Study On Hygrothermal Coupling Effect In Triangular Rigid Frame Area Of Long-Span V-Shaped Pier Rigid Frame Bridge

The V-shaped pier rigid frame bridge can effectively reduce the calculated span of the main beam and improve the bending angle of the structure,so that the structure not only has the bending resistance of the beam bridge,but also has the compression characteristics of the arch bridge,and the mechanical performance is good.However,its unique structural form has complex stress,large stiffness,and significant secondary internal force effect in the triangular rigid frame area where the V pier is rigidly connected to the No.0 block.In addition,due to the characteristics of thermal expansion and wet expansion and shrinkage of the concrete itself,and the excellent stability of the triangular rigid frame area,the structure is limited to offset the strain caused by temperature and humidity through free deformation.As a result,the triangular rigid frame area bears the temperature and humidity loads in the natural environment to produce large temperature and humidity secondary stresses,even exceeding the stress generated by the structure itself.When the tensile stress is too large,cracks appear on the outer surface.The combined effect of surface cracks,corrosive ions,loads and other unfavorable factors makes the cracks develop rapidly to the inside,which seriously affects the bearing capacity and durability of the structure and produces bridge operation safety problems.However,at present,the research on the local hygrothermal effect in the triangular rigid frame area of V-shaped pier rigid frame bridge is relatively scarce,which restricts the engineers ’ cognition of the hygrothermal effect in the triangular rigid frame area.Therefore,this paper relies on the Myanmar Gunnong Bridge to carry out the research on the thermal effect,wet effect and hygrothermal coupling effect in the triangular rigid frame area of V-shaped pier.The main work and conclusions are as follows :(1)Based on the European standard,the temperature and humidity variables are introduced into the thermal conductivity coefficient and the moisture diffusion coefficient,and the concrete heat and moisture coupling conduction model is constructed.The Hundt test is reduced and compared to verify the reliability of the wet heat conduction model in this paper.(2)The two-dimensional temperature field and humidity field of box girder are studied.The results show that the humidity diffusion speed will increase with the increase of temperature,but the temperature conduction speed is not affected by the humidity of concrete.The temperature gradient distribution under the coupled heat and humidity transmission is more similar to the actual situation than the temperature gradient of the single temperature field,and the provisions of the highway code for the temperature gradient do not consider the influence of regional climate factors,which causes inconvenience in the use process and needs to be further corrected.More reasonable.(3)The hydrothermal coupling effect and treatment measures of the triangular rigid frame area of the V-shaped pier rigid frame bridge are studied.The results show that the temperature plays a leading role in the hydrothermal effect of the concrete structure,but the humidity factor cannot be ignored.At the same time,the hydrothermal effect is not a simple superposition of the thermal effect and the wet effect.The thermal effect can be multiplied by the correction coefficient of 1.15 as the hydrothermal coupling effect stress of the structure.The application of white and other light paint on the outer surface of concrete structure can effectively reduce the value of tensile stress caused by hygrothermal effect and achieve the effect of controlling hygrothermal effect of concrete.(4)The influence parameters of hygrothermal coupling effect in triangular rigid frame area of V-shaped pier rigid frame bridge are studied.The results show that the hygrothermal stress of box girder and V-pier has a linear positive correlation with temperature and environmental relative humidity,and has a nonlinear relationship with environmental wind speed.The sensitivity of structural hygrothermal stress to temperature factor is always greater than that of relative humidity factor,while the sensitivity of wind speed factor is greater than that of temperature factor when it is less than 6m / s,and less than that of temperature factor when it is greater than 6m/s.