UAV inspection-based aftershock fragility analysis of deteriorated PSC bridge structure considering mainshock-aftershock sequences

Past earthquake events show that aftershocks may arise within a short interval following a mainshock. Structural deformation caused by a mainshock can affect structural responses during an aftershock. Therefore, this study explores the aftershock fragility analysis of a bridge structure considering mainshock-aftershock sequential ground motions, and the result of sequential ground motion is compared with that of aftershock ground motion. In the numerical example, an in-service prestressed concrete (PSC) bridge that was constructed more than forty years ago is selected as the target structure. To consider structural deterioration of the bridge, a recently proposed approach based on unmanned aerial vehicle (UAV) damage detection is introduced. In the approach, the percent reduction in elastic modulus is computed in accordance with the selected damage states. To derive aftershock fragility curves, nonlinear time-history analyses are conducted using ten sets of mainshockaftershock sequential ground motions, and the analyses are also conducted using the single aftershock ground motions for comparison. The result shows that the failure probability of the target structure increased due to the mainshock effect.