Study On Shrinkage And Creep Effect Of Core Concrete Of Concrete-filled Steel Tube Arch Bridge

In the concrete-filled steel tube structure,the steel tube and the core concrete interact and complement each other to give full play to their respective advantages.But on the other hand,we must also see that the structural deflection changes caused by the shrinkage and creep of the core concrete and the redistribution of the stress after the system conversion have become increasingly prominent,which directly affect the durability of the structure.Therefore,the shrinkage and creep problem has become a factor that needs to be paid attention to in structural construction monitoring.Shrinkage and creep are the inherent properties of concrete under long-term load.Although domestic and foreign experts and scholars have studied this theory for nearly a hundred years,they have not reached a consistent conclusion on the selection of the calculation mode of shrinkage and creep of concrete filled steel tube.Moreover,the research on the shrinkage and creep effects of the core concrete of the concrete-filled steel tube arch bridge is mostly focused on the timeliness,and there is less research on the uncertainty.This paper takes the 457.6-meter-span Minjiang River Bridge as the engineering background,uses MIDAS/Civil finite element software to establish a real bridge model,and develops the time-dependent and uncertain shrinkage and creep behavior of long-span concrete-filled steel tube arch bridges.(1)Compare the consideration factors of each prediction model and its scope of application,and select CEB-FIP 1990,ACI 209R-92 and JTG/T D65-06-2015 three classic models at home and abroad to analyze the shrinkage and creep effects of the bridge,Compare the difference of the calculation results of the three prediction modes,and study its influence on the displacement and stress distribution of the main arch ring.(2)Conduct a half-year on-site real bridge deformation observation of the Minjiang Extra Large Bridge,compare the measured deformation value of the main arch ring section of the bridge with the calculated value of the shrinkage and creep mode,and select the shrinkage and creep prediction mode suitable for the Minjiang Extra Large Bridge.This lays the foundation for the study of bridge shrinkage,creep equivalent cooling value and uncertainty in this paper.(3)Inversely calculate the exact value of shrinkage,creep and temperature reduction in the "Code for Design of Highway Concrete Filled Steel Tubular Arch Bridges"(JTG-T D65-06-2015)through the selected shrinkage and creep prediction model,and select a new bridge example.verification.Compare the calculation of shrinkage and creep coefficient custom input in MIDAS with the calculation results of shrinkage and creep mode in the specification,and get the difference,and combine the shrinkage and creep properties of concrete-filled steel tube to explain how to accurately realize shrinkage and creep in the software Calculation of variable effects.(4)Based on the selected CEB-FIP 1990 shrinkage and creep model,the Latin hypercube sampling stochastic finite element method is used to carry out probability statistical analysis of uncertain factors,focusing on shrinkage,creep,28-day average compressive strength of concrete,The influence of the four uncertain factors of environmental relative humidity on the shrinkage and creep effect of arch rib core concrete,predict the long-term deformation and stress distribution interval of the Minjiang Bridge caused by the uncertain factors,and consider the most unfavorable shrinkage and creep to the greatest extent Happening.