抗剪强度指标可靠度分析

RELIABILITY ANALYSIS ON SHEAR STRENGTH PARAMETERS

由试验确定抗剪强度指标, j c的分布规律时,常遇到的问题是样本有限,并且, j c是存在着较强负相关的二维联合概率分布,按某一强度保证率不能唯一地确定一对分项系数设计所需要的抗剪强度标准值。一般地说,单点试验成果(iist ,)无法唯一地确定)(iic,j。采取一种新的思路,假定对每个试验点(iist ,)都存在相应一组)(iic,j,该)(iic,j是所有满足试验点(iist ,)的组合中出现概率最大的组合。这样求解)(iic,j的问题即成为可靠度方法求解设计验算点的问题。一旦所有的)(iic,j全部定出,, j c的分布规律时也随之确定。在确定)(iic,j的同时,该点的可靠度指标ib也随之确定,可以用ib来衡量各点离散度,这样一个二维联合概率分布便转换为一个一维的概率分布问题。由此只需给出一保证率, 即可定出该保证率下的, j c值。

A reliability model of shear strength of rocks and soils from test data is proposed. The model possesses special advantage for limited test samples. The shear strength parameters,j and c,generally are of two dimen- sional probability distribution with strong negative correlation. Using this reliability model,one single guaranteed factor can be used to determine uniquely the design values of j and c.