Lifetime maintenance strategies for deteriorating structures

In general, systems such as buildings, bridges, and offshore platforms experience decrease in reliability and need appropriate maintenance actions during their service life. The objective of management of civil infrastructure systems is to allocate and use the limited resources to balance lifetime reliability and life-cycle cost in an optimal manner. This objective can be effectively achieved when the time-varying characteristics of structural systems are considered.; Recent studies indicate that similar structures designed and constructed to the same requirements end up with different reliability levels. Several studies also indicate that the deterioration rates of these structures are different. As a result, the likelihood of occurrence of limit state violation at any stage during the intended service life of a group of similar structures has to be based on whole-life performance reliability studies.; In this study, the framework of lifetime reliability-based optimum maintenance for deteriorating structures is developed. The time-varying reliability index profile for a group of similar structures including uncertainties existing in variables and parameters is investigated. Several ways are suggested to generate the reliability profile considering the effects of essential and preventive maintenance. Existing data are studied based on statistical methods to obtain and calibrate the main descriptors of random variables associated with the reliability profile. Monte Carlo simulation is used to take into account the propagation of uncertainties during the service life of deteriorating structures. Evaluation of the rehabilitation rates is approached from a reliability viewpoint. Sensitivity measures are defined and evaluated to investigate the influence of the random variables on the rehabilitation rate.; Cost analysis is one of the important processes in life-cycle management of civil infrastructure systems. In this study, the interaction between maintenance costs and reliability profile is considered. A continuous mathematical programming method is modified to solve the reliability-based lifetime maintenance cost optimization problem. The branching technique and the multi-dimensional interpolation method are adopted to increase the efficiency of the optimization process.; Three computer programs REHAB, FMAINT, and MLTR have been developed during this study. The proposed approach is applied to both single and groups of deteriorating structures. The proposed framework can be applied to the lifetime maintenance of any structural or non-structural system under time-varying reliability conditions.