Seismic response of pile groups supporting long-span cable-stayed bridge subjected to multi-support excitations

Abstract

Long-span cable-stayed bridge is one of the main structures for highways and railways crossing wide rivers. Seismic response of an integral 1:70 scaled model for a long-span cable-stayed bridge was studied with multifunctional shake tables. The bridge model includes synthetic soil, pile groups and long span cable-stayed bridge structure. Seismic responses of pile groups supporting bridge structural systems of different stiffness, namely the floating system, the elastically constrained system and the supporting pier system are studied considering the seismic soil-pile-structure interaction (SSPSI). The accelerations, bending moments and displacements of piles supporting pylons, auxiliary piers and transition piers are discussed. The wave passage effect on pile foundation supporting long-span cable-stayed bridge is studied by tests for the first time. Results showed that compared with the floating system and the elastically constrained system, the bridge girder of long natural period has larger impact on pile foundations in the supporting pier system under uniform excitations. When subjected to non-uniform excitations, different seismic load generates from the superstructure and acts on the substructure. As a result, seismic response of pile foundation supporting long span bridge under non-uniform excitations is different from that under uniform excitations. The wave passage effect has little influence on seismic response of piles in the floating system and the elastically constrained system. However, in the supporting pier system, with shear wave velocity decreased from infinity to 1000m/s, the Fourier amplitudes of pile accelerations, bending moments and relative displacements at 3.50Hz decreased dramatically. The peak bending moments at the head of piles supporting auxiliary piles decreased about 50%.