Study On Reasonable Value Of Target Reliable Index For Long-Span Cable-Stayed Bridgeby

The reliability theory of engineering structure is more and more applied to the design and evaluation of long-span steel cable-stayed bridge.One of the important parameters-the target reliability index directly affects the accuracy of the analysis results.For the study of this object long-span cable-stayed bridge steel main beam,if the direct use of the existing "highway engineering structure reliability design uniform standard" recommended target reliable indicators,there are two shortcomings:one,did not consider the service structure of the resistance time-varying;the second is for small and medium-span concrete bridge for a large number of statistical work after the calibration obtained.Based on this,this paper studies the relationship between the target reliability index and the design life span of the main girder of the long span cable-stayed bridge,and provides a certain value for the reliability evaluation and design of the long-span steel cable-stayed bridge The theoretical basis.The main work of this paper is as follows:(1)In view of the environment and characteristics of long-span steel cable-stayed bridge,it is considered that corrosion and fatigue are the two main factors that affect the attenuation of its resistance.The influence of the bending modulus and the alternating load of steel box girder under atmospheric corrosion is discussed The change of the residual stress of the steel box girder is proposed,and a resistance decay function for the main girder of the cable-stayed bridge is proposed,which can predict the change of the resistance of the steel box girder during service.(2)The probability distribution function and statistical parameters of the dead load of cable-stayed bridge are obtained by combining and calculating the weight of steel box girder with different weight of cable-stayed bridge.According to the existing literature,the results show that the proposed method is applicable to the long-span steel cable-stayed bridge.After the calibration of the existing standard,the recommended value of the constant and reliable index for the long-span steel cable-stayed bridge is given.(3)Through the finite element software ANSYS,the maximum distribution of the load effect of the steel cable-stayed bridge is analyzed,and the relationship between the load effect distribution at any time point and the maximum value distribution of the design reference load is obtained.When the cable-Change the law of change.(4)By analyzing the relationship between the time-dependent reliable index and the evaluation of the benchmark value of the reliable index,the time point of the maintenance and reinforcement of the long-span steel cable-stayed bridge is predicted.Based on the relationship between the reliable index difference and the time function,The relationship between the target reliability index and the service life of the bridge is considered as the function of the bridge.