统计意义一致的弹塑性设计位移谱

Statistical property-consistent elastic-plastic displacement design spectra

在统计意义上设计反应谱通常表示多条地震波反应结果的平均,利用等延性强度折减系数谱对弹性设计位移谱进行折减间接建立的弹塑性设计位移谱,在这方面与弹性设计位移谱并不能很好对应.为此基于3类场地各20条地震波的统计分析,研究了利用等延性强度折减系数谱间接建立的弹塑性位移谱与统计平均的弹塑性位移谱的偏差.结果发现前者会导致偏于危险的结果,特别是对软弱场地和位移延性系数大于4时.通过对国内外学者建议的6组等延性强度折减系数谱的比较分析,以精度较高的V id ic等建议的强度折减系数谱为准,并在间接方法中引入与位移延性系数、场地条件及结构周期相关的修正系数,建议了与弹性设计位移谱统计意义一致的弹塑性设计位移谱.

The design spectra usually represent the statistical results of some SDOF system subjected to ground motions, but elastic displacement design spectra are not consistent with the elastic-plastic design spectra derived indirectly from the reduction of elastic displacement design spectra by the strength reduction factor spectrum. The discrepancies between above indirect elastic-plastic spectra and statistical spectra are studied based on the statistical analysis of the response of SDOF system subjected to 20 seismic ground motions separately under three kinds of site soil conditions, and it is known that the former might underestimate the earthquake displacement demands especially on soft site or when displacement ductility factor is larger than 4. Then the simplified Vidic＇s strength reduction factor spectrum with higher accuracy is selected and a modified factor related to the displacement ductility factor, the site condition and the system period is introduced to the indirect elastic-plastic spectra, and the statistical property-consistent elastic-plastic displacement design spectra derived by the reduction of elastic displacement design spectra is proposed finally.