近活动断裂带大跨悬索桥抗震性能研究

Study of Seismic Performance of Long-Span Suspension Bridge Located Near Active Fault

为了解近活动断裂带大跨悬索桥的抗震性能,以主缆跨径(125+485+125)m的双塔单跨钢板组合梁悬索桥——紫坪铺特大桥为背景,采用SAP2000软件建立桥梁有限元模型,计算桥梁结构动力特性,采用非线性时程分析法分析地震作用组合下桥塔和桩基的内力及加劲梁位移,并提出设置粘滞阻尼器的减震优化设计。结果表明:大跨悬索桥高阶振型密集,应重视高阶振型对结构动力特性的影响;E2地震作用下,桥塔和桩基各关键截面弯矩需求均小于截面抗弯能力,符合E2地震性能目标,塔柱横梁地震响应不大,采用常规设计可满足性能要求;纵向+竖向E2地震作用下,加劲梁梁端纵向位移较大,在加劲梁梁端与桥塔横梁间纵向设置粘滞阻尼器[阻尼系数C=2000 kN/(m/s)α,速度指数α=0.3],可有效限制加劲梁在地震作用下的纵向位移。

The seismic performance of the long-span suspension bridge located near an active fault is studied,based on the case of Zipingpu Bridge.The bridge is a two-tower single-span suspension bridge and the main cables measure 485 in the central span and 125 m in the two side spans.A finite element model of the bridge was established by SAP 2000 to calculate the dynamic property of the bridge structure.A non-linear time-history analysis method was used to analyze the internal forces of the towers and foundations as well as the displacement of stiffening girder under combined loads.It is proposed to install viscous dampers to improve the seismic performance of the bridge.The results of the analysis show that the higher-mode vibrations of the long-span suspension bridge are dense,the effect of which on the dynamic property of the structure should be given great concern.Under the action of E2 earthquake,the bending moment requirements of each key cross-sections of the towers and pile foundation are all less than the cross-section flexural resistance,complying with the seismic performance target in E2 earthquake events.The seismic response of the tower cross beam is moderate,and the conventional design is sufficient to make the structure meet the seismic performance requirements.Under the longitudinal and vertical E2 earthquakes,the girder-end longitudinal displacement of the stiffening girder is big,to install longitudinal viscous dampers(with damping coefficient C of 2000 kN/(m/s)and velocity exponentαof 0.3)in the tower cross beam can effectively restrict the longitudinal displacement of the stiffening girder under the action of earthquakes.