Research On Shrinkage And Creep Effect Of C60 Low Shrinkage And Low Creep High Performance Concrete And Influence

With the wide application of high-performance concrete in long-span bridge structures,problems such as deflection,prestress loss and stress redistribution of in-service bridge structures caused by concrete shrinkage and creep have become increasingly prominent,which are directly related to the service life of bridge structures.Therefore,it is very necessary to carry out research on the shrinkage and creep effect of high performance concrete.At present,there are few studies on the shrinkage and creep effect of C60 low-shrinkage and low-creep high-performance concrete,which seriously restricts the promotion and application of C60 low-shrinkage and low-creep high-performance concrete in concrete structures.To this end,this paper,funded by the Open Project of the Bridge Structural Health and National Security Key Laboratory(BHSKL20-07-GF),has carried out the following work on the shrinkage and creep effect of C60 low-shrinkage,low-creep high-performance concrete and its influence:(1)Through the research on shrinkage and creep of C60 low shrinkage and low creep high performance concrete at different ages(7d,24d)and different stress levels(0.2fc,0.3fc,0.4fc,0.5 fc),it was revealed that C60 low shrinkage The shrinkage and creep mechanism of low creep high performance concrete was analyzed,and the relationship between shrinkage and creep with time was analyzed,and it was deduced that the boundary point between linear creep and nonlinear creep was about 0.5 fc.At the same time,the basic mechanical test research of C60 low-shrinkage and low-creep high-performance concrete for multiple ages was carried out,and the time-varying law of mechanical properties of C60 low-shrinkage and low-creep high-performance concrete was analyzed.(2)By comparing the shrinkage and creep test results of C60 low shrinkage and low creep high performance concrete with the shrinkage and creep calculation results of common domestic and foreign standard models(ACI-209,GL2000,JTG 3362-2018 and AASHTO),the test was analyzed.The difference between the results and the calculation results of the specification model,then,based on the test results,the JTG 3362-2018 specification model was revised,and a prediction model for the shrinkage strain and linear creep coefficient of C60 low-shrinkage and low-creep high-performance concrete in a conventional environment was established.The prediction accuracy and the nonlinear creep law of 0.5fc are obtained.(3)Taking a long-span prestressed continuous rigid frame box girder bridge as an example,a finite element model was established to analyze the structural internal force,stress,stress and stress of the C60 low-shrinkage,low-creep high-performance concrete shrinkage and creep effect during the service period of the bridge.The effect of deflection and prestress loss.In addition,the time-varying reliability calculation model of the bridge’s flexural bearing capacity and the lower deflection limit state is established.By integrating the prior information of concrete materials and data samples,the model parameters are updated using the Bayesian method,and the time-varying reliability of the bridge’s service life is predicted.