极罕遇地震作用下铅芯橡胶隔震支座基础隔震结构抗震性能研究

基础隔震结构在设计地震和罕遇地震作用下具有良好的抗震性能。随着GB 18036—2015《中国地震动参数区划图》引入了极罕遇地震作用,有必要探讨基础隔震结构在极罕遇地震作用下的抗震性能。以两自由度体系(简化模型)和多自由度体系(纤维模型)的铅芯橡胶隔震支座(LRB)基础隔震结构为研究对象,基于弹塑性时程分析的统计结果,分析并比较了设计、罕遇和极罕遇地震作用下上部结构屈服承载力(即降低上部结构抗震设防烈度)和LRB隔震支座力学性能参数对整个LRB基础隔震结构抗震性能的影响。分析结果表明:极罕遇地震作用下,采用降低抗震设防烈度的方式对隔震后的上部结构进行结构设计并不可取;为了保证在极罕遇地震作用下LRB基础隔震结构的上部结构和LRB隔震支座不发生破坏,应尽可能使用大直径和低橡胶剪切模量的LRB隔震支座;如何保证LRB基础隔震结构在设计地震和罕遇地震作用下的性能要求以及在极罕遇地震作用下的安全性能是一个具有挑战性的问题。

Investigation of seismic performance of LRB base-isolated structures subjected to extremely rare earthquakes

It is well accepted that base-isolated structure has excellent seismic performance subjected to design and rare earthquakes. With the introduction of extremely rare earthquake into GB 18306—2015 ‘Seismic ground motion parameters zonation map of China’, it is necessary to investigate the seismic performance of base-isolated structures subjected to extremely rare earthquakes. In this study, a LRB base-isolated structure is modelled by a two-degree-of-freedom-system (simplified model) and a multi-degree-of-freedom-system (fiber model). Based on the numerical results from nonlinear time history analysis, the influences of yielding strength of the superstructure (i.e., reducing the seismic fortification intensity of the superstructure) and mechanical parameters of the LRB isolation system on the seismic performance of the LRB base-isolated structure have been investigated. It is indicated that it is not feasible to design isolated superstructures by reducing the seismic fortification intensity if the extremely rare earthquake is under consideration. Moreover, in order to ensure the safety of the isolated superstructure and LRB isolation bearing, it is necessary to use the LRB isolation bearings with large diameter and low rubber shear modulus. Finally, how to simultaneously ensure the safety of LRB base-isolated structures under design , rare and extremely rare earthquakes is still a challenging problem.