Study On Temperature Field And Temperature Effect Of Long-span Cfst Arch Bridge In Plateau Region

The CFST arch bridge is exposed to the natural environment,and the influence of environmental factors such as sunshine radiation,diurnal temperature change and so on will inevitably cause some adverse effects on the bridge itself.Especially the CFST is constructed in the plateau region,which has a great change in the temperature of the day and night,the rapid drop in temperature and other complex environmental conditions,the impact may be greater.In this paper,the temperature field and temperature effect of a long-span CFST arch bridge in plateau region are studied.The main research conclusions are as follows:Based on the finite element theory of temperature effect and the influence factors of the temperature field of the bridge,the boundary conditions of the temperature change between the surrounding environment and the bridge are determined.The finite element analysis software ANSYS was used to establish the two-dimensional model of concrete-filled steel tubular arch section.The temperature distribution of the main arch rib section is obtained by taking into account the different factors.Then the temperature field of concrete filled steel tubular arch rib is analyzed.The main conclusions are as follows:The temperature field of arch rib section is showed as outside high and internal low in day,internal high and outside low in night.Under the condition of sunshine in summer,the maximum temperature difference reaches 31.31℃;Under the condition of sunshine in winter,the maximum temperature difference reaches 23.93℃.The bottom chord due to occlusion effect,the maximum temperature difference of the summer section is 25.91℃,the maximum temperature difference is less than the top chord section.As the diameter of the steel pipe is changed from small to large,the maximum temperature of the section is bigger and bigger,and the minimum temperature is getting smaller and smaller.In this paper,the temperature gradient of the arch section of the CFST arch bridge is larger than the specified temperature gradient.Based on the finite element analysis software ANSYS,the whole bridge model is established.Combined with the existing norm of the CFST arch bridge and the environmental characteristics of the bridge site,the maximum and minimum effective temperature are determined.The uniform temperature effect is analyzed.Based on the gradient temperature of this paper and the standard gradient temperature,the gradient temperature effect is analyzed.The main conclusions are as follows:The effect of uniform temperature has a great influence on the arch foot.With the constant load and the overall temperature of 20℃,A large bending moment is generated at the arch foot of the arch rib,and the direction of bending moment is the same as that of the constant load.With the constant load and the overall temperature of-30℃,the arch foot of top chord also produce tensile stress.The gradient temperature has a great influence on the top chord,but has little effect on the bottom chord,and the temperature gradient of this paper has a greater effect on the gradient temperature effect of the CFST arch bridge than the standard temperature gradient.