Transverse Seismic Behavior Studies of a Medium Span Cable-Stayed Bridge Model with Two Concrete Towers

Due to lack of investigation on nonlinear seismic behavior of cable-stayed bridges under strong earthquake excitation, the concrete towers, as the main gravity-carrying component, are usually required to remain nearly elastic. However, in order to achieve this high seismic performance objective, the reinforcement ratio of the tower legs and the tower struts need to be greatly increased in addition to its static loading requirement. To study the potential plastic region and possible failure mode of the cable-stayed bridge, a 1/20-scale full bridge model from a typical medium span concrete cable-stayed bridge was designed, constructed and tested on 4 linear shake tables using a site specific artificial wave in the transverse direction. Test results showed that the damage characteristics of the bridge model were as follows: (1) the severe damage was observed at the upper strut, with several steel bars fractured at both ends; (2) the repairable damage was observed at tower legs at the bottom and the middle part, with concrete cover spalling and exposure of steel bars; (3) the minimal damage was observed at the lower strut and the both sides of the side bents, with only slightly concrete spalling; and (4) no damage was observed at the auxiliary bents, the superstructure and the cables. Numerical results and test results were further compared and showed good agreement in low amplitudes of excitations. The test also proved that the bridge system was stable in flexural failure of upper struts, and had the negligible residual displacement subjected to high amplitudes of excitations.