近场地震作用下考虑P-Δ效应的首层柱顶隔震结构地震反应分析

Seismic analysis of first-floor column top isolation structures subjected to near-field ground motions considering P-Δ effects

近场地震所具有的位移和速度脉冲,会使得结构隔震层处形成较大的层间位移,结构的二阶效应不容忽视。首先,构造水平力偶来代替结构轴向力形成的附加弯矩,得到了一几何刚度矩阵,在此基础上提出了求解层间隔震结构P-Δ效应的免迭代计算方法;其次,分别选取了10组近场地震波和10组远场地震波,对层间隔震结构作了时程分析,研究了近场地震波对层间隔震响应的影响;最后,分析了近场地震作用下,P-Δ效应对层间隔震系统下部结构的影响。研究表明:近场地震作用下,层间隔震结构反应显著增大,在PGA=200cm/s2输入地震波下,P-Δ效应使得下部结构的响应增加50%左右。

Displacement and velocity pulses of near-field ground motions would yield larger storey drifts at the isolation layer of the structures,consequently the second order effects could not be neglected in this case.Firstly,based on a geometric stiffness matrix obtained by constructing the horizontal force couple to replace the additional moment induced by P-Δ effects,this paper represents a non-iterative method for evaluating performance of the inter-storey isolated structure considering P-Δ effects;Secondly,the influences of near-field ground motions on the responses of the isolated system are investigated by analyzing the responses of the inter-storey isolated structure with 10 near-field and 10 farfield earthquake records,respectively;Finally,the impacts of P-Δ effects on the responses of the substructure under near-field ground motions are discussed.The results show that the responses of the inter-storey isolated structure increase significantly when subjected to near-field ground motions,P-Δ effects enlarge the responses of the substructure about 50% under the input earthquake ground motions with PGA=200 cm/s2.