An Investment Staging Model for a Bridge Replacement Problem

This paper discusses the formulation and solution of a mathematical model of the selection and staging of bridge replacements in rural road networks. Both relaxation and decomposition strategies are used. First, a relaxation of the problem into a decomposable shortest path problem allows the identification of the bridge replacement alternatives which are most promising with respect to user cost. Next, the planning horizon is divided into time periods which are then ordered according to their relative importance. Finally, another decomposition in the form of a lexicographic optimization is used to select and schedule the bridge replacements. Within this lexicographic optimization a sequence of computationally feasible integer programming problems is solved.