The Probabilistic Model Of Resistance Degradation For Corroded Reinforced Concrete Beam

Severely affected by material aging、poor environment and misapplication，theresistances of reinforced concrete（RC）beams deteriorated so that the safety anddurability decreased. With the increase of collapse、maintenance and reinforcementfor bridges, the durability of corroded RC components were focused by researchers.The steel-bar corrosion is the overriding reason in all factors that lead to theresistance degradation of RC beams. Therefore, the accurate assessment ofresistance of corroded RC beam is very important .This research project is supported by National Natural Science Fund of Chinaunder the Project No. 50878031“research on shear capacity deterioration modeland reliability of existing RC bridge”and Excellent Postgraduate Innovation Fundof Hunan Province under the Project No. CX2011B355“the time-variant reliabilitycalculation of RC beam bridge with considering the resistance deterioration”. Thispaper focused on the resistance degradation of RC components in chlorideenvironment. The main research works included as follow:(1) Based on the existing research on steel-bar corrosion, the sectional area andyield strength degradation curves of reinforcements were plotted for local corrosionand the impact of concrete cover on sectional area degradation was discussed.(2) The flexural capacity formula of corrosion beam was adopted based onimproved strain relations between reinforcement and concrete. Combined with thedegradation models of corroded reinforcement for area and strength, the probabilitymodel of flexural capacity degradation for corroded RC beam was presented. Incomparison of the parameter sensitivity analysis, the results showed that the impactof concrete cover on the flexural capacity degradation rate was the most significant(3) The difference between the flexural capacity degradation models that basedon the improved strain relations and bond strength loss were comparativelyanalyzed. The calculation results showed that the maximum difference of flexuralcapacity degradation was 12%.(4) The probability models of shear capacity degradation that based on theexisting codes were compared. The result showed that the maximum difference was 3%. In comparison of parameter sensitivity analysis, the thickness of stirrup coverand chloride concentration had more impact on the degradation initiation time.However, the thickness of diagonal reinforcement cover and chloride concentrationhad more impact on the shear capacity degradation rate.(5) The degradation curves of shear and flexural capacity in 100 years wereplotted and compared. The results showed that the shear capacity degraded fasterthan flexural capacity but slower than that after the 63rd year.