Analysis Of Temperature Field And Temperature Effect For Long Span Concrete Box Girder Bridges In Cold Regions

Temperature effect is one of the main causes of cracks in concrete box-girderbridge, the temperature gradient mode and value on concrete box-girder did not gainconsensus in different countries and different regions. Northeast cold areas is thehighest latitude and the most easterly longitude area in our country, the uniquegeographical position causes the special climate, winter is cold and long,temperature is10℃lower compared with other parts of same latitude, summer iswarm and rainy, spring is drought and windy, autumn is cool sharp. Temperaturedistribution of large span concrete box-girder bridge in cold areas is different fromother regions, influence of temperature cracks on structure safety and durability isbigger, so research on temperature distribution and temperature effect of long spanbox-girder bridge, in which the temperature gradient mode which is more suitable incold region is determined, has very important significance.In this paper, based on the long term observation of temperature field ofconcrete bridges in cold region, combined with finite element analysis, thetemperature field and temperature effect features of large span concrete box-girderbridge is studied deeply, the temperature gradient mode in cold region is determined,The main research contents and achievements are summed up as follows:The temperature field is observed continuously for more than one year in threelarge span concrete box-girder bridge in Heilongjiang province on the same period,based on the massive measured data, temperature field distribution characteristics inconcrete box-girder, caused by solar radiation and cooling, resulting from wintercold environmen, is analysis in detail.Temperature field of box-girder is calculated using ANSYS program, and thecomparative analysis of calculated value and measured value indicates that thetemperature field which is precise enough in engineering could be got using ANSYSprogram. According to the results of finite element analysis, the measuredtemperature distribution is complemented and perfected.Using the finite element model, transforming parameter values ofmeteorological conditions, the material thermal physical properties and cross sectionshape, temperature field of box-girder is calculated. The rule of temperature fieldchanging with the solar radiation intensity, air temperature, cross section height,coefficient of thermal conductivity, concrete specific heat etc. is obtained. For thepavement which is often used in bridge deck structure, the influence to temperaturefield is researched in cases of heating and cooling. The results showed that theintensity of solar radiation and the deck pavement is the main factor of concrete box girder temperature field.The cross, vertical and longitudinal temperature stress distribution of theproject box-girder is analyzed using2D model. At the same time, temperature stresswere compared using3D model and plane rod system program, and the difference oftemperature stress using different model is got. Using a6x150m continuousbox-girder bridge as the research object, the vertical temperature gradient mode andthe longitudinal temperature stress according to the different regulation is comparedand analyzed. The results show that the transverse tensile stress at lower edge of theroof caused by the sun radiation is bigger, larger longitudinal tensile stress couldbeen caused by negative temperature difference at lower edge of section.Based on the measured data of two bridge in qiqihar area and the results offinite element calculation, a temperature gradient mode which is suitable for qiqihararea is obtained. Combined with the conclusions of the study about the influencefactors of box-girder temperature field and temperature effect of box-girder, atemperature gradient mode which is suitable for cold regions is put forwardconsidering the bridge geographical latitude, bridge web azimuth and deckpavement correction.