Dynamic Model Testing of Low-Gravity-Center Cable-Stayed Bridges with Different Girder-to-Tower Connections

Abstract

To investigate the seismic response characteristics of low-gravity-center cable-stayed bridges with twin towers, a simplified mechanics model was established based on the transmission path of the horizontal seismic inertial forces of the girder under earthquake excitation. The definition of a low-gravity-center cable-stayed bridge with twin towers was proposed. Two 1:75 scale models, a floating system (FS) cable-stayed bridge and a fixed-hinge system (HS) cable-stayed bridge, were fabricated, and shaking table tests were conducted. The results of these tests showed: (1) horizontal cracks appeared at the bottom and middle areas of the main tower in the Test Model FS, whereas diagonal cracks together with concrete spalling formed at the bottom area of the main tower and the bottom crossbeam in the Test Model HS; (2) the Test Model FS experienced a larger displacement response but a smaller acceleration response compared to the Test Model HS; and (3) the reinforcement strain response at the bottom of the main tower of the Test Model HS is smaller than those of the Test Model FS, which is in good agreement with the theoretical analysis of the low-gravity-center cable-stayed bridges. In general, the fixed-hinge system cable-stayed bridge can reduce the overall structural damage under strong earthquakes and is therefore suggested to be used in low-gravity-center cable-stayed bridges. The research results help to understand the failure characteristics of the cable-stayed bridges and to provide a reference for the seismic design of low-gravity-center cable-stayed bridges in practical engineering applications.