Name: Pedram Tabatabaei Araghi Personal Number: 19910702-0472 Supervisor: Anders Ansell, Richard Malm KTH email: Pedramta@KTH.se

Seismic design of concrete buildings according to EC8

Introduction

Designing structures with respect to dynamic vibrations is getting more and more usual for all kinds

of structures. Dynamic vibrations can have many sources, such as:

Vibration caused by drilling and blasting; e.g. vibrations related to rock-reinforcement

influencing other structures nearby the vibration area, during tunneling.

Traffic induced vibrations; e.g. vibrations due to high-speed trains.

Flow induced vibrations; e.g. vibrations in foot-bridges and buildings.

Seismic vibrations; in Sweden, nuclear power plants and some other buildings, such as

Turning Torso in Malmö, are designed with respect to earthquake induced vibrations [1].

Knowledge within designing structures with respect to earthquake induced vibrations is relatively

limited in Sweden, compared internationally. The most recent alarming earthquake in Sweden

happened 16th of December 2008 in Skåne with a magnitude of 4,9 in the Richter-scale. Also in year

1902 Sweden experienced an earthquake of magnitude 6,0 in the Richter-scale, in Oslofjorden [2].

Sweden’s focus on earthquake resistance for some structures such as nuclear power plants has

increased significantly since the beginning of the 21st century. 34 countries started to participate in a

project led by the European Commission to prepare the nuclear power plants for any extreme

circumstances and events such as earthquakes. In early days Sweden didn’t have any specific

requirements regarding earthquake on designing power plants. The new earthquake-specific

regulations that were addressed during 2005 placed demands on the operators to ensure that their

nuclear power plants meet the requirements [3].

As mentioned earlier, some buildings, such as Turning Torso in Malmö, are designed to meet the

requirements of specific earthquake resistance. Turning Torso is designed to withstand a quake of

magnitude 7 in the Richter-scale [1].

For other structures that are designed to meet the earthquake resistance requirements in Sweden,

we can mention the Öresund bridge, that is designed to withstand a quake with a magnitude of 5.7 in

the Richter-scale [4].

Some researches have been conducted to see if earthquake could be a hazard for Swedish dams. One

of these studies was made by Anders Bodare and Ota Kulhanek. Their conclusion was that there is no

hazard against dams in south-western Sweden, but hazard for dams in middle and north of Sweden is

small. In the case were dams are founded on soil, they stated that it needed more detailed

investigations [5].

Eurocode 8 is dedicated for designing according to earthquake resistance. The purpose of this Msc

project is to analyze the application of Eurocode 8 on a three-story concrete structure.

Name: Pedram Tabatabaei Araghi Personal Number: 19910702-0472 Supervisor: Anders Ansell, Richard Malm KTH email: Pedramta@KTH.se

SMART-project

SMART-project stands for Seismic design and best estimate Methods Assessment for Reinforced

concrete buildings subjected to Torsion and non-linear effects.

SMART, 2008

The SMART-project is a project that was started in the year 2007. It was supported by Commissariat à

l’Energie Atomique et aux Energies Alternatives (CEA) and Electricité de France (EDF). This project’s

objectives were to evaluate:

Conventional design methods for structural dynamic response

Compare best-estimated methods for structural dynamic response

The results were presented in July 2008 [6].

SMART, 2013

A new SMART-project was started in the year 2011, named SMART 2013-project. The purpose of this

project was to improve the knowledge of seismic behavior of such reinforced concrete structure as

was modeled. The main differences with respect to the original SMART-project are related to the

seismic loading. These differences are:

The input signals are real ones and not synthetic ones.

High intensity seismic loadings are applied

The effect of an aftershock is considered

The project is estimated to be presented in November 2014 [6].

The three story structure that was used in SMART-project, will be analyzed in this Msc project to

clarify the applications of Eurocode8 and detailed analysis of ductile design.

The data from the laboratory tests that has been done during SMART-project will be used for more

detailing analysis on the design applications according to Eurocode 8.

Name: Pedram Tabatabaei Araghi Personal Number: 19910702-0472 Supervisor: Anders Ansell, Richard Malm KTH email: Pedramta@KTH.se

Method of analysis

This MSc project is going to be performed in collaboration with a structural company named KE-

gruppen. This company was established in 1986 and has finished several structural projects in

Sweden and internationally as well, for instance Täby Centrum.

In this MSc project, the areas of interest that were chosen by the Division of Concrete Structures and

KE-gruppen, will be studied. In this study, Eurocodes that are related to the interest areas will be

applied on a three story concrete structure. The possible topics for analysis are:

Conceptual Design

Ductile Design

Reinforcement Design

Structural Analysis

Conceptual Design:

In seismic regions, on the early stages of a building, the seismic hazard shall be taken into account in

the conceptual design. This will enable the achievement of a structure system, which satisfies the

fundamental requirements of “no-collapse” and “damage limitation” in earthquake design.

According to Eurocode 8 conceptual design is considered in six different principles:

Structural Simplicity

Uniformity, symmetry and redundancy

Bi-directional resistance and stiffness

Torsional resistance and stiffness

Diaphragmatic behavior at story level

Adequate foundation

Ductile Design

The term “ductility” in earthquake design explains the ability of the structure to undergo large cyclic

amplitudes of deformations in the inelastic range without a substantial reduction in strength.

Structures that are designed to be ductile are able to dissipate significant amounts of energy caused

by cyclic deformations [7].

In Eurocode 8, concrete buildings have two different levels of ductility. They are presented as high

(DCH) and medium (DCM) ductility classes.

Name: Pedram Tabatabaei Araghi Personal Number: 19910702-0472 Supervisor: Anders Ansell, Richard Malm KTH email: Pedramta@KTH.se

Reinforcement Design

Reinforced concrete frames are used as part of a seismic force-resisting system in buildings that are

designed to resist earthquake actions. Reinforced concrete beams, columns and the joints between

these two, must be designed in such a way that they can resist flexural, axial and shearing actions

caused by earthquake ground motion[8].

Structural Analysis

Structural analysis is made to determine the effects of loads on a structure and its components. The

type of analysis, depends on the type of the structure.

According to Eurocode 8, structural analysis is presented in:

Modelling

Accidental torsional effects

Methods of analysis

Displacement calculations

None-structural elements

Additional measures for masonry infilled frames

This MSc project’s interest falls into the first four topics; modeling, accidental torsional effects,

methods of analysis and displacement calculations.

Name: Pedram Tabatabaei Araghi Personal Number: 19910702-0472 Supervisor: Anders Ansell, Richard Malm KTH email: Pedramta@KTH.se

Aim

To be able to analyze Eurocode 8 applications, we need to apply it on an actual model of a structure.

The structure that will be analyzed in this thesis is a structure that was modeled in the SMART

project.

This structure is a reduced scaled model (1/4th scale) representative of a typical, simplified half part

of an electrical nuclear building [6]. It is considered a multi-story structure and is shown in figure1

below:

Figure1, Simplified, half part of an electrical nuclear building, in 1/4 scale.

This MSc project is going to treat the application of Eurocode 8 on designing and modeling concrete

buildings with respect to earthquake actions. One of the main purposes of this project is to clarify the

practical procedure for modeling and analyzing concrete structures considering earthquakes. This

purpose will be accomplished by literature studies on topics that were discussed earlier. Another

purpose is to investigate and analyze ductile design more detailed.

The same structure as in the SMART-project, but in full scale, is to be analyzed to accomplish the

aims of this MSc project.

Name: Pedram Tabatabaei Araghi Personal Number: 19910702-0472 Supervisor: Anders Ansell, Richard Malm KTH email: Pedramta@KTH.se

References

[1] Varnar för fler skalv. 2008 dec 17 [cited 2013 Nov 10]; Available from:

http://www.expressen.se/kvp/varnar-for-fler-skalv/

[2] De största svenska jorbävningarna. 2009 Apr 01 [cited 2013 Nov 10]; Available from:

http://fof.se/tidning/2009/3/de-storsta-svenska-jordbavningarna

[3] Swedish focus on earthquake protection. 2011 Nov 04 [cited 2013 Nov 11]; Available from:

http://www.world-nuclear-news.org/RS_Swedish_focus_on_earthquake_protection_0411111.html

[4] Öresundsbron påverkades inte av jordskalvet. 2008 Dec 16 [cited 2013 Nov 11]; Available from:

http://www.byggvarlden.se/nyheter/byggprojekt/article87778.ece

[5] Anders B, Ota K. Dam Safety – Earthquake hazard for dams in Sweden. Stockholm (STO): Elforsk

(SWE); 2006 Nov. 22 p. Report No.:06:72

[6] SMART 2013. [cited 2013 Nov 12]; Available from: http://smart2013.eu/

[7] R. Park. Evaluation of ductility of structures and structural assemblages from laboratory testing.

(NZ): Bulletin of the New Zealand national society for earthquake engineering (NZ); 1989 Sep. 155 p.

Vol. 22, No.:3

[8] Jack P. M, John D. H, Chris D. L. Seismic Design of Reinforced Concrete Special Moment Frames: A

Guid for Practicing Engineers. (US): National Institute of Standards and Technology (US); 2008 Aug.

01 p. Seismic Design Technical Brief No.:1.

Figures

Figure1. Thierry C, Sandrine L. SMART program presentation. Saclay (SAC): CEA/EMSI Laboratory(FR);

2008 Jul 01-02 [cited 2013 Nov 13]. 01 p.