Study On Sunshine Temperature Field And Temperature Effect Of PC Composite Box Girder Bridge With Corrugated Steel Webs

At present,more than 100 PC composite box girder bridges with corrugated steel webs have been built in China.There are a lot of research results on the mechanical properties of this kind of bridges,such as bending,shear and torsion.However,the research on the sunshine temperature field and temperature effect remain undeveloped,and the domestic design specifications are also lack of relevant recommended values of sunshine temperature gradient.The temperature of bridge exposed to atmospheric environment changes with solar radiation and air temperature,which has adverse effects on the safety and durability of bridge structure.Based on the real bridge temperature observation test and finite element numerical simulation,the sunshine temperature field and temperature effect of PC composite box girder bridge with corrugated steel webs are analyzed.The main content and conclusions are as follows:(1)Comparing the real bridge temperature observations with the finite element results,the results show that the finite element model can simulate the sunshine temperature field more accurately.Based on the finite element model of temperature field and historical meteorological data,the semi empirical and semi theoretical formula for vertical positive temperature gradient of PC composite box girder bridge with corrugated steel webs is obtained:The roof temperature difference decreases exponentially from the upper edge to the lower edge;The temperature difference of steel webs exposed to direct sunlight is more than three times similar along the vertical direction;The temperature difference of the steel webs on the back side is evenly distributed;The temperature difference of the floor increases linearly from the upper edge to the lower edge.(2)Based on the finite element model of the whole bridge,the temperature effect of PC composite box girder bridge with corrugated steel webs under sunlight is analyzed.The results show that the maximum longitudinal compressive stress of box girder section concrete appears at the upper edge of the roof,the maximum tensile stress appears at the lower edge of the roof,and the transverse tensile stress and longitudinal tensile stress are at the same level.The results show that the transverse tensile stress of the section with lining concrete is higher than that of the section without lining concrete;The transverse tensile stress of the lower edge of the roof will be increased by the restraint of the diaphragm.(3)Based on the finite element model of temperature field,the parameter analysis of influencing factors of sunshine temperature field of PC composite box girder bridge with corrugated steel webs is carried out systematically.The results show that the temperature difference along the thickness direction of the roof is positively correlated with the air temperature and the solar radiation absorption coefficient of concrete,and negatively correlated with the environmental wind speed,geographical latitude and the thickness of asphalt pavement;The temperature difference along the thickness direction of the roof is the largest in summer.The vertical temperature difference of steel webs and the temperature difference of steel webs on both sides are positively correlated with the height of box girder,air temperature and solar radiation absorption coefficient of steel,and negatively correlated with the length of cantilever plate,ambient wind speed and geographical latitude.The analysis of the direction of the bridge axis shows that when the angle between the bridge axis and the due south direction is about 45 °The vertical temperature difference of steel webs and the temperature difference of steel webs on both sides are the largest.The temperature difference along the thickness direction of the bottom slab is positively correlated with air temperature and wind speed.