峰值速度对单自由度体系地震反应的影响分析

Influence of ground-motion peak velocity on non-linear dynamic response of single-degree-of-freedom system

研究了在加速度反应谱与峰值位移不变的条件下,输入地震动峰值速度对单自由度体系动力反应、尤其是弹塑性反应的影响。首先,利用在时域内叠加窄带时程的方法合成加速度反应谱和峰值位移相同,但峰值速度相差1倍的两组人工地震动时程。其次,按照《建筑抗震设计规范》的要求,将合成的输入地震动标定为不同设防烈度区下多遇地震的加速度峰值,进行结构弹性计算,结果表明:输入地震动峰值速度的变化对结构弹性反应基本无影响。然后,将输入地震动标定为相应烈度区下罕遇地震的加速度峰值,并以上述多遇地震下弹性反应的最大变形作为罕遇地震作用下结构弹塑性分析的屈服变形,进而分析输入地震动峰值速度变化对结构弹塑性反应的影响规律。其结果表明,峰值速度的增大将会明显增大中长周期结构弹塑性位移反应和速度反应,且这种放大效应对位移反应尤为显著。这种规律在不同烈度区基本具有一致性,随着烈度增大,输入地震动峰值速度的增大引起的大部分中长周期结构弹塑性位移及速度反应的放大效应减小。因此,在进行结构动力分析时,应充分考虑输入地震动峰值速度变化对计算结果的影响。

In this paper, the influence of ground-motion peak velocity on the dynamic is studied, especially non- linear dynamic, responses of single-degree-of-freedom （SDOF） systems, under the condition that the response spectrum and the peak displacement 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 displacements are same, while the peak velocity of one group is double the other. Secondly, in accordance with the requirements of the ＂Building Seismic Design Code＂, the synthesized input ground motions are calibrated to accelerate peak values under a frequently occurred earthquake in areas with differ- ent seismic fortification intensity, then the calculation on the structural elastic-plastic response is worked out. The results show that the variation of the peak velocity of the input ground motion basically has no effect on the structur- al elastic response. Then, the input ground motions are calibrated to the acceleration peak of a rarely occurred earthquake in the area with corresponding seismic fortification intensity, and the maximum deformation of the elastic response under a frequently occurred earthquake is set as a yielding deformation for structural elastic-plastic analysisunder the action of the rarely occurred earthquake, then the law of the influence of input ground motion peak veloc- ity on structural elastic-plastic response is made. The results show that the increase of peak velocity will significant- ly increase the elastic-plastic displacement and velocity of the long periodic structures, and the amplification effect is especially significant on displacement. This law is basically consistent with different intensity regions, and with the increase of intensity, the amplification effect of the elastic-plastic displacement and velocity response of the long periodic structures, which is caused by the increase of the peak velocity of the input ground motion, will de- creased. Therefore, when the structural dynamic analysis is carried out, the influence of the variation of the varia- tion of the peak velocity of the input ground motion on the calculation results should be considered.