中美抗震规范地震记录选取比较

Comparison of ground motion selection in seismic design codes between China and United States

摘要:

为研究国内外强震动记录选取方案存在的差异,以中国建筑抗震设计规范（GB 50011—2010）和美国建筑与其他结构的最小设计荷载和相关标准（ASCE/SEI 7[KG-2mm]-16）为例,对比其记录选取结果和结构响应的差异.本文通过设计谱参数转换,在中国同一设防水准的两个工况下分别按照两国规范的方法进行地震动记录选取,并分别输入到4层和12层混凝土框架结构中,对层间位移角和层间剪力进行了对比.结果表明:中国规范基于单一方向选取和调幅,可能导致另一方向的地震动与目标谱匹配度不高,计算结果离散度偏大；美国规范采用最大方向谱选取,具有更明确的物理意义；此外,中国规范仅规定了记录反应谱的相对误差,而美国规范规定了反应谱的下限.虽然中国做法避免了结果的保守,但是可能导致一条或几条记录与目标谱差距过大,容易造成结果存在离散性不可控；建议结合二者的优点,在控制相对误差的同时,也引入下限限制的遴选机制.

Abstract:

In order to study the differences in ground motion selection schemes at home and abroad, code for seismic design of buildings (GB 50011—2010) and minimum design loads and associated criteria for buildings and other structures (ASCE/SEI 7[KG-2mm]-16) were taken as examples, and the corresponding selection results were compared. Through the conversion of design spectrum parameters, ground motion records were selected at the same seismic fortification level under two working conditions according to the methods in two codes, which were then used as dynamic time history input for 4-story and 12-story concrete frame structures to compare the story displacement angle and story shear force. Results show that the selection and amplitude scaling based on a single direction according to the Chinese seismic code may result in a low matching degree in the other direction and a large dispersion of the calculation results. The American seismic code adopts the maximum direction spectrum, which has clearer physical meaning. In addition, the Chinese code only specifies the relative error of the recorded response spectrum, while the American code specifies the lower limit of the spectrum. Although the Chinese code avoids the conservativeness of the results, it may lead to significant disparities between one or more records and the target spectrum, which may cause the dispersion of the results to be uncontrollable. Hence, it is suggested to combine the advantages of the two methods to control the relative error and the lower error limit.