Study On Vibrational Control Of Longitudinal Freely Supported Bridge Based On Cable Restrainer And FPB

With the rapid development of China’s social economy in recent years, long-span bridges have been quickly constructed. Longitudinal freely supported bridge is a kind of common structure style in long-span bridge design. This kind of bridge is non-restraint in longitudinal direction and it allows the oscillation of the girder which can achieves the dissipation of vibrational energy. However, excessive longitudinal displacement induced by seismic loadings and vehicle braking force, affects the normal use of the bridge, even leads to girder falling. Therefore, it is necessary to be controlled by taking appropriate measures. Taking the Pingsheng Bridge as an engineering example, study on control of vibrational (seismic) response mitigation under vehicle braking forces and seismic loadings has been investigated, based on cable restrainer and friction pendulum bearings (FPB). The main contents are as follows:(1) Spatial finite element model for Pingsheng Bridge is established using finite element software MIDAS. Dynamic analysis results indicate that the natural frequency of the structure system of longitudinal freely supported bridge is0.0643Hz. Cable restrainer and FPB can effectively improve the longitudinal stiffness of the bridge.(2) Vibrational mitigation under vehicle braking forces is analyzed by time history analysis method, based on MIDAS software. The results verify the cable restrainer is significantly effective for mitigating the girder displacement under vehicle braking force, and also it can adapt for two kinds of service-stage conditions (temperature and main-span covered) well.(3)FPB parameters are optimized using the orthogonal test method, then the control with the optimal parameter for seismic response mitigation is analyzed. The results show that the longitudinal displacement of the girder reduce by26.75%,19.27%,36.46%subjected to the seismic loadings including the Pingsheng wave, the El-Centro wave, the Taft wave respectively. (4) Seismic response mitigation with cable restrainer and FPB is analyzed using software ANSYS, and the results indicate that the control effect of the girder displacement mainly come from the FPB and the cable restrainer used for reducing the girder displacement under vehicle braking force will be snapped subjected to seismic loadings.