# 6.1 Explicit Method

The basic idea of the explicit method is to evaluate an expanded system model that is constructed by modeling the occurrence of each CC as a basic event shared by all the components affected by this CC in the original system model [8,9].

## 6.1.1 Two‐Step Method

The explicit method involves a two‐step process given below.

*Step 1: Build an expanded FT*. To consider effects of CCFs, a logic OR gate is introduced for each component affected by at least one CC, and each CC is modeled as a repeated input event to all component OR‐gates failed by this CC.*Step 2: Evaluate the expanded FT*. The expanded FT can be evaluated using any traditional FT reliability analysis method, e.g. the binary decision diagram (BDD)‐based method (Section 2.4) to obtain the system unreliability, considering effects of CCFs.