大兴路立交匝道桥震害原因分析及修复方案

Cause Analysis and Rehabilitation Alternative for Seismic Damage to Ramp Bridge of Daxing Road Interchange

汶川地震中,位于汶川地震烈度较低区域的西安市大兴路立交发生了较大的破坏。为分析该桥震害原因,采用MIDAS Civil软件建立该桥有限元模型,运用非线性时程方法分析结构的地震响应。分析结果表明:该桥较多滑动支座的支承体系降低了其对主梁变位的约束能力;场地地震动的长周期特性使梁体与支座产生滑移后自振周期延长,导致结构从地震波中吸收了较多能量,加剧了震害。对比2种支承体系修复方案的抗震性能后,推荐支承体系修复方案采用四氟滑板橡胶支座(边墩)、普通板式橡胶支座(中墩)的方案。

During the Wenchuan Earthquake,the ramp bridge of the Daxing Road Interchange,Xi′an City,located in the low intensity area of the Earthquake,sustained rather severe damage.To analyze the causes of the damage,the software MIDAS Civil was used to set up the finite element models for the bridge and the nonlinear time-history method was used to analyze the seismic response of the structure.The results of the analysis showed that the displacement restraint capacity of the main girder was weakened owing to the utilization of a number of the supporting systems of slide bearings,the long period characteristic of ground motion at the bridge site prolonged the natural vibration period when the sliding between the girder and bearings occurred,which hence caused the structure to absorb a great deal of energy from seismic waves and consequently intensified the damage.After the seismic performance of the rehabilitation alternatives of two types of the supporting systems were compared,it was recommended that the rehabilitation alternative that the polytetrafluoroethylene sliding plate rubber bearings（for side piers） and the common plate rubber bearings（for intermediate piers） should be used.