Potential Use of Inventory Theory to Bundle Interventions in Bridge Management Systems

Before an optimal bridge management strategy can be determined in existing bridge management systems, there must first be a determination of the type and schedule of interventions to be performed on each element of the bridge to achieve a minimal-cost long-term steady state. Once these element-level strategies are known, they are grouped together, or bundled, to develop a management strategy for the bridge. This is currently done with a set of agency rules without regard to whether the bundle of interventions is optimal. Interventions are bundled because it is not desirable to perform interventions on the same bridge in successive years, principally because of user costs. The work discussed here uses inventory theory to bundle interventions on bridges optimally with multiple elements. Two examples are presented. Example 1 shows how a basic joint replenishment model can be used on a multielement bridge to determine optimal management strategies when interventions are bundled and a single-stage policy is used. Example 2 shows how a joint replenishment model with quantity discounts can be used to alleviate some of the problems with a basic joint replenishment model. The optimal management strategy determined in Example 2 is compared with the optimal management strategy determined when interventions are not bundled. Direction for future work is given.