Probabilistic seismic performance and loss assessment of a bridge-foundation-soil system

This paper presents the probabilistic seismic performance assessment of an actual bridge-foundation-soil system, the Fitzgerald Avenue twin bridges. A two-dimensional plane strain finite element model of the longitudinal direction of the bridge-foundation-soil system is modeled using advanced soil and structural constitutive models. Ground motions are selected based on the seismic hazard deaggregation at the site, which is dominated by both fault and distributed seismicity. Based on rigorous examination of several deterministic analyses, engineering demand parameters (EDP’s) are determined which capture the global and local demand and damage to the bridge and foundation, and multiple ground motions at various intensity le-vels are used to conduct seismic response analyses of the system. A probabilistic seismic loss assessment of the structure considering both direct repair and loss of functionality consequences was performed to holisti-cally assess the seismic risk of the system. It was found that the non-horizontal layering of the sedimentary soils has a pronounced effect on the seismic demand distribution to the bridge components, of which the north abutment piles and central pier are critical in the systems seismic performance. The consequences due to loss of functionality of the bridge during repair were significantly larger than the direct repair costs, with over a 2% in 50 year probability of the total loss exceeding twice the book-value of the structure