考虑上部结构非线性的LRB基础隔震建筑结构动力特性研究

Investigation into the dynamic behavior of LRB base-isolated building structure considering the nonlinearity of superstructure

以两自由度体系的LRB基础隔震建筑结构为对象,在同时考虑LRB隔震系统以及上部结构非线性的基础上,提出综合利用Fourier级数展开、谐波平衡法以及梯度法对该两自由度体系在简谐地震动激励作用下的稳态响应进行求解的方法。以此为基础通过参数分析对考虑上部结构非线性的LRB基础建筑结构的动力特性进行研究并发现:非线性上部结构基底固定时,随着结构延性的增加,结构的耗能能力也随之增加,而且结构自身的频率随之降低,远离发生共振的频率,从而有效地抑制结构延性的快速增加;非线性上部结构自身频率的变化并不会根本改变整个LRB基础隔震建筑结构的频率,由于低频的简谐地震动激励限制非线性上部结构自身的耗能能力,从而导致在激励幅值不断增加的情况下,上部结构的延性需求急剧增加。

In this paper,under harmonic ground excitation,computational method which combines Fourier series expansion,harmonic balancing method and gradient method is proposed to solve two-degree-of-freedom system of LRB base-isolated building structure where the nonlinearity of both LRB isolation system and superstructure are taken into consideration.Dynamic behavior of LRB base-isolated building structure is investigated through parametric study.It is observed that capacity of energy dissipation of fixed-base structure is enhanced with the increase of the ductility,and at the same time its frequency moves away from the resonant excitation frequency due to the significant frequency decrease,which effectively controls the rapid increase of ductility demand.It is shown as well that the change of superstructure frequency dose not fundamentally change the natural frequency of the overall LRB base-isolated system;low excitation frequency has the effect on reducing the capacity of energy dissipation of superstructure,which leads to the rapid increase of ductility demand of superstructure with the increase of low-frequency excitation amplitude.