Optimal design of series-parallel systems considering maintenance and salvage value

A reliability based design model is developed for a series-parallel system with deteriorating components in order to minimize the life cycle cost of the system. The effects of fixed asset depreciation, preventive maintenance and minimal repair are incorporated in the model. We also propose equations to model the effects of preventive maintenance on the system's failure rate and the salvage value as functions of time. Genetic algorithms are used to perform constrained optimization of the system cost function subject to both active and non-active constraints. The results are useful for engineering economists, reliability engineers, and system designers.