中美设计规范中场地分类和场地效应的比较

COMPARATIVE ANALYSIS OF SITE CLASSFICATION AND SITE EFFECTS BETWEEN CHINESE CODE GB50011—2001 AND FEMA450

主要研究中美抗震设计中的场地分类和考虑场地效应的差异问题。首先,比较分析了一般场地、20 m深度范围内含软弱夹层场地、20 m深度以下含软弱土层场地的分类结果,发现FEMA450的场地分类对20m深度范围内软弱夹层厚度的反映比GB50011—2001更敏感,对20 m深度以下软弱土层厚度的考虑比GB50011—2001更细致。然后进行了不同场地、不同地震动水平下的反应谱比较,结果表明,FEMA450更合理地考虑了不同地震动特性下的场地效应。

The difference of site classification and site effects between Chinese Code GB 50011--2001 and FEMA450 is studied in this paper. Firstly, comparative analysis of site class of ordinary site, site with soft interlayer within 20 m depth and site with soft soil layer below 20m depth is presented, it is found that the thickness of soft soil layer is more vulnerable to change site class of FEMA450 than that of GB50011--2001 for site with soft interlayer within 20 m depth, and more careful to be considered in FEMA450 for site with soft soll layer below 20m depth. Then, the response spectrums at all sites under different ground shaking are compared, and the results indicate that the effects of soil conditions on ground motion characteristics is more reasonable to be considered in FEMA450 than that in GB50011--2001.