近场地震作用下库区深水钢筋混凝土高墩地震易损性分析

Seismic Fragility Analysis of Deep-water Reinforced Concrete High-pier in Reservoir Area under Near-fault Earthquakes

为研究近场地震作用下库区深水钢筋混凝土高墩的概率损伤特性,以90 m高的矩形空心薄壁钢筋混凝土深水高墩为研究对象,综合考虑桥墩设计参数和近场地震动的随机性,基于OpenSees软件建立深水高墩有限元模型,开展不同水深的7种工况(水深:0、15、30、45、60、75、90 m)下,顺桥向和横桥向近场地震激励的增量动力非线性分析。以截面临界曲率值为损伤指标,研究深水高墩的易损性。结果表明:各工况下,轻微损伤、中等损伤和严重损伤阶段的损伤概率均随地震波峰值加速度的增加而增大,并且当峰值加速度达到1.0g时损伤概率达到最大,而完全损伤阶段的损伤概率则在峰值加速度为0.5g时出现峰值点;近场地震顺桥向激励时,墩身中上部和墩底区域均较容易损伤,而横桥向激励时仅墩底区域较容易损伤;当水深超过45 m后,高墩最大损伤概率变化不大且截面曲率概率需求基本一致,45 m水深为深水高墩显著水深。因此,应重点分析水深达到高墩高度一半时深水高墩的损伤情况。

In order to study the damage probability characteristics of deep-water reinforced concrete high-pier in reservoir areas under near-fault earthquakes,a rectangular hollow thin-wall reinforced concrete deep-water high-pier with the height of 90 m is taken as the research object.Considering the randomness of design parameters of the bridge pier and the randomness of near-fault earthquakes,the deep-water high-pier finite element model is built based on the software OpenSees,and the incremental dynamic nonlinear analyses in the longitudinal and transverse directions are carried out on near-fault seismic excitation considering seven different water depths(0,15,30,45,60,75,90 m).The vulnerability of the deep-water high-pier is studied by using the critical curvature values of the cross sections as the damage parameters.The results show that the damage probability of slightly damaged,moderately damaged,seriously damaged stages increases with the increase of peak ground acceleration(PGA),and the damage probability reaches a maximum when the PGA reaches 1.0 g.While the peak value of the damage probability of the completely damage stage occurs when the PGA is 0.5 g.When the near-fault earthquake excitation is along the longitudinal direction,both middle-upper and bottom areas of the high-pier are easier to damage.The bottom area of the high-pier is easier to damage when the near-fault earthquake excitation is along the transverse direction.When the water depth exceeds 45 m,the maximum damage probability of the high-pier changes slightly and the probability demand value of cross section is basically identical.The water depth of 45 m is the significant water depth of the deep-water high-pier.Therefore,it is recommended to analyze the damage situation of deep-water high-piers when the water depth reaches half of the high-pier height.