Study On Mechanical Properties Of Fabricated Hollow Slab Bridge Hinge Joints Under The Load

Fabricated concrete hollow slab bridges are applied widely in bridge engineering, because of its simple prefabrication and construction craft, lower cost and lowest construction height etc. However, some typical diseases have been found according to the operation condition of some bridges. Through analysis of research studies show that the most prominent problems that should impact the normal use of hollow slab and its structural safety are due to the weaker horizontal ties,the lower veneer stiffness, and the root reason of the damage of the bridges is the destroy of hinge joints. Hinge joints between hollow concrete slab broken off, large areas of leakage, it might cause the damage of beam itself, and also cause the damage of bridge deck, expansion join, and bearing, even though leading to the lower deck flatness, bridge deck over, broken off and so on. This is not only seriously affected the traffic comfortable, an increase the traffic safety problems, but also greatly reduce the bearing capacity of overall bridge.In this dissertation, a large number of relevant literatures and research analysis of the damaged reasons and the general characteristics for the hollow slab bridge hinge joints are discussed. The nonlinear theory and its approach are introduced to hollow slab bridge with ABAQUS finite element method. The article involved material nonlinearity and contact conditions nonlinearity,the non-linear material uses Newton-Raphson method to solve, the contact conditions use the penalty function formula of Coulomb friction law to deal with. The concrete damaged plasticity model and the classic plasticity metal models of ABAQUS finite element are provided for hinge joint concrete and steel respectively.Contrast the test results with the calculation results, hollow slab bridge numerical simulation is feasible, reasonable and effective for ABAQUS6.8. It is feasible for using sliding friction contact system to simulate the contact conditions of slab and hinge joints.With Finite Element Method ABAQUS6.8, the analysis is included:(1)For changing the transverse and longitudinal load positions. The most unfavorable position of loading was found. And the mechanical property of hinge joints has been analyzed under those unfavorable conditions.(2)Hollow slab bridges of different span are analyzed in the same load, The transverse distribution coefficient of the different length hollow slab is not the same, the smaller the span was, the greater the transverse distribution coefficient is. In the same number slab, the vertical stress increases with the span. As the span increasing, the load transfer rate was increasing gradually.(3)The effect of the overload is the biggest factor to hollow slab bridge, the overload proportion increasing can enlarge each stress, even lead to the hinge joints destroy because the tensile stress would surpass concrete tensile strength.(4)Friction coefficient is related to the bridge floor rough degree, vehicles speed, vehicle tyre style. The horizontal load equal to the vertical load multiplied the friction coefficient. In this dissertation we discuss the influence about stress and deformation of the hinge joints under the change horizontal loads. .(5)Thickness change of asphalt concrete pavement has a greater impact to the stress of hinge joints, increasing the thickness of pavement layer will reduce the maximum vertical tensile stress, and the remaining pavement thickness in 10cm ~ 12cm ,the stress decay rate is big, and then decay rate become gradually slower. Attenuation of shear stress in which is larger, when the thickness changed from 4cm to 20cm, the maximum shear stress decay nearly 90.4%. Obviously, increasing the thickness of pavement layer structure is effective method to reduce the shear stress of hinge joint.(6)Elastic modulus of asphalt concrete pavement will change greatly with the outside temperature and load period, with the elastic modulus of asphalt concrete pavement enlarging, all the stress are reduced, and increased elastic modulus of pavement impacts the shear stress largely in hinge joints structure.(7)When thickness of pavement is a certain, using rigid reinforced concrete and steel fiber concrete as the bridge deck pavement material have more favorable mechanical properties for the hinge joints structure.(8)The different grades of concrete is simulated by changing the elastic modulus of hinge joints, it is found in the study: with increasing elastic modulus, the greatest stress is increasing, the vertical displacement is decreasing.(9)The affect of stress and deflection in hinge joints structure are not obvious by changing Poisson's ratio of hinge joints concrete .(10)The contact state is complex for bridge deck and hinge joints. It is found that the contact state is obviously effect for the shear stress of hinge joints. Improving the contact state, hinge joints structure will have favorable mechanical properties.(11)By changing the density of hollow slab bridge, It is showed that the favorable mechanical properties is obtained by reducing dead weight for hinge joints structure in the same span and cross-section cases.(12) The common programs of the hinge joints reinforcement were analyzed, it is found that exerting lateral tendons has the best affect, followed by bold steel hinge joints, but the first method is not easy to construction, using bold in design is appropriate to the newly building bridge. Secondly the program of increasing the steel plate at the bottom and at the top of the hinge joints was discussed, these two programs has effective reinforcement and convenient construction.Small and medium-span fabricated hollow slab bridge is widely used in China and Inner Mongolia province. However, when the bridge has been completed and operations, there are also some the more typical diseases of hinge joints. The research conclusion of the dissertation must be serving for the small and medium span bridge in the western region projects, improve the quality of the projects and ensure the structure safety and durability of the hollow slab bridge, reduce the workload of the highway conservation, as well as substantial saves conservation funds, and develop the promotion of local socio-economic. It is an immediate problem and has an important meaning.