Effect of Different Limit States on Life-Cycle Cost of RC Structures in Corrosive Environment

Abstract

The paper considers the comparative effect of ultimate limit states and a serviceability limit state associated with cracking and spalling of the concrete cover on the expected life-cycle cost of reinforced concrete (RC) structures subject to chloride-induced corrosion. A simple computationally efficient method for the evaluation of the expected costs of failure due to ultimate and serviceability (i.e., spalling) limit states is described. Ratios between the expected costs of failure associated with spalling and with ultimate limit states have been estimated as a function of the time between repairs for different design specifications, environmental conditions, and discount rates. Using these results, in the cases when the expected cost of failure associated with ultimate limit states is quite significant compared to that due to spalling and hence, cannot be neglected in a life-cycle cost analysis can be easily determined. Optimum times between repairs, which minimize the total expected cost of failure, have been calculated as a function of the ratio between the failure costs for ultimate and serviceability limit states. The effect of other parameters such as concrete strength, thickness of the concrete cover, the discount rate, and exposure conditions on the optimum times between repairs has also been examined.