The Temperature Field Of Ballast Track Steel Box Girder And Its Action Effect Research

The impact of temperature loading on railroad bridge structures has been extensively acknowledged within the engineering community.Exposure of ballasted track steel box girders to atmospheric conditions for prolonged periods leads to temperature deformation under the influence of temperature.If the deformation of the bridge is constrained,it results in significant temperature stress.The design process poses a challenge in predicting the actual temperature field of steel box girders in advance,as the temperature effect is contingent on factors such as bridge location,orientation,temperature,wind speed,solar radiation intensity,and cross-section shape of the girder.With the rapid growth of steel box girders today,investigating the temperature field and temperature gradient of ballasted track steel box girders has become an urgent research topic.This research focuses on a ballast track steel box girder bridge located in Lanzhou City as the engineering context to investigate the impact of temperature field on steel box girders under typical weather conditions,seasonal variations,atmospheric temperature,and solar radiation.The key areas of investigation encompass the following:(1)The solar radiation intensity at the bridge site is computed using a compatible solar radiation model,and appropriate boundary conditions,initial conditions,insolation parameters,and material parameters are established to investigate the transient temperature field of the steel box girder with and without deck pavement using finite element simulation software.The study also analyzes the temperature variation behavior of the steel box girder during summer.The findings indicate that the temperature field of the steel box girder manifests a similar variation pattern to that of the ambient air temperature,characterized by a sinusoidal function variation.(2)By utilizing the transient temperature field model,the temperature stresses in the steel box girder are determined and evaluated.The analysis reveals that the temperature stresses are primarily concentrated in the web of the steel box girder,as well as the weld joints of the vertical flange plate and the top and bottom plates,U-shaped ribs and the top and bottom plates,plate ribs and the top and bottom plates,and plate ribs and the cross partitions.(3)Through simulation analysis,the temperature fields of steel box girders with two different paving layers,namely fiber concrete and ballast fiber concrete,were examined.The outcomes demonstrate that both types of paving layers can considerably lower the temperature of the top slab of the steel box girder,thereby mitigating the temperature impact during daylight conditions.Furthermore,each part of the box girder exhibits a certain degree of hysteresis concerning the surface temperature changes.(4)The study conducts a parametric analysis of crucial factors such as emissivity,wind speed,temperature around the bridge site,thermal conductivity of steel plate surface,and specific heat capacity and thermal conductivity of fiber concrete and ballast.The results indicate that all the key factors mentioned above can have a significant impact on the temperature field of the steel box girder,highlighting the importance of selecting appropriate parameter values.