MODIFIED – MSRS ANALYSIS OF AYALA BRIDGE DUE TO SPATIAL VARIATION OF GROUND MOTION (SVGM)

Abstract

Extended structures, such as bridges, experience variations in ground motion, which cause multiple excitations in the supports. Spatial variation in ground motion is primarily influenced by factors such as incoherence, wave passage effects, and local site conditions. Philippine Highway Bridges are designed using the DPWH–BSDS 2013, in which the seismic excitations are uniform across bridge supports, neglecting the spatial variability of motion. In this research, the concern for the difference in ground motion experience between supports was addressed, considering a Multiple Support Excitation for the Ayala Bridge. The dynamic analysis was performed in ANSYS, which allows varying ground motion conditions. For the Uniform Support Excitation, the DPWH–BSDS 2013 was used for generating the Response Spectrum and used Single–Point Response Spectrum analysis. On the other hand, a Multi–Point Response Spectrum analysis was used to account for the effects of MSE through a modified response spectrum generated in MATLAB, which accounts for SVGM. A significant impact on the bridge’s seismic performance was observed, as indicated by the p-values related to displacement and shear responses of 0.0012 to 0.0037 and 0.0000 to 0.0268, respectively, across all piers; and in moment response with 0.0012 to 0.0237 for piers 2 to 6. The seismic performance of the bridge is significantly affected by the type of excitation experienced by the bridge supports. Therefore, considering MSE when designing highway bridges is necessary because it can affect the overall bridge performance.