Incorporating common-cause failures into nonrepairable multistate series-parallel system analysis

This paper adapts the universal generating function method of multistate system reliability analysis to incorporate common-cause failures (CCF). An implicit 2-stage approach is used. In stage #1, a polynomial representation of system-output performance distribution is obtained without considering system elements which are subject to CCF. In stage #2, the contribution of CCF is correctly included based on information stored in vector-indicators that describe states of system elements belonging to various common-cause groups. A straightforward procedure is suggested for evaluating reliability functions of nonrepairable series-parallel multistate systems with CCF. This procedure allows the reliability functions to be obtained numerically. Examples are given.