Research On The Stress And Cracks Of Long-span Box Girder

At present, stabling for a large part of long-span bridge is the prestressed concrete box girder bridge. Prestressed concrete continuous box girder bridges, prestressed concrete continuous rigid frame box girder bridge with its structural rigidity, the driving comfort, small joints and conservation simple, receive the favorite by the owners, the designers and builders. Thus, in our road and railway construction, the application of long-span box girder bridge have been more and more widely.Large span prestressed concrete continuous box girder bridge, prestressed concrete continuous rigid frame box girder bridge in the construction or operation of the process, there are many different types of concrete box beam cracks, the most common is the box girder of the diagonal crack. In this paper, Combine the Communications and Technology Project of Shaanxi Province, through the finite element analysis and field test methods, research the box girder cross-section of the complex stress state.In this paper, the control section of the stress difference between theory and measured; partial cross section for the details of the stress research; also analyzed the vertical sections of the girder prestress stress.The research shows that in the construction process the stress of the control section presents the "negative shear lag effect"; by the theory analysis on the 14th section of the stress block shows the regularity of stress distribution in sections of the girder; through the roof sections of the girder on the 13th block of research and analysis, obtained the stress in the longitudinal prestressed box girder roof anchoring process also presents the "negative shear lag effect"; by the 3rd block box girder section of the complex stress state, obtained in the course of construction a larger section of the bridge root principal tensile stress occurs, and the direction of principal tensile stress cracks in the basic vertical and inclined web; block box by the 13th section of the normal stress of web analysis, web sections obtained discrete distribution of normal stress; block on the 14th, and prestressed box girder cross-section of vertical beam under bending analysis, obtained vertical sections of the girder prestress stress distribution and crack prevention play an important role, while curved beam under tension sections of the girder will produce vertical tensile stress. Based on the study, this paper analyzes the factors affecting web cracking of the box girder, presents specific sections to improve the stress distribution and the prevention of web cracking from two aspects of the design and construction.