Numerical Simulation Of Welding Deformation Of Steel Box Section Bar In Bridges

Members with box section are often used in steel bridge, such as truss beam bridge, truss arch bridge, stiffening girder in suspension bridge and cable-stayed bridge. The welding deformation is the main reason that influences the efficiency and quality of these members. As the welding deformation is a difficult issue in the manufacturing process of members, in this thesis, thermal elastic-plastic FEM was used and a finite element model was built by ANSYS. The section size of the studied member is 40 cm × 40 cm,2 cm thick and 2 m long. The welding process of 4 main welds was simulated to find the deformation rules, which can be used to predict and control the welding deformation.The main conclusions are listed as follows:(1) A whole manufacturing process of box section member was summarized and a thermal elastic-plasticity finite model was built according to the real welding sequence. The parameters used in the FEM model, such as boundary conditions, material parameters and welding heat source, were introduced, and confirmation of these parameters was discussed.(2) The shrinkage, bending and torsion of steel member in 4 different welding sequences were calculated, and the results were compared with the ones by empirical formula. It is confirmed that the numerical simulation results were reliable. The interaction characteristics of 4 main welds were summarized. With the welding technique used nowadays in the factory, the torsion deformation caused by the main welds was small, while the bending deformation needs to be controlled by some measures.(3) Several control measures commonly used in the welding process for steel members with box section were summarized. The stress state near the welds while welding had a significant influence on plastic strain and deformation. The stress state can be controlled by the cooling time and the prestress force, two feasible measures used to control the welding deformation were proposed.