Analysis of common mode failures of redundant system with dependent human error

Abstract

The purpose of this thesis is a theoretical investigation of CMFs on the failure probability of redundant system. It is assumed that total CMFs are divided into two kinds: one is caused by human errors during maintenance and the other is caused by earthquake, fire, missile, etc. The latter is called by potential CMFs. Two programs are developed for calculating the failure probability of the redundant system considering CMFs. One is developed using the modified Karnaugh map and it can analytically calculate the failure probability of simple system. The other is developed using minimal cut set and it gives the conservative solution, however it is applied to the complicated system. It is shown that as the dependence between human errors is lower, the failure probability strongly depends on the mechanical failure, and as the dependence is higher, human error is stronger contributor to the failure probability.