Crack Analysis And Control Measures For Continuous Rigid Frame Bridge With Box Girder

Continuous rigid frame bridge with large span capacity, convenient construction, economical cost driving comfort and other advantages, has been favored by engineer. Based on large number of continuous rigid frame bridge detection found that the bridge cracks appeared in quite a number of cracks in the stage of construction and operation stage,has a negative influence on the safety durability of the bridge. Continuous rigid frame bridge has broad prospects, research on the crack with of continuous rigid frame box girder bridges are favorable for bridge construction, design and maintenance.This paper mainly based on Gan-Shui bridge as the engineering background,calculation of bridge in construction stage and finished stage girder stress, analysis of crack width of box girder structure. Using Midas civil to Gan-Shui bridge construction process analysis,focused on the analysis of the internal force changes of the beam bridge system conversion, compared the different stages of construction closure section of floor stress changes. The establishment of the model of the whole bridge using ANSYS shell element SHELL63,analysis of wide box beam shear lag and distortion, the shell element and beam element calculation results were compared, in order to get the shear lag coefficient. Analysis of the spatial mechanical behavior of box girder with three direction prestressed concrete. Mainly to the following :comparison and analysis on the roof wide box girder transverse, longitudinal stress distribution in the roof and no roof transverse prestressed. analysis of control effect of vertical prestressed on web stress. Calculate and compare with the principal stress in web with different degrees of loss of vertical prestressed analysis of different beam section of the web tension stress. analysis of the effect of prestress loss stress of the girder deflection and bottom stress. Through the finite element analysis of the box girder, some measures for cracks are put forward. To do the following works: calculate the radial calculate the radial force of different the bottom line. Compare with the principal stress of wide box girder with the transverse rib and without the transverse rib. To establish different web thickness of the webs of the box girder model calculate the principal stress of the web. through the radical force formula to calculate the radical force and establish the closure segment the finite element model. Calculate the different bottom stress with different thickness of protection layer and analysis the stress around pore wall.Through the calculation, know the closure section of the bridge in the process of system transformation floor is subjected to radial force. The radical force due to bottom deformation, effect of Poisson’ ratio of concrete and the longitudinal steel beam tension cause of longitudinal crack. Beam segment around the center with high power bottom line is not easy to crack. Adding the transverse rib to the beam with much radial force can increase the lateral stiffness, reduce the transverse tensile stress, prevent to crack. Bottom protective layer thickness is little affect the pore wall stress and reducing the bottom tension. The roof transverse prestressed make roof with storage pressure, transverse bending make the lower edge of the flange tension, so it is easy to crack. The vertical steel and shear control web principal stress, when the force of vertical prestressed loss to a degree,the vertical is little effect to control to principle stress of web.