Residual Stress And Weld Arrangement Of Welded Joints Of Box-section Single-layer Lattice Shells

The structure of single-layer reticulated shells is complex and its nodes are formed by the convergence of many rods.It is a key point for the transmission of internal forces.The design of the nodes is very good,and the performance of the structure,manufacturing and installation,the amount of materials used,and the cost are very high.The big influence is also the key to the success or failure of the overall design of the shell.Compared with the conventional steel pipe section bars,under the same bearing capacity and functional conditions,the box section bar parts save more steel,save cost,and have better permeability and viewability than the ring section bars.It is suitable for bearing bi-directional bending moments,large torsional stiffness,stable ultimate load-bearing,good cleaning during use,low maintenance cost,and a more compact and beautiful overall appearance.Box-section single-layer lattice shell welded joints,welding process will form a non-uniform temperature field near the weld,the difference in temperature gradient,so that the welding node is prone to residual deformation,and after cooling the components,the weld will be around Generates great residual stress.Welding residual stress will reduce the fatigue strength of welded joints,cause stress corrosion cracks in the welds,and make the structure vulnerable to safety problems.In the field of construction engineering,there is little research on the residual stress of box section welded joints,and the design of the nodes is related to the safety and economy of the nodes.The layout of the weld layout in the design drawings is highly active,and the welding process parameters,joint types,welding sequence,bevel shape,and other factors are low in the design and construction drawings,and are treated as usual,with limited potential.According to the research background of box-section welded joints at home and abroad,the main contents of this paper are as follows:(1)Research status quo of welded joints of box-section single-layer lattice shells,research status of welding numerical simulations,and research status of welding numerical simulation heat sources.(2)Solidworks was used to build 3D model,ABAQUS and VisualMesh were used for grid processing.Then the welding process was numerically simulated with misufact.welding to analyze the temperature field and stress field during the welding process of the three box section bars,and the box section was analyzed.The residual stress and welding deformation of the rods are used to find a reasonable solution for the weld arrangement of the box-section rods.(3)Under a reasonable weld layout scheme,when the rods are connected to the nodes and the number of welds is large,the welding process is numerically simulated and a reasonable welding sequence is found through comparative analysis of residual stress and deformation.(4)Under the reasonable welding sequence,analyze the influence of the ratio of width to thickness of the box-section bar flange plate on the residual stress and deformation.(5)Based on the above research conclusions,using the cross-section rods with reasonable weld arrangement,complete the design of four six-way intersection welding nodes,simulate the welding process of the nodes,compare and analyze the residual stress and deformation of the four welding nodes,and find out Weld joint layout design a more reasonable node type.(6)Taking the reasonable node type as the research object,analyze the stress state of the joint under axial load and bending moment.Analysis of the lack of nodes,through the thickening of the flange plate thickness at the node to optimize the design of the node to improve the node bearing capacity,to obtain the optimal node flange thickness,so that the design of the node is economically reasonable...