地震作用下基于性能的中小跨径梁桥横向支承约束系统设计优化

Design and optimization of a seismic bearing restraint system for small- and medium-spangirder bridges in transverse direction using performance-based methodology under earthquakes

支承约束系统对中小跨径梁桥抗震有显著意义,该研究提出一种基于性能的方法优化桥梁的支承约束系统参数。以汶马高速公路中的简支梁桥群组为例,采用铅芯橡胶支座进行桥梁横桥向的抗震性能优化。首先参数化建立桥梁的OpenSees有限元模型,对桥梁支座—挡块组成的支承约束体系的初始设计进行非线性时程分析;由logistic回归得到了以工程需求参数(engineering demand parameter, EDP)为条件的桥梁构件级易损性函数,推导了桥梁的统一系统级性能指标修复成本比(repair cost ratio, RCR),将其作为优化程序的目标函数;利用遗传算法建立了支承约束系统设计参数的优化程序。研究结果表明:在以EDP为条件建立的桥梁构件级易损性函数中,桥墩和支座的损伤概率对不同的支承约束系统设计不敏感,推导的RCR可以涵盖不同的支承约束系统。利用该程序优化了案例桥梁群组的铅芯橡胶支座约束系统设计参数,当支座屈服强度约为(0.16±0.02)倍的桥墩屈服强度,支座屈服后刚度约为(0.054 8±0.008 1)倍的桥墩弹性刚度,挡块与主梁的间距为0.098 m,挡块刚度取为185×104kN/m时,桥墩和支座产生的地震响应能够显著降低桥梁的RCR。

A bearing restraint system is of great significance to the seismic performance of small-and medium-span bridges.A performance-based methodology was adopted to optimize the parameters of bearing restraint systems in this work.Based on the simply supported girder bridge portfolios in the Wenchuan-Ma’erkang highway,lead rubber bearings were employed to optimize the seismic performance in transverse direction.First,nonlinear time-history analyses for the initial designs of the bearing restraint systems composed of the bearings and shear keys were per formed by the parametric OpenSees finite element models of the bridges.The bridge component-level fragility functions conditioned on the engineering demand parameters(EDPs)were established by the logistic regression method,and the uniform system-level performance indices of the bridges were derived by repair cost ratios(RCRs),as the objective function of the developed optimization program.The optimization program for the design parameters of the bearing restraint systems was developed based on the genetic algorithm.Results show that the damage probabilities of piers and bearings with respect to the bridge component-level vulnerability functions conditioned on EDPs were not sensitive to the different bear in grestraint system designs,and the derived RCRs can cover the various bearing restraint systems.Using the developed procedure to optimize the lead rubber bearing restraint system design parameters of the prototype bridges,bearings with yield strength of approximately(0.16±0.02)times pier yield strength and post-yielding stiffness of approximately(0.0548±0.0081)times pier elastic stiffness,and the gap between the shear keys and main girder with the value of 0.098 m and the shear key stiffness chosen as 185×104 kN/m were found to the resulting seismic responses of the piers and bearings,which can significantly reduce the RCR of bridges.