Spatial Mechanical Research On Extra Wide Stiffening Girder Of Self-anchored Concrete Suspension Bridge

Self-anchored suspension bridges differ from conventional suspension bridges because the main cables are secured to each end of the stiffening girder. Because the stiffening girder supports the cable tension, the girder must be placed before the main cable can be erected. The two fundamental characteristics lead to more complicated mechanical behavior of the girder. The Mechanic performances of concrete self-anchored suspension bridges with widen double girders show obvious spatial effect. In order to study the longitudinal and transverse stress distribution of the stiffening girder, finite element models were built to conduct the mechanic analysis of a concrete self-anchored suspension bridge. The main process and results of the research are as follows:In order to study the stress distribution of the stiffening girder of self-anchored suspension bridge during construction process, the Shear Grid Method of the Flexible Beam is used to analyze force performance of the stiffening girder and establish space Finite Element Beam of grid model by Midas/Civil. The results show that the longitudinal stress of the girder changes considerably. Range of stress value variation in the system conversion process is greater than stress value in finished bridge state. The rule of stress variation is up to the value of dead load(includes secondary dead loads)and hanger force. The maximum compressive stress of the upper plate appears in the last step of process active hanger tensioning process. Both the process of prestressed tension and system conversion shows that the stress transverse distribution of the stiffening girder shows obvious nonuniformity. And the layout position of prestressed reinforcement and the structural style of the girder.A finite element model was built to analyze the effects of shrinkage and creep in operation.Stiffening girders under the action of hanger force, dead weight, cable force and prestress are investigated to study the mechanism of the stress change during operation.. It shows that the mid-span deflection of the middle span continues increasing and the compression stress in the bottom slab of the stiffening girder continues decreasing under the effects of shrinkage and creep.The analysis shows that the decrease of the hanger and cable force and the prestress loss caused by the effects of shrinkage and creep is the main reason for the compression stress decrease and mid-span deflection. The reasonable stress state of the girder in the finished bridge state is that increase the compression stress in the lower margin and decrease the stress in the upper margin of the middle span, and decrease the compression stress in the lower margin and increase the stress in the upper margin of girder of tower area. By increase the hanger force of Hunan Road Bridge,the stress state of the stiffening girder of the initial and final completed bridge states will be effectively improved.A finite element analysis model built with solid element was used to conduct the transversestress analysis of the concrete girder of self-anchored suspension bridge. The three analysis cases are as follows: the prestressed tension process, the finished bridge state and the vehicle loading condition. The studies indicate that transverse bending deformation is quite obvious in each case.Too much transverse prestressed reinforcement will lead to severe transverse bending deformation after the system conversion, and transverse tensile stress may appear in the girder which is not safe for the structure. The variation of the transverse stress of the girder caused by vehicle load mainly appears in the top plate area between the two main girders.