Reliability Optimization for Complicated Systems with a Choice of Redundancy Strategies

Redundancy allocation is one of the common techniques to increase the reliability of the bridge systems. Many studies on the general redundancy allocation problems assume that the redundancy strategy for each subsystem is predetermined and fixed. In general, active redundancy has received more attention in the past. However, in real world, a particular system design contains both active and cold-standby redundancies, and the choice of the redundancy strategy becomes an additional decision variable. So, the problem is to select redundancy level for each subsystem, component and the best redundancy strategy in order to maximize the system reliability under system-level constraints. This paper presents a new mathematical model for redundancy allocation problem (RAP) for the bridge systems when the redundancy strategy can be selected for individual subsystems. The problem is classified as an NP-hard problem. In this paper, a special version of genetic algorithm (GA) is applied, which has been modified for constrained integer nonlinear problems. Finally, computational results for a typical scenario are presented