The Remaining Service Life Forecast Of Existing Reinforced Concrete Beam Bridge Based On The Fuzzy Time-Varying Reliability Theory

Since 1950 s,great achievements have been made in bridge construction in China,and a large number of reinforced concrete bridges have been built.However,due to the material properties of aging,the increasing traffic flow,reduce the durability,the reliability of existing reinforced concrete bridge analysis and evaluation become one of the key problems of domestic and international bridge in academic circles at present.Through the reliability analysis and residual life prediction of existing reinforced concrete bridges,it not only can reveal the potential danger,but also has important significance for the scientific and economic decision-making of bridge maintenance and demolition.Based on the existing reinforced concrete simply supported T beam bridge as an example,consider the impact of both the cracks appear on the bridge the bridge resistance,through the introduction of fuzzy mathematics,considering the fuzziness and randomness,a fuzzy reinforcement area,steel strength and concrete strength time-varying probability model establishment.The fuzzy time-varying probability model of the flexural member is established,and the fuzzy random time-varying function and the standard deviation fuzzy random time-varying function are obtained.Because of existing reinforced concrete bridge weight distribution statistical parameters by measuring the exact value of the constant load distribution parameters is affected by many uncertain factors,by considering the fuzziness,fuzzy membership function changes using the selected threshold to solve the existing reinforced concrete bridge dead load distribution statistical parameters variation the problem.According to the existing bridge traffic load effects are fuzzy and time-varying,the design reference period is altered as the evaluation target,evaluation target in the period of maximum distribution of vehicle load effect using fuzzy extreme value I distribution,establishes the fuzzy vehicle load effect time-varying probability model.The fuzzy limit state equation of the bearing capacity of the bridge is established by considering the fuzzy time-varying of the resistance and the vehicle load,and the fuzziness of the dead load.Based on the improved JC method and the MATLAB software,a program for calculating the fuzzy time-varying reliability index is developed.The results of this study can be concluded that: with the increase of time and the change of threshold value,the bridge reliability index is in the fuzzy state between the upper surface and the lower surface.The design life of the bridge is 50 years,when the threshold value,in the general operating state of the bridge is designed to meet the requirements of the service life.When the operation is 15%,the remaining life of the bridge is about 47 years,and the remaining life of the bridge is about 38 years when the operation is concentrated in a state of about 30%.It can be seen that the operational status of the bridge to a large extent affect the service life of the bridge.