Analysis Of Oblique Section Space Stress And Reinforcement Calculation For Prestressed Concrete Box Girder Bridge

After decades of large-scale infrastructure construction, PC continuous box girder bridge are widely used with its unique advantages. With the improvement of economic development and use of functional requirements, large wide span box girder bridge is also increasing. However, some problems from engineering practice, the box girder webs occurs in various forms of crack on the different degree, especially web inclined cracks is widespread, even to 95% of the web cracks, the existence of diagonal crack seriously affected the usability and the durability of the bridge structures. In view of the universality of this kind of disease, this art icle studied the defect causes and cracking mechanism of inclined cracks by the space effect of box girder, the design calculation method, prestressed reinforcement and the construction technology. And give the reinforcement suggestion to control the principal tensile stress.First of all, in this paper, the web plate diagonal crack disease related literature to carry on the statistical research, has defined the properties of diagonal crack and discuss the mechanism of shear failure.Multi-wide web box girder bridges have significant spatial effects, the commonly used simplified analysis method and the simple bridge current specification does not fully reflect the spatial effect of box girder is one of the important cause of cracking of box girder web; Vertical prestress calculation under the underestimation of prestressing loss and the longitudinal prestressed curved tendons set unreasonable, it is difficult to play the role of restricted principal tensile stress result in the crack of the web; Construction organization and management is not reasonable and extensive construction, not strictly in accordance with the design requirements for construction is also the important cause of web plate crack.Secondly, by study the space effect of box girder and stress of the box girder web plate theory calculation method, the regularity has been clear about the box girder web. This paper relies on Liao Yang Hong Wei Bridge, using MIDAS/FEA finite element analysis method fine analyzed the oblique section space stress from the construction phase and completion state separately, and compare separately with construction monitoring data and beam element calculation results. The solid element calculation results show that near L/4 span and side span fulcrum is the location of the principal tensile stress larger, and the actual webs inclined cracks appear consistent position.Box girder web plate shear force distribution is not uniform, the standard isn’t explicitly stated lead to web principal tensile stress calculation is inaccurate and bring potential safety hazard to design.Finally, this article study and evaluate the existing method of prestressed reinforcement on the basis of grasp of the multi-web wide box girder bridges oblique section space stress.The factors of vertical and longitudinal prestressing tendons on the web by force are studied and give the reinforcement suggestion to control the principal tensile stress.