Local Stress Analysis Of Steel-Box Girder Which Constructed By The Walking-Type Incremental Launching Technology

Firstly, this thesis briefly introduces the application and the development history of incremental launching method, and makes comparisons between the traditional drag-type technology and the new walking-type incremental launching technology by enumerating the advantages and disadvantages of them. After that, based on the background of Kunming South connecting line railway flyover bridge, author describes the control system and the construction procedures of the new walking-type incremental launching technology in detail. On this basis, the author applies the finite element analysis software Midas Civil to establish the pole system FEM of the whole bridge, and accomplishes the whole-process simulation analysis of the incremental launching construction. With this analysis, the author comes to know the global stress of the whole bridge. Then the most unfavorable loading states of concrete slab and steel-box girder are identified; Under the most unfavorable loading states, a Beam-Shell-Solid-Contact mixed FEM is built by large-scale finite element analysis software ANSYS. This part focuses on the analysis of contact states between the rubber layer and the steel-box girder in order to explain the situation of local stress of main girder components. Lastly, combining the practical engineering, the author sets some relevant parameters and analyze that how these parameters influence the local stress of steel-box girder. With the parameters analysis, the author sumamarise some laws which can be reference for more and more bridges constructed by the walk-type incremental launching technology in the future. The conclusions of the study are as follows.In steel-concrete composite bridge, the concrete slab integrates with the steel-box girder by shear connectors, so that they can bear the load jointly. This leads to high stress of the concrete slab in this area. And at some construction states, the top surface of concrete slab is under the risk of cracking.The rubber layer adapt to the angular displacement of the main girder in the bearing region easier than the steel layer. This characteristic makes the steel-box girder stressed uniformly. On the contrary, with the steel layer, girder’s local stress effect is prominent. Stress level of the components is higher.The smaller elastic modulus of rubber layer affects the local stress of components by improving the inhomogeneity of contact between the rubber layer and the girder’s bottom face. At the same time, the width of rubber layer affects the local stress of components by shifting the action point of support reaction transversely.The local stress analysis of components which are affected by jacking hydraulic asynchrony shows that the longitudinal asynchrony has greater impact than the vertical asynchrony. And all these asynchrony would result in the steel-box girder’s lateral displacement. At last, we determine the safety control threshold value of this bridge which is under the condition of jacking hydraulic asynchrony.