Temperature Field And Temperature Effect Influence Of Concrete Rail Beam Of Magnetic Suspension Railway

The temperature effect of reinforced concrete structure under the action of temperature gradient load is an important reason for the cracking of concrete structure.The rail bearing beam of middle and low speed maglev rail transit in Beijing is a portal reinforced concrete structure fixed on box girder,which belongs to the rib statically indeterminate structure.The research on the effect of temperature cracks of such beams is lack.In this essay,the vertical temperature field of concrete in Beijing and Hebei area is studied.Based on that,the temperature effect of rail bearing beam is analyzed.The main contents include:(1)The internal temperature test of thick concrete slab is carried out,and the monitoring data are analyzed.The vertical temperature field of the structure is simulated by finite element method,and the results are compared with the measured data.The vertical temperature gradient model is determined by fitting,and compared with the standard of Chinese railway bridge and culvert and the standard temperature gradient of highway bridge and culvert in China,the study shows that the measured vertical temperature gradient is slightly larger than that of the standard value.(2)A field test of the internal temperature of Thin-walled box concrete structure was carried out.On the basis of the analysis of the test data,approaches of exponential function and broken line function are adopted to fittng vertical temperature gradient,than the most unfavorable temperature effect is selected to analyze the temperature effect of the structure.(3)The finite element modle of the linear and curvilinear parts on the S1 line of Beijing magle rail transit are separately setted up.The stress and displacement of track beam based on temperature gradient load are calculated and analyzed.Under the effect of the temperature gradient load,the maximum lateral tensile stress of the straight line rail structure occurs at the top of the roof,the maximum tensile stress is 3.57MPa,the maximum vertical temperature stress appears on the inner side of the web,about 5.56MPa,and the minimum longitudinal temperature stress is about 1.26MPa.It is found that the stress of the rail beam on the curve section is slightly smaller than that of the straight line under the effect of the temperature gradient load.(4)The stress behavior of the rail beam under the action of temperature and other effects is studied.The results show that the stress and displacement response of the structure can be ignored only under the static vertical load.The stress of the structure increases obviously after considering the temperature load,and the vertical stress is up to 3.2MPa;Considering the lateral guiding force of maglev traffic,the structural stress change is not obvious.(5)The causes of concrete shrinkage crack are expounded in detail,and the effect of concrete shrinkage on structural stress and displacement is studied by the equivalent cooling method,and some control measures for crack control are put forward.