Abstract
This paper assessed the service life of RC bridges subjected to carbonation under a changing climate based on time-dependent reliability analysis. First, a simplified carbonation model and the corresponding incremental method were briefly reviewed. Then, the fatigue damage prediction model and climate model were briefly introduced. Afterward, the Monte Carlo simulation-based time-dependent reliability analysis procedure for service life assessments was presented, which integrated the carbonation depth prediction model, fatigue damage prediction model and climate model. Based on the analysis procedure, a comprehensive case study was conducted to estimate the effects of climate change, fatigue damage, concrete cover thickness and concrete grade on the service life under different reliability levels. The case study showed that the service life under a reliability level of 2 is around half of that under the reliability level of 1. Under the reliability level of 1.5, the service life under RCP8.5 (a high emission scenario defined by Intergovernmental Panel on Climate Change) can be 28 years shorter than that under no climate changes. The service life at girder top undergoing compressive fatigue damage can be 49% shorter than that without fatigue damage and 25 years shorter than that at girder bottom undergoing tensile fatigue damage. The service life at girder top with a concrete cover thickness of 45 mm can reach 2.6 times that with a concrete cover thickness of 25 mm. The service life of C50 concrete can reach approximately 2–3 times that of C30 concrete. These findings inform civil engineers that for existing RC bridges, the effects of climate change and fatigue damage should be properly considered when the remaining service life of RC bridges is concerned. Moreover, for planned RC bridges, higher concrete grade and thicker concrete cover are two effective choices to achieve a longer service life.
Highlights
Corrosion of steel reinforcements is the key to deterioration of the mechanical performance of reinforced concrete (RC) members and structures [1,2,3,4,5]
The numerical carbonation model predicts carbonation depths in fatigue-damaged concrete with very good accuracy, the huge computational costs required for solving partial differential equations make the numerical carbonation model difficult to handle by civil engineers
The carbonation depths predicted by the simplified carbonation model showed acceptable agreement with both the ones reported by experiments and the ones predicted by the numerical carbonation model
Summary
Corrosion of steel reinforcements is the key to deterioration of the mechanical performance of reinforced concrete (RC) members and structures [1,2,3,4,5]. Because of the time-variant stochastic nature of fatigue damage and environmental actions, uncertainty of concrete property and randomness of concrete cover thickness, the time to corrosion initiation, or the service life, as well as the carbonation depth evolution, in realistic RC bridges is highly scattered. Thiery et al [22] conducted probabilistic analysis of carbonation depths and assessed the time to corrosion initiation of steel reinforcements which considered the randomness of environmental actions, concrete properties and concrete cover thickness They ignored the effects of global climate change, i.e., time-varying annual mean values of temperature and CO2 concentration. In this paper, the authors conducted time-dependent reliability-based service life assessment of RC bridges subjected to carbonation under a changing climate with considerations of time-varying fatigue damage and environmental actions.
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