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地形和土-结相互作用效应对三维跨峡谷 桥梁地震响应的影响分析

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

  • 摘要: 评估跨峡谷桥梁的地震性态需要考虑地形效应、行波效应以及土-结相互作用效应.将峡谷-桥梁系统在地震波输入下的反应分析看作波动散射问题,即桥梁及其邻近非规则区域对峡谷场地"自由场"的扰动. 基于此思想,本文发展了一套跨峡谷桥梁地震反应分析方法,通过二维模型分析得到峡谷场地的"自由场", 结合人工边界输入到峡谷-桥梁体系,采用土-结相互作用分区并行方法对其进行分析, 并编制了相应的分析程序.该方法可在自由场分析时考虑非垂直入射地震波, 计入行波效应,因此可综合考虑行波效应、地形效应和土-结相互作用效应. 通过峡谷场地分析算例,验证了自由场和人工边界实施的正确性; 并以马水河大桥为对象,通过5种计算模型结果的比较,分析了地形效应和土-结相互作用效应对跨峡谷桥梁地震反应的影响, 算例结果表明,地形效应对墩底剪力、弯矩和轴力有明显影响,对位移的影响要比对剪力、弯矩的影响小; 土-结相互作用对桥梁反应的影响较大,较大地减小了桥梁反应.

     

    Abstract: 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.

     

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