ABSTRACT
Reinforced concrete (RC) structures may be subjected to harsh environments during their service life. Deterioration of structural performance can jeopardize serviceability or even structural safety. Therefore, necessary maintenance/strengthening interventions must be scheduled during and/or after the design service life of a structure. As a RC bridge continues to age, the lifecycle cost of strengthening can become tremendous so that the scheduling and selection of strengthening interventions must be optimized to minimize the life-cycle cost.
Time-dependent reliability analysis has been used to schedule maintenance actions of deteriorating structures based on a reliability threshold. Existing algorithms for time-dependent reliability problems usually adopt a deterministic function to model structural deterioration. An unfavorable implication of using a deterministic deterioration function is that the time-dependency of uncertainty in resistance is totally neglected.
The present paper presents an improved threshold-based approach for rational scheduling and selection of maintenance actions for deteriorating RC structures, with particular application to the fiber-reinforced polymer (FRP) strengthening of RC bridge girders in marine environments. By virtue of this approach, life-cycle performance in terms of time-dependent reliability can be evaluated for deteriorating RC structures before and after maintenance interventions. A simplified method is proposed to consider the time-dependent uncertainty in structural resistance in a computationally efficient manner. State-of-the-art deterioration models for FRP-strengthened RC bridge girders exposed to a marine environment are adopted to evaluate the time-dependent reliability of RC bridge girders before and after strengthening. The methodology is demonstrated in detail using a numerical example.
From the study, it is found that the influence of time-dependency of uncertainty in resistance should not be ignored in the threshold-based scheduling of maintenance actions. Omission of this factor may cause substantial maintenance delays, as shown in Figure 1. Time-dependent failure probability of the RC girder: effect of time dependency of uncertainty in resistance. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig172_1.tif"/>
The proposed approach is applicable to the scheduling and selection of various maintenance actions that enhance the load-carrying capacity of the structure. The effectiveness of the proposed approach hinges on the accuracy of the structural performance deterioration models employed in the analysis. For the proposed approach to be used in the scheduling and selection of externally-bonded FRP strengthening systems in practice, more research is needed on the modeling of deterioration of FRP composites and FRP-concrete bonded interfaces.
