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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
-56
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.
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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.
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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.
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