A numerical study is then developed to investigate the influence of some parameters which affect the bearing capacity of compressed members. The work also shows how the element can be 'used to simulate the braces in order to predict the seismic behaviour of plane braced pin-end structures, and the evaluation of the behaviour factor of this type of structures.

KEY WORDS: steel structures; seismic design; stability; braces; compression members.

TAYEM, A. and GOEL, S. (1984) CYCLIC BEHAVIOR OF ANGLE X-BRACING. ASCE Structures '84 Congress, San Francisco, October, 1/3.10.84, 22 pages. *19*

Five full scale X-bracing specimens are tested under quasi-static cyclic loading with a view to explore their response and then ultimately to synthesize a composite hysteresis model for the two X-members. The main parameters of the study are: 1) Mode of buckling; 2) Interaction between the two members; 3) Slenderness ratio and 4) Width-thickness ratios. The general cyclic behaviour, behaviour of compression diagonal, local buckling and hysteresis loops of the tested specimens are presented in this work.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; stability.

68

GHANAAT, Y. (1980) STUDY OF X-BRACED STEEL FRAME STRUCTURES UNDER EARTHQUAKE SIMULATION. Report No. UCB/EERC 80/80, Earthquake Engineering Research Center, University of California, Berkeley, April, 226 pages. *20*

This report presents experimental results on the seismic performance of a model three-story building frame, both unbraced and with three different wind bracing systems and correlates these results with analytical predictions. Considerable compression buckling and tension yielding of the diagonal bracing members are observed in the tests, but the bracing provided significant reductions in the lateral displacements when compared with the unbraced frame response. Analytical techniques employing three different hysteresis models to represent the three types of bracing systems are shown to predict the response of braced frames with good accurancy.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; stability.

Kahn, L. and Hanson, R. (1976) INELASTIC CYCLES OF AXIALLY LOADED STEEL MEMBERS. ASCE Journal of the Structural Division, ST5, page 947-959. *21*

The object of this investigation was to experimentally determine the hysteretic characteristics of axially loaded steel members subjected to alternating tension and compression. Sixteen steel bars of various lengths were tested under both static and quasi-dynamic loads, the principal result was the determination of axial load-deflection curves for members subjected to cycles of post-buckling deflections and high tension loads. The results of these are particularly applicable to the seismic design of bracing members where large cyclic deflections may not lead to collapse of the entire structure.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; stability.

Jain, A., Goel, S. and Hanson, R. (1978) INELASTIC RESPONSE OF RESTRAINED STEEL TUBES. ASCE Journal of the Structural Division, ST6, page 897-910. *22*

The purpose of this experimental investigation was to determine the hysteresis behaviour of axially loaded steel bracing members with rotational end restraint provided by connections and to study the influence of connection flexural strength, stiffness and change of member length on the hysteresis behaviour. The .experimental results are compared with theoretical results obtained by other authors.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; stability.

69

Popov, E., Zayas, V. and Mahin, S. (1979) CYCLIC INELASTIC BUCKLING OF THIN TUBULAR COLUMNS. ASCE Journal of the Structural Division, STll, page 2261-2277. *23*

In this paper, experimental results from tests on six tubular columns subjected to severe cyclic loading are considered. The one-sixth scale specimens were so chose so that their diameter-to-thickness ratios and fixities are representative of members encountered in practice. Experimentally obtained hysteretic loops for axial force versus elongation, as well as versus the maximum lateral deflection are presented and interpreted. Suggestions for analytic (computer) representation of the hysteretic loops are also given. The paper concludes with an examination of possible approaches for analyzing braced offshore towers and recommendations for additional research.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; stability.

Toyama, K. (1983) SEISMIC BEHAVIOUR OF STEEL BENT-BRACING SYSTEMS. Kajima Institute of Construction Technology Report No 41, 47 pages. *24*

In this paper, in order to improve the aseismic characteristics of braced frames, a special bracing called "bent-bracing" having stable restoring force characteristics is applied to the braced frame, and the effects is studied both experimentally and analytically. Bent-bracing has the initial deflection provided at the center of bracing by previously bending the section. The skeleton curve of bent-bracing and the practical evaluation method of the hysteresis model are also presented.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; stability.

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2.11 - ECCENTRIC BRACING BEHAVIOUR

ANDERSON, J. (1975) SEISMIC BEHAVIOR OF K-BRACED FRAMING SYSTEMS. ASCE Journal of the Structural Division, ST10, page 2147-2159. *1*

The purpose of this work is to evaluate the inelastic seismic response of three K-brace framing systems to strong earthquake motions. The framing systems considered in this work are ten stories high with three equal bays. In all cases, the primary K-bracing is located in the center bay with the bracing members oriented so as to form a vee. The seismic response of those frames are determined by a numerical analysis which is briefly described. The comparison of the seismic response of the three systems is evaluated in terms of the following parameters: 1) Absolute maximum lateral displacement; 2) Maximum relative displacement; 3) Ductility requirement; 4) Hysteretic behaviour; 5) Time history.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; ductility.

HUCKELBRIDGE, A. and CLOUGH, R. (1978) SEISMIC RESPONSE OF UPLIFTING BUILDING FRAME. ASCE Journal of the Structural Division, ST8, page 1211-1229. *2*

This work shows the results of an experimental and analytical research program on seismic response of uplifting building frames. In the experimental tests a one-third scale model of a nine story steel moment frame prototype with special detail of the footing to allow column uplift on the shaking table was used. In the nonlinear analytical procedure it was employed bilinear elastic foundation elements with zero tensile capacity in the upward direction to accurate behaviour during uplift motion of the frame. The results of the two analyses are confronted for two cases: fixed and uplift foundation. In the end a discussion of the results obtained are presented with some conclusions.

KEY WORDS: steel structures; seismic design; frames; uplift; foundations.

JAIN, A. and GOEL, S. (1980) SEISMIC RESPONSE OF ECCENTRICALLY BRACED FRAMES. ASCE Journal of the Structural Division, ST4, page 843-859. *3*

The purpose of this paper is to define the situation in which a bracing member can be treated as rigid-connected nonbuckling type, rigid-connected buckling type, or pin-connected buckling type so that an appropriate hysteresis model can be used in the seismic analysis of eccentrically braced frames. The seismic response of three eccentrically braced frames with different member proportions are also compared so as to study the merits of different design philosophies used to proportion the frame members.

KEY WORDS: steel structures; seismic design; frames; buckling; eccentric braces.

71

POPOV, E. (1980) SEISMIC BEHAVIOR OF STRUCTURAL SUBASSEMBLAGES, the Structural Division, ST7, page 1451-1470. *4*

ASCE Journal of

In this paper some types of hysteretic loops which can be observed in inelastic experiments with structural members and systems under cyclic loads are presents. Attention is directed to structural steel and reinforced concrete members and subassemblages. The distinction among the" various ductility factors are emphasized. The relationship between the response spectrum approach and conventional code design procedure is also examined. This paper may serve as an aid for evaluating the numerous hysteretic loops which are becoming available in the literature.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; ductility; subassemblages.

POPOV, E. (1980) AN UPDATE ON ECCENTRIC SEISMIC BRACING. AISC Engineering Journal, n.3, page 70-71. *5*

This general paper presents some considerations on the seismic design of diagonal braced frame systems with eccentric connections, with special attention on the design of the shear link, i.e., the beam element between the face of the column and the brace. The paper ends with some remarks on the buckling of the web and the flanges in the shear link as well as the future investigation to do in this type of eccentric braces.

KEY WORDS: steel structures; seismic design; connections; buckling; eccentric braces.

POPOV, E. and ROEDER, C. (1978) DESIGN OF ECCENTRICALLY BRACED STEEL FRAME. AISC Engineering Journal, n.3, page 77-81. *6*

In this paper it is summarized the design requirements for diagonal braced frame systems with eccentric connections. According to the authors, for these type of frames, a'good design is achieved if plastic hinges form at both ends of the eccentric beam element shortly after shear yielding. Therefore, the eccentricity and plastic moment capacity must be carefully balanced to assure the proper yield mechanism. Based in these considerations a design example is solved.

KEY WORDS: steel structures; seismic design; connections; ductility; eccentric braces.

Some authors (1979) Discussion on "ECCENTRICALLY BRACED STEEL FRAMES FOR EARTHQUAKES" by W. Roeder and E. Popov, ASCE Journal of the Structural Division: ST2, page 462-463; ST3, page 687-689; STll, page 2471-2472. *7*

In these discussions, some points have been analized, namely: the comparison between the dynamic responses of the concentrically and eccentrically braced structures; the relative savings in weight of steel for braced structures, and the extent of damage and cost of repair of the alternate bracing systems. In the STll the authors reply to the questions and the discussion is closed.

KEY WORDS: steel structures; seismic design; connections; ductility; eccentric braces.

72

LIBBY, J. (1981) ECCENTRICALLY BRACED FRAMES CONSTRUCTION - A CASE HISTORY. Engineering Journal, n.4, page 149-153. *8*

AISC

The principal purpose of this paper is to describe why eccentrically braced frames were selected for the San Diego Bank of America building. Some topics are analized, namely: 1) General requirements of the client; 2) Detail of the tower structure; 3) Rationale for using eccentrically braced frames; 4) Structural details of the lateral load resisting system; 5) Summary of quantities and cost. The paper ends with some concluding remarks on the eccentrically braced frames.

KEY WORDS: steel structures; seismic design; connections; ductility; eccentric braces.

OSTRIKOV, G. and MAKSIMOV, Y. (1982) NEW CONSTRUCTIVE FORMS OF STEEL EARTHQUAKE RESISTANT FRAMES. Proc. of the VII European Conf. on Earthquake Engineering, Athens, page 341-346. *9*

This general paper presents a design solution and experimental studies data for energy absorbing capacity and durability of main beams with corrugated webs as well as of ring-type, tube-type and beam-type energy absorbers used in braced frames structures. Dynamic tests for a thirty storeyed spatial framed structure model with ring type energy absorbed are refered and economic efficiency of application of suggested solutions in earthquake resistent engineering are discussed.

KEY WORDS: braces.

steel structures; seismic design; connections; ductility;

POPOV, E. and MALLEY, J. (1983) ECCENTRICALLY BRACED FRAMES. ASCE Manual on Beam-to-Column Building Connections. January, Draft of the Chapter 11 of the upcoming ASCE Manual on Beam-to-Column Building Connections under preparation. (To be published), 59 pages. *10*

This report is divided in five parts. In the first, "Introduction", general remarks on the analysis and characteristics of eccentrically braced frames as well as the classification of active links are presented. The second, "Experimental results on link behavior", is concerned with the experimental setup for studying links and the principal test conclusions. The third, "Design and detailing of active link connections", provides guidance for connection design and details in eccentrically braced frames. In the fourth, "Non-seismic application of eccentric bracing", are refered other possibles application for eccentric braces. The report ends with the projected research on eccentrically breed frames.

KEY WORDS: steel structures; eccentric braces.

seismic design; connections; frames;

POPOV, E. (1982) SEISMIC STEEL FRAMING SYSTEMS FOR TALL BUILDINGS. AISC Engineering Journal, n.3, page 141-149. *11*

This state of the art reviews the advantages and disadvantages of three framing systems: 1) Moment resisting frames; 2) Concentrically braced frames and, 3) Eccentrically braced frames. The choice of a particular framing system and its functional requirements are discussed. According to the author, in some applications eccentric bracing may be the most economical, being given for this system some design guidelines.

KEY WORDS: steel structures; seismic design; multy-storey buildings; frames; braces.

73

HJELMSTAD, K. and POPOV, E. (1983) SEISMIC BEHAVIOR OF ACTIVE BEAM LINKS IN ECCENTRICALLY BRACED FRAMES. Report No. UCB/EERC - 83/15, Earthquake Engineering Research Center, University of California, 169 pages. *12*

This report has two parts. In the first part, the results of an experimental study of the behaviour of active links are presented. The study includes fifteen tests on full sized active links, which are performed to determine the general response characteristics of this type of element, especially as regards the buckling and post-buckling behaviour. The second part of the report concerns the elasto-plastic analysis of eccentrically braced frames, with emphasis on accurately modeling the active link elements. For this purpose two analytical models are developed. An appendix dealing with the effects of warping restraint in thin walled beams is presented.

KEY WORDS: steel structures; seismic design; connections; hysteretic behaviour; eccentric braces.

HJELMSTAD, K. and POPOV, E. (1984) CHARACTERISTICS OF ECCENTRICALLY BRACED FRAMES. ASCE Journal of the Structural Engineering, vol. 110, n.2, February, page 340-353. *13*

In this paper, some of the fundamental characteristics of the elastic and inelastic behaviour of eccentrically braced frames are examined by studying some simple examples. The behaviour of the segment of the beam (active link) in which is dissipated large amounts of input energy of a severe seismic event is briefly analysed, followed by some remarks on detailing this connection. The results provide a qualitative assessment of the behaviour of the eccentrically braced frames for use in seismically active regions.

KEY WORDS: steel structures; seismic design; connections; frames; eccentric braces.

MALLEY, J. and POPOV, E. (1984) SHEAR LINKS IN ECCENTRICALLY BRACED FRAMES. ASCE Journal of the Structural Engineering, vol. 110, n.9, September, page 2275-2295. *14*

The results of an experimental investigation of the effects of inelastic loading history, connection details, and web stiffener details on active link behaviour are presented. The test results are evaluated using energy dissipation as the basic parameter. A design procedure for active links which yield primarily in shear is outlined. This procedure includes recommendations on structural configuration, member sizes, link connection details, and web stiffener details. Suggested connection and stiffener details are illustrated.

KEY WORDS: steel structures; seismic design; connections; shear; eccentic braces.

74

2.12 - INTERACTION BETWEEN FRAMES AND BRACINGS

CLOUGH, E. and GHANAAT, Y. (1979) SEISMIC BEHAVIOR OF DIAGONAL STEEL WIND BRACING. Proc. of the 2nd U. S. Nat. Conf. on Earthquake Engineering, EERI, Standford University, page 313-322. *1* The purpose of this paper is to give experimental data on the seismic performance of a building frame with diagonal wind bracing, and to correlate these results with computer analyses. The test structure is a three-story steel building frame, and the motions are applied by a shaking table. Two test series with different bracings (rod bracing and welded pipe X bracing) are performed. The experimental results are compared with an analytical model giving a satisfactory correlation. KEY WORDS: steel structures; seismic design; braces; frames; ductility.

MAZZOLANI, F. and FAELLA, C. (1977) ANALYSIS OF HIGH STRENGTH STEEL BARS UNDER REPEATED AXIAL LOADING. Università" degli Studi di Napoli, Quaderni di Teoria e Tecnica delle Strutture n.430, 6 pages. *2* In this general paper, the analysis of pre-and post-buckling behaviour of high strength steel bars under reapeated axial loading process is investigated by means of an incremental simulation method. The material is interpreted through an elastic strain hardening bilinear relationship which considers the Bauschinger effect. Some numerical results are shown, allowing to derive informations about the influence of various parameters on the load carrying capacity. KEY WORDS: steel structures; seismic design; braces; stability; buckling.

MAZZOLANI, F. and FAELLA, C. (1974) INFLUENZA DELL'EFFETTO BAUSCHINGER SUL COMPORTAMENTO DI ASTE METALLICHE SOTTO CICLI DI ELONGAZIONI. Estratto dalla rivista "La Ricerca", Maggio-Agosto, page 59-79. *3* In this paper, the analysis of pre-and post-buckling behaviour of steel bars with Bauschinger effect under reapeated axial deformation is investigated by means of an incremental simulation method. The Bauschinger effect is interpreted through the three classical models: ideal, semideal and isotropical hardening. Some numerical results are shown, allowing to derive informations about the influence of various parameters particulary the increase of the lowering of the load carrying capacity in post-buckling range, strictly depending upon the assumed Bauschinger effect model. i

KEY WORDS: steel structures; seismic design; braces; stability; buckling.

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IGARASHI, S., INOUE, K., ASANO, M. and OGAWA, K. (1973) RESTORING FORCE CHARACTERISTICS OF STEEL DIAGONAL BRACINGS. V World Conf. on Earthquake Engineering, Rome, page 2162-2171. *4*

This work studies the load-deformation relationship and the dynamic response characteristics of the steel X-bracing structures under earthquake ground motions. An axial load-deformation relationship of the bracing member is suggested and employed to calculate the dynamic response of a X-braced structure with one degree-of-freedom. The influence of the slenderness ratios on the dynamic response of X-braced structures is also analysed.

KEY WORDS: steel structures; seismic design; braces; stability; hysteretic behaviour.

MAISON, B. and POPOV, E. (1980) CYCLIC RESPONSE PREDICTION FOR BRACED STEEL FRAMES. ASCE Journal of the Structural Division, ST7, page 1401-1416. *5*

In this paper, some experimental results on the behaviour of half-scale K braced building frames subjected to severe cyclic loading are reviewed. This is followed by a presentation of the experimentally determined hysteretic behaviour for the individual braces used in the test frames. An improved procedure for a computer simulation of brace behaviour is then described. Using this formulation, the overall inelastic cyclic response of one of the test frames is compared with the predicted results. The agreement between the experimental and analytical results are good.

KEY WORDS: steel structures; seismic design; braces; frames; hysteretic behaviour.

POPOV, E. (1979) INELASTIC BEHAVIOR OF STEEL BRACES UNDER CYCLIC LOADING. Proc. of the 2nd U. S. Nat. Conf. on Earthquake Engineering, EERI, Standford University, page 923-932. *6*

The paper presents and discusses the results of some experiments on cyclically loaded members into the inelastic range. The speciments are selected from standard structural steel shapes. Some speciments have pinned ends and others are fixed at one end and pinned at the other. The experiments are performed by slowly applying cyclic axial displacements. Some experimental results are shown, allowing to derive informations about the parameters that reduce the initial buckling capacity of the strut.

KEY WORDS: steel structures; hysteretic behaviour.

seismic design; braces; stability;

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SHIBATA, M., NAKAMURA, T., YOSHIDA, N., MORINO, S., NONAKA, T. and WAKABAYASHI, M. (1973) ELASTO-PLASTIC BEHAVIOR OF STEEL BRACES UNDER REPEATED AXIAL LOADING. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 845-848. *7*

This state of the art presents and discusses seme results of experimental and theoretical studies on the elasto-plastic behaviour of steel braces under repeated loading. The hysteretic behaviour of braces is briefly commented to a better understand of its contribution to the strength and rigidity of steel framed structures during the earthquakes.

KEY WORDS: steel structures; seismic design; braces; stability; hysteretic behaviour.

WAKABAYASHY, M., NAKAMURA, T. and YOSHIDA, N. (1977) EXPERIMENTAL STUDIES ON THE ELASTIC-PLASTIC BEHAVIOR OF BRACED FRAMES UNDER REPEATED HORIZONTAL LOADING. Bulletin of the Disaster Prevention Research Institute, Kyoto University, vol.27, Part 3, n. 251, September, page 121-154. *8*

An experimental study is conducted to obtain the hysteretic characteristics of the brace itself in a braced frame under repeated loading. Braces with an H-shaped cross section are tested in a single or a double bracing system. The effects of the slenderness ratio, the buckling plane and the local buckling are investigated. The fundamental properties of a brace for the formulation of the hysteretic characteristics under repeated loading are extracted.

KEY WORDS: steel structures; seismic design; braces; stability; hysteretic behaviour.

WAKABAYASHY, M., NAKAMURA, T., SHIBATA, M., YOSHIDA, N. and MASUDA, H. (1977) HYSTERETIC BEHAVIOR OF STEEL BRACES SUBJECTED TO HORIZONTAL LOAD DUE TO EARTHQUAKES. Proc. of the VI World Conf. on Earthquake Engineering, New Delhi, India, vol.3, page 3188-3194. *9*

This general paper discusses the elasto-plastic hysteretic behaviour of steel braces. In the first part, the experimental and theoretical investigations by the authors, on the braces are briefly introduced. In the second part, idealized post-buckling curve and hysteresis loops of the brace members are formulated and proposed for the design use, based on the parametric analysis of the experimental and theoretical results.

KEY WORDS: steel structures; seismic design; braces; stability; hysteretic behaviour.

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WAKABAYASHY, M., NAKAMURA, T. and YOSHIDA, N. (1980) EXPERIMENTAL STUDIES ON THE ELASTIC-PLASTIC BEHAVIOR OF BRACED FRAMES UNDER REPEATED HORIZONTAL LOADING. Bulletin of the Disaster Prevention Research Institute, Kyoto University, vol.29, Part 4, n. 266, March, page 143-164. *10*

Experimental studies are conducted to investigate the hysteretic behaviour of one story-one bay braced steel frames whose braces are made of built-up H-shapes and whose columns and beams are made of rolled H-shapes. Hysteretic behaviour and change of load carrying capacity of each component member of a frame, i.e., braces, columns and beams under repeated horizontal load are examined individually, as well as the hysteretic behaviour of a braced frame as a whole. Interaction behaviour between the braces built in a frame and the components of the surrounding frame is also discussed.

KEY WORDS: steel structures; seismic design; braces; stability; hysteretic behaviour.

TAKANASHI, K. and OHI, K. (1984) SHAKING TABLE TESTS ON 3-STORY BRACED AND UNBRACED STEEL FRAMES. Proc. of the VIII World Conf. on Earthquake Engineering, San Francisco, 8 pages. *11*

A series of shaking table tests are performed on three-story moment resistant steel frames and braced steel frames. Two sets of moment resistant frames, each one is designed to have a different story shear strength, are subjected to earthquake acceleration records to examine the response shear forces and the damage concentration. Braced frames with X-type braces are also subjected to the acceleration records. The results of response displacements and story shear forces are used to verify the analytical procedure where the inelastic behaviour of the structural elements are presumed.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; frames.

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2.13 - STRUCTURAL SYSTEMS

ANDERSON, J. (1975) SEISMIC BEHAVIOUR OF K-BRACED FRAMING SYSTEMS. ASCE Journal of the Structural Division, STlO, page 2147-2159. *1*

The purpose of this work is to evaluate the inelastic seismic response of three K-brace framing systems to strong earthquake motions. The framing systems considered in this work, are ten stories high with three equal bays. In all cases, the primary K-bracing is located in the center bay with the bracing members oriented so as to form a vee. The seismic response of those frames is determined by a numerical analysis which is briefly described. The comparison of the seismic response of the three systems is evaluated in terms of the following parameters: 1) Absolute maximum lateral displacement; 2) Maximum relative displacement; 3) Ductility requirement; 4) Hysteretic behaviour; 5) Time history.

KEY WORDS: steel structures; seismic design; braces; hysteretic behaviour; ductility.

BEA, R. (1979) EARTHQUAKE AND WAVE DESIGN CRITERIA FOR OFFSHORE PLATFORMS. ASCE Journal of the Structural Division, ST2, page 401-419. *2*

In this work, a process for development of earthquake design criteria for offshore platforms is presented. The process considers: 1) Projected environmental conditions; 2) Platform system characteristics; 3) Environmental loadings and forces on the platform systems; 4) Uncertainties in projected environmental conditions, forces, and platform response; 5) Platform system performance, particulary inelastic behaviuor during extreme overload conditions; 6) Reliability quantified as the ability of the platform system to perform satisfactorily in the full range of projected environmental conditions; 7) Decisions on what constitutes acceptable performance and reliability.

KEY WORDS: steel structures; seismic design; offshore structures; calculation methods; planning.

BEA, R., AUDIBERT, J. and AKKY, M. (1979) EARTHQUAKE RESPONSE OF OFFSHORE PLATFORMS. ASCE Journal of the Structural Division, ST2, page 377-400. *3*

The purpose of this article is to give a better understanding of the key aspects and factors that may determine the response and performance of one class of offshore platforms, i.e., steel, tubular membered, truss-framed structures supported by tubular piles and conductors, during intense ground motions. In appendix, a long reference list is given in order to built a more complete understanding of the behaviour of these stuctures.

KEY WORDS: steel structures; seismic design; offshore structures; calculation methods; structural systems.

79

BERTERO, V., BRESLER, B., SELNA, L., CHOPRA, A. and KORETSKY, A. (1973) DESIGN IMPLICATIONS OF DAMAGES OBSERVED IN THE OLIVE VIEW MEDICAL CENTER BUILDINGS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 51-65. *4*

This article examines the possible causes and design implications of the observed damages in the Olive View Medical Center produced by the San Fernando erathquake. The buildings under study are of reinforced concrete. Special attention is given on the aspects involved in the seismic design, ground motion, material characteristics and structural features of individual buildings. Some recommendations with a view to minimize earthquake damage are presented.

KEY WORDS: steel structures; seismic design; damages; ductility; detailing.

BLUME, J. (1972) ANALYSIS OF DYNAMIC EARTHQUAKE RESPONSE. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 191-211. *5*

This state of the art, is concerned with the dynamic response of tall buildings under earthquake ground motions. It is divided in twelve parts: 1) Introduction; 2) Types of tall buildings; 3) Behaviour of tall buildings; 4) Idealized linear systems; 5) Idealized inelastic systems; 6) Analysis; 7) The reserve energy technique; 8) Vertical motions; 9) Probabilistic analysis; 10) Equipment and appendages; 11) Long periods of vibrations; 12) Need for future research and development.

KEY WORDS: steel structures; seismic design; structural systems; multy-storey buildings; planning.

CARPENTER, L. and LU, LE-WU (1973) REVERSED AND REPEATED LOAD TESTS OF FULL SCALE STEEL FRAMES. AISI Bulletin n.24, April, 38 pages. *6*

In this bulletin is described the tests done in full sized single bay steel frames subjected to constant gravity loads on the beams and columns and cycles of reversed and repeated displacements. Some particular problems are investigated, namely: the effect of the local buckling of the beam in the single story frame; the behaviour of the columns in the inelastic range and of the beam to beam-column connections; the effect of the localization of the plastic hinges in the behaviour of a two story frame. The bulletin describes the design of the steel frames, the technique developed to test those frames, the experimental behaviour of the frames and the observations drawn out from the experimental results.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; connections ; frames.

80-

CLOUGH, R. , REA, D., TANG, D. and WATABE, M. (1973) EARTHQUAKE SIMULATOR TEST OF A THREE STORY STEEL FRAME STRUCTURE. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 308-311. *7*

This paper shows the results of experimental tests conducted on a three story steel frame structure using a square shaking table. In this structure, the panel zones are left understrength so that yielding would occur first in the panel zone. The intensity of the table motions are increased progressively until a peak acceleration of 0.5 g to cause yielding in the panel zones. The results described could be used in analytical studies to determine the accurancy of the computer programs for predicting the behaviour of steel frames under large vibrations enough to cause inelastic behaviour.

KEY WORDS: steel structures; seismic design; ductility; buildings; frames. low-rise

CHENG, F. and OSTER, K. (1976) ULTIMATE INSTABILITY OF EARTHQUAKE STRUCTURES. ASCE Journal of the Structural Division, ST5, page 961-972. *8*

An analytical technique for dynamic instability analysis of structural systems subjected to time dependent axial force, lateral force or ground motions is suggested. The general formulation is presented and applied in two numerical examples. Special attention is paid to the effects of 2nd order, outlined that the vertical force may not always be critical to dynamic response and can actually cause certain structures to have smaller deflections than that of the associated systems without consideration of these effects.

KEY WORDS: steel structures; hysteretic behaviour; stability.

seismic design; structural systems;

CLOUGH, R., NIWA, A. and CLOUGH, D. (1979) EXPERIMENTAL SEISMIC STUDY OF CYLINDRICAL TANKS. ASCE Journal of the Structural Division, STI2, page 2565-2590. *9*

In this work, it is summarized the most significant results of an experimental investigation on the earthquake response behaviour of flexible cylindrical liquid-storage tanks. described, followed by a short summary of testing the 3.70m x 1.80m tank. The results 4.60m tank are considered more thoroughly, findings of a static-test program carried Finally, comparisons are made between the experimental observations quantities predicted by standard design procedures, and conclusions drawn concerning the adequacy of these design methods.

The test procedures are the observations made in obtained with the 2.40m x including the principal out with this speciment.

and are

KEY WORDS: steel structures; seismic design; stability; structural systems; vessels.

-81

EDISHERASHVTLI, N. and SHAISHMELASHVILI, V. (1973) EXPERIMENTAL STUDIES OF DYNAMIC CHARACTERISTICS OF MULTY-STOREY STEEL FRAME BUILDING LARGE-SCALE MODELS WITH DIFFERENT VERTICAL BRACINGS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 299-303. *10*

Herein are presented results of experimental studies of large scale models (1/6 of natural size) of steel carcass buildings with frame and frame bracing systems. The carcass models are tested for: free, forced (resonance) vibrations and static very intensive horizontal loads permitting to cause destruction of model constructions. Special attention is paid to variation of vibration frequencies and to the damping decrement of models when plastic deformations are developed in them.

KEY WORDS: steel structures; seismic design; braces; frames; multy-storey buildings.

FARDIS, M., CORNELL, C. and MEYER, J. (1979) ACCIDENT AND SEISMIC CONTAINMENT RELIABILITY. ASCE Journal of the Structural Division, STI, page 67-83. *11*

An integrated reliability study of a containment vessel of a nuclear power plant is presented. The study focuses'on events and features of the behaviour that may prohibit the fulfillment of the containment safety role. It is shown how the probabilistically described safety-significant damage that is caused by accidents or earthquakes can be coupled with a probablistic description of these events to yield reliability estimates for the entire plant lifetime. The superposition of the effects of those events when they act simultaneously or separately is also analysed.

KEY WORDS: steel structures; seismic design; structural safety; damages; vessels.

GOEL, S. and HANSON, R. (1973) SEISMIC BEHAVIOR OF MULTISTORY BRACED STEEL FRAMES. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 2934-2943. *12*

This paper presents and discusses the results of a numerical study on the influence of the method of design and different arrangements of the bracing members (fully braced, bottom story open, alternate stories open and completely unbraced) in the seismic response of multistory steel frames. The dynamic response is computed by assuming an elasto-plastic type hysteresis behaviour in tension only for the diagonal bracing members, in bending for the girders, and the 2nd order effects for the columns. In the end, some curves for different response parameters are shown.

KEY WORDS: steel structures; seismic design; calculation methods; braces; ductility.

-82

HUCKELBRIDGE, A. and CLOUGH, R. (1978) SEISMIC RESPONSE OF UPLIFTING BUILDING FRAME. ASCE Journal of the Structural Division, ST8, page 1211-1229 *13*

This work shows the results of an experimental and analytical research program on seismic response of uplifting building frames. In the experimental tests a one-third scale model of a nine story steel moment frame prototype with special detail of the footing to allow column uplift on the shaking table was used. In the nonlinear analytical procedure it was employed bilinear elastic foundation elements with zero tensile capacity in the upward direction to accurate behaviour during uplift motion of the frame. The results of the two analyses are compared for two cases: fixed and uplift foundation. In the end, a discussion of the results obtained are presented with some conclusions.

KEY WORDS: steel structures; seismic design; frames; uplift; foundations.

JAIN, A. and GOEL, S. (1980) SEISMIC RESPONSE OF ECCENTRICALLY BRACED FRAMES. ASCE Journal of the Structural Division, ST4, page 843-859. *14*

The purpose of this paper is to define the situation in which a bracing member can be treated as rigid-connected nonbuckling type, rigid-connected buckling type, or pin-connected buckling type so that an appropriate hysteresis model can be used in the seismic analysis of eccentrically braced frames. The seismic response of three eccentrically braced frames with different member proportions are also compared so as to study the merits of different design philosophies used to proportion the frame members.

KEY WORDS: steel structures; seismic design; frames; buckling; eccentric braces.

KATO, B., AKIYAMA, H., SUZUKI, H. and FUKAZAWA, Y. (1973) DYNAMIC COLLAPSE TESTS OF STEEL STRUCTURAL MODELS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 1457-1460. *15*

This general article presents the results of a experimental study on the dynamic behaviour and strength of beam-columns with H-shaped cross section. The beam-columns are fixed at both ends and are tested on a shaking table which can generate simulated earthquake motions. The results of the experimental tests are compared with those of the numerical analysis which take into account the strain-hardening of the steel and the 2nd order effects.

KEY WORDS: steel structures; seismic design; columns; stability; hysteretic behaviour.

KHAN, A., LEE, P., MEHTA, D. and WANG, G. (1978) ANALYSIS AND DESIGN OF SEISMIC CATAGORY I THIN SHEET STRUCTURES. ENGINEERING DESIGN FOR EARTHQUAKE ENVIRONMENTS, I Mech E CONFERENCE PUBLICATIONS 1978-12, London, page 111-118. *16*

The design criteria for seismic Category I thin sheet structures and restraints in nuclear power plants is presented in this paper. Structural design considerations, loads, load combinations, design allowables and analytical methods for design and analysis of such structures and its restraints are also presented. The analytical methods presented include procedures for analysis of this thin structures due to internal negative pressure, seismic and gravity loads.

KEY WORDS: steel structures; seismic design; structural safety; vessels; design criteria.

-83-

KONNO, T. and KIMURA, E. (1973) EARTHQUAKE EFFECTS ON STEEL TOWER STRUCTURES ATOP BUILDINGS. Proc. of the V World Conf. on Earthquake Engineering, Rone, page 184-194. *17* This article presents the results of the full scale measurements and earthquake response analysis carried out on some steel towers for microwave antennes in Japan, as well as the results of vibration tests performed by using steel tower and building models. It is outlined that the steel tower atop building may be affected by the vibrational characteristics of the building and consequently generate high seismic forces at the time of a strong earthquake since the damping of tower is very small. Finally, some remarks on the seismic forces acting on the steel towers are presented.

KEY WORDS: steel structures; seismic design; towers; vibration; multy-storey buildings.

KOSTEM, C. and HECKMAN, D. (1979) EARTHQUAKE RESPONSE OF THREE DIMENSIONAL STEEL FRAMES STIFFENED BY OPEN TUBULAR CONCRETE SHEAR WALLS. Proc. of the 2nd U. S. Nat. Conf. on Earthquake Engineering, EERI, Standford University, page 969-977. *18*

This work shows the results of a numerical study on the dynamic behaviour of frame-shear wall systems. An open tubular concrete shear wall (U-shaped) extending through the height of the building is considered. Special attention is paid to the effect of the changes in the dimentions (length and thickness) of the open tubular concrete shear wall in the fundamental frequencies of this structural system.

KEY WORDS: steel structures; seismic design; multy-storey buildings; shear; frequency.

LORD, J. (1972) INELASTIC DYNAMIC BEHAVIOR OF TALL BUILDINGS. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 291-297. *19*

In this general article, it is 'presented seme energy and drift considerations involved in determining the inelastic dynamic behaviour of tall buildings. The energy considerations are related with the stability of the structure and the distribution of energy dissipation during an earthquake event, while drift considerations are refered to the drift control and the inelastic drift predictions.

KEY WORDS: steel structures; seismic design; multy-storey buildings; stability; drift.

MURAKAMI, M., TAMURA, R., TANAKA, Y., GAMI, K., OSAWA, Y. and UMEMURA, H. (1973) EARTHQUAKE RESISTANCE OF A STEEL FRAME APARTMENT HOUSE WITH PRECAST CONCRETE PANEL. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 2688-2697. *20*

The dynamic behaviour of a steel frame apartment house with precast concrete wall panels and its surrounding soil during actual earthquakes is investigated in this work. Sixteen sets of the electro-magnetic seismometers are installed to measure the earthquake acceleration records under, around and inside the building. With those records it is possible to establish an appropriate dynamic model for the soil-building system to study the dynamic behaviour of this kind of building under severe earthquake exitations. Seme results and concluding remarks are presented in the end.

KEY WORDS: steel structures; seismic design; multy-storey buildings; vibration; frames.

-84

OKADA, H., TAKEDA, T., YOSHIOKA, K., OMOTE, Y. and NAKAGAWA, K. (1973) EXPERIMENTAL AND RESEARCH ON THE RESPONSE OF STEEL MODEL STRUCTURES SUBJECTED TO IMPACT HORIZONTAL LOADING AND TO SIMULATED EARTHQUAKES. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 2721-2730. *21*

The behaviour of steel frames under impulsive loading and earthquake motions are reported in this article. It is divided in two parts: in the first part, experimental results of one-bay one-storied steel portal frames (four speciments) under impact loading at their base with the use of a shock table are reported and compared with the elasto-plastic analysis. In the second part, experimental results of a two-bay three-storied portal frame under simulated earthquake motion using a vibration table are presented together with the theoretical analysis.

KEY WORDS: steel structures; seismic design; impact; vibration; frames.

OSAWA, Y. (1972) OBSERVATION OF STRUCTURAL BEHAVIOR. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. lb, page 213-227. *22*

This state of the art summarizes briefly the available methods to observe or to check the (1) rigidity, strength and hysteresis characteristics of structures and structural components against lateral forces and (2) the natural periods and damping characteristics of buildings. The items are: 1) Static laboratory studies; 2) Dynamic laboratory studies; 3) Static field studies; 4) Dynamic field studies.

KEY WORDS: steel structures; seismic design; calculation methods; structural systems; earthquakes.

POPOV, E. (1980) SEISMIC BEHAVIOR OF STRUCTURAL SUBASSEMBLAGES, the Structural Division, ST7, page 1451-1470. *23*

ASCE Journal of

In this paper, some types of hysteretic loops which can be observed in inelastic experiments with structural members and systems under cyclic loads are presented. Attention is directed to structural steel and reinforced concrete members and subassemblages. The distinction among the various ductility factors are emphasized. The relationship between the response spectrum approach and conventional code design procedure is also examined. This paper may serve as an aid for evaluating the numerous hysteretic loops which are becoming available in the literature.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; ductility; subassemblages.

TANG,D. and CLOUGH, R. (1979) SHAKING TABLE EARTHQUAKE RESPONSE OF STEEL FRAME. ASCE Journal of the Structural Division, STI, page 221-243. *24*

This paper presents the results of an experimental and analytical investigation on the seismic behaviour of a large scale steel structure. The test structure consists of two identical 5.30m high three story frames having a bay width of 3.70m and to excite the structure a shaking table motion is used. After a brief account of the planning of the test structure and test program the most significant results are examined. The description of suitable analytical models for computing the seismic behaviour of the structure, the effects of various model parameters and the experimental results are presented in the last part.

KEY WORDS: steel structures; connections.

seismic design; ductility; frames;

85

TANSIRIKONGKOL, V. and PECKNOLD, D. (1979) EQUIVALENT LINEAR SDF RESPONSE TO EARTHQUAKES. ASCE Journal of the Structural Division, STI2, page 2529-2545. *25*

This paper presents seme remarks on the available numerical information on the accuracy of the equivalent linear approach for earthquake response of histeretic single degree-of-freedom (SDF) systems. The qualitative behaviour of bilinear SDF systems is presented together with the equivalent linear system. Expressions for linear stiffness and damping in terms of maximum earthquake response are developed. Some numerical results, in order to investigate the influence of some parameters (earthquake imput, system yield level, elastic natural frequency, bilinear hardening and viscous damping) on the accurancy of response prediction, are presented and discussed in the end.

KEY WORDS: steel structures; seismic design; earthquakes; calculation methods; structural systems.

UCHIDA, N., AOYAGI, T., KAWAMURA, M. and NAKAGAWA, K. (1973) VIBRATION TEST OF STEEL FRAME HAVING PRECAST CONCRETE PANELS. Proc. of the V World Conf. on Earthquake Engineering, Rome, page 1167-1176. *26*

In this work are reported the tests conducted in a two-storey, two-bay steel frame model having full-size precast concrete panels in order to obtaining some basic data on the effects of precast concrete panels on the vibration characteristics of the highrise building, and the behaviour of the panel fastening system. The tests conducted are: 1) Forced vibration test; 2) Free vibration test; 3) Dynamic load test. Special attention is paid to the modes of deflection of precast 'concrete panels and slabs.

KEY WORDS: steel structures; seismic design; panels; vibration; frames.

WERNER, S., LEE, L., WONG, H. and TRIFUNAC-, M. (1979) STRUCTURAL RESPONSE TO TRAVELING SEISMIC WAVES. ASCE Journal of the Structural Division, STI2, page 2547-2563. *27*

The influence of the traveling seismic waves in the earthquake response of structures is analysed in this paper. It consists of two main part: The first part briefly summarizes a new methodology for analyzing the three-dimensional dynamic response of soil-structure systems subjected to traveling seismic waves. The second, and principal part of the paper, describes an example application of the methodology to a single-span bridge subjected to incident plane SH-waves. The purpose of this application is to demonstrate basic phenomena associated with the three-dimensional vibrations induced in bridge-type structures by traveling seismic waves.

KEY WORDS: steel structures; seismic design; earthquakes; vibration; structural systems.

86-

WAKABAYASHI, M. (1973) STUDIES ON DAMPING AND ENERGY ABSORPTION OF STRUCTURES. IABSE, Symposium on Resistance and Ultimate Deformability of Structures Acted on by Well Defined Repeated Loads, Lisboa, page 27-46. *28*

The significance of damping and energy absorption of structures and structural elements under earthquake exitation is first described, as veil as the details of these phenomena in relation to the equivalent viscous damping coefficient. Some mathematical models representing the hysteretic behaviour of materials, members, connections and frames are shown. Finally, seme important problems are indicated for the symposium discussions.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; damping; connections.

WAKABAYASHI, M. (1977) BEHAVIOR OF SYSTEMS. Proc. of the VI World Conf. on Earthquake Engineering, New Delhi, India, January, vol.1, page 65-75. *29*

This paper discusses the general performances of some structural systems under earthquake events. The systems discussed are: 1) Reinforced and prestressed concrete systems; 2) Steel systems; 3) Mixed steel and concrete systems; 4) Masonry systems. The general performances of these systems are refered to its hysteretic behaviour, energy dissipation capacity and ductility. Some design problems with referring to the research work done in the past are also presented.

KEY WORDS: steel structures; seismic design; hysteretic behaviour; structural systems; ductility.

YAMADA, M. (1972) EFFECT OF CYCLIC LOADING ON BUILDINGS. Proc. of the Int. Conf. on Planning and Design of Tall Buildings, ASCE-IABSE, Lehigh University, Bethlehem, Pennsylvania, vol. II, page 725-739. *30*

In this article are presented seme recomendations that provide fatigue and fracture criteria for cyclic loading. These recommendations are refered to: 1) Loading related to fatigue and fracture of tall steel buildings; 2) Low cycle fatigue characteristics of structural steels; 3) Low cycle fatigue fracture limits of structural members as the evaluation basis or design criteria for aseismic capacity.

KEY WORDS: steel structures; seismic design; fatigue; fracture; design criteria.

87 -

MAZZOLAMI, F. and RAMASCO, R. (1971) STATICA DEI SISTEMI INTELAIATI SPAZIALI CON IRRIGIDIMENTI DI FORMA QUALSIASI. Estratto dal Giornale del Genio Civile, fase. 3, Marzo, page 196-217. *32*

The analysis of space structures for tall buildings under later forces is emphasized in this paper. A general calculation method based on matrix algebra for space structures with frames and walls variously shaped under lateral forces is presented. This procedure is developed through two stages: the first studies the behaviour of each single plane structure; the second one calculates the whole space structure. The torsional behaviour of walls with thin open cross-section is also examined taking into account the warping effect. Finally, seme numerical applications of this procedure are shown.

KEY WORDS: steel structures; seismic design; torsion; frames; multy-storey buildings.

MAZZOLÄNI, F. and RAMASCO, R. (1973) BEHAVIOR OF STRUCTURES UNDER LOADS CAUSING TORSION by Jacobus Wynhoven and Peter Adams (July, 1972), (Discussion), ASCE Journal of the Structural Division, ST8, page 1788-1791. *33*

The behaviour of multistory framed structures under loads causing torsion is briefly discussed in this article. It is outlined that the correct analysis of the ultimate load carrying capacity of multistory structures with reinforced concrete channel walls must take warping effect into account especially when the ultimate load produces large torsional rotations of floors.

KEY WORDS: steel structures; seismic design; torsion; warping; multy-storey buildings.

89

C H A P T E R - 3

THE EXPERIMENTAL ASSESSEMENT OF SEISMIC STRENGTH AND DUCTILITY

OF

STRUCTURAL ELEMENTS AND CONNECTIONS

91

TABLE OF CONTENTS

Page

3.1- INTRODUCTION 92

3.2 - THE ECCS RECOMMENDED TESTING PROCEDURE FOR ASSESSING THE BEHAVIOUR OF STRUCTURAL STEEL ELEMENTS UNDER SYCLIC LOADS ... 99

3.2.1 - INTRODUCTION 102 3.2.2 - ASPECTS OF THE TESTING PROCEDURE FOR ASSESSING

THE BEHAVIOUR OF STRUCTURAL STEEL ELEMENTS 103 3.2.3 - COMPLETE TESTING PROCEDURE 103 3.2.4 - SHORT TESTING PROCEDURE Ill 3.2.5 - END OF TEST 112 3.2.6 - COMBINATION OF LOADS 113 3.2.7 - COMMENTARY ON POSSIBLE DEFINITIONS OF Fy 113

3.3 - TESTS FOLLOWING THE ECCS RECOMMENDATIONS 115

3.3.1 - BEHAVIOUR OF BRACINGS 11.7

3.3.2 - BEHAVIOUR OF BEAM-TO-COLUMNS CONNECTIONS 124

3.4 - VALIDITY OF THE ECCS RECOMMENDATIONS 130

3.5 - CONSIDERATIONS ON b/t RATIOS 153

3.6- REFERENCES 159

92

3.1 - INTRODUCTION

Everyone agrees on the necessity to define a unique procedure and

interpretation of tests, |l|, |2|, |3|, but up till now insufficient work has

been done in this field.

The main reason for this, is the amount of difficult questions that arise on

many aspects of the problem: definition of the investigation method to predict

the seismic behaviour of a structure; definition of the loading conditions to

apply on a structural element or even a complete structure, in order to simulate

the earthquake event; definition of the main parameters to characterize the

structural behaviour.

The task in an experimental investigation are first to model as accurately as

possible the physical domain of the problem and then to excite the model in a

meaningful way. For this purpose, various methods of investigation have been or

are used to predict the seismic behaviour of a structure 141. Among them, it is

possible to consider:

a) The use of the shaking tables to simulate earthquakes for to test structures

or moderate-scale model of these structures. This certainly comes closer to

actual reality, but requires a sophisticated equipment which implies high

capital and running costs.

b) The use of a static equipment |5|, |6|, |7| to impress a slowly-varying

alternate loading to the structure or moderate-scale model. The capital

93

involved is lesser than the previous one, but the testing procedure

nevertheless involves high running costs.

c) The application of a quasi-static cyclic loading |8|, |9|, |10|, |ll| to

individual members or structural subassemblages to collect information in the

most critical zones of the structure. This procedure does not necessitate

extremely costly equipment and it is particulary suitable for comparing

different solutions regarding a particular structural member or

subassemblage.

d) The use of suitable numerical models |12|, |13|, |l4|, |15| to define the

structure. It is certainly the most inexpensive, but has the risk of giving

unrealistic results.

e) The interaction between the actual testing of a member or even a part of a

structure and the numerical analysis. This interesting approach known as

"pseudo-dynamic" |16|, |17|, is still under investigation and the small

quantities of results available are insufficient to its appreciation.

Summing everything up, it seems that the use of a testing apparatus able to

inpress cyclic loadings (or displacements) slowly in time to test an isolate

part of the structure provides an attractive way and avoid thecnical and

economical difficulties.

Some types of loading conditions have been or are used in practice. Beside of

the monotonicaily increasing load of the static test, loads can, for instance be

1X81 :

94-

- cyclic with no force reversal;

- cyclic with force reversal, but no deformation reversal;

- cyclic with partial deformations reversals;

- cyclic with full deformation reversals;

- random cyclic;

- shakedown.

As the real loading history in future earthquakes is unknown, the loading

history to be used in tests should not be linked with that "imput" aspect of the

problem, but rather in a way to make the peculiarities of the structural

behaviour best visible. Defining an appropriate link between the structural

response to a test and to a peculiar earthquake is another problem.

Displacement increase should be preferred to load increase, for the following

practical reasons:

The resistance of a structural element may decrease after a few cycles

because of cracking or instability. Load increase is then surely inappropriate,

because the test cannot be controlled and may bring a sudden and complete break

on the tension side while the compression side would still be interesting (or

reverse). This interest canes from the fact that the element is only a part of

the structure and its own fall of resistance in tension (or compression) does

not necessarily means an important fall in resistance for the whole structure.

The way to impose the cyclic displacements to the structure must also be

defined. Displacements can be increased at each cycle or after a set of cycles

with equal maximum displacement. Tests performed on concrete elements subjected

to either three or ten load reversals at each displacement level indicate that

95 -

increasing the number of reversals above three does not alter the response

substantially |l9|. So, as suggested by Higashi |19| the number of cycles at an

equal displacement should not be less then three, but need not, in general, more

then three.

From the above considerations, it is reasonable to expect that the test could

have the following characteristics:

- impose displacements and measure loads;

- three or more complete cycles at each considered displacement level;

- cycles with full or partial reversal.

To interpret the tests, it is advantageous the use of some parameters able to

characterize the structural behaviour of substructures or even complete

structures.

Popov 1201 suggests the use of the "displacement ductility factor" as a

parameter able to provide an index for overall behaviour of a structure, i.e. of

a structure's ability to safety deform inelastically beyond the elastic range.

This displacement ductility factor,u , is the ratio of the ultimate or maximum o

horizontal deflection 6m of a structure at a selected story, to the

deflection 6 at the same point at the yield, i.e. :

h " TT (1>

In this definition of ductility as a parameter to be deduced from tests, the

debate is mainly on the definition of the 5 and 6m

96

Popov 1201 suggests that we can call 6y the beginning of significant

deviation from linearly elastic behaviour of the force-displacement relationship

of the whole system to define 6y . Still another possible approach for

defining the value of 6, , consists of finding the intersection of the

asymptotes to the elastic and plastic ranges.

For the definition of the maximum horizontal deflection 5 , the debate

in on the origin to be considered: the original origin of displacement or the

intersection between the "Ô" axis and the "F - 6" curve in a particular cycle.

(Figure 3.1)

Figure 3.1

97

In this case, we could expect two definitions of ductility factors: one Ô

associated with the total excursion of displacement for one half cycle, and the

other 6" associated with the part of the excursion of displacement included in

the positive part of the "F - 6 " diagram.

These definitions are not fully satisfactory because they partly ignore the

energy content of the earthquake resistance problem. If for instance, we

consider the two diagrams of the Figure 3.2, they give the same ductility

factor, though the energy absorbed in the (a) cycle is roughly a half of the (b)

one.

/

f

f ~7 / V i ,

— ^ "

y i

/ntycle

6

a) b)

Figure 3.2

98

So, it will be advantageous to define another parameter able to take into

account the area involved by one cycle or a group of cycles.

The stability of a structure is directly connected with the strength capacity

of their stiffening elements. An unstable element is characterized by a

hysteretic loop in which for a increasing in the displacement correspond a

decreasing resistance. The stability of a structure must certainly cannot be

assured if all stiffening elements are running altogether on such a decreasing

part of the hysteretic loop. However, when combined with stable elements they

can offer a really available resistance, of which it is interesting to take

account. A definition of a parameter able to characterize the resistance or

rigidity of the structure or substructure will be also important.

From the analysis developed hereabove, we could expect that the main

parameters to characterize the structural behaviour may be able to define the

ductility, energy absortion and strength capacity of the structural element or

even the complete structure.

-99 -

3.2 - THE ECCS RECOMMENDED TESTING PROCEDURE FOR ASSESSING THE BEHAVIOUR OF

STRUCTURAL STEEL ELEMENTS UNDER CYCLIC LOADS

Preliminary remark

In the following definitions, the word load or force is to be taken in a

general meaning. It may be a classical tensile force load. It may be a bending

moment, if bending is the normal work of the structural element. It also may be

shear. Accordingly the word displacement is to be taken as an elongation for

tensile force, rotation X for bending moment, rotation y for shear.

Symbols

A. : area of the positive force range half cycle in the load-displacement

diagram.

A. : same, negative.

F : force.

F. : positive force corresponding to displacement e. in cycle i.

F. : same, negative.

F : yield load in positive force range.

F : same, negative.

100

v : absolute value of the displacement.

v^ : absolute value of the maximum positive displacement in the i cycle.

v. : same, negative.

v : absolute value of the displacement defined as F +/tga +.

v : same, negative.

Av. : absolute value of the maximum displacement in the positive force

range in the i cycle.

Av. : same, negative.

i : index of the number of achieved cycles in a test.

tga . : slope of the tangent to the (F - v) curve when F changes from

negative to positive at the i cycle.

tga . : same, reversed in sign.

tga : slope of the tangent at the origin of the (F - v) curve, when F y increases in positive side.

tga : same, negative.

H : general symbol for partial ductility, see next line.

^oi : Partial ductility at the i cycle for the positive displacements.

M . : same, negative.

101 -

\i . : full ductility, at the i cycle for the positive displacements.

a ." : full ductility, at the i cycle for the negative displacements.

£. : resistance ratio, at the i cycle, for the positive force range.

£. : resistance ratio, at the i cycle, for the negative force range.

E(H ) : relative resistance function.

+ iu .) : resistance drop ratio on the F positive side at the i cycle.

_* — e (u .) : same, negative.

e ( ) : resistance drop function, o

Ç. : rigidity ratio on the positive side of force at the i cycle.

Ç. : same, negative.

f(u ) : relative rigidity function. ' o

i|i. : full ductility ratio on the positive side of force at the i cycle.

»(/. : same, negative.

ib (ii ) : full ductility function. " o

n . : absorbed energy ratio on the positive side of force at the i cycle.

r\. : same, negative.

r| ( |J. ) : relative absorbed energy function.

102

3.2.1 - INTRODUCTION

The following testing procedure is intended as a reference, to produce an

adequate and, as much as possible, an unified way to carry out tests in order to

characterize the structural behaviour of structural components, substructures or

even complete structures.

The necessity of a testing procedure and of having test results is

unquestionable, because the real cyclic behaviour of structural element may

differ by far from the ideal reference of the perfect elasto-plastic behaviour.

Testing may be necessary in order to prove the adequacy of a substructure or

a structural detail to fulfill the demande of local ductility as specified by

seismic recommendations.

The testing procedure explained here consists in defining the way to apply on J

a structural element to be tested the part of the testing action corresponding

to seismic action.

The testing procedure should in particular help to verify the common design

relation between a pseudo-static horizontal force and 'a specified ductility or

displacement given by Codes and Recommendations, such as, for instance the ECCS

Recommendations for Steel Structures in Seismic Zones.

The procedure has been chosen to set forward the characteristics of the

element in that peculiar context. The complete definition of the test also

-103

requires datas on the combination of seismic and not seismic loads. Paragraph

3.2.6 is devoted to that aspect of the definition of the testing procedure.

3.2.2. - ASPECTS OF THE TESTING PROCEDURE FOR ASSESSING THE BEHAVIOUR OF

STRUCTURAL STEEL ELEMENTS

The testing procedure may include preliminary classical monotonie

displacement increase tests or obviate them. In the first case, it is called

complete testing procedure (Paragraph 3.2.3). In the opposite case, it is called

short testing procedure (Paragraph 3.2.4). The possibilities for restricted

reversal tests are mentioned at paragraph 3.2.6.

The procedure can be applied to plane 3 dimensional tests. The possibility of

having various law for increasing various forces in various directions is not

considered in this reference procedure.

3.2.3 - COMPLETE TESTING PROCEDURE

Introductory remark

Each of the three following tests, will be performed on a different specimen.

3.2.3.1 - First test

The first test performed on the structural element is a classical monotonie

displacement increase test.

104

The increases are on the tension range defined as positive. From the recorded

F-v curve, the conventional limit of elastic range F and the corresponding + displacement v may be deduced as follows (Figure 3.3)

Figure 3.3

- evaluate the tangent at the origine of the F-v curve; it gives a tangent

modulus E. = tga ; ^ y

- locate the tangent that has a slope of E. /10; - the intersection of the two tangents defines the level of F + ;

- v is the displacement corresponding to-that intersection.

105

The above definition is the general definition of F . Any other definition

of F nay be used, if properly justified by design or testing context. A

commentary on possible definitions of F is given at paragraph 3.2.7.

3.3.3.2 - Second test

The second test also is a classical monotonie displacement increase test,

but it is performed on the compression (negative) range. The procedure is the

same as in the first test. F and v are deduced. Y Y

3.2.3.3 - Third test

The third test is a cyclic test with increase of displacement, which has the

following characteristics:

- one cycle in the v /4, v /4 interval;

- one cycle in the 2v /4, 2v /4 interval;

- one cycle in the 3v /4, 3v /4 interval;

- one cycle in the v , v interval;

- three cycles in the 2v , 2v interval;

- three cycles in the (2 + 2n) v , (2 + 2n) v interval (n = 1,2,...).

More cycles or more intervals may be use if necessary.

3.2.3.4 - Parameters of interpretation for one cycle

The absolute values of the following quantities are deduced from the F-v

diagram after each cycle (Figure 3.4) in the range of v > v .

106

Figure 3.4

- the extremes of displacement v. and v. ;

- the values of the force F. and F. corresponding to the extremes of

displacement v. and v. ;

- the extremes of displacement in the positive and negative range of the applied

forces, Ãv. and AV. ;

- the tangent modulus corresponding to the change of the sign of the applied

load, tg a . and tg a . ;

107

the areas A. and A. of the positive and negative half cycles (Figure 3.5)

Figure 3.5

The following quantities, considered as characterizing paramaters are then computed :

108

Partial Ductility : ii . = v. / v *- r o i l ' y u . = v. / v r o i l ' y

Comment - this parameter represents the ratio between the absolute value of the maximum positive (or negative) displacement in the i cycle, and the absolute value of the displacement defined as F /tg (or F /tg Q ). So much high is this ratio, so much greater is the structure^capacity to absorb large deformations out the elastic range.

Full Ductility : r- = Av. / v

M . = Av. / v "i l ' y

Comment - this parameter represents the ratio between the absolute value of the maximum displacement in the positive force range (or negative) in the i cycle, and the absolute value of the displacement in elastic range defined as F /tg a (or F /tga ). So much high is this ratio, so much greater is the structure capacity to absorb large deformations out the elastic range.

Full Ductility ratios : i|>. = Av. / (v. + (v.~ - v ~) )

<l» ." = Av." / (v." + (v.+ - v +) ) Ti i ' i i y

Comment - this parameter represents the ratio between the absolute value of the maximum displacement in the positive force range (or negative) in the i cycle, and the global displacement that one would have in a perfect elasto-plastic behaviour. It is a measure of the deterioration of the cycle. So much high is this ratio, so much greater is the deterioration of the structure due for instance: loss of stiffness, slip, etc.

Resistance ratios : e . = F. / F i l ' y e." = F." / F ~ i i y

Comment - this parameter represents the ratio.between the force corresponding to the maximum displacement in the i cycle, and the yield force that one would have in a perfect elasto-plastic behaviour. Depending on the definition of the yield force, this ratio could give values >1 .

109

Rigidity rat ios : Ç . = tg a. / tg a

Si" = t g a i ~ / t g Q y ~

Comment - this parameter is the ratio between the rigidity of the structure in " the i cycle, and the initial rigidity. A little value of this ratio ( « 1 ) indicates a large loss of rigidity of the structure. This can be caused by instability phenomena, Bauschinger effect exhibited by the steel subjected to inelastic load reversals or the residual curvature during previous cycles.

Absorbed Energy ratios : n. =A. /(v. + v. - v - v ) * F " 'i i i i y y y tl . = A. / (v. + v. - v - v ) * F 'i i i i y y y

Comment - this parameter represents the ratio between the energy absorbed by the structure in a real cycle, and the energy absorbed in perfect elasto-plastic behaviour with the same maximum displacements.

Comment - all these parameters are defined as the ratio between the value find in the cyclic testing procedure and,that one that would have in a reference test to which is assumed a perfect elasto-plastic behaviour. The behaviour of the real structure is so much better as its behaviour is near of the perfect elasto-plastic behaviour, that is, values of these parameters near 1. A little value of these parameters ( « 1 ) can be assumed as an index of the end of the test, because in this case one have a great loss of resistance, rigidity or energy dissipation.

3.2.3.5 - Specific parameters for a group of 3 cycles of equal displacement

The behaviour of tested piece is characterized after each group of three

cycles of equal displacement by the following parameters. The partial

ductility \i . , where i is the index of the last cycle of the group, being taken

as variabile, the parameters are:

-110

- ijí ( \Í . ) , minimum value of the three i|» . evalueted in the group of three

cycles

- £ ( M • ) , minimum value of the three e. evalueted in the group of three

cycles

- Ç (U . ) , minimum value of the three Ç. evalueted in the group of three

cycles

- r\ ( |i • ) , aver ege value of the three TI . evalueted in the group of three cycles +* + + +

- e (U. ) = F. / F . J , defined as the resistance drop ratio of the group of three cycles in the range of positive forces.

Similary, I|J (\LQÌ ) , e (|ÌQÌ ) , Ç (l1^") ' are the ndnimum value of the three i|i . , e. and Ç . evalueted in the group of three cycles.

1 (|i . ) is the averege of the r\ . of the group.

£ (\i . ) = F. / F ._„ is the resistance drop ratio of the group of three

cycles in the range of negative forces.

3.2.3.6 - Parameters of interpretation for the whole test

The partial ductility \i being taken as the variable, the test is

characterized by the following functions, which are continuous functions defined

on the basis of a limited number of values established in 3.2.3.5.

- Full ductility function f ( \i ).

- Relative resistance function e(u ),

- Relative rigidity function Ç(|i ) .

- Relative absorbed energy function T|(Ji. ),

111

* Resistance drop function e (|i ).

The number of cycles n up to end of test must also be given.

3.2.4 - SHORT TESTING PROCEDURE

In that case, the first and second test of the complete testing procedure + - + -are not executed. The third test is executed alone, but F , F , v and v

are not known at the beginning of the test, so that the procedure is as follows:

- The test should be performed with step of displacement sufficiently small to

ensure that at last four levels of displacement are reached before v and

v . Y - The tangent moduli at the origin tg a and tga are evaluated from the

first cycle curve.

- As in the complete procedure, F is defined by the intersection of the two

tangent lines or any other justified definition. In the first case, one

tangent is evaluated at the origin (slope tg a ); the other one is the

tangent to the envelope curve of the cycles with a 0.1 tga curve (Figure

3.6).

Again, v is the displacement corresponding to the intersect.

- Similar definition are used on the negative side for F ~ and v y Y

- As soon as these F , F , v and v are defined, the testing procedure

becomes the same as in 3.2.3.3.

- The parameters of interpretation are the same as in 3.2.3.4, 3.2.3.5 and

3.2.3.6.

112

Figure 3.6

3.2.5 - END OF TEST

The test may be stopped at any level of displacement decided with regard to

a specific code or research requirements.

113

3.2.6 - COMBINATION OF LOADS

The principles uses in tests for combined loads are those of the design

codes. In general, they are as follows:

- the seismic action should be considered as an accident situation; hence, the

values assigned to variable actions of long duration should be "most probable

values", while other short duration actions (such as wind forces) should not

be considered.

- the combination of seismic action with long duration actions which have no

reversal in sign may bring unsymmetrical demand on structural elements. In

this case test may be performed with a partial reversal of displacement. This

partial reversal can be of various forms and must be properly justified.

3.2.7 - COMMENTARY OF POSSIBLE DEFINITIONS OF Fy

There are many possible definitions of a conventional limit of the elastic

range F . Let us mention, amongst others:

a) The value corresponding to first yield somewhere in the tested piece

Figure 3.7 a;

b) The maximum reached load, Figure 3.7 b;

c) The value corresponding to a deformation is a certain time the deformation

which would have been obtained in a purely elastic behaviour. Figure 3.7 c

gives an example with two times the elastic deformation.

d) Figure 3.7 d recalls the definition recommended in the present document.

e) In some cases, F could be a reference load deduced for computation.

114

Figure 3.7

Each definition offers sane advantages and disadvantages.

Definition a) ignores the post elastic resources.

Definition b) are interesting in the buckling context, but may correspond to

exagerated deformation in flexural behaviour of beams or joints. On the contrary

the definition c) applies well to beams or joints but not to buckling problems.

The ECCS recommended definition (Figure 3.7d) applies in all cases.

Definition e) corresponds to the case where design resistances would have been

defined previously to any test.

-115

3.3 - TESTS FOLLOWING THE ECCS RECOMMENDATIONS

In order to obtain some experimental data on the behaviour of structural

components or substructures, and to check the validy of the ECCS

recommendations, it was designed and developed | 4 | in the Structural Engineering

Department of the Politecnico di Milano a testing apparatus able to impress

cyclic displacements slowly in time to structural components or subassemblages.

The general view of the equipment is shown in the photo 1 and it is

schematically represented in Figures 3.8 and 3.9.

Photo 3.1

-116

Figure 3.8

I I I ' 1 ! î.liî Ä.ltt ' ' ' ' '_!±íí ' i ; ■ ■■» * J • • *» » )

1Î 1Í f

*fc*H

im i !î!

!'¡

f-^-^

Figure 3.9

-117 -

Its main components are:

- A foundation composed of reinforced concrete slab which is part of the testing

apparatus available in the Laboratory of the Structural Engineering Department

of the Politecnico di Milano.

- A supporting girder with longitudinal dimension 6.57 m which acts as a

mounting of specimens and axial-loading system that are bolted on.

- A counterframe composed of one column and two truss systems inclined at 60

toward each other.

- A power jackscrew which displays a 100 KN capacity, a 300 mm stoke and

1.7cm/mim of feed rate.

- A axial-loading system able to impress axial deformations to beam to column connections.

- A lateral bracings system to prevent specimens lateral displacements.

Throughout a cyclic test, the load applied to the specimen and the

displacement are measured continouosly.

3.3.1 - BEHAVIOUR OF BRACINGS

The most important result from cyclic experiments with frames or braced

frames subjected to cyclic horizontal displacements is the hysteretic curve

which relate the applied horizontal force F at the top of the frame, to the

-118

horizontal displacement v in the same point. Some examples of hysteretic curves

for single and double braced frames with braces of different cross-section and

slenderness ratio are shown in Figure 3.10 to 3.13.

~r -7

— i — -5

300-

200-

"T" 5 7

-400-

Figure 3.10

119-

3Z 80 X = 114

400 -

- 5 0 0 -

Figure 3.11

-120-

Figure 3.12

-121

Figure 3.13 I

-122

From these hysteretic curves some indications can be appointed.

When a brace buckles, during the subsequente cycles the same capacity in

compression cannot be reached. Two main causes contribute to the decrease in

strength capacity of the braced frames during the inelastic loadings. These are

the Bauschinger effect, exhibited by the steel subjected to inelastic load

reversals, and the effect due to the residual curvature of the brace resulting

from plastic hinge rotation during previous cycles. In double braces this

decrease is less pronounced due the combined action of the post-buckling

behaviour of the compression member and the yielding behaviour of the tension

member. Photo 3.2 and 3.3 show an example of local buckling occured in a double

braced frame.

Photo 3.2

123

Photo 3.3

The deterioration of the critical buckling force is related to the

slenderness ratio X of the brace. The hysteretic curves for braced franes with

great values of the slenderness ratios exhibit a more rapid deterioration in

their compressive strengths than those with small values of the X The

slenderness ratio of the braces appears to be the single most important

parameter in determining the hysteretic behaviour of braced frames.

124

According to Popov experiments |10|, 1111 , 1201 the cross-sectional shape of

the braces affects also the hysteretic behaviour of braced frames. He has

observed in some braces with singly symmetric sections (tee and double-angles)

lateral-torsional buckling. This was due to geometric proportions of the

cross-section which cause buckling in the direction perpendicular to their axis

of symmetry. In such cases, flexural and lateral-torsional buckling take place

simmultaneously causing a lower critical load than that which would develop in

pure flexural buckling. This tends to contribute to the somewhat poorer

performance of the tees and double-angles in comparison with tubes and wide

flanges.

3.3.2 - BEHAVIOUR OF BEAM-TQ-COLUMNS CONNECTIONS

Joints of steel structures in current design are usually assumed to behave as

simple hinged or full fixed. In the case of elastic design, it is not

unrealistic to make these simplified assumptions for the following reasons:

a) The resulting analytical models lead to reasonable results in terms of

reliability;

b) In several cases these models do correspond to the actual behaviour.

On the contrary, when analyzing the post-elastic and cyclic behaviour of

structures, it is necessary to take into account the complex constitutive laws

of the joints undergoing cyclic loading together with the way in which the

energy is dissipated both under monotonie or cyclic loading.

In some cases it is important to introduce the actual restraint conditions of

joints even if the analysis is limited to the elastic range. This is the case of

125

steel structures in which the importance of the P­A effects calls for a more

realistic model of the restraint conditions of bars by means of appropriate

fixity factors which take into account the increased deformability of the

structure.

Actual restraint conditions of joints in steel structures are characterized

by a complex behaviour both under monotonie and cyclic loadings, the moment

rotation relationships being generally non linear with different degrees of

deterioration as far as the number of cycles increase.

The typologies of beam­to­column joints in framed structures can be examined

with respect to three types of behaviour which can be characterized by a

monotonie test identifying three categories with increasing lowering degree

(Figure 3.14):

ir*—r

.

— t —

■

_

© - V

, ©

—V—

' — V

1 1 1 1.

*t

i ' i ■ i i

1

Figure 3.14

126-

st 1 Category: comprises welded joints with stiffners in the column web. 2 Category: comprises end-plate joints with or without stiffners. rd 3 Category: comprises shear bolt joints.

All types of connections can be included in the three above mentioned

categories.

In order to have a homogeneous comparison, it is necessary to refer to full

strength joints which provide an .ultimate moment at least equal to the one of

the cross-section of the connected member.

The lowering degree is therefore represented by a reduction of stiffness from

one category to the next one.

It should be noted that the first category is characterized by a quite rigid

behaviour. The lowering degree is only due to the nodal panel deformation caused

by the highly concentrated forces, which can cause local buckling phenomena.

This deterioration is dependent upon the stiffness and reaches its maximum when

the column web is unstiffened.

In the second category the degrading phenomena characteristic of the first

one (nodal panel flexibility) are increased by the effects of flexural

deformation of the column flange and the end plate in addition to axial

deformation of bolts, depending upon the tightening force.

In the third category, in addition to the previous degrading phenomena,

slipping of bolts arises due to bolt-hole clearance.

From the cyclic behaviour point of view the joint constitutive relationship

can be stable if it exhibits the same behaviour of the monotonie test even if

the number of cycles increases. On the other hand, the behaviour can be unstable

when its stiffness decreases with number of cycles.

127

Under cyclic loading, the three categories of connections are characterized

by three typical behaviours (Figure 3.15):

Figure 3.15

a) The joints of the first category exhibit a stable behaviour characterized by

hysteresis loops having the same area inside the curve which remains constant

with increasing number of cycles.

b) The joints of the second category, instead, exhibit an unstable behaviour due

to permanent deformations in holes and bolts, thus reducing the stiffning

effect of the tightening force. Therefore, for constante amplitude cyclic

loading, we observe hysteresis loops with increasing deformations up to the

complete collapse. The slope of the hysteresis curves characterizing the

stiffness of the i cycle is continuously decreasing.

c) The joints of the third category exhibit un unstable behaviour characterized

by slipping of bolts. This phenomenon significantly modifies the shape of the

curve by reducing the dissipated energy for the same values of deformations. '

128

Main causes of the increasing deterioration have to be ascribed to the

permanent deformations of holes and shanks.

Cases b) and c) lead to collapse due to deterioration of stiffness (low-cycle

fatigue).

Testing results on actual joints under repeated loading conditions confirm

the above described behaviours.

The first example is related to a beam-to-column stiffned welded joint

(Figure 3.16). This joint exhibits almost a stable behaviour with small

deterioration of stiffness, so that it can be considered of the first category

defined above.

Figure 3.16

129 -

The second example is related to an end plate beam-to-column joint without

stiffners subjected to cyclic opposite constant loads (Figure 3.17).

T M

Figure 3.17

This joint exhibits a deterioration of stiffness together with increasing

slippage phenomena. This behaviour can be therefore ascribed to the third

category described above.

130

3.4 - VALIDITY OF THE ECCS RECOMyENDATIONS

The good correlation between experimental and numerical analysis induce the

evaluation of the main parameters used to define the behaviour of structural

elements. At this point, it is necessary to control if these parameters are

really able.to describe the behaviour of structural elements under cyclic loads.

This control consists in examine if these parameters are characteristics of the

tested elements and not dependent of the applied loading history.

The comparison between the adymensional parameters of resistence, ductility

and energy dissipation may allow a control of the truthfulness of these

parameters.

As the experiments are performed using as control parameter a displacement

component, some numerical simulation analogous to the tests are realized, in

which the cycles of loading are characterized by different values of the maximum

component of the displacement. In this way the effects related with the

experimental procedure are divided from these characteristics of the tested

elements.

In the numerical analysis eigth simulations are performed for each element;

the maximum displacement (v. + v. ) of each simulation is the same of that used

in experiments. The simulation are organized in order to evidence all the

possible behaviours of the element. Their main characteristic are the following:

1 test - After executing some cycles in elastic range, elastoplastic cycles are

performed using an increment two time greater than that used in the

experimental tests.

-131 -

2 test - Similar to the previous one, but the increase of displacement starts

with a different initial displacement.

3 test - Similar to the both previous, but without cycles in elastic range.

4 test -.It has cycles in elastic range, but the increment of the displacement

is a half of that using in the experimental tests.

5 test - Similar to the previous one, but without cycles in elastic range.

In these five tests positive and negative displacements have the same

absolute value (|v. | + |v. | ) .

6 test - It has symmetrical cycles in elastic range; over this range the

displacement increases only in negative field.

7 test - Similar to the previous one, but with increment of displacement only in

positive field.

8 test - It is a random cyclic test; the only limitation is related with the

maximum excursion of the displacement (v. + v.~) which must be equal

or lesser than that reached in the experimental test.

For each simulation the force-displacement diagram is plotted. This is

diagrammatically shown in Figures 3.18 to 3.21. In Tables I to IV the sequence

of cycles employed in the numerical analysis are given. The Figures 3.22 to 3.25

represent the diagrams related to the following parameters:

- resistance ratio in positive range

- resistance ratio in negative range

- Ductility ratio in positive range

- Ductility ratio in negative range

- Absorbed energy ratio in positive range

132-

- Absorbed energy ratio in negative range

- Total accumulated energy

These diagrams show the ratio between the parameters evaluated during the

numerical simulation and those that one could find in an ideal element with an

elasto-plastic behaviour; in ordinate are represented the value of those

parameters and in abscissa the sum of positive and negative displacement for

each cycles.

Each diagram presents the rielaboration of the eigth simulations executed for

each element; in this way, it is possible to certify that the parameters have

similar values for different history displacements; that allows to conclude that

they are really characteristics of the tested elements and not linked to the

history displacements.

In particular the differences between the single simulation that one can find

in seme diagrams regarding the resistance ratio, are due to the fact that using

as control parameter a displacement component, the resistance ratios are

strictly influenced by the imposed displacements. Ductility ratios generally

show a good agreement between the different tests; the values exhibited by the

absorbed energy ratios near the maximum dispacement are generally equals.

-133

2L 80x8 one brace

T 1 1 1 r

Figure 3.18 a

134

Figure 3.18 b

135

Table I

2 L 80x8 one brace

Cycle

1

2

3

4

5

6

7

8

9

10

11

12

13

Exp.

5.0 -5.0

6.0 -6.0

15.0 -15.0

20.0 -20.0

25.0 -25.0

30.0 -35.0

30.0 -40.0

1

5 -5

8 -8

15 -15

25 -25

35 -40

35 -35

0 0

0 0

0 0

0 0

0 0

.0 0

2

5 -5

8 -8

12 -12

20 -20

30 -30

35 -40

0 0

0 0

0 0

0 0

0 0

.0 0

3

12 -12

20 -20

30 -30

35 -35

.0

.0

.0

.0

.0 0

.0 0

4

5.0 -5.0

7.5 -7.5

12.5 -12.5

15.0 -15.0

17.5 -17.5

20.0 -20.0

22.5 -22.5

25.0 -25.0

27.5 -27.5

30.0. -30.0

32.5 -32.5

35.0 -35.0 37.5 -37.5

5

15.0 -15.0

17.5 -17.5

20.0 -20.0

22.5 -22.5

25.0 -25.0

27.5 -27.5

30.0 -30.0

32.5 -32.5

35.0 -35.0

37.5 -37.5

6

7.0 -7.0

20.0 -15.0

30.0 -15.0

40.0 -15.0

50.0 -15.0

60.0 -15.0

7

8.0 -8.0

15.0 -20.0

15.0 -30.0

15.0 -40.0

15.0 -50.0

15.0 -60.0

8

7.0 -10.0

15.0 -20.0

25.0 -15.0

20.0 -30.0

15.0 -45.0

20.0 -40.0

45.0 -30.0

Exp. Experimental patterns 1,2... 8 numerical tests Assumed maximum displacements [ mm ] for each Cycle

136-

2C 80 one b r a c e

Figure 3.19 a

137

Figure 3.19 b

138

Table II

2 C 80 one brace

Cycle

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

Exp.

20.0 -10.0

20.0 -15.0

20.0 -20.0

25.0 -25.0

30.0 -30.0

35.0 -35.0

40.0 -47.0

45.0 -45.0

45.0 -50.0

1

8 -8

10. -10

15 -15

25 -25

35 -35

45 -45

0 0

0 0

0 0

0 0

0 0

0 0

2

5 -5

9 -9

20 -20

30 -30

40 -40

45 -45

.0 0

0 0

0 0

0 0

0 0

.0 0

3

15 -15

25 -25

35 -35

40 -40

45 -45

.0

.0

.0

.0

.0

.0

0 .0

.0

.0

4

7.5 -7.5

10.0 -10.0

12.5 -12.5

15.0 -15.0

17.5 -17.5

20.0 -20.0

22.5 -22.5

25.0 -25.0

27.5 -27.5

30.0 -30.0

32.5 -32.5

35.0 -35.0

37.5 -37.5

40.0 -40.0

42.5 -42.5

45.0 -45.0

5

17.5 -17.5

20.0 -20.0

22.5 -22.5

25.0 -25.0

27.5 -27.5

30.0 -30.0

32.5 -32.5

35.0 -35.0

37.5 -37.5

40.0 -40.0

42.5 -42.5

45.0 -45.0

6

8.0 -8.0

15.0 -20.0

15.0 -30.0

15.0 -40.0

15.0 -50.0

15.0 -60.0

20.0 -70.0

7

8.0 -8.0

15.0 -20.0

25.0 -20.0

35.0 -20.0

45.0 -20.0

55.0 -20.0

65.0 -25.0

8

7.0 -10.0

10.0 -10.0

20.0 -30.0

10.0 -50.0

50.0 -20.0

35.0 -40.0

25.0 -65.0

139

2L 50x6 two braces

Figure 3.20 a

140

i ■ 1 1 1 1 1 r

Figure 3.20 b

-141 -

Table III

2 L 50x6 two braces

Cycle

1

2

3

4

5

6

7

8

9

10

11

12

Exp.

5.0 -5.0

10.0 -10.0

15.0 -15.0

20.0 -20.0

25.0 -25.0

30.0 -30.0

35.0 -35.0

1

5 -5

12 -12

20 -20

30 -30

35 -35

0 0

.0 0

0 0

0 0

0 0

2

5 -5

15 -15

25 -25

30 -30

35 -35

.0 0

.0 0

0 0

0 0

0 0

15 -15

25 -25

35 -35

3

.0

.0

.0

.0

.0

.0

4

7.5 -7.5

10.0 -10.0

12.5 -12.5

15.0 -15.0

17.5 -17.5

20.0 -20.0

22.5 -22.5 25.0 -25.0

27.5 -27.5

30.0 -30.0

32.5 -32.5

35.0 -35.0

5

15.0 -15.0

17.5 -17.5

20.0 -20.0

22.5 -22.5

25.0 -25.0

27.5 -27.5

30.0 -30.0 32.5

-32.5

35.0 -35.0

6

7.0 -7.0

15.0 -10.0

15.0 -20.0

15.0 -30.0

15.0 -40.0

15.0 -50.0

15.0 -50.0

7

10.0 -10.0

20.0 -15.0

30.0 -15.0

35.0 -15.0

40.0 -15.0

45.0 -15.0

50.0 -15.0 55.0 -15.0

8

7.0 -7.0

20.0 -15 0

20.0 -25.0

40.0 -15.0

20.0 -40.0

35.0 -35.0

-142

2C 80 tuo braces

Figure 3.21 a

143

Figure 3.21 b

144-

Table IV

2 C 80 two braces

Cycle

1

2

3

4

5

6

7

8

9

10

11

12

13

Exp.

30.0 -30 .0

35.0 -35 .0

40.0 -40 .0

45.0 -45 .0

1

12.0 - 1 2 . 0

15.0 -15 .0

25.0 -25 .0

35.0 -35 .0

45.0 - 4 5 . 0

2

12.0 -12 .0

20.0 - 2 0 . 0

30.0 -30 .0

40.0 - 4 0 . 0

45.0 - 4 5 . 0

30 -30

35 -35

40 -40

45 -45

3

.0

.0

.0

.0

.0

.0

.0

.0

4

15.0 -15 .0

17.5 -17 .5

20.0 -20 .0

22.5 -22 .5

25.0 -25 .0

27.5 -27 .5

30.0 -30 .0

32.5 -32 .5

35.0 -35 .0

37.5 -37 .5

40.0 -40 .0

42.5 -42 .5

45.0 -45 .0

5

25.0 -25 .0

27 .5 - 2 7 . 5

30.0 - 3 0 . 0

32 .5 - 3 2 . 5

35.0 - 3 5 . 0

37.5 - 3 7 . 5

40.0 -40 .0

42 .5 - 4 2 . 5

45.0 -45 .0

6

12.0 -12 .0

25.0 -30 .0

25.0 - 4 0 . 0

25.0 -50 .0

25.0 -60 .0

25.0 -65 .0

7

12.0 -12 .0

20.0 25.0

20.0 -25 .0

30.0 -25 .0

35.0 -25 .0

40.0 -25 .0

45.0 -25 .0

50.0 -25 .0

55.0 -25 .0

60.0 -25 .0

65.0 -25 .0

8

12.0 -12 .0

40.0 -25 .0

55.0 -20 .0

20.0 -60 .0

35.0 -50 .0

25.0 -65 .0

145­

2L 80x8 one brace PESISTENCE RRTIO RESÏSTEflCE RATIO ­

? LS I « 'y

(5

\ F

20 SO 40 SO SO 70 U i + -t- U l - tmmJ

10 20 30 40 SO SO 70 IO 30 U i + + U i - (mm 1

FULL DUCTILITY RATIO + RJLL DUCTILITY RATIO

T T i 7 m'

10 ZO SO . 40 SO SO 70 SO SO Ul* ♦ Ul- limn)

Figure 3.22 a 10 CO 30 40 SO SO 70 10 90

Ul* + Ul- (mini

-146

ABSORBED EMERGY PPT IO * ABSORBED ENERGY RATIO

10 ZO M « SS £0 70 SO 30 U i + + U l - [ m m ! io zo 30 40 ss so 70 go ao

U i * + U l - t mm I

CUflULFITED ENERGY

Fi giare 3.22 b

1 0 ZO 30 « EO EO 70 10 U l + + U I - [mm]

147 -

2C 80 one b r a c e RESISTENCE RAT IQ + RESISTERE RATIO -

j * «

Mi W.

30 40 so sa 70 Ui + + U i - tmml

io zo 30 « so so 70 eo 30 U i + + « J l - t m m l

FULL DUCTILITY RATIO FULL DUCTILITY RATIO

Mt m.

.r* t*.

IO 20 30 40 SO CO 70 (0 U i + + U l - ( m m )

io zo 3o 40 so ca 70 eo so U î + * U I - Imml

Figure 3.23 a

148

ABSORBED EI1ERGY RATIO ABSORBED EflERGY RATIO -

>0 20 SO « SO SO 70 SO SO U i + + U l - [mm]

10 20 SO 40 SO CO 70 CD 30 III* + U l - t mm J

XXinULflTED ETIERGY

Figure 3.23 b

10 20 SS 40 SO CO 70 «0 U l + + U l - (mml

149

2L 50x5 tuo braces RESISTENCE RATIO * RESISTERE RATIO ­

.in o\.

.U) "V

■CM W .

m zo 30 io so co 7o so so U i + + U ¡ - (mm ]

10 ZO 30 40 EO EO 70 SO 30 U i * + U i - [mml

FULL DUCTILITY RñTIO + FULL DUCTILITY RATIO

,<n ci.

.in in

10 ZO 30 «0 SO CO 70 60 30 U l + + U l - (mml

Figure 3.24 a 10 20 30 40 SO CO 70 10 30

Ul+ + Ul- tmml

150

f1JJS0R£EJJ EMERGY RATIO ABSORBED EMERGY RATIO

io zo M 40 sa so 7o eo so U i + + U i - (mm! 30 40 SO CO 70

Ul + + U i - [mm]

CUMULATED EMERGY

Figure 3.24 b !

SO 40 SO EO 70 IO 90 U l + ♦ U l - [mm!

151 2C 80 two braces

RESISTENCE RATIO * RESISTENCE RATIO -

10 ZO 30 40 50 £0 70 SO 30 Ui+ + U l - imm]

10 ZO 30 40 EO SO 70 10 30 Ul + + U i - Imm]

1=

FULL DUCTILITY RATIO •* FULL DUCTILITY RATIO -

SO 40 SO « 70 U l + ♦ U l - (mml

•1 Figure 3.25 a

30 40 SO CO 70 Ul + + U l - (mml

-152

RESORBED ENERGY ¡MT IO ABSORBED ENERGY RATTO -

10 20 30 40 SO CO 70 U 30 U i' + * U1 - t mm 1

10 20 30 40 SO SO 70 so so U i * + VJi- tmml

•CUnULflTEIl ENERGY

Figure 3.25 b

10 Z9 30 40 SO CO 70 CO 30 U l + + U i - t mm]

-153

3.5 - CONSIDERATIONS ON b/t RATIOS

In Figures 3.26 to 3.29 are presented some hysteretic curves of cantilever

beams with welded H and box-shaped cross sections with different width-thickness

ratios. In those curves is represented the horizontal load at the top the beam

versus the deflection at the same point.

UELDED H 10 nwi

-+ i—i

/rj/iw>i

200.00 .

150.00 .

-150.00.

-200^00.

Figure 3.26

, i0° i («i

UELDED H 4 mm

154-

rmr»»*$»f99i

1 1 r - 7 . 0 0 - 5 . 0

80.00

2 0 0 (m* |

- , ¡ j _ 00 7.00

BOX I J mo»

155

-200.00.

Figure 3.28

156

BOX 4 nm

fwwrnrwrum

200.00 .,

150.00 .

100.00 .

SO. 00

-100 .00

- 1 5 0 . 0 0 .

- 2 0 0 . 0 0 .

-l 1-(ml

Figure 3.29

-157 -

Based on these curves seme conclusions may be advanced:

- Cyclic loops of load versus deflection are generaly symmetric respecting to

deflections axis.

- The maximum load both in compression as in tension is reduced as cycle

increases. This reduction is so much higher as larger as the width-thickness

ratio (b/t) of the flange. This is due to the early occurence of local

instability of flange elements.

- For large b/t ratios, the flange instability occurs at an early stage of

bending and the contribution of the flange elements to the bending strength of

the H welded or box beam may be reduced as cycles increases.

In photo 3.4 and 3.5 can be recognized the out-of-plane deformation of the

flange element.

Photo 3.4

-158-

Photo 3.5

The failure patterns of flange and web plate elements after cycles can be

characterized by the occurence of highly localized deformations of the whole

section.

At present, it is in progress some work in order to develop non-linear

structural programs for the analysis of bent sections and braced frame

structures. The purpose of these programs is undertaken as an effort to gain a

better understanding of the manners in which these structural elements could

dissipate energy imputed by an earthquake event, and to avoid the use of

experimental tests everytime one need to know the hysteretic characteristics of

a subassemblage or even a complete structure.

159-

3.6 - REFERENCES

|l| Bertero, V. (1979) SEISMIC BEHAVIOUR OF STRUCTURAL CONCRETE LINEAR

ELEMENTS AND THEIR CONNECTIONS. AICAP - CEB Symposium, Rome, May, CEB

Vol. No. 131.

|2| Borges, J. (1979) RECOMMENDED FOR THE DESIGN AND CONSTRUCTION OF CONCRETE

STRUCTURES IN SEISMIC ZONES. AICAP - CEB Symposium, Rome, May, CEB Vol.

No. 131.

|3| Grandori, G. (1979) OBSERVATION OF ACTUAL STRUCTURES AND LABORATORY

TESTS. AICAP - CEB Symposium, Rome, May, CEB Vol. No. 131.

|4| Bailio, G. and Zandonini, R. (1985) AN EXPERIMENTAL EQUIPMENT TO TEST

STEEL STRUCTURAL MEMBERS AND SUBASSEMBLAGES SUBJECT TO CYCLIC LOADS.

Ingegneria Sismica, No. 3.

151 Carpenter, L. and Lu, Le-Wu (1973) REVERSED AND REPEATED LOAD OF FULL

SCALE STEEL FRAMES. AISI Bulletin, No. 24, April.

|6| Wakabayashi, M., Matsui, C , Minami, C. and Mitani, I. (1973) INELASTIC

BEHAVIOUR OF STEEL FRAMES SUBJECTED TO CONSTANT VERTICAL AND ALTERNATING

LOADS. Proc. of the V World Conference on Earthquake Engineering, Rome,

25-29/6/73.

|7| El-Tayem, A. and Goel, S. (1984) CYCLIC BEHAVIOUR OF ANGLE X-BRACING.

Proc. of the ASCE Structures 84 Congress, San Francisco.

160

|8| Popov, E. and Pinkley, B. (1969) CYCLIC YIELD REVERSAL IN STEEL BUILDING

CONNECTIONS. ASCE Journal of the Structural Division, vol. 95, No. ST3.

|9| Tanabashi, R., Kaneta, K. and Ishika, T. (1973) ON THE RIGIDITY AND

DUCTILITY OF STEEL BRACING ASSEMBLAGES. Proc. of the V World Conference

on Earthquake Engineering, Rome, 25-29/6/73.

|10| Popov, E. and Maison, B. (1980) CYCLIC RESPONSE PREDICTION FOR BRACED

STEEL FRAMES. ASCE Journal of the Structural Division, vol. 106, No. ST7.

|11| Popov, E. and Black, G. (1981) STEEL STRUTS UNDER SEVERE CYCLIC LOADINGS.

ASCE Journal of the Structural Division, vol. 107, No. ST9.

|12| Anderson, J. (1975) SEISMIC BEHAVIOUR OF K-BRACED FRAMING SYSTEM. ASCE

Journal of the Structural Division, No. ST10.

|13| Bailio, G., Gobetti, A. and Zanon, P. (1979) SIMULATION OF DYNAMIC

BEHAVIOUR OF PIN JOINTED STRUCTURES WITH NON SYMMETRICAL CONSTITUTIVE

LAW. Simulation of System '79, Sorrento, North-Holland Pubi. Comp.

1141 Perotti, F., Rampazzo, L. and Setti, P. (1984) DETERMINAZIONE DEL

COEFFICIENTE DI STRUTTURA PER COSTRUZIONI METTALICHE SOGGETTE A CARICHI

ASSIALI. 2 Convegno Italiano d'ingegneria Sismica - Rapallo, 6-9 Giugno.

1151 Fukumoto, Y. and Kusarna, H. (1985) CYCLIC BEHAVIOUR OF PLATES UNDER

IN-PLANE LOADING. Engineering Structures, vol. 7, January.

|16| Takanashi, K., Udagawa, K and Takana, H. (1982) PSEUDO-DYNAMIC TESTS ON A

2-STORY STEEL FRAME BY COMPUTER LOAD TEST APPARATUS HYBRID SYSTEM. Proc.

of the VII World Conference on Earthquake Engineering, Athens.

161

1171 Shing, P. and Martin, S. (1984) PSEUDODYNAMIC: TEST METHOD FOR SEISMIC

PERFORMANCE EVALUATION THEORY AND IMPLEMENTATION. EERC Report 01/84,

January.

|18| DEFINITION OF A CYCLIC LOADING TESTING PROCEDURE FOR EARTHQUAKE

RESISTANCE EVALUATION OF STRUCTURAL ELEMENTS - Draft from Technical

Committee 13 of European Convention of Structural Steelwork. Paris, 1983.

|19| Higashi, Ohkubo and Ohtsuka (1977) INFLUENCE OF LOADING EXCURSIONS ON

RESTORING FORCE CHARACTERISTICS AND FAILURE MODES OF REINFORCED CONCRETE

COLUMNS. Proc. of the VT World Conference on Earthquake Engineering,

New-Delhi.

120 Popov, E. (1980) SEISMIC BEHAVIOUR OF STRUCTURAL SUBASSEMBLAGES. ASCE

Journal of the Structural Division, vol.106, No. ST7.

163

C H A P T E R - 4

THE ASSESSEMENT OF q FACTORS

165

TABLE OF CONTENTS

Page

4.1- INTRODUCTION 166

4.2- METHOD FOR STATE THE BEHAVIOUR FACTOR q 168

4.3 - ONE FLOOR CANTILEVERS 171

4.4- FURTHER INVESTIGATIONS AND CODE APPROACH •. 180 4.5- REFERENCES 188

166

4.1 - INTRODUCTION

In current codes |l|, | 21, |3|, is commonly accepted that the design of

structures in seismic zones may be based on a linear elastic analysis combined

with a control of the plastic deformability of the structures. In such case,

large plastic deformations may occur during a seismic event if the elastic limit

of the structure is surpassed.

The seismic forces to apply as part of the elastic analysis are usually

indicated by identifying a normalized spectrum depending on the soil nature and

the features of the ground.

The design spectrum can be derived thereform through the introduction of a

coefficient which takes into account the energy dissipation capacity of a

ductile response. The values of this coefficient depend on the basis of

classification of structural systems according to ductility levels. This

coefficient, the so called "behaviour factor" is commonly designated by "q". Its

values depends on the non-linear dynamic behaviuour of the structure as well as

on its ability to undergo plastic deformation.

The Euroccde No. 8 - Common Unified Rules Por Structures in Seismic Zones,

recently issued by the Commission of the European Communities |4| states the

design spectrum:

C(T) = AR(T) / q (1)

where:

C(T) is the value of the design spectrum at the period T.

167 -

A is the design value of the ground acceleration which depends on the degree

of local seismic activity. Suggested values of A are between 0.15 and

0.35g.

R(T) is the value of the normalized design spectrum. It depends on the soil

nature and it is stated on the basis of 5% of the damping ratio.

q is the behaviour factor.

With regard to the above approach two design methods are possibles:

- the structure is designed to resist seismic actions elasticaly. In such case,

it is not necessary the consideration of dissipative zones (q = 1).

- the structure is designed to exit from the elastic range under strong

earthquakes. Thus, the consideration of dissipative zones is necessary and

must be examined in these zones both strength and ductility (q > 1). In non

dissipative zones only strength must be assessed.

Summing everything up, for a reliable and economic design a correct

definition of the behaviour factor q seems foundamental.

-168

4.2 - METHOD FOR STATE THE BEHAVIOUR FACTOR q

For structures which can be modelled as systems with one degree of freedom, a

numerical approach is suggested |5|, and used to determine the behaviour factor

q of some floor cantilevers.

With reference to the structures under investigation, the maximum force to be

expected in an elastic oscillator can be expressed as:

F = A R(T) m (2)

where:

F is the maximum static force expected during a strong earthquake.

A is the maximum ground acceleration (in the sense of peak value) expected during a strong earthquake.

R(T) is the normalized design spectrum,

m is the mass of the oscillator.

T is the period of the oscillator.

The maximum displacement v is assumed equal to:

v = A R(T) T 2 / 4TT2 (3)

Let us consider two analogous oscillators with the same period T, the same

normalized design spectrum R(T) but under different acceleration peak A, and A„.

The behaviour of the two oscillators will not be the same, but the following

relation of proportionality will be valid:

-169

Al Fl vl

Ä2 F„

(4)

2 v2

If the ductility factor theory is valid, we may assume that even in the case

of non-linear behaviour of the oscillator, its maximum displacement is still

proportional to the peak acceleration, while the maximum load is limited to the

ultimate load.

According to the Eurocode No. 8 |4|, the design spectrum is:

C(T) = A R(T) / q (!)

The static force F¿ to be applied in elastic designing is:

Fd = Ad R ( T ) m = ( A / q ) R ( T ) m (5)

The behaviour factor q corresponds to the ratio between seismic intensity (in

the sense of the peak value A) which cause the collapse of the structure and the

attainment of the elastic limit state A, = A/q.

If Fd corresponds to the yield stress of the structure F , the validity of

the ductility factor theory implys that the structure be able to resist to an

acceleration equal to A, q time larger than the acceleration A, that produce the

first plastification of the structure, since its ductility factor be greater

than q.

It is not necessary that F¿ be related with the admissible ductility of the structure.

Even not having a perfect relationship between the elasto-plastic

displacement of the structure and its elastic displacement, the seismic design

170-

based on (1) and (5) could result safe or unsafe according the elasto-plastic

response of the structure be lesser or greater the amplified elastic response.

Three patterns are possibles, Figure 4.1

q=q|A/Al

Figure 4.1

Pattern "a" corresponds to a behaviour in complience with the results of the

ductility factor theory. Pattern "b" shows an unsafe behaviour because

everywhere v > q v,. Pattern "c" presents a first safe range (v < q v,) followed

by an unsafe one. The values of q = v / v, for which the ductility factor theory

is accomplished may be choosen as q values for the structures and v / y, = q

represents the ductility overall demand of the structure.

-171

The procedure to obtain the behaviour factor q can be summarized as follows:

- evaluation of the inertia and strength characteristics of the structure as

well as its period T in elastic range. The second order effects, if they are,

may be taken into account in the evaluation of the period of the structure.

- selection of an accelerogram which normalized spectrum for a unitary peak

origine to the period T a response equal toR(T).

- several elasto-plastic analysis are performed at an increasing amplification

of excitation and the par of values v / v, and q = A / A, are represented in

a diagram form.

- the interception of these points with the bisectrix v / v, = q gives the behaviour factor q to the structure.

4.3 - ONE FLOOR CANTILEVERS

The method previously explained was used for assessing q factors for one

floor cantilevers.

Numerical analysis have been performed on HEA series columns, which were

deflected both in the plane of maximum and minimum rigidity. The

tested-out-members had slendernesses ranging from 50 to 200, while the axial

load has been made to vary from 0.00 to 0.20 of the Euler force N . The mass m, e

governing the system's inertia, has been preserved independent of the axial load

and selected in such a way that a previously assigned value of the natural

period ranging from 1.0 to 2.5 sees, corresponded to each case. In all analysis

172-

a damping value equal to 0.03 of the critical damping has been considered. Two

different numerical simulations have been accomplished for each instance, using

two artificially developed accelerograms according to the procedure described in

reference |6| based on the normalized spectrum defined in |4| and applied to

designing.

Two different guidelines have been followed in order to shape and design

samples:

- in the first case, the natural period has been computed regardless of the

reduced stiffness associated with the axial load.

- in the second case, on the contrary, the period variation caused by the sample

design was taken into account.

Both approaches highlight the significance of the designing criterion: if the

natural period is computed disregarding the second-order effects, one is on the

safe side, since the earthquake intensity is overrated through the function

R(T), expressing the design spectrum. In fact, R(T) decreases as the period goes

up in the range of greatest significance for the type under consideration.

The results of all cases tested for deflection in the plane of the greatest

rigidity are reported in Table I and II. They refer to the first and second

designing standards adopted respectively.

The following data are given for each cases: natural period T,

slenderness X , axial load as compared to Euler critical load N / N , and the

value find to the behaviour factor q.

173-

Table I

N°

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

T

1.0 1.0 1.0 1.0 1.0 1.0 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

X

50 50 50 100 100 100 50 50 50 50 50 100 100 100 100 100 150 150 200 200 50 50 50 50 50 100 100 100

N/Ne

0.00 0.05 0.10 0.00 0.05 0.10 0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.00 0.05 0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10

q

5.4 2.9 2.3 5.5 2.9 2.3 > 8 3.4 3.2 3.0 2.6 > 8 3.4 3.2 3.0 2.5 > 8 3.3 > 8 3.3 > 8 4.1 3.4 3.6 4.5 > 8 4.1 3.4

N°

29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55

T

2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5

X

100 100 150 150 100 200 200 200 50 50 50 50 50 100 100 100 100 100 150 150 150 150 150 200 200 200 200

N/Ne

0.15 0.20 0.00 0.05 0.10 0.00 0.05 0.10 0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10 0.15

q

3.6 4.5 > 8 4.1 3.4 8

4.2 3.4 > 8 > 8 3.5 3.7 4.1 > 8 > 8 3.5 3.7 4.1 > 8 > 8 3.5 3.7 4.1 > 8 > 8 3.5 3.7

Table I I

N°

1 2 3 4 5 6 7 8 9

T

1.0 1.0 1.5 1.5 1.5 1.5 1.5 1.5 1.5

X

50 50 50 50 50 50 150 150 150

N/Ne

0.05 0.10 0.05 0.10 0.15 0.20 0.05 0.10 0.15

q

2.3 2.1 3.1 3.0 3.1 3.0 3.1 3.0 3.0

N°

10 11 12 13 14 15 16 17 18

T

1.5 2.0 2.0 2.0 2.0 2.5 2.0 2.0 2.5

X

150 50 50 50 50 50 50 50 50

N/Ne

0.20 0.05 0.10 0.15 0.20 0.05 0.10 0.15 0.20

q

3.0 4.1 4.0 3.5 3.4 > 8 2.9 2.9 2.9

-174

Figures 4.2 and 4.3 show diagrammatically the procedure adopted to determine

Figure 4.2 Figure 4.3

175

Figure 4.4 to 4.7 indicate individually, for all the natural periods considered, the value (function of the slenderness X ) of the behaviour factor arrived.

6.

2.

T : 1.0 S N:0.0

_.N:.05Ne -«NÎ.IONE

4 50 100 150 200 X

«U

A.

3.

2.

T: 1.5 S

"" N:.10NE N:.15NE

-.N:.20Ne

-N:.05NE

50 100 150 200 A

Figure 4.4 Figure 4.5

176-

6.

5.

<U

T : 2.0 S 6

-*Nr .20N E -• . . N : . 0 5 N E 4

^N:.15Ne

50 100 150 200 1

3_

2 .

1 .

Ts2.5 S

- . N : . 2 0 N E . N- . .15NE » N I . I O N E

50 100 150 200 X

Figure 4.6 Figure 4.7

177

A comparison among the q values as function on the N / N ratio obtained

following the two guidelines descriebed above are shown in Figures 4.8 to 4.9.

0 0.05 0.10 0.15 0.20 N / 0 'NE

0.05 0.10 0.15 0.20 N / N£

Figure 4.8 Figure 4.9

178

For oscilations in the plane of the minimum stiffness, the results are

summarized in Table III.

Table III

N°

1 2 3 4 5 6 7 8 9 10 11 12 13

T

1.0 1.0 1.0 1.0 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

X

100 100 150 150 100 100 100 100 100 150 150 150 200

N/Ne

0.00

0.05

0.00

0.05

0.00

0.05

0.10

0.15

0.20

0.00

0.05

0.10

0.00

q

8.5 8.5 8.3 8.2 8.9 8.9 7.9 8.8 > 9

8.9 > 9

7.9 8.9

N°

14 15 16 17 18 19 20 21 22 23 24 25

T

1.5 1.5 2.0 2.0 2.0 2.0 2.0 2.5 2.5 2.5 2.5 2.5

X

200 200 100 100 100 100 100 100 100 100 100 100

N/Ne

0.05

0.10

0.00

0.05

0.10

0.15

0.20

0.00

0.05

0.10

0.15

0.20

q

> 9

7.9 > 9

8.6 9.0 > 9

> 9

> 9

> 9

> 9

> 9

> 9

179

The Figures 4.10 and 4.11 show the procedure adopted to determine the behaviour.'factor q.

«

12.

1 1 .

10.

9 .

a.

7 .

6 .

5 .

4 .

3 .

2 .

1 .

V V.

^ r-

A j loo N10.10 Ni T.tl .5 8

a ■ ■ t a«

- i 1 1 » 8 0

Figure 4.10 Figure 4.11

-180

Based on this numerical research |7| on the structural behavior factor of one

floor cantilevers some conclusions may be reached which have important design

implications.

1) Apparently, the behaviour factor q depends upon the period, whereas it is

unaffected by slenderness. Nevertheless, it is heavily dependent of the

section shape.

2) The consideration of the second order effects is important. The N / N ratio

seems not affect in a large measure the evaluation of the q factor.

3) For HEA series columns which are deflected in the plane of the maximum

stiffness a value of 2.5 for the behaviour factor seems adequate.

4) For HEA series columns which are deflected in the plane of the minimum

stiffness a value of 8 for the behaviour factor seems excessive because needs

a greater value for the ductility of the columns.

4.4 - FURTHER INVESTIGATIONS AND CODE APPROACH

As regard the behaviour factors q to adopt in seismic design of structures

the Eurocode No 8 - Catimon Unified Rules for Structures in Seismic Regions 141,

indicates that their values are given in the appropriate material chapters. For

steel structures, the values of the q factors are make dependent of the

structural type and the ductility level. According to Eurocode No 8, a structure

can be inserted in one of the following structural type to which three ductility

levels are possibles:

181 -

Frames and trusses

A structure behaves as a frame if lateral forces are mainly supported by

bending moments. Energy dissipation may occur where plastic hinges form.

A structure behaves as a truss if lateral forces are mainly supported by

axial forces. Energy dissipation occurs when diagonals in tension become

plastic as the compressed members may have only a so small amount of energy

dissipation that it may be disregarded.

A structure behaves as an eccentric truss if lateral forces are mainly

supported by axial forces but bending moments and shear forces locally occur

due to eccentricities. Energy dissipation may occurs where bending and shear

cause plastifications.

Unbraced frames

if : a, is the multiplier to the design load corresponding to the first

attainment of the elastic design capacity in one or more bent sections.

a is the multiplier of the design loads corresponding either to the

attainment of the ultimate design capacity in a number of bent sections

sufficient to transform the structure into a mechanism or to the

attainment of any kind of buckling in one structural member.

Ductility level III characterizes a frame in which the P-A effects are

negligible and the ratio ac /a, is greater than 1.20.

Ductility level II characterizes a frame in which the P-A effects are

negligible and the ratio ac /a, is limited between 1.10 and 1.20.

Ductility level I characterizes a frame in which the ratio ac / a, is less

than 1.10.

-182

Unbraced frames in which the connections in dissipative zones don't have a

strength greater than 1.00-1.20 times the one corresponding the gross area of

the connected members must be designed without taking into account dissipative

zones.

■> r

mm. 77777Z

LEVEL III

LEVEL II

Qt * a

c

LEVEL I

Figure 4.12

183 -

- Truss bracings

a - A tension diagonal bracing is a bracing in which compressed diagonal are

negleted in the design,

b - A tension and compression diagonal bracing is a bracing in which

compressed diagonals are taken into account for equilibrating external

loads.

Figure 4.13

Ductility level III characterizes a tension diagonal bracing in which the

connections in dissipative zones have a strength greater than 1.00-1.20 times

the one corresponding the gross area of the connected members, diagonal

bracings have a slenderness lesser than X B=V2 being Xe = nVE/f ¡ and the

tensile forces under design loads reach the 80% of full plastic resistance of

the corresponding sections in at least 50% of diagonals.

-184-

Ductility level II characterizes others tension diagonal bracings for which

only the connections in dissipative zones have a strength greater than

1.00-1.20 tines the one corresponding the gross area of the connected members

and diagonal bracings have a slenderness lesser than X e - v V being Åe = TTVE/fy .

Ductility level I characterizes tension and compression diagonal bracings for

which the connections in dissipative zones have a strength greater than

1.00-1.20 times the one corresponding the gross area of the connected members

and diagonal bracings have a slenderness lesser than \ e=V2 being

Bracings in which the connections in dissipative zones don't have a

strength greater than 1.00-1.20 times the one corresponding the gross area of

the connected members, and diagonal bracings have a slenderness greater than

\ e-V2 being X0 = TTVE/f must be designed without taking into account

dissipative zones.

Eccentric bracings

Ductility level III characterizes eccentric bracings in which the connections

in dissipative zones have a strength greater than 1.00-1.20 times the one

corresponding the gross area of the connected members, diagonal bracings have

a slenderness lesser than A e=V2 , being XB = nVE/l and the design loads

reach at least the 50% of the members designed for bending and shear reach the

80% of their ultimate plastic capacity.

Ductility level II characterizes eccentric bracings for which only the

connections in dissipative zones have a strength greater than 1.00-1.20 times

185 -

the one corresponding the gross area of the connected members and

diagonal bracings have a slenderness lesser than X e=V2 being À 8 = TTVE/| .

Eccentric bracings in which the connections in dissipative zones don't have

a strength greater than 1.00-1.20 times the one corresponding the gross area

of the connected members, and diagonal bracings have a slenderness greater

than X e-V2 being Ae = nVE/f must be designed without taking into account

dissipative zones.

- Braced frames

Braced frames are compound systems in which both frames and truss bracings

are considered acting together at the same row.

Ductility level III characterizes braced frames having frame and truss bracing

both of ductility level III. In adi tion the frame must be designed to sustain

alone at least 50% of the total design load.

Ductility level II characterizes braced frames having frames and truss bracing

both of ductility level II.

For each structural type and ductility level the Eurocode No 8 suggests the

following values to the behaviour factor q.

186

Table IV

Ductility level

III

II

I

elastic model dissipative

without zones

Structural type

braced and unbraced frames, eccentric

bracings

truss bracings

braced and unbraced frames, eccentric

bracings

truss bracings

braced and unbraced frames

truss bracings

all types

Behaviour factor q

6.00

5.00

4.00

3.00

2.00

1.00

These values are valid only for structurally regular buildings. For structurally non regular buildings provision shall be taken by dividing the q factors by 1.20.

Other structural types are allowed provided that q factors are worked out by analysis.

187

Based on the research presented in 4.3 on the q factor values for one floor

cantilevers, it is possible to conclude that the value suggested in Eurocode No

8 for this structural type is conservative. In fact, for columns which are

deflected in the plane of the maximum stiffness a value of 2.5 for the behaviour

factor q seems adequate, while the Eurocode No 8 suggests 1.0 disregarding the

ressource of stiffness of this structural type. If the deflection occurs in the

plane of the minimum stiffness a greater value of the q factor can be utilized,

but in this case a greater ductility demand will be necessary. However, a

behaviour factor q = 2.5 for one floor cantilevers seems suitable.

Nevertheless, insufficient data are available to analyse the truthfulness of

the other structural types. It will be necessary in future realize experimental

tests and develop numerical programs in order to study in a meaninful way the

behaviour factors q to adopt in a reliable and economic design of steel

structures. The work carried on the cantilevers may be considered as an example

of such activity. At present, some work is in course to assess the behaviour

factors of steel braced frames.

188-

4.5 - REFERENCES

|1| CEB - MODEL CODE FOR SEISMIC DESIGN OF CONCRETE STRUCTURES- CEB Bulletin

of Information No. 160 - 1984.

|2| COMISION FEDERAL DE ELECTRICIDAD (1981) MANUAL DE DISEÑO DE OBRAS

CIVILES, ESTRUTURAS, CRITERIO DE DISENO. Cl.3 Diseno por Sismo.

131 TENTATIVE PROVISIONS FOR THE DEVELOPMENT OF SEISMIC REGULATIONS FOR

BUILDINGS. ATC Publication ATC 3-06 Applied Technology Council, June,

1978.

|4| EUROCODE n.8 - COMMON UNIFIED RULES FOR STRUCTURES IN SEISMIC ZONES - EUR

8850.

|5| Setti, P. (1984) UN METODO PER LA DETERMINAZZIONE DEL COEFFICIENTE DI

STRUTTURA PER COSTRUZIONI METTALICHE IN ZONA SISMICA. Costruzioni

Mettaliche n.4.

|6| Vanmarche, E. and Gasparini, D. (1976) SIMQKE - SIMULATED EARTHQUAKE

MOTIONS COMPATIBLE WITH PRESCRIBED RESPONSE SPECTRA. MIT Report R76-4.

|7| Perotti, F., Rampazzo, L. and Setti, P. (1984) DETERMINAZIONE DEL

COEFFICIENTE DI STRUTTURA PER COSTRUZIONI METTALICHE SOGGETTE A CARICHI

ASSIALI. 2 Convegno Italiano d'Ingegneria Sismica - Rapallo, 6-9 Giugno.