土体地震反应分析的简化有效应力法

A SIMPLIFIED EFFECTIVE STRESS METHOD OF SOIL MASS EARTHQUAKE RESPONSE ANALYSIS

本文提出了一个计算二维土体地震反应的简化有效应力法。该方法将整个地震持时分成若干时段,对每个时段用等效线性迭代进行多次线性分析,等效剪应变幅值取为该时段剪应变均方根值的2^(1/2)倍。本法不仅考虑了动模量与动剪应变之间的非线性关系,而且还考虑了振动孔隙水压力的增长对土的模量和强度的衰退作用。最后,以饱和砂土水平场地为例,用本文建议的方法分析了场地的地震反应特性,并与常规的等效线性总应力法的计算结果作了对比。

Based on the principle of effective stress a simplified method of 2-D soil mass earthquake response analysis is presented in this paper. The basic premise of the method is that soil moduli and damping ratios can be updated at various time intervals so as to be consistent with the root-mean-square (rms) values of the shear strain during the same interval.i. e. the duration of earthquake is divided into several time intervals and a series of iterative linear analyses for each and every time inteval are performed and the equivalent shear strain amplitude in the linear iteration is equal to multiplied by the rms value of the shear strain during the same interval. By this method not only the non-linear relationship between dynamic shear strain and modulus is considered but also the degradation of the shear modulus and strength of saturated sandy soils due to the effect of excess pore-water pressure builtup is considered. At last as an example of the proposed method a detailed numerical analysis of site earthquake response for horizontal layered saturated sand is given and comparison of the results with those of routine equivalent linear analysis on total stress method is also given.