Loss estimation of curved bridges considering the incidence angle and spatial variability of earthquake ground motion

The consideration for the angle of seismic incidence (ASI) is critical for the seismic design of curved bridges. Previous studies indicate that the effect of ASI weakens as the damage develops throughout the structure. Since curved bridges often extend over long distances and cross varied geological conditions, the spatial variability of earthquake ground motions (SVEGMs) may significantly affect their responses. However, the concurrent effects of ASI and SVEGM on the system performance of curved bridges have yet to be explored, and there are currently few reliable methodologies for conducting relevant research. To this end, this study takes the monetary repair costs as the metric for representing the entire performance of the bridge, and the impact of ASI on the total loss of long multi-span curved bridges considering the spatially variable nature of earthquake ground motions is investigated in a probabilistic manner. A multi-directional loss assessment approach is derived based on the extension of an existing loss methodology, and an already constructed, 638-m-long, twelve-span prestressed concrete curved bridge is selected as the test-bed. Twenty non-stationary and spectrum-compatible spatially variable earthquake ground motion (SVEGM) pairs are generated based on the Eurocode 8 (EC8) design spectrum and soil conditions of the bridge site for each ASI. Three seismic input motion scenarios are assumed according to the characteristics of SVEGMs, and variabilities of bridge loss with respect to the ASI under the scenario earthquakes are investigated for each excitation case. On these bases, the original ground motion records are amplified by 2 and 4 times, respectively, and 4320 (3 earthquake intensity levels x 3 excitation scenarios x 24 ASIs x 20 ground motion pairs) nonlinear response-history analyses (NRHAs) are implemented to identify the influence induced by the ground motion intensity on the loss variability. Results indicate that the impacts of ASI and SVEGMs weaken as the ground shaking intensity increases and the damage accumulates in the structure.