Impact of Near-Fault Ground Motions on Longitudinal Seismic Response of CHRF Bridges

Abstract

Curved high-pier rigid frame bridges (CHRF bridges) are unavoidably affected by near-fault ground motions (NFGMs), and seismic pounding between adjacent components of CHRF bridge has a significant effect on the seismic performance of CHRF bridges. The seismic response and seismic pounding laws of CHRF bridges under NFGMs need further investigation. In this study, the influence of NFGMs with impulse and directional effects on the dynamic response of CHRF bridges was studied. Subsequently, the pounding responses between adjacent components of CHRF bridge were systematically analyzed. The results showed that the impulse and directional effects of NFGMs have a significant impact on the seismic response of CHRF bridges. The seismic response of CHRF bridges under near-fault impulse-like ground motions (IPGMs) is greater than that under near-fault non-pulse-like ground motions (NPGMs). CHRF bridges have the lowest seismic response under far-fault ground motions (FFGMs). The seismic response of CHRF bridges is significant under backward region ground motions (BRGMs) and the lowest under forward region ground motions (FRGMs). The IPGMs induce larger pounding force (PF) and a smaller number of poundings (PN) compared with FFGMs. The PF and the PN increase from the FRGMs to the BRGMs. Because of the pounding, the impulse and directional effects of NFGMs cause the shear force of the main pier and the auxiliary pier of CHRF bridges to increase significantly and the relative bending moment decreases. Moreover, the shear force and bending moment of the tie beam increases significantly owing to pounding.