Analysis Of Temperature Field And Temperature Effects For Concrete Box Girder And Hollow High Pier

Due to the poor thermal conductivity, the surface temperature of concretestructures will be rapidly increased or decreased by the surrounding ambienttemperature, solar radiations and other actions while the internal temperature remainsthe same; furthermore, the surface temperature will suddenly reduce in case of coldwaves wile the internal temperature remains the same, leading to large temperaturedifference between inside and outside the concrete, the formation of a large temperaturegradient in concrete structures and that different parts of concrete structures are atdifferent temperatures. Such temperature differences will result in temperaturedeformation; when the structure is impeded by internal and external constraints, it willgenerate significant thermal stress. The temperature stress and deformation have a directimpact on the safety, durability and applicability of concrete structures. Therefore, withthe research background of the fifth sub-topic of the technology topic in the Ministry ofRailways–Study on key technology in high-speed railway bridges in mountainous, inthis paper, the following works were completed successful.According to the theory of heat transfer, astronomy and solar physics, theoreticalcalculation model was established for sunshine temperature field of bridge structure,with a comprehensive consideration of the heat exchange between the concrete structureand the outside boundary. The finite element analysis models of temperature field forbox girder were established and calculated by APDL. The time required to reachthermal steady state of fluctuation was analyzed on the basis of initial temperature.1:1model of1m high middle section of12#pier of Xingfuyuan Bridge and thepier models with different wall thickness were designed and made for model test. Someimpact on the pier temperature field distribution factors are analyzed through theestablishment of the pier finite element temperature field analysis model by APDL, suchas azimuth angle, thermal conductivity, and transparency of the atmosphere and wallthickness. By comparision of the three results (test results on site, model test results,theoretical analysis results), the temperature difference curves along the wall thicknessof hollow concrete piers were summed up.For concrete box girder, the temperature field was calculated as changing thethickness of the panel. It was found that The thicker of the tops and webs(roof≥50cm,webs≥40cm), the more stable temperature difference curve would be obtained. However, it was defined that the exponential coefficient would stable at10when thethickness of the roof (or web) was not less than26cm in china’s railway norms.For highway concrete box girder，the calculation and comparison of the threemodels (box without pavement,50mm asphalt concrete pavement,100mm asphaltconcrete pavement)was completed. The point that the box girder with50mm asphaltconcrete pavement affect the structure adversely in vertical temperature gradient, wassummed up. The recommended valueT1was27when50mm asphalt concretepavement. Subsequently, the simplified and semi-analytical algorithm of temperaturefield for box with different pavement is obtained.By analyzing the effects of section shape and dimension and section chamfer ontemperature stress, we found that when calculating transverse stress, China’s existingrailway bridge design specifications (TB10002.3-2005) assumed equal thickness of boxgirder wall and plate and also ignored the effects of chamfer, thus making thetemperature stress calculation results smaller and unsafe.Visualization modules for calculation of temperature field and its effect ofprestressed concrete box girder with long-span, were developed by the three languagefor secondary development named APDL, UIDL and UPF, with the style consistent withthe ANSYS. The value of thermal elastic modulus for temperature stress at present wassummarized.