On selecting components for redundancy in coherent systems

We study the problem of selecting components for redundancy in coherent systems to maximize system reliability. For this optimization problem most of the previous results are obtained under the assumption that the values of component reliabilities are known, or at least an ordering of them must be known in advance. However, in many practical situations such information about component reliabilities is unobtainable. In this paper we propose selection criteria based solely on structural information, and show that the resulting selections from the criteria are optimal when certain conditions are satisfied. Some numerical examples illustrate that the selection methods we propose are easy to apply and perform quite well in practical structures.