VERTICAL EARTHQUAKE RESPONSE ANALYSIS OF GIRDER BRIDGES CONSIDERING INFLUENCE OF PIERS AND SUPPORTS

The piers and supports are simplified as a vertical series spring system and the vertical dynamic analysis model of the girder bridge considering effects of axial deformation of piers and supports is established. Considering the boundary conditions, the differential quadrature method (DQM) is applied to discretize the continuous model of the bridge to a MDOF (multi-degree-of-system) system in spatial domain. Then the responses of the MDOF system are calculated by step-by-step integration method. In addition, effects of discrete point number of spatial domain and axial deformation of piers and supports to vertical dynamic responses of bridge are studied, and the effect of stiffness of piers and supports to bridge seismic response is analyzed due to different external excitations. The research found the effects of discrete point number of spatial domain to calculation convergence and results are very small without considering the influence of piers and supports, but the effects of discrete point number of spatial domain have an enormous influence on calculation convergence with considering the effect of piers and supports. For different external exactions, the effects of piers and supports to dynamic response of bridge are different and the effects depend on the spectrum characteristic of earthquake-induced ground motion.