Mechanism Properties And Experimental Investigation Of Multi-beam Steel Concrete Composite Girder Bridge

In recent years, steel-concrete composite structure is applied in bridge engineering step by step. At present, the researches of multi-beam steel-concrete composite box-girder bridge are few in the references and specifications. In order to provide the causes of the design and management, this paper has studied the mechanical properties of multi-beam steel-concrete composite box-girder bridge.The mechanical properties of steel concrete composite girders in hybrid-fiber are studied through the tests, numerical simulation and specification comparison of14push-out tests and two steel concrete composite girders. The load-slip formula and the calculation method of bearing capacity of the stud connector in hybrid-fiber concrete and the mechanical properties of steel concrete composite girders in hybrid-fiber in elastic state and failure state are gotten. Then the advised design method of bearing capacity of steel concrete composite girders in hybrid-fiber concrete is obtained. Compared with steel concrete composite girders in normal concrete, the toughness and durability of the steel concrete composite girders in hybrid-fiber concrete are better.A theory model is proposed for steel-concrete composite girders with the slip between the steel beam and concrete slab, shear deformation in the steel beam and the shear lag effect in the concrete slab. Different parabolic warping shape function accounting for the non-uniform transverse distribution of longitudinal displacements in the concrete slab and steel floor and transverse shear deformation of the girder web are introduced into Newmark’s model. Then analytical solutions for the cases of simply supported composite girder under uniform distribution load and end concentrated load are derived. The analytical solutions agree with the test results. The shear lags coefficient decrease at the web and middle of concrete slab in the mid-section when increasing thickness of concrete slab and height of steel beam. While the ratio between the width and span of composite girder declines, the shear lag coefficient decreases at the web and increases at the middle of concrete slab in the mid-section. It is also indicated that the shear lag effect is more apparently varying with different factors under end concentrated load compared with uniform distribution load. The variation of the slip stiffness has a negligible effect to the shear lag coefficient.The eccentric-pressed method and rigid jointed girder method are modified considering the interface slippage’s effect of multi-beam composite small box-girder bridge. The results obtained from FEM validated by experiments are compared with the modified theoretical algorithm, and the result shows that slippage considered rigid jointed girder method is applicable for calculating mid-span load transverse distribution of multi-beam composite small box-girder bridge. For narrow bridges, it is better to use slippage considered eccentric-pressed method. Furthermore, when designing multi-beam composite small box-girder bridge, the author suggests using incomplete shear connection form to reduce the bridge of the partial load effect.In the end, the analysis model about multi-beam steel-concrete composite box girder bridge is built and the integral analysis of the differential equations are obtained under the uniform load by the simulation plate method. Then the slip equation and deflection equation are obtained under the uniform load by simplified method. The analytical solutions agree with the FEM and other research results through the example. Finally, the stiffness variation of the shear connector has a neglected effect on the defection and an obvious effect on the slip.