Numerical Analysis And Control Measures For Crack Problem Ofprestressed Concrete Box Girder Bridge

Prestressed concrete box girder bridges have been widely used in the bridge’sconstruction by the superiority of its structure. Unfortunately a considerable part of thebridge had various forms of cracks during the construction and service stage, it directlyaffects the safety and durability of structures. Engineering circles urgently need acorrect understanding of the mechanism of cracking of prestressed concrete box girderbridges, thus take corresponding preventive measures at the beginning of theconstruction, design and construct health bridges, As far as possible to avoid or limit thecracks appear. Design whether the part of the concrete girder will crack or not is basedon its stress state, therefore, calculate the stress state of bridge structure accurately isprerequisite to solve the crack problem of concrete box girder bridges. This papermainly analyzed and researched factors which influence the cracks in the bottom plateand webs of prestressed concrete box girder bridges. Then put forward someimprovement suggestions from the design and construction.Documentaries about crack problem of concrete box girder bridges at home andabroad were consulted, on the base of analysis and study of existing research results,systematical analysis and summary are made regarding to crack types and positionproducing, forming reasons and influencing factors in prestressed concrete box girderbridges.This paper uses ANSYS finite element software establish finite element models ofa typical prestressed concrete continuous rigid frame bridge, and spatial stress analysiswas finished, mainly analyzed and researched the stress state of bottom slab at themiddle and webs in l/4midspan. The results shows that the transverse stress on bottomslab is the main causes of longitudinal cracks in bottom slab, the principal tensile stressis the main causes of inclined cracks in the webs.The influencing factors of the transverse stress and the principal tensile stress arediscussed. Increasing the thickness of bottom slab at the middle or installing diaphragmscan reduces the transverse stress of bottom slab,For this bridge, installing5diaphragmswith the distance of9m has the best effect; The principal tensile stress of webs in l/4midspan is sensitive to its vertical prestress, Imposing vertical prestress cansignificantly reduce principal tensile stress of webs and improve the Anti-CrackingStrength for Inclined Section of webs. Increasing thickness of webs can improve shearresistance capacity of box beam section, but has little effect on reducing principal tensile stress.Put forward some improvement suggestions from the design and constructionaccording to.the crack problem of prestressed concrete box girder bridges, then providescontrol methods and treatment measures of cracks.in concrete box girder bridges.