Seismic Analysis and Design of a Concrete Arch Bridge

119 Pages·2010·7.29 MB·English

by  Trausti Hannesson

Trausti Hannesson
Seismic Analysis and Design of a
Concrete Arch Bridge
Direct Displacement-based Design Approach to
Seismic Isolation
Master’s Thesis, April 2010

Trausti Hannesson
Seismic Analysis and Design of a
Concrete Arch Bridge
Direct Displacement-based Design Approach to
Seismic Isolation
Master’s Thesis, April 2010

Seismic Analysis and Design of a Concrete Arch Bridge, Direct Displacement-based
Design Approach to Seismic Isolation
This report was prepared by
Trausti Hannesson
Supervisors
Christos Georgakis, Technical University of Denmark
Bjarni Bessason, University of Iceland
Department of Civil Engineering
Technical University of Denmark
Brovej building 118
DK-2800 Kgs. Lyngby
Denmark
www.byg.dtu.dk
Tel: [phone]
E-mail: [email protected]
Release date: April 2010
Category: 1 (public)
Edition: First
Comments: ThisreportispartoftherequirementstoachievetheMasterof
ScienceinEngineering(M.Sc.Eng.) attheTechnicalUniversity
of Denmark. This report represents 30 ECTS points.
Rights: ©Trausti Hannesson, 2010

Preface
The work presented here is part of the requirements to achieve the Master
of Science in Engineering (M.Sc.Eng.) at the Department of Civil Engi-
neering at the Technical University of Denmark. This report represents 30
ECTS points. The work was performed at the Faculty of Engineering at the
University of Iceland.
I am grateful to my supervisor professor Bjarni Bessason at the University
of Iceland for his guidance, ideas and encouragement during my thesis work.
IwouldalsoliketothankprofessorChristosGeorgakisattheTechnicalUni-
versity of Denmark for his comments and for giving me the opportunity to
do my studies in Iceland. Finally I would like to thank Helgi Valdimarsson,
Managing Director at Almenna Consulting Engineers for providing me with
a working space during my thesis work.
Akureyri, April 2010
Trausti Hannesson [s080012]

Abstract
In this thesis the response of a concrete arch bridge to seismic loads corre-
sponding to the South Iceland Seismic Zone (SISZ) is calculated. The an-
alyzed bridge was originally designed for non-seismic load conditions. The
South Iceland Seismic Zone is an active seismic zone and several times since
the settlement of Iceland structures have collapsed and casualties been re-
ported in earthquakes in that area.
The main objective of this thesis is to evaluate the effect of changing the
bridge location and come up with a suitable design alternative. Linear re-
sponsespectrumanalysisisperformedwiththegeneralpurposeFE-program
SAP2000 from which it is clear that the bridge is in need of redesign to
withstand the seismic loads occurring in the South Iceland Seismic Zone.
A direct displacement-based design approach is employed to design an isola-
tion system using lead rubber bearings. Linear response spectrum analysis
isperformedusingequivalentlinearstiffnessanddampingtomodelthenon-
linear behavior of the base isolation. The nonlinear behavior of the isolation
system was then further investigated with nonlinear time history analysis
using artificial ground motions.
Thestudyshowsthatbyintroducingleadrubberbearingsastheonlychange
to the original design the response to seismic loads can be significantly im-
proved. The direct displacement-based design approach to the design of
seismically isolated structures proved to be simple and to offer control of
the total structural response. Simple hand calculations were verified by
linear response spectrum analysis but considerable difference was observed
betweenthelinearandnonlinearmethodsintermsofexpecteddisplacement
of the bridge deck and hence section forces. Results from response spectrum
analysis were in all cases conservative.
Keywords: seismic engineering, bridge engineering, direct displacement-based de-
sign, seismic isolation, lead rubber bearings