2022年泸定地震某隔震建筑铅芯橡胶支座地震反应分析

Seismic Response Analysis of the Lead Rubber Bearings in a Base-Isolated Building in the 2022 Luding Earthquake,China

在2022年9月5日四川泸定6.8级地震中,位于震中附近的一栋地上4层的隔震建筑的隔震层正常发挥作用,上部结构和非结构构件均基本完好,但是隔震层中的铅芯橡胶支座、排水管线和隔震缝附属非结构构件等均发生了不同程度的破坏。在介绍该建筑主要震害的基础上,通过基于简化分析模型和邻近烈度仪实际强震记录的非线性地震反应分析,推测该建筑的地震反应,并重点考察铅芯橡胶支座的竖向应力在地震中可能发生的变化。结果表明,尽管该场地附近的强震记录表现出明显的近断层脉冲特性,但在其作用下,该建筑上部结构的最大层间位移角小于设防地震下混凝土框架结构1/400的限值,隔震层也有效地减小了上部结构的楼面水平加速度反应。受比较显著的竖向地震作用影响,绝大多数隔震支座均可能短暂地处于拉剪耦合受力状态,但其最大拉应力水平远低于根据既有试验得到的相应水平剪应变下的极限拉应力。该建筑隔震层中橡胶隔震支座的大量破坏不能简单地归因于竖向地震作用。

In the M6.8 Luding earthquake in China,a four-story base-isolated building near the epicenter sustained extensive damage at the lead rubber bearings,sewage pipes in the isolation layer,and nonstructural elements of the isolation joint,while the superstructure slided on the isolation layer and exhibited only minimum damage.Following an introduction on the typical damage of buildings,this paper summarizes the results of nonlinear time-history analysis of the building under an excitation of two strong ground motion records obtained from the earthquake site.The results show the maximum inter-story drift ratios of the superstructure under two input motion records are below 0.25%,which is the limit for reinforced concrete frame superstructures of base-isolated buildings under design basis earthquakes.The isolation layer effectively reduces the horizontal acceleration of the superstructure.Due to the significant vertical component of ground motion,most rubber bearings can sustain a combined shear-tensile loading.However,the maximum tensile stress is much lower than the ultimate tensile stress under a combined shear-tensile loading based on the existing experimental data.It can be misleading to attribute the fracture of the rubber bearings in this building solely to the vertical component of ground motion.