Experimental studies on seismic response characteristics of dynamic interaction system of pile-soil-cable-stayed bridges

The seismic response of long-span cable-stayed bridges with lower structural frequencies and damping may be significantly affected by the properties of the pile foundation and site soil. However, few experimental studies on the full model for long-span cable-stayed bridges including the pile foundation, site soil and superstructure are available because of the limitations of shaking table testing facilities and technology. A 1/70-scaled full model for a cable-stayed bridge, which includes the pile groups, artificial site soil and superstructure, is designed and constructed according to the trial designed long-span cable-stayed bridge with the main span of 1400 m. The shaking table tests on the full model are conducted to study the seismic response characteristics of the dynamic interaction system of the pile-soil-cable-stayed bridge under uniform earthquake excitations with various frequency components and shaking intensities in the separately longitudinal and transverse directions. The experimental results show that: (1) The pile-soil-structure interaction effects significantly affect the seismic response of the full model for the cable-stayed bridge, but the degree of the influence is closely related to the spectral characteristics of various earthquake waves. (2) The influences of the peak acceleration of the ground motions on the pile-soil-structure interaction effects are not significant when the full model is subjected to the uniform earthquake excitations in the longitudinal direction. However, the pile-soil-structure interaction effects gradually decrease as the peak acceleration of the ground motion increases under transverse uniform earthquake excitations. (3) The higher order mode shapes of the tower make a significant contribution to its seismic response. (4) The seismic response of the dynamic interaction system of the pile-soil-cable-stayed bridge is obviously affected by the spectral characteristics of various earthquake waves. Especially, the vertical seismic response of the girder notably increases when it is subjected to the Mexico City waves with long period components.