TOPOGRAPHY AND SOIL-STRUCTER INTERACTION EFFECTS ON THE SEISMIC RESPONSE OF THREE-DIMENSIONAL CANYON-CROSSING BRIDGE

When evaluating the seismic performance of a bridge across the canyon, it is necessary to consider the influence of topography effects, traveling wave effects, and soil-structure interaction effects. In this paper, the response analysis of the canyon-bridge system under the input of seismic waves is regarded as a wave scattering problem, which is the disturbance of the "free field" of the canyon site by the bridge and its adjacent irregular areas. Based on this idea, a method for seismic response analysis of canyon-crossing bridges is developed and the code is programmed. The "free field" of the canyon site is obtained as input through two-dimensional FEM, and canyon-bridge system is analyzed through partitioned method of soil-structure interaction. This method can consider the non-vertically incident seismic waves in the free field analysis to include the traveling wave effect. Therefore, the traveling wave effect, topography effect and soil-structure interaction effect can be considered together. Firstly, the method for the free field and the artificial boundary implementation are verified through a canyon site analysis. Then, by comparing the results of five calculation models,seismic response of the Mashuihe Bridge is analyzed using the proposed method, and the influence of the topography effect and the soil-structure interaction effect on the response of the bridge across the canyon is analyzed. The topography effect has obvious influence on the shear force, bending moment and axial force at the bottom of the pier, but it has less effect on displacement than shear and bending moment. The soil-structure interaction has a great influence on the bridge response, which greatly reduces the bridge response.