Seismic Analysis For Welded Joints Of Steel Frame Structures Considering Welding Residual Stress

Steel structures are widely used in the construction engineering. There are many chord members are jointed together at the welded joint which may produce a complicated stress state. Studies shows that welding residual stress produced in welding process would form an internal self-balanced force system.When the structural member subjected to external loads,especially long-term dynamic cyclic loading, the superimposed stress of the stress caused by external loads and welding residual stress would make certain parts of structures advanced to yield strength, and produce plastic deformation, which will seriously affect the bearing capacity of the structures.These series results would reduce the structure safety performance and even lead collapse of structures.In order to ensure the safety and reliability of welded structure,accurate prediction for welding residual stress is an important project for the steel structures design.In present engineering practice, the welding process is very complicated, and welding residual stress is affected by many factors.Therefore, using the experimental testing methods for the accurate prediction of welding residual stress is certain limited by complex construction conditions.This paper introduces a complete dynamic finite element analysis method for welding residual stress, and a finite element analysis program ANSYS is used to carry out a coupled thermodynamic and thermal elastic-plastic analysis to obtain the welding residual stress. In this paper, the techniques of’Life-Death’element and thermal-structural coupling resolve are adopted to accomplish the three dimension dynamic simulation through changing the element attributes of the beam-column welded joint in a steel frame structure. And the finite element analysis of temperature fields and stress fields for joints are also finished. The analysis results reaches a significant conclusion that the maximum value of welding residual stress close to, or even exceed the material yield strength. At the same time, as the welded joints are adopted to groove weld, and its ends presents obvious stress concentration phenomenon near the geometrical mutation edge, which lead a large value of welding residual stress. This paper carried out the dynamic response analysis for a steel frame structure under seismic action,and then built a method for stress field analysis for steel frame structures.The first step of the method is to get the dynamic stress response of the large scale of the structure and the boundary condition for the key welded joints; the second is to establish the refined solid finite element model of the key joint, and then dynamic simulation of welding temperature field and stress field on the joint is completed,on the next work the boundary condition are applied to the key joint for small scale dynamic analysis which take the welding residual stress as the initial stress;then gains the stress state of the welded joint of steel frame structure;Finally,stress field analysis for the key welded joints considering welding residual stress is achieved under seismic action.