考虑谱形影响的地震动强度指标研究进展

STATE OF THE ART OF GROUND MOTION INTENSITY MEASURES ACCOUNTING FOR THE INFLUENCE OF SPECTRAL SHAPE

合理地选择与调整地震动记录是影响结构弹塑性时程分析结果可靠性的重要因素之一。该文首先选择15条地震动记录作为输入,以基本周期T1对应的谱加速度Sa(T1)作为地震动强度指标来调整原始地震动记录,对一榀六层三跨钢筋混凝土平面框架结构进行了增量动力分析,分析了结构线性和非线性地震响应指标如最大层间位移角与不同周期处谱加速度值的相关性。分析结果表明,不同周期处谱加速度值与结构地震响应的相关性不同,且相关程度与结构是否进入非线性和进入非线性的程度有关。这一结果表明,由于高阶振型的影响或进入非线性阶段的周期延长效应,仅按单一强度指标如Sa(T1)调整地震动记录对结构进行动力分析,所得结果的离散性必然较大。因此发展考虑地震动谱形特征的强度指标是进一步完善结构地震反应分析和抗震性能评估的基础。基于此,该文较为系统地对目前已提出的能够考虑谱形的地震动强度指标及其应用现状进行了综述总结,以期为我国开展合理的地震动记录选择与调整等研究提供一定的参考。

Selecting and scaling ground motion records reasonably is one of very important issues to affect the reliability of elastic-plastic time history analysis results of a structure. In this paper, a six-storey planar reinforced concrete frame structure with three bays under 15 ground motion records was taken as case study. 15 ground motion records were selected and scaled by the intensity measure Sa（T1）, spectral acceleration at the fundamental period first. Then this frame was analyzed via incremental dynamic analysis （IDA）. And the correlation of linear and nonlinear seismic responses of the structure, such as maximum inter-story drift ratio with the spectral acceleration values at different periods, was investigated. The results show that the correlation of seismic responses with the spectral acceleration values at different periods is different and the correlation level also depends on nonlinear level. This indicates that the variation of the dynamic analysis results must be larger if the ground motion records are just scaled based on the single intensity measure such as Sa（T1） due to the higher-mode effect and elastic-plastic period elongation. Thusly, the development of intensity measures, which can account for the influence of ground motion spectral shape, is necessary for the improvement of seismic response analysis and seismic performance evaluation of structures. Furthermore, in order to provide the reference for conducting thefurther research on this issue in China, the state-of-the-art developments of the intensity measures accounting for the ground motion spectral shape and reasonable methods for selecting and scaling ground motion records are summarized comprehensively.