地震动峰值位移对单自由度体系非线性动力反应的影响

INFLUENCE OF GROUND-MOTION PEAK DISPLACEMENT ON NON-LINEAR DYNAMIC RESPONSE OF SINGLE-DEGREE-OF-FREEDOM SYSTEM

研究了在输入地震动加速度反应谱与峰值速度不变的条件下,地震动峰值位移对单自由度体系(SDOF)动力反应、尤其是非线性动力反应的影响。首先,利用在时域内叠加窄带时程的方法合成出加速度反应谱与峰值速度相同、但峰值位移相差2倍的两组人工地震动时程。其次,利用理想弹塑性SDOF体系的初始自振周期描述其刚度特性、利用屈服强度衰减因子描述其非线性力学行为的发展程度,通过比较体系在上述两组输入地震动作用下地震反应的差异,揭示了地震动峰值位移对体系弹塑性地震反应的影响规律:当结构非线性力学行为得以充分发展时,在输入地震动的反应谱与峰值速度相同的情况下,其峰值位移的增大将会显著增加较长周期结构的弹塑性速度与位移反应,而且这种增大效应对于位移反应而言更为显著。

In this paper,studied is the influence of ground-motion peak displacements on the dynamic,especially non-linear dynamic,responses of single-degree-of-freedom（SDOF） systems,under the condition that the response spectrum and the peak velocity of the input ground motion are fixed.Firstly,by the method of superimposing narrow-band time histories in the time domain,two groups of artificial ground-motion time histories are synthesized,whose response spectra and peak velocities are same,while the peak displacement of one group is double the other.Secondly,by utilizing the initial natural period and the yielding strength reduction factor to describe the stiffness and the degree of the non-linear mechanical behavior of an ideal elastic-plastic SDOF system,respectively,and by comparing the seismic responses invoked by these two groups of input ground motion,the influence of ground-motion peak displacements on the elastic-plastic seismic responses of a system is analyzed.It has been concluded that,under the condition that the response spectrum and the peak velocity of input ground motions are identical,if the non-linear mechanical behavior of the system gains enough development,the increase of ground-motion peak displacements would significantly increase the elastic-plastic velocity and displacement responses of long-period structures.And such effect is more distinct for the displacement response.