The Numerical Analysis Of The Crack Of Prestressed Concrete Continuous Box Girder Bridge In Cold Area

With the rapid development of infrastructure in out country, the prestressed concrete continuous bridge which is commonly used in highway construction, is famous for its smooth driving for automobiles, less contraction joint and convenience for curing. The cracking phenomenon at different spot of the box girders under the construction and operation phrase will have directly effect on the safety, durability and service life of bridges. So the cracking in bridge engineering has drawn many engineers' concern.In this paper, at the basic of cracking problem which already exist in prestrssed concrete continuous bridges, we have done a through study on the sensitive factors causing the cracking by finite element numerical analysis. This article summarize the cracking phenomenon and causing factor of the existing prestressed concreted concrete continuous bridge. At the basic of this, we analyze the cracking mechanism and relevant affecting factors in cold region. It is concluded that the sensitivity factors which cause the box girders cracked are concrete strength, elastic modulus of concrete, temperature effect, shrinkage and creep of concrete, foundation deformation and so on.Having Balageer bridge project as background, the transversal and longitudinal variation regularity of the top plate, bottom plate, web plate of the box girder under the action the temperature gradient load was analyzed through finite element numerical analysis. By comparing the stress caused by temperature gradient and overall warming, the temperature stress caused by temperature gradient is the main factor to cause cracking.The stress and deflection variation in top plate, bottom plate of the Balageer bridge was analyzed under the action of shrinking and creep. It is found that under the action of shrinking and creep, the stress of box girders occurred redistribution, local tensile stress increases, the deflection of the midline position of the bottom of box girders increases.The stress variation in top plate, bottom plate of the Balageer bridge was analyzed under the action of found deformation. According to the calculated results, the tensile stress of the top plate of box girders in the right fulcrum of side span and nearby bearing of middle span overlarge. The tensile stress of the bottom of box girders in mid-span of side span and middle span overlarge, which may cause box girders crack.