| Single box double room concrete huge section box girder is based on the ordinary concrete box beam, increasing the the section size, canceling the conventional diaphragm, opening necessary holes in webs, and making its roof and nether plate become bridge floor system to realize double traffic.The huge section box grider birdge improves greatly urban traffic availability in the limited land resources and space. It corresponds with the requirement of sustainable development which provides new structure for the urban multi-lanes rails , urban light rail and three-dimensional transportation. The thesis does the following main research work, and draws the conclusions:1.Through a lot of investigations and studies ,and refering to the current related technical specifications and relevant reference, and combining with the characteristics of the ordinary concrete box section component , single box double room concrete huge section box girder which can realize city bridges double traffic is devised creatively,considering of the need of structure and function. The bridge span is 60m, and the height is 6m. The width-span ratio is 0.313.The bridge has double deck. The upper deck is designed for the two-way and four-lane highway, and its width is 18.8 m. the under deck is designed for two-way and two-lane highway,and its width is 11.0 m.In order to make full use of the space , bottom cantilever plates are setted on each side as sidewalks which is 2.0 m width.Escaping hole and vents in the sides of roof and floor place are opened.2.Through choosing proper element type and material modle,the designed single box double room concrete huge box grider is modeled by the nonlinear analysis software ANSYS. The stress distribution law is concluded by analysising the integral space stress and displacement, the stress of local beam section and near the hols in different load type. And the stress and displacement can satisfy the requirements of specification, which can verify that the design of the box girder is reasonable.3.The shear lag effect of the concrete huge section box girder is studied by applying fourload conditions including prestressed load, the upper and lower live load and double live load. Parameter analysis are done ,which include the load type ,the surport type and width-span ratio to the influence of shear lag effect.Furthermore, effects on shear lag of box girder are analyzed based on bottom cantilever plate, stiffener in the box ,openings in the web and transverse prestress.The results are shown as follows: there exists shear lag effect to some extent under the four loadings and the effect is not obvious in different loading; Different load types have certain influence on the shear lag of concrete huge section box girder in which concentrated load has a great impact on the shear lag in mid-span cross-section. So concentrated load should be paid attention in design. The influence of the width-span ratio on shear lag is greater. There is an approximate proportional relation between width-span ratio and shear lag coefficient. Thus, width-span ratio should be seriously limited. The influence on shear lag of box girder is less in different support type and whether setting cantilever plate as footway or not ,which can be ignored in design. The setting of stiffener and web-perforated have an evident impact on box girders shear lag which must be considered.The effect of applying transverse prestressing is equivalent to poisson effect which makes the flexural vertical stress reduce. Though it can play a certain role for box girders section stress, it is not obvious for shear lag improvement. |
