Life-Cycle Cost Assessment of Maintenance Strategies for RC Structures in Chloride Environments

Abstract

Corrosion of the reinforcing steel can cause cover cracking and eventual spalling of reinforced concrete (RC) surfaces, resulting in costly and disruptive repairs. The present paper will compare the effect of maintenance and repair strategies on the timing, extent, and cost of remediation actions over the service life of a RC structure in a chloride environment. The paper presents a probabilistic reliability analysis, which is used to predict the likelihood and extent of corrosion-induced cracking to RC structures. A spatial time-dependent reliability model has been developed where concrete properties, concrete cover, and the surface chloride concentrations are treated as random fields. This allows for the calculation of the probability that a given extent of damage will occur for any time period. Maintenance strategies and repair efficiencies are incorporated in a Monte-Carlo event-based simulation analysis, allowing a comparison in terms of cost and number of repairs over the service life of a RC structure. Thus, the expected timing and extent of repairs can be predicted for various design parameters, inspection intervals, repair thresholds, maintenance strategies, and efficiency of repairs. Results are presented for a RC bridge deck subject to a marine environment. The life-cycle cost (LCC) analysis considers repair and user delay costs. User delay costs can be up to ten times higher than the cost of repair itself. The statistical variability of predicted LCCs can be large, with coefficients of variation exceeding one.