基于耐震时程法的连续刚构桥地震损伤分析

Application of the endurance time method to the seismic analysis and damage evaluation of a continuous rigid-frame bridge

探讨了在真实成桥内力状态下,耐震时程法(Endurance time method,ETM)评估连续刚构桥地震反应与损伤的准确性和有效性.以一座典型非规则连续刚构桥为背景,采用MIDAS/Civil模拟实际施工过程,经施工阶段分析得到10 a收缩徐变下的成桥内力状态,再借助等效荷载法建立考虑成桥内力状态的OpenSees动力分析模型;通过与天然地震动下的增量动力分析(Incremental dynamic analysis,IDA)结果相对比,验证了采用ETM可快速准确地得到地震反应的适用性;通过该方法分析了墩顶位移、梁端位移及碰撞力等地震反应,并采用位移延性系数和Park-Ang损伤指数对桥墩损伤进行了量化分析与评估.结果表明:ETM可以有效地预测真实成桥内力状态下连续刚构桥达到某一损伤程度的时间;耐震时间较短时主桥桥墩较引桥桥墩的损伤要小,耐震时间较长时则反之.

The endurance time method(ETM) is a novel dynamic analysis method in which artificially intensified accelerograms characterized by the increase in seismic intensity with time are used as loading inputs.In this method,various dynamic responses,i.e.,ranging from elastic to failure,under seismic excitations of different intensity levels are estimated with a reduced dynamic calculation effort.Based on these merits,this study investigated the accuracy and effectiveness of ETM in predicting the seismic responses and damage to continuous rigid-frame bridges considering the real internal force state(called element initial strain state) of the completed bridge.In detail,first,a typical irregular continuous rigid-frame bridge was selected as the target of the analysis,and its finite element model considering the real construction process was established by MIDAS/Civil.Then,the real internal force state considering the 10-year concrete shrinkage and creep was determined through construction phase analysis,and a dynamic analysis model considering the real internal force state was built via OpenSees utilizing the equivalent load method.Subsequently,the incremental dynamic analysis results under natural ground motions were obtained and compared with the results of the ETM,and the applicability of the ETM to obtain seismic responses rapidly and accurately was verified.Finally,the seismic responses of pier displacement,girder displacement,and pounding force were analyzed using the ETM,and the damage to piers was evaluated using the displacement ductility factor and Park–Ang damage index.The results indicate that ETM can predict the time when a continuous rigid-frame bridge reaches a certain damage status under the real internal force state of the completed bridge.Moreover,the damage to the main-bridge pier is smaller than that of the approach-bridge pier when the endurance time is short.However,when the endurance time is long,the opposite is true.