Effects of Near-Fault Motions and Artificial Pulse-Type Ground Motions on Super-Span Cable-Stayed Bridge Systems

This paper evaluates the seismic responses of a super-span cable-stayed bridge subjected to near-fault ground motions. A new method, record-decomposition incorporation (RDI), is proposed to synthesize the artificial near-fault pulse-type ground motions by combining the high-frequency background record (BGR) with simple equivalent pulses. The effects of forward-directivity pulses and fling-step pulses on the responses are assessed for the Sutong cable-stayed bridge (with a main span of 1,088 m) in China. The results show that the near-fault pulse-type ground motions generate larger displacement and internal force to the bridge compared with the nonpulse ground motions, and the fling-step ground motions are more damaging to the bridge than those of the forward-directivity ground motions. The high-frequency components of near-fault records have a significant effect on the responses of the bridge. Subsequently, the longitudinal displacement and bending moment of the tower induced by artificial ground motions with different pulse parameters (i.e., pulse period, velocity amplitude, and numbers of pulselike wave peaks) are analyzed. Last, the effects of artificial ground motions incorporating actual records originally exhibiting fling-step effects with a forward-directivity pulse model on the responses of the tower are assessed. The arrival time of the peak has notable effects on the responses of the tower.