Research On Durability Of Cable-stayed Bridges In Service Based On Time-varying Reliability Theory

As an important type of city bridge,cable-stayed bridge has the advantages of beautiful shape,economical application and high crossing ability.It is the bridge type that most countries in the world strive to develop.However,with the increase of operating time,the change of natural environment,traffic is becoming more and more busy and load level enhances unceasingly,the disease is increasingly serious,rapid degradation resistance,cause a lot of cable-stayed bridge structure had not reached the design service life,durability and the insufficient bearing capacity,can not meet the normal operation of the bridge structure,scientific and reasonable to the durability and reliability of the cable-stayed bridge structure in service evaluation,has become an important in the field of Bridges at home and abroad academic research projects.By studying the durability of cable-stayed bridges on the fly based on the theory of time-varying reliability,one can effectively solve the problems related to durability in the design,construction and operation of cable-stayed bridges;on the other hand,It can contribute to the scientific management and maintenance of cable-stayed bridge structures in service.In this paper,based on the theory of time-varying reliability,combined with the current research results in the durability and remaining service life prediction of prestressed concrete and steel strands,carbonization of prestressed concrete,strength degradation,steel corrosion,The durability of the cable-stayed bridge mechanism in service is analyzed in terms of the corrosion of the prestressed steel bar,the durability degradation of the cable stayed cable considering the corrosion and fretting fatigue,and the load effect,and the remaining service life is predicted and analyzed.The specific research content is as follows:1.Through the on-the-spot investigation and inspection of related data,this paper statistically analyzes the common disease conditions of cable-stayed bridges in service,and analyzes the main disease damage mechanisms and the influencing factors of durability in depth.Influence of Common Diseases of Cable-Stayed Bridge Structures(Crack,Steel Bar Corrosion,and Loss of Prestress)on Their Durability.2.Based on the actual characteristics of resistance degradation and load action of cable-stayed bridges in service,this paper considers many uncertain factors affecting its durability,and adopts the theory and method for calculating the structural reliability of cable-stayed bridges in service.With respect to the time-varying characteristics of resistance degradation and load effects of the bridges of prestressed concrete beams(towers)and cable stayed-stayed bridges,a durability degradation model based on time-dependent reliability theory was established for cable-stayed bridges in service.3.This paper takes the Yintan Yellow River Bridge in Lanzhou City as the engineeringbackground,combines the theory and model of the time-varying reliability calculation and analysis established in chapters 3 and 4 of this paper,and uses the reliability JC method compiled by MATLAB to calculate the program and its time-variable reliability.The indicators are analyzed and calculated,and the durability of the indicators is analyzed based on the calculated time-varying reliability index.The remaining service life of the bridge structure is predicted by combining the calculated time-varying reliability index with the bearing capacity life prediction criteria of the bridge structure.