脉冲型地震作用下RC框架结构抗震性能评估

Seismic performance evaluation of an RC frame structure subjected to pulse-like ground motions

通过选取脉冲型地震记录100条,拟合脉冲型加速度反应谱后与中美规范谱进行比较,利用拟合的反应谱转换成需求谱,对一10层RC框架结构进行基于Pushover分析的抗震性能评估,研究脉冲型地震动对RC框架结构抗震性能的影响。研究结果表明:通过对比拟合谱与中美规范谱,我国规范谱不考虑脉冲效应,在速度敏感区内取值偏小;UBC97规范谱通过增大加速度敏感区的宽度及增加位移敏感区的平台段来考虑脉冲效应,取值偏保守。8度多遇、罕遇地震时,拟合需求谱下结构基底剪力和最大层间位移角都远大于规范需求谱下结构基底剪力和最大层间位移角。8度罕遇地震时,规范需求谱下只有框架梁出现塑性铰,框架柱未出现塑性铰;拟合需求谱下底层框架柱柱脚出现塑性铰,局部框架梁塑性铰变形加大且塑性铰分布范围更广,表明脉冲型地震对结构提出更高的位移和能量耗散需求。

100 pulse seismic records are selected for fitting with the acceleration response spectrum to be subsequently compared with the design spectrum of Chinese Seismic Code and the Uniform Building Code 1997.The fitting response spectrum is converted into the demand spectrum for the Pushover analysis of a 10-layer RC frame structure in order to research the influence of the pulse seismic oscillation on the anti-seismic property of RC frame structure.The research shows:Through the comparison with fitting spectra and the design spectra of Chinese Seismic Code and the Uniform Building Code 1997,it is found that the value of Chinese Seismic Code spectrum tends to be unsafe in the speed sensitivity zone.It is reasonable to consider the near-field earthquake effects of UBC97 design spectrum through magnifying the width of the speed sensitivity zone and increasing the platform segments of displacement sensitivity region,but the platform segments are too conservative.Frequent-earthquake and Rare-earthquake Pushover analysis shows that the structure base shear force and the maximum inter-story displacement angle in the fitting demand spectrum are greater than the corresponding values in the standard demand spectrum.Rare-earthquake Pushover analysis shows that the frame column does not have any plastic hinge under the standard demand spectrum;the base frame column has plastic hinge at the pedestal under the fitting demand spectrum.For some frame girders,the plastic hinges are significantly deformed and widely distributed.