IMPACT OF SPATIAL VARIABILITY OF EARTHQUAKE GROUND MOTION ON SEISMIC RESPONSE OF A RAILWAY BRIDGE

This paper studies the impact of spatially varying ground motions on the responses of a railway bridge. The evaluation of the seismic hazard for a given site is to estimate the seismic ground motion at the sur- face. This is the result of the combination of the action of the seismic source, which generates seismic waves, the propagation of these waves between the source and the site, and the local conditions of the site. Firstly, the seismic ground motions are modelled by assuming the base rock motions of the same intensity and modelling them with a filtered Tajimi-Kanai power spectral density function and a spatial ground motion coherency loss function. Then, the power spectral density function of ground motion on surface is derived by considering the site amplification effect based on the one-dimensional seismic wave propagation theory. A comparison between the bridge responses to uniform ground motion, to spatial ground motions with and without considering local site effects is established. Discussions on the seismic ground motion spatial variability and local site conditions effects on structural responses of railway bridge are made.