基于ANSYS的大跨斜拉桥地震响应分析及性能评估

为研究西部高烈度地区大跨度斜拉桥的地震响应特点，以兰州市南绕城高速公路上一座跨径为177 m+360 m+177 m的结合梁斜拉桥为研究对象，利用有限元软件ANSYS建立其空间计算模型，分析了该桥的动力特性。运用非线性时程分析法计算桥梁结构在50年超越概率10%和2%两种地震水平作用下的地震响应，并以构件的能力需求比评估了该桥的抗震性能。结果表明:地震作用下主梁纵向振动与横向振动基本不耦合，其竖向位移受纵向地震作用影响较大；由于结构的非对称性，5#塔（南桥塔）的塔顶位移及塔底弯矩均大于4#塔（北桥塔）；在E1和E2两种水平地震作用下，各桥墩和桥塔关键截面以及斜拉索最小能力需求比均大于1，满足抗震性能要求；各桥墩纵桥向能力需求比小于横桥向，而桥塔纵桥向能力需求比大于横桥向，建议在过渡墩和辅助墩上安装减隔震装置，加强其纵桥向抗震性能。

Seismic Response Analysis and Performance Evaluation of Long-span Cable-stayed Bridge Based on ANSYS

In order to study the seismic response characteristics of the long-span cable-stayed bridge in the western high-intensity area, a long-span cable-stayed bridge with span of 177 m+360 m+177 m on Lanzhou south bypass expressway was taken as study object. The spatial dynamic model was established by finite element software ANSYS, the dynamic characteristics of the bridge were analyzed. The nonlinear seismic time-history analysis was used to calculate the seismic response of bridge structure under the 50-year probability of over 10% and over 2%. Besides, the seismic performance of the bridge was evaluated by the capacity demand ratio method. The results show that the longitudinal vibration of the main girder is not coupled with the lateral vibration under the earthquake. The vertical displacement of the main girder is greatly influenced by the longitudinal seismic action. Due to the asymmetry of the structure, the tower top displacement and the bottom bending moment of the tower 5 (south bridge tower) are all larger than those of the tower 4(north bridge tower). Under the two kinds of horizontal earthquakes of E1 and E2, the minimum capacity demand ratios of the key sections of piers and towers and the cables are greater than 1, and the seismic performance requirements are met. The longitudinal capacity demand ratio of piers is smaller than transverse ratio, while the longitudinal capacity demand ratio of bridge tower is larger that transverse ratio. It is recommended to install the anti seismic device on the transition pier and the auxiliary piers to strengthen the longitudinal bridge seismic performance.