Simulation-based Non-destructive Inspection Scheduling of Steel Bridges

A procedure for selecting an optimal NDI (non-destructive inspection) technique and associated schedule for fracture-critical member inspections on a specific steel bridge is presented. Information related to the probability of detection (POD) function (a measure of inspection quality) of alternative NDI techniques is utilized. Calculations based on use of the POD function together with Monte Carlo simulations of crack propagation in the detail of interest are performed. A cost function is formulated that includes inspection costs as well as possible failure costs with each candidate NDI technique and alternative inspection schedule. The selection of an NDI technique together with an associated schedule for fracture-critical inspections is thus formulated as an optimization problem that can guarantee minimum total cost. An optimal inspection frequency is sought as part of the optimization which utilizes appropriate constraints on inspection intervals and a minimum acceptable (target) structural safety level. A case study involving a box girder bridge is presented to illustrate the proposed probabilistic method.