基于实际场地和碰撞双重效应的高墩大跨连续刚构桥易损性分析

Fragility Analysis of High-pier and Long-span Continuous Rigid Frame Bridge Based on Double Effects of the Actual Site and Collision

为了研究实际场地和碰撞双重效应对高墩大跨连续刚构桥易损性的影响,以某高墩大跨连续刚构桥为研究对象,基于OpenSees软件建立不同伸缩缝宽度取值对应的有限元模型,并将基岩地震波按桥位处实际土层特性转化为地表地震波,进行增量动力非线性分析(多点激励),同时与未考虑实际土层过滤影响(一致激励)的结构响应进行对比分析.研究表明:随伸缩缝宽度的增大,碰撞效应使2#墩(次高墩)在一致激励作用下的损伤概率逐渐大于多点激励情况,最大差值为0.28;碰撞效应使3#墩(最高墩)损伤概率降低,且一致激励低估了3#墩各损伤阶段的损伤概率,最大低估量为0.35;随基岩地震波加速度峰值的增加,一致激励作用下2#墩的位移延性系数概率需求值逐渐大于多点激励时的需求值,而多点激励作用下3#墩的位移延性系数概率需求值均大于一致激励情况.实际场地和碰撞效应对大跨度连续刚构桥的高墩和低墩易损性影响不同,需在抗震设计中综合考虑.

The influence of the double effects of actual site and collision on the fragility of high-pier and long-span continuous rigid frame bridge was studied.A real high-pier and long-span continuous rigid frame bridge was taken as the research object,and some finite element models of the bridge were built for the various separation distances between deck and abutment based on the OpenSees software.And the bedrock seismic waves were converted into surface seismic waves according to the filtration of actual soil characteristics at the bridge location for incremental dynamic analysis(multi-support excitation).The results were compared with the structural responses which do not consider the effect of actual soil filtration(uniform excitation).The results show that with the increase of the width of expansion joint,the damage probability of Pier 2#(second highest pier)under the uniform excitation is gradually becoming larger than that of multi-support excitation with the maximum difference of 0.28.The collision effect reduces the damage probability of Pier 3#(the highest pier),and the uniform excitation method underestimates the damage probability of Pier 3#in each damage stage,with an underestimation up to 0.35.With the increase of peak acceleration of bedrock seismic wave,the probability demand value of displacement ductility coefficient of Pier 2#under the uniform excitation is gradually growing larger than that of the multi-support excitation,while the probability demand values of displacement ductility coefficient of Pier 3#under multi-support excitation are all larger than those of uniform excitation.The influence of the double effect of actual site and collision on the fragility of bridge structures depends on the heights of piers of long-span continuous rigid-frame bridge,so it should be consi-dered synthetically in seismic design of bridge.