Time-varing Characteristics And Control Of Moisture Filed In Arch Bridge Reinforcement Structual

When reinforced the concrete arch bridge structure by enlarging the section,the new concrete layer is easy to crack because of the large age difference between the new concrete layer and the existing structure.The decrease of internal relative humidity is the driving force of shrinkage and cracking.In order to study the time-varying characteristics of humidity field and shrinkage strain in concrete structure and explore the method of restraining the cracking of new concrete layer of reinforced concrete structure,the basic mechanical properties,the time-varying characteristics of internal humidity field and shrinkage strain of concrete of two strength grades under different curing conditions and strengthening tests are compared and analyzed in this paper.The finite element calculation model is calibrated by inversion of test data parameters.The long-term time-varying characteristics of moisture field and shrinkage strain in concrete structure and reinforced structure are numerically simulated.The experimental results show that the surface sealing treatment can effectively improve the tensile strength and elastic modulus of concrete,but reduce the compressive strength;it shows that the sealing treatment can effectively reduce the decrease of relative humidity and shrinkage strain in concrete;at the same time,according to the data of relative humidity and shrinkage strain,it is proved that there is a linear relationship between relative humidity and shrinkage strain in a certain range of humidity.The finite element model calibrated by parameter inversion of test data can truly reflect the time-varying characteristics of moisture field and shrinkage strain in concrete.The calculation model of test data calibration is applied to engineering example,and the crack depth of new concrete layer is deeper when the unclosed treatment is applied.The humidity gradient and uneven shrinkage between existing structure and new concrete layer can be effectively reduced by sealing treatment,and the crack risk of new concrete layer of reinforced structure can be reduced.The reinforcement test data show that the humidity of the existing structure increases rapidly and the shrinkage strain decreases rapidly after reinforcement.Surface sealing treatment can effectively reduce the shrinkage strain of the new concrete layer.The results of experiment and numerical analysis are applied to the reinforcement project of Quma Bridge.The research shows that the unclosed treatment is easy to cause cracks in the newly concrete layer,and the depth of cracks is deep.Surface sealing treatment can effectively reduce the humidity gradient between the existing structure and the newly concrete layer,and reduce the risk of cracking in the newly concrete layer of the reinforced structure.The experimental and theoretical analysis results show that the surface sealing treatment can effectively improve the splitting tensile strength of concrete,effectively prevent the decrease of relative humidity in concrete,reduce shrinkage strain and improve the crack resistance of components.