| Temperature stress is one of the important reasons for cracks in concrete box-girderbridge. The regulations of box-girder temperature load are not the same in differentcountries and different regions, and the temperature stress of box-girder varies widelyunder different temperature gradient mode. Therefore, it is meaningful to study thetemperature field and the effect of continuous box-girder bridge in a certain area.Taking Baotou Yellow River Second Highway Bridge as the research object, thetemperature field of bridge has been long-term monitored during the operation period, thetemperature field and effect characteristics of long span concrete box-girder bridge areobtained. In addition, the mode of temperature gradient is defined in this area. The maincontents and results are summarized as follows:Temperature distribution disciplinarian are obtained by the measured data statistics ofbox-girder temperature field, which are located in the roof, the bottom and the web of box-girder. Based on theoretical of heat transfer, the various factors of heat exchange isconsidered between the box-girder surface and the outside world. By means of the thirdkind of boundary conditions, box girder temperature distribution in every moment aregained by using the finite element analysis. The result shows that the finite elementanalysis results coincide well with the measured temperature value. On this basis, thispaper combines the measured data with software simulation value, by using the methods ofmathematical statistics, the recommended temperature gradient mode has been defined forthe same type bridges in local area.The three-dimensional solid model of box-girder bridge is established by ANSYS.Using the roof heating and environmental sudden cooling as calculation cases, thedistribution rule of transverse and longitudinal transient temperature stress are obtained inthe critical section. The analysis results show that the heating effect is opposite to thecooling effect, but the temperature stress is larger. During the model of heating, the box- girder longitudinal tensile stress is gradually spread with the reducing of beam height，thetensile stress is distributed most widely in the mid-span section. Besides, a rather bigtransverse temperature tensile stress will be produced in the roof lower border, it is harmfulto the structural safety.The whole bridge model is established by MIDAS/Civil, using the recommendedtemperature gradient and four kinds of temperature gradient mode at home and abroad asanalysis cases, the steady temperature effect is obtained. The results show that thedistribution of effect has a certain similarity under different temperature gradient mode, butthe temperature effect value varies greatly with the difference of temperature distributionalpattern and characteristic value. In addition, the tensile stress caused by temperature effectis produced in the primary beam hemline, which is correspond to vehicle load effect.Therefore, the action of temperature should be fully considered in bridge design. |
