ANALYSIS ON VEHICLE-BRIDGE-COUPLING VIBRATION OF A NEW TYPE OF CABLE-GRIDER EMERGENCY BRIDGES

In view of light weight and small stiffness of the new type of cable-grider emergency bridges, vehicle-bridge coupling vibration is worth studying. The vibration differential equations of the vehicle-bridge system were established by the dynamic equilibrium theory and finite element method, and the Newmark-β method was used to solve the differential equations. Analysis programs of vehicle-bridge coupling vibration programming by APDL language in ANSYS, to analyse the dynamic responses of bridges in different connection types of main girders, vehicle speeds, vehicle masses, road surface grades and damping ratios of the bridge. The results indicated that connection types of main girders had a significant impact on vibration responses of bridges, especially on vertical vibration displacement and axial stress of suspenders. With the vehicle velocity increase, although the peak reponses of different location in grider spans were of different trends, the mean responses of vibration increased fundamentally. The dynamic responses of bridges kept close relationships with road surface grade of of bridges, especially with vertical vibration acceleration. With the vehicle-weight increase,the dynamic responses increased linearly. The dynamic responses decreased with the increase of damping ratios of bridges, but the amplitudes changed slightly. The analysis revealed that the vehicle weight could not exceed 30 tons and the vehicle speed coult not exceed 30 km/h. The scheme of emergency bridges needed further improvement if the safeguard capacity needed to be increase.