抗震设计反应谱特征周期研究

Research on Characteristic Periods of Seismic Design Response Spectrum

摘要:

搜集整理1933—2015年美国西部地区166个有详细钻孔资料台站场地上的1 237条水平方向强震记录，按照我国建筑抗震设计规范（GB 50011-2010）中反应谱的形状对强震记录的加速度反应谱进行拟合，提取反应谱的特征周期。分析特征周期随场地类别、震级、震中距的变化特征；按特征周期分区统计计算不同场地类别上的特征周期平均值，并与我国现行的建筑抗震设计规范中给定的特征周期值进行对比研究；最后探讨地震动峰值加速度对特征周期的影响。根据研究分析结果提出关于抗震设计反应谱特征周期值的改进建议。

Abstract:

In this study, we collected 1,237 horizontal strong ground motion records, including detailed borehole data, from the 1933—2015 period at 166 sites in the Western United States. We fit the standard response spectrum to the Chinese Code for the Seismic Design of Buildings (GB 50011-2010) and extracted the characteristic periods of the response spectrum. In this paper, we discuss the influences of site, magnitude, and epicentral distance on the characteristic period of the response spectrum and prove that these periods increase when the site becomes soft. The characteristic periods of the response spectrum increase with increasing magnitude within the same scope of epicentral distance. With increases in the epicentral distance, the characteristic period lengthens within the same range of magnitude. The magnitude and epicentral distance have some influence on the characteristic period. With respect to a single factor of magnitude or epicentral distance, which influences the characteristic period values at the same site classification, research shows that the magnitude has more influence than distance. We divide characteristic periods at class II sites into three zones. The method for partitioning the characteristic periods at other sites is the same as that at class Ⅱ sites. We determined the scope of the characteristic period of the acceleration response spectrum according to the seismic ground motion parameters zonation map of China (GB 18306-2015). We statistically analyzed the averages of the characteristic period of the response spectrum at different sites based on the zones of the characteristic periods and discuss the reasonable characteristic period values in the current seismic design code. Compared with the characteristic period values in the Code for Seismic Design of Buildings in China, we found most of the statistical characteristic period values to be larger. We divided the strong motion records of class Ⅱ sites into groups based on their scopes of magnitude and distance. We calculated the average peak ground acceleration for each group and, based on the general rule that peak ground acceleration decreases with decreases in magnitude and increases in the epicentral distance, we ascertained the partitions of the peak ground acceleration. We found the partition of peak ground acceleration for site Ⅰ₀, Ⅰ₁, and ⅢI classes to be the same as that at class II sites. Next, we calculated the average characteristic period value in each zone of peak ground acceleration for different sites and discuss the influence of the seismic peak ground acceleration on the characteristic periods. Our results show that the characteristic period of the response spectrum has clear distinctions within different partitions of the peak ground acceleration. Based on these results, we offer some proposals regarding the characteristic periods of the response spectrum.