Analysis Of Temperature Field Distribution And Its Effect On Structure Behavior Of Long-span Concrete Cable-stayed Bridge

In long-span concrete cable-stayed Bridges,temperature effect is one of the important factors affecting the structural behavior of cable-stayed Bridges.The stress effect produced by temperature effect in concrete box girder Bridges can be comparable to the live load effect,and climate factor is the most important cause of temperature effect.In this paper,the temperature effect of the long-span concrete box girder bridge caused by sunshine is analyzed by using ANSYS two-dimensional finite element simulation technology.Relying on the long span concrete cable-stayed bridge project in Chongqing,the most unfavorable positive temperature gradient of main girder and main tower is worked out by comparing the finite element calculation results with the measured values,and the Midas full bridge model is used for analysis.The standard temperature gradient is compared with the actual most unfavorable positive temperature gradient.This paper introduces how to make the first tension of the form and cable force considering the influence of temperature in beam sections with different cantilever lengths,and puts forward two correcting methods.The main work is as follows:(1)According to the heat transfer theory,the concrete thermal conductivity coefficient,specific heat,short-wave radiation absorption rate,surface reflection absorption rate,atmospheric transparency coefficient,and other parameters are reasonable values,the radiation heat exchange coefficient,convective heat exchange coefficient is calculated;According to the astrophysical theory,combined with the local temperature and geographical location information of Chongqing,the solar altitude Angle,solar azimuth Angle and solar hour Angle are calculated.The atmospheric temperature change is simulated as a sine function.Combined with the above three parameters,the heat flux of the main girder and the main tower under different boundary conditions is obtained.(2)The ANSYS two-dimensional solid model of main girder and main tower was established.The initial temperature and boundary conditions were given to obtain the temperature field distribution and temperature time history curve of main girder and main tower during the sunshine time.The temperature values of measured points in the temperature field distribution calculated by the model were compared with the measured values.Using the measured data,the least square method is used to fit the most unfavorable vertical and transverse positive temperature gradients of the main girder,and the formula is modified to obtain a temperature gradient in the form of piecewise function.(3)The MIDAS full-bridge model was established to compare and analyze the temperature gradient in piecewise function form proposed in this paper with the standard temperature gradient;to analyze the deflection of the pylon under the action of temperature and analyze of the change of cable force caused by the temperature difference between the cable beam and cable tower.(4)In the sunshine temperature field,the paper analyzes how to determine the elevation of the form and the first tension cable force of the stay cable in beam sections with different cantilever lengths considering the effect of temperature,and puts forward two correction methods.