峰值位移输入对单自由度体系地震反应的影响

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

在加速度反应谱与峰值速度不变的条件下,研究输入地震动峰值位移对单自由度体系动力反应、尤其是弹塑性动力反应的影响。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速度相同而峰值位移相差1倍的两组人工地震动时程,按照GB 50011—2010《建筑抗震设计规范》的要求,将合成的输入地震动采用不同设防烈度多遇地震的峰值加速度标定,进行体系的弹性分析。结果显示,输入地震动峰值位移的变化对弹性动力反应基本无影响。将输入地震动采用相应烈度罕遇地震的峰值加速度标定,并以上述多遇地震作用下弹性最大位移反应作为罕遇地震作用下结构弹塑性分析的屈服位移,进而分析输入地震动峰值位移变化对弹塑性动力反应的影响规律。结果表明:峰值位移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,这种放大效应对位移反应尤为显著,其规律在不同设防烈度区具有一致性,即随着设防烈度的提高,输入地震动峰值位移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位移变化对计算结果的影响。

The influence of ground-motion peak displacement on the dynamic, especially non-linear dynamic responses of single-degree-of-freedom （SDOF） systems was studied under the condition that the response spectrum and the peak velocity of the input ground motion were fixed. By the method of superimposing narrow-band time histories in the time domain, two groups of artificial ground-motion time histories were synthesized, whose response spectra and peak velocities were the same, while the peak displacement of one group was double the other. In accordance with the requirements of the code for seismic design of buildings, the synthesized input ground motions were calibrated to peak acceleration values under a frequent earthquake in areas with different seismic fortification intensities, and then the calculation on the structural elasto-plastic response was conducted. The results show that the variation of the peak displacement of the input ground motion basically has no effect on the structural elastic response. Then, the input ground motions were calibrated to the peak acceleration of a rare earthquake in the area with corresponding seismic fortification intensity. The results show that the increase of peak displacement will increase the elasto-plastic displacement and velocity of the structures with medium-long periods, and the amplification effect is especially significant on displacement. This rule is basically consistent with different intensity regions, and with the increase of intensity, the amplification effect on the elasto-plastic displacement and velocity response of the structures with medium-long periods, which is caused by the increase of the peak displacement of the input ground motion, will be decreased. Therefore, when the structural dynamic analysis is carried out, the influence of the variation of the peak displacement of the input ground motion on the calculation results should be considered.