Mechanical Performance Analysis Of Crossing Railway Line Steel Box Girder Based On Incremental Launching

The steel box bridge girders endure complex forces during launching, thus, FEMsoftware like ABAQUS was used to simulate the launching procedure in order to determinatethe stress distribution on the steel box girder. During launching, local buckling happened to theweb plates of Hou Dingxiang No.1bridge, while according to the original design, the webshould be able to bear the supporting force during launching, the reason why the bucklingproblem emerges was analyzed in this paper. Traditionally, box with upper plates is used in thesteel box bridge incremental launching, the heavy box itself makes higher requirements oflaunching equipment, construction accuracy, strong temporary piers and strong bridge girder,all of these requests will cause the cost increasing, this paper focus on an improved launchingmethod to deal with this problem. To solve the buckling problem during launching, an analysishas been made on the reinforcement, so as to ensure the safety of construction. The mainworks and conclusions are as follows:(1) Through analyzing the incremental launching process, the bridge is found to meet thelaunching requirements in general, but some local buckling may appear. Post buckling methodwas introduced to analyze the potential damages when concentrated force acts on the web, theresults demonstrate that, slightly irreversible deformation may occur under the mostunfavorable condition. Therefore ensuring the support bearing fine contact with the bridgegirder is the solution to solve the local buckling problem.(2) After analyzing the numerical model and the original calculation process, we find thatthe deformation caused by bridge girder hogging, as well as the contact area decrease and thestress concentration caused by this deformation was ignored in the original design, which isnot consistent with the actual construction, that is the situation left out by the software whichis based on beam elements method. Through the analysis of elevating the adjacent bear, theresult shows that the maximum stress in the structure can be reduced effectively by sharingthe loads.(3) Launching without upper plate is an improvement on the traditional incrementallaunching method, FEM software was used to analyze the stress distribution and flexuralbuckling at the mid-span, the result shows that the improved method meets the demands of construction.(4) The numerical model of reinforcement demonstrates that:1) Using triangular platesalone can’t reinforce the box girder efficiently, but can only reduce the stress on the web andthe bottom of the steel box girder. Moreover, this method will lead the stress on the diaphragmrising, which makes the diaphragm buckling.2) To meet the launching requirements,triangular steel plates, thickening the diaphragm and web plates can reduce the stress of steelbox efficiently, but it will lead the stress on bottom plate rising, which will bring moredifficulties for construction.3) Using0.5m×0.5m triangular concrete bands to reinforce thebox girder and bonding the concrete with the web and bottom of the steel box with shear studsis an good solution. The result shows that the stresses on the web, bottom and diaphragm meetthe launching requirements after using the concrete to reinforce the steel box girder.