| The durability of reinforced concrete bridges has become one of the most concerned problems in the field of engineering at home and abroad due to the continuous attack of corrosion factors in the service environment and the increasing of performance load.The durability assessment and reliability analysis of reinforced concrete bridges can not only reveal the potential risks faced by the structures in service,and facilitate the scientific and reasonable arrangement of maintenance resources,but also can be used to guide the structural design.The comprehensive effect of various corrosion factors(such as freeze-thaw,carbonization,chloride erosion,etc.)in the service environment leads to the deterioration of structural material properties,which eventually leads to the decline of resistance and durability life,bringing hidden dangers to the safe performance of bridges.In this paper,the environment with multiple corrosion factors in north China is analyzed,the time-varying bending resistance model based on reliability theory is established,and the dynamic reliability index of existing bridges are calculated by solving the durability limit state equation.This method is in harmony with the current unified standard method of reliability design.Firstly,this paper analyzes the main corrosion factors(freeze-thaw,carbonization,chloride erosion)that affect the durability of reinforced concrete bridges and their mechanism of action systematically.And the influence of corrosion factors on material properties is mainly discussed.Considering the service environment with multiple corrosion factors and referring to the research results of previous scholars,the degradation rules of concrete strength,steel strength and steel cross-sectional area are analyzed.Based on the fine modeling of ANSYS finite element software and considering the bond and slip relationship between steel and concrete,this paper explores the degradation model of the co-working coefficient of corroded steel and concrete,and finally establishes the bridge bending resistance degradation model in the multi-factor corrosion environment.Based on the current standard vehicle load data,this paper establishes the maximum load distribution function of the vehicle under different operating conditions during the service period.Based on the survey data of vehicle load,the probability distribution model of measured load in bridge service period is established by analyzing the effect of vehicle load in Luogang Section of National Highway No.107.On the basis of the resistance degradation model and the load probability model,the random process is variablized by using the reliability theory,and the first-order second-moment method is employed to solve the structural dynamic reliability index.Based on the MATLAB platform,a program is developed to solve the dynamic reliability index of bridge structure by JC method.The dynamic reliability index is calculated and the influencing factors are analyzed for an engineering example. |
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