我国现行抗震设计规范中场地评定方法的比较和评述

DISCUSSION ON SITE ASSESSMENT METHODS USED IN CURRENT ASEISMIC DESIGN CODES

目前,我国抗震设计规范中采用的场地评定方法主要有两种,一是建筑抗震设计规范(GBJ11-89)采用的场地分类的方法,一是构筑物抗震设计规范(GB50191-93)和电力设施抗震设计规范采用的场地指数法。前者是把场地影响按照场地分类指标划分成若干场地类别,因此,确定的地震荷载是不连续的,跳跃变化的。后者是一种以模糊推论的综合评判方法导出的场地指数为指标进行连续评定的新方法,在这种方法里,场地性质的差异是以连续变化的场地指数表示的,地震反应谱(地震荷载)是用场地指数的函数形式表示的连续谱,因而克服了场地分类跳跃变化的不合理性。本文对上述两种方法进行比较,并重点论述了场地指数法在评定场地中的合理性和适用性。

At present mainly two kinds of site assessment methods are used in the ascismic design codes in China. Namely the site classification method used in the building ascismic design code (GBJ11-89) and the site index method adopted by the aseismic design code for structures (GB50191-93) and the aseismic design code of electric installations. For the former the site influence is expressed by dividing sites into several categories according to the classification index. Therefore the determined earthquake load is discontinuous and jumpy. The latter is a new continuous assessment method which uses the site index based on the synthetic assessment with fuzzy inference as the criterion. For this method the difference of the site characteristics is expressed by continuously changeable site index the earthquake response spectrum is a continuous spectrum as the function of the site index without the unreasonable jumping by the site classification. In this paper the above two methods arc compared and the rationality and applicability of the site index method in site assessment are emphatically discussed.