Reliability allocation with partial redundancy

Concentration on the modeling of failure rates has produced a body of results only tangentially useful in the logistics modeling applications. The rate of occurrence of failures (ROCOF) is a more pertinent measure for such problems. This useful measure has been largely overlooked as a result of the relative rarity of redundancy. Increasingly complex systems and stringent operational demands have increased the degree of redundancy recently, however, and the utility of the ROCOF concept has increased (parri passu). This paper develops a generalized ROCOF solution for k of n systems, carefully distinguishing between the frequency of system failure (the ROCOF) and an allied concept, the rate at which demands are placed on the support infrastructure. It concludes with a discussion of reliability allocation in the presence of redundancy.