Integrated Life-Cycle Framework for Optimal Inspection, Monitoring and Maintenance under Uncertainty: Applications to Highway Bridges and Naval Ship Structures

Existing engineering structures are continuously deteriorating and their lifetimes are limited. In order to help ensure the structural safety and extend the service life of existing deteriorating structures, significant research efforts for establishing cost-effective maintenance strategies have been made. A life-cycle analysis usually depends on structural assessment and prediction models under uncertainty. The accuracy associated with these models can be considerably improved if the data from structural health monitoring (SHM) are used efficiently. Therefore, integration of SHM into maintenance management has recently been considered as a significant tool for rational maintenance planning. Improved accuracy of structural performance assessment and prediction by SHM can lead to timely and appropriate maintenance interventions, resulting in reduction of both expected failure cost and expected maintenance cost of deteriorating structural systems. In order to maximize this potential benefit of SHM, information from monitoring has to be used appropriately, and an effective optimum monitoring planning is necessary. Furthermore, lifetime optimization of inspection, monitoring, and maintenance strategies needs to be investigated in a life-cycle management framework. The main focus of this study is the development of a rational probabilistic integrated framework for optimum inspection, monitoring and maintenance planning. Based on concepts of probability and reliability, novel approaches to assess and predict the structural performance using SHM data are developed and applied to existing highway bridges. For optimum inspection and monitoring planning under uncertainty, several probabilistic approaches are developed in this study. Optimization formulations for these approaches are based on the concepts of availability, damage detection delay, and time-based safety margin. The inspection or monitoring plan is a solution of a multi-objective optimization problem under uncertainty. The uncertainties associated with damage occurrence and propagation, and quality of inspection method are considered within the optimization problem. These approaches are applied to deteriorating structures (i.e., highway bridges, naval ships) under various deterioration mechanisms (i.e., corrosion, fatigue). Furthermore, considering the effects of probabilities of damage detection and repair on future structural performance, the optimum inspection and maintenance strategy under uncertainty are addressed to extend the lifetime of deteriorating structures