Significance of SSI and nonuniform near-fault ground motions in bridge response I: Effect on response with conventional expansion joint

This paper studies the influence of spatially varying near-source ground motions and soil–structure interaction (SSI) on the relative response of two bridge frames. The spatial ground motions are simulated according to a near-fault ground motion model with different wave apparent velocity and a coherency loss function. Numerical calculations of bridge structure responses including pounding and SSI effect to a number of simulated spatially varying ground motions are carried out. The study reveals that the assumption of uniform ground excitation and fixed base in the analysis and design might not provide a realistic estimation of the pounding responses of bridge frames. The consequence of adjusting bridge fundamental frequency ratio towards unity to minimize relative response and consequently girder pounding potential as recommended by current design regulations is also evaluated.