Integrated Analysis Model for the Seismic Responses of Cable-Stayed Bridges Near Active Faults

Abstract

To study the special behaviors of seismic responses regarding a cable-stayed bridge under an active fault earthquake, a novel numerical algorithm named Structure-Medium-Fault (SMF) Integrated Model, in which the interaction of the three parts can be considered, is proposed. The mechanical simplification of causative faults' rupture, numerical simulation of stress wave propagation and the artificial boundary conditions (ABC) for the infinite body laid the groundwork of this model. Initially, the mechanical model for the structures and earth medium was established. Afterwards, the equivalent initial stresses of causative seismic sources can be calculated according to the monitored data of active faults. Thirdly, the function of the equivalent initial stress of seismic source time was derived by the second derivation of Brune source function. Finally, the viscoelastic boundary was chosen for the model as ABC. A cable-stayed bridge (600 m main span) above the causative fault was analyzed using the novel model. Consequently, vertical effect, velocity pulse effect and directivity effect were all confirmed by the analytical results. The model can reflect the mutual influences of near-fault structures, medium and causative faults. The seismic responses of the bridge under a near-fault earthquake can thus be obtained.