강도노후화 모델을 적용한 철근콘크리트 보의 시간의존적 신뢰성해석에 관한 연구

Reinforced concrete structures in service are generally deteriorated with time due to environmental stressors. To further use the degraded structures, it is required to analyze quantitatively the resistance of the structural system at the present time, and the method to analyze the effect of the degradation on the structural system should be developed. But not much study has been done in this area and the reliability theory can be a candidate to be applied for the quantitative analysis, because the factors affecting the degradation can be treated as probabilistic variables and there are also many uncertain factors to estimate the strength or the resistance of existing structures, e.g. errors of the design or the construction, severe applied loads, occurrence rate of concrete crack, and especially the corrosion rate of reinforcement, etc. Corrosion of reinforcement in concrete may lead to the loss of the strength and serviceability of the existing concrete members and to the ultimate failure of the structure. The rate of the strength loss depends on the resistance degradation mechanism, e.g. sulfate attack, alkali-silica reaction, freeze-thaw cycle attack, carbonation and maximum crack width of concrete and corrosion. To assess the existing members quantitatively and reasonably, methods are developed using the time dependent reliability (TDR) analysis in structural reliability principles. Consequently, this study was executed to analyze a structural resistance degradation model for the existing girder in the 3-story building to be remodeled. The probabilistic random variables in this study were dealt with an in-situ and current maximum crack width, current density and diameter of reinforcement with time and corrosion initiation time, which were gained by TDR analysis to calculate the reliability index, the failure probability, the degradation level and the flexural strength loss in reinforced concrete girders due to corrosion of steel reinforcement.