非线性基础隔震结构复振型反应谱设计方法

采用铅芯橡胶支座、弹性滑板支座或摩擦摆支座的基础隔震结构,在利用反应谱方法进行设计时,需要考虑支座的非线性特征.在传统非线性振动分析平均方法或慢变振幅法中引入激励随机性,以等效线性系统和原非线性系统势能和阻尼耗能相等为原则,提出了基于能量平衡的随机等效线性化方法.在该方法中,等效刚度和等效阻尼系数表达为振动幅值的期望,...

Complex modal response spectrum approach for design of nonlinear base-isolated structures

Nonlinearities of isolators need to be considered when the response spectrum method is used for the design of base-isolated structures with lead rubber isolators,elastic sliding isolators or frictional pendulum isolators.By introducing the randomness of excitation into the conventional averaging method or slowly varying amplitude method for nonlinear vibration analysis,and making the potential energy and damping energy of an equivalent linear system be equal to those of the original nonlinear system,a statistical linearization method based on energy balance was proposed.In this method,the equivalent stiffness and damping coefficient were expressed in terms of the expectation of vibration amplitude.The two equivalent parameters could then be associated with the response spectrum values and a linearization method based on response spectrum was further developed.In the linearization of isolators,the isolated structure became a non-classically damped system due to the equivalent damping.To consider the effect of the nonclassical damping,the combination rule of complex modal peak responses,i.e.,CCQC,was employed in the response spectrum linearization method.For regular structures,analysis results show that the response spectrum linearization method is mainly suitable for the cases of the yield displacement of the isolation layer being less than 20 mm,the postyield stiffness ratio being close to 0.2 and the yield weight ratio being less than 4%.For the case of the post-yield stiffness ratio being less than 0.2,the calculated base shear is larger than that from nonlinear time history analysis.This also ensures the design safety of an isolated structure with elastic sliding isolators or frictional pendulum isolators.The irregular base-isolated Benchmark model,as a numerical example,further demonstrates the significant effectiveness of the response spectrum linearization method.The results show that the inter-story drifts and story absolute accelerations can be evaluated well.The accuracy of internal forces and reinforcements in structure members is thus guaranteed.Nevertheless,the calculated displacement of the isolation layer is smaller and a nonlinear time history analysis is required to examine the response in practical applications.