Analysis Of Temperature Field And Temperature Effect Of Long-span Cable-stayed Bridge

The occurrence of cracks is an important reason that affects the durability of concrete structures.There are many factors that affect cracks in concrete bridges,and temperature load is an important factor for cracks in concrete bridges.Due to the poor thermal conductivity of the concrete structure,a nonlinear temperature gradient will be generated inside the structure under the influence of external factors such as solar radiation and temperature changes.This nonlinear temperature gradient will generate a considerable amount in the concrete bridge structure.Then,temperature deformation will cause temperature stress,which in turn can cause cracks in the concrete structure.The problem of temperature effect on concrete structure is getting more and more attention from the engineering community.In this paper,the temperature field and temperature effect of the long-span cable-stayed bridge are mainly analyzed with the engineering background of the Chishi Extra Large Bridge(165+3x380+165)m in Chenzhou City,Hunan Province.According to the distribution of the measured temperature field about the concrete box beam,the vertical temperature gradient function of the main beam is fitted by the method of least squares and exponential function based on the theoretical knowledge of astrophysics,meteorology and heat transfer.Comprehensive considering various influencing factors,the boundary conditions required for finite element analysis are established.I use ANSYS software to establish a two-dimensional thermal analysis model that ignores longitudinal heat conduction,and conduct transient thermal analysis of the temperature field about the main beam section to obtain the temperature distribution of the box beam section at each time.And I analyze the sensitivity parameters of the verified model.Then,the ANSYS software was used to establish the plane strain element model and the indirect coupling method was used to calculate and solve the lateral temperature stress and longitudinal temperature self-stress.The MIDAS/CIVIL software is used to establish the full-bridge finite element model.The equivalent linear temperature difference of the nonlinear temperature gradient is obtained according to the principle of uniform deformation,and then the longitudinal temperature secondary stress is solved.Secondly,the vertical temperature gradients stipulated in different national regulations and the temperature effects caused by the vertical temperature gradients that were fitted in this paper were calculated and analyzed.The main comparative analysis was about the magnitude of temperature stress and displacement generated under a temperature gradient with different vertical directions during the maximum cantilever stage and the bridge operation stage.