以结构反应均值估计为目标的时程分析输入地震波选择研究

SELECTION AND SCALING OF GROUND MOTIONS IN TIME-HISTORY ANALYSIS FOR ESTIMATES OF MEAN STRUCTURAL RESPONSES

地震动输入是导致结构时程分析结果不确定性的最重要的影响因素,如何选择地震波实现对结构反应的“准确、有效、一致”估计是时程分析中的一项重要任务。该文对以结构反应均值估计为目标的时程分析选波问题,基于目标谱法进行了系统深入的研究。针对谱匹配,引入具有明确物理含义的权重系数,对提出的可考虑多振型影响的双指标多频段工程经验选波法和理论更加完备的最小二乘加权调幅选波法,进行了详尽的算例分析。研究表明,双指标多频段经验法可满足现有规范要求。通过与国内学者、人工波方法和NGA-West2强震数据库选波模块的比较,论证了加权调幅法在估计结构反应均值方面具有可靠的准确性,并具有广泛的适用性,也包括减隔震结构。通过比较研究也进一步明确了加权调幅法的优势在于可明显降低结构反应的离散性,更适于长周期结构的弹塑性时程分析。针对目标谱选择,提出以Newmark三联谱作为目标谱的选波方法,拟解决长周期及超长周期结构的选波问题。

The selection of ground motions has significant effects on structural response evaluation in timehistory analysis.It is an important problem how to select ground motions to provide accurate,efficient,and consistent estimates of“true”mean structural responses.This paper focuses on the selection and scaling of ground motions in time-history analysis for estimates of mean structural responses by target spectral matching method.In the research of spectral matching,the normalized modal-mass participation factors are used as the weight factors to consider significant contributions of higher modes.Many detailed structural analysis examples are used to check the double parameters empirical multi-band matching method and the weighted scaling method based on least squares method with more complete theory.It is proved that the double parameters empirical multiband matching method can satisfy the requirements of the code for seismic design of buildings.The weighted scaling method is compared with the methods developed by other local scholars,the artificial wave method and the method based on NGA-West2 database.The comparative study demonstrates that the weighted scaling method has reliable accuracy for estimates of mean structural responses and wider applicability including the base-isolated buildings.Through the comparative analysis,it is found that the significant advantage of the weighted scaling method is reducing the variability of structural responses and this method is more suitable for the nonlinear time-history analysis of long period structures.In the research of target response spectra selection,a Newmark spectrum is preliminarily used as a target spectrum,which may be a solution for long and overlong period structures.