Seismic Analysis and Design of a Concrete Arch Bridge

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Seismic Analysis and Design of a Concrete Arch Bridge Direct Displacement-based Design Approach to Seismic Isolation

Author: Trausti Hannesson | Size: 7.3 MB | Format: PDF | Quality: Unspecified | Publisher: Technical University of Denmark Bjarni Bessason, University of Iceland | Year: APRIL 2010 | pages: 119

In this thesis the response of a concrete arch bridge to seismic loads corresponding to the South Iceland Seismic Zone (SISZ) is calculated. The analyzed 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 reported in earthquakes in that area.
The main objective of this thesis is to evaluate the e ect of changing the bridge location and come up with a suitable design alternative. Linear response spectrum analysis is performed with the general purpose FE-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 isolation system using lead rubber bearings. Linear response spectrum analysis is performed using equivalent linear sti ness and damping to model the nonlinear behavior of the base isolation. The nonlinear behavior of the isolation system was then further investigated with nonlinear time history analysisVusing arti cial ground motions.
The study shows that by introducing lead rubber bearings as the only change to the original design the response to seismic loads can be signi cantly improved.
The direct displacement-based design approach to the design of
seismically isolated structures proved to be simple and to o er control of the total structural response. Simple hand calculations were veri ed by
linear response spectrum analysis but considerable di erence was observed
between the linear and nonlinear methods in terms of expected displacement
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 design,
seismic isolation, lead rubber bearings

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