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Effects of structural characterizations on fragility functions of bridges
subject to seismic shaking and lateral spreading

Jian Zhang, Yili Huo, Scott J. Brandenberg and Pirooz Kashighandi
Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA

Abstract: This paper evaluates the seismic vulnerability of different classes of typical bridges in California when
subjected to seismic shaking or liquefaction-induced lateral spreading. The detailed structural conigurations in terms of
superstructure type, connection, continuity at support and foundation type, etc. render different damage resistant capability.
Six classes of bridges are established based on their anticipated failure mechanisms under earthquake shaking. The numerical
models that are capable of simulating the complex soil-structure interaction effects, nonlinear behavior of columns and
connections are developed for each bridge class. The dynamic responses are obtained using nonlinear time history analyses
for a suite of 250 earthquake motions with increasing intensity. An equivalent static analysis procedure is also implemented to
evaluate the vulnerability of the bridges when subjected to liquefaction-induced lateral spreading. Fragility functions for each
bridge class are derived and compared for both seismic shaking (based on nonlinear dynamic analyses) and lateral spreading
(based on equivalent static analyses) for different performance states. The study inds that the fragility functions due to either
ground shaking or lateral spreading show signiicant correlation with the structural characterizations, but differences emerge
for ground shaking and lateral spreading conditions. Structural properties that will mostly affect the bridges¡¯ damage resistant
capacity are also identiied.

Keywords: fragility functions; bridge; seismic response; liquefaction; lateral spreading; structural characterization