Xiangtan Four Bridge Side Span Cable-stayed Arch Bridge In The Main Beam Power Performance And Horizontal Analysis Method

The main bridge of the Fourth Xiangtan Xiangjiang River Bridge in constructing at present, is cable-stayed flying swallow type concrete-filled steel tubular tired rod arch bridge with the total span of 120m+400m+120m, which is the first cable-stayed arch bridge in China. Cable-stayed arch bridge is a new pattern composed system bridge, which is composed of concrete-filled steel tubular main arch, concrete side arch, tower, stayed cable, box-type side-span beam, tired rod, hanger, cross beam, etc. Its conformation and mechanics performance are complex comparatively. Its side-span beam is two boxes one cell prestressed concrete structure, and it is joined with side arch, stayed cable, tired rod, and such component. The distance between the center of two boxes is 22.3m. The deck is wide, to strengthen its unitary, and so 28 diaphragm beams every 5.0～6.0m are set in the boxes and between the two boxes. The bridge is in a complex mechanics state. According to these, the present thesis explores mechanics performance of the side-span beam, especially the transverse mechanics performance, and the analysis method, finishing the following tasks:1. Three kinds of spacial finite element model are established, including spacial solid finite element model, spacial beam system finite element model and spacial suppositional longeron grillage finite element model. Mechanics performance of the side-span beam, especially the transverse mechanics performance, is analysed and researched, and that validate rationality of the design. Based on the analysis results, the thesis puts forwards correlative improved suggestions. First, mechanics performance of the side-span box beam is well. Second, because of local stress concentricity, it brings a greater stress phenomenon, some places such as the anchor area at the end of the beam, side-fulcrum position, corner area of bracket, and pedestrian hole of crossbeam in the box, and furthermore the thesis puts forwards suggestions on local structure design. Third, in allusion to box beam transverse mechanics problem, suggestions that it needs to strengthen transverse prestressed reinforcement of the two side diaphragm beam, are put forwards.2. Three kinds of plate beam element model are established, including plate four-fulcrum beam element model, plate two-fulcrum beam element model and plate six-elasticity-fulcrum beam element model. The transverse mechanics performance of the side-span beam is analysed and researched. The mechanics performance is well.3. The transverse mechanics computational results of plate model and spacial model are compared and analysed. The results show that plate beam element model is inadequately accurate at the end crossbeam, but apply well to the central section crossbeam.4. Solid finite element method model is complex, its computational period is long, and data processing is multifarious. As a result, the thesis suggests that solid finite element model is used in the local mechanics performance. Grillage analysis method is precise, computational result is extracted expediently. To be a conclusion, Grillage analysis is an effective method to the transverse mechanics performance of the side-span beam. In addition, considering the effect of the deck between the two boxes, spacial suppositional longeron grillage finite element model have a higher precision than double-chine model. The thesis suggests adopting the method in design and structure analysis.