Study On Temperature Distribution And Thermal Stress Of Steel Box Girder Due To Solar Radiation

The influence of temperature load on bridge structure has become a consensus in the engineering field.The bridge structure is exposed to the natural environment for a long time and subjected to temperature action,which leads to temperature deformation of the structure.When the temperature deformation is hindered by the internal and external constraints of the structure,considerable temperature stress will be generated.In the process of bridge design,it is difficult to predict the actual temperature field of the structure in advance,which brings a series of difficulties to the analysis of temperature effect in bridge design.The temperature effect of bridge structure is closely related to the geographical location of bridge site,bridge orientation,temperature,wind speed,sunshine radiation intensity,box girder section shape and other factors.With the development of long-span steel box girder bridge,the research on temperature gradient of steel box girder is particularly urgent.In this paper,taking luojiagou self anchored suspension bridge in Tianshui City as the engineering background,the representative season,weather and external environment temperature are selected to analyze the influence of solar radiation on the temperature field of steel box girder.The main research contents are as follows:(1)Through the solar radiation model,the solar radiation intensity of the bridge location is calculated.Establish reasonable initial conditions and boundary conditions,select reasonable sunshine parameters and material thermal parameters,use finite element software to establish the transient temperature field of steel box girder without deck pavement,and analyze the temperature change of steel box girder from summer to day.The results show that the temperature field of the steel box girder is similar to that of the outside air temperature,which basically shows a sine function change,and the period is basically the same as that of the outside air temperature.(2)Through the transient temperature field model of steel box girder,the temperature stress change of steel box girder is calculated.The results show that there are obvious stress concentration in the flange vertical plate,the weld joint of web and top and bottom plate,the weld joint of top and bottom plate and U-rib,plate rib,and the weld joint of diaphragm and plate rib.(3)At the bridge site,select representative weather conditions,simulate the temperature field of steel box girder paved with asphalt concrete pavement,and analyze the corresponding temperature effect.The results show that the asphalt concrete pavement can significantly reduce the temperature of steel box girder roof,and then reduce the sunshine temperature effect.The temperature of each part of the box girder lags behind the surface temperature.(4)The parameters of steel surface emissivity,external temperature,wind speed,thermal conductivity and specific heat capacity of asphalt concrete are selected for parametric analysis.The results show that: the temperature field of steel box girder is related to these parameters,so it is very important to select the parameters reasonably.