基础隔震结构直接基于位移设计的一体化抗震设计方法

Integrated seismic design method for base-isolated structure incorporating direct displacement-based design procedure

为更加合理地进行基础隔震结构的抗震设计,以使用铅芯橡胶隔震支座(LRB)的基础隔震结构作为研究对象,提出了基础隔震结构直接基于位移设计(DDBD)的一体化抗震设计方法。对于给定地震水准下预先设定的性能目标(即LRB隔震系统最大水平变形和上部结构最大层间位移角),通过所提出的一体化抗震设计方法可以确定LRB隔震系统的力学性能参数并进行上部结构的结构设计。在该一体化抗震设计方法中,首先采用标准的DDBD方法并根据上部结构的目标位移曲线将上部结构等效为一个线性单自由度体系,从而将基础隔震结构等效为两自由度(2DOF)模型;然后通过LRB隔震系统的等效线性化和振型分解反应谱法,建立等效2DOF模型中隔震层和上部结构的位移反应与结构参数之间的解析表达式;基于该解析表达式,结合标准的DDBD方法提出了基础隔震结构直接基于位移设计的一体化抗震设计方法及流程。以一榀典型的钢筋混凝土基础隔震框架结构为算例,给出了使用一体化抗震设计方法的设计步骤和结果,并对所设计的基础隔震结构进行非线性时程分析。时程分析结果证实了该一体化抗震设计方法的有效性,该方法也适用于使用不同类型隔震系统的基础隔震结构。

In order to make the seismic design of base-isolated structures more reasonably,an integrated seismic design method for base-isolated structures with lead-rubber bearing(LRB)isolation system,which incorporates the direct displacement-based design(DDBD)procedure,is proposed in this study.In the proposed design procedure,the performance objectives,defined in terms of maximum displacement of the LRB isolation system and maximum interstory drift ratio of isolated superstructure,are achieved by appropriately designing the mechanical parameters of LRB isolation system.The key aspect of the proposed DDBD procedure is that an equivalent linear two-degree-of-freedom(2DOF)model is taken as the substitute structure for the base-isolated building structure.In this equivalent 2DOF model,the isolated superstructure is substituted by an equivalent single degree-of-freedom model according to the target displacement profile for the base-isolated building structure.The LRB isolation system together with isolation level is represented by another degree-of-freedom.Modal analysis and response spectrum analysis of this equivalent 2DOF model have been carried out.Then,a closed-form relationship between structural characteristics and seismic displacements is established.Once the displacement requirements are given,the closed-form relationship could facilitate obtaining the solution of the structural parameters of the base-isolated structures.Following the standard steps of DDBD and utilizing this equivalent 2DOF model as the substitute for the original nonlinear structural model,an integrated seismic design method is then developed and detailed.In order to validate the effectiveness and accuracy of the proposed design procedure,nonlinear time-history analyses with a set of spectrum-compatible ground motions are conducted for a base-isolated building structure.The numerical results indicate that the proposed design procedure is reliable and can be applied to base-isolated structures with different types of isolation system.