Effects of Ground Motion Incident Angle on Inelastic Seismic Demands of Skewed Bridges Subjected to Mainshock–Aftershock Sequences

Several aftershocks can occur after a strong mainshock and lead to additional structural damage. The investigation of the seismic response of bridges is more challenging when the effects of incident angles of mainshocks and subsequent aftershocks are considered. This study investigates the effects of the ground motion incident angle on the nonlinear structural responses of skewed bridge structures against mainshock–aftershock sequences. For this objective, the seismic performance of a 60° skewed bridge located in San Fernando, California, is examined under real bidirectional mainshock–aftershock sequences. In this study, ground motion directionality effects were investigated considering the relative difference between mainshock and corresponding aftershock incident angles. The results showed that taking into account the incident angles of both mainshock and the corresponding aftershock can significantly affect the seismic performance of skew bridges. In particular, when the difference between the angles of the mainshock and corresponding aftershock was considered, the nonlinear responses of the case study increased up to 65.56%.