Fracture Behavior Test And Finite Element Study Of Welded T-stub Of High Strength Steel

As the strength of high-strength steel increases,the welding sensitivity of high-strength steel is higher,and the fracture problem of welded joint is more prominent.For beam-to-column welded joints,butt welds are prone to fracture.During the Beiling earthquake in the United States and Osaka-Kobe earthquake in Japan,a large number of beam-to-column welded joints fracture at the butt weld of beam-to-column flange.Therefore,how to prevent the crack at the butt weld of beam-to-column flange needs further study.Scholars at home and abroad have studied the fracture behavior of high-strength steel,but the research content is not comprehensive enough.In this paper,the fracture behavior of simplified T-stub of Q690 high-strength steel beam-column welded joints with different loading systems and different welding forms of the access hole liner are studied by experiment and finite element numerical simulation.The main research contents include:(1)Based on the fracture resistance of simplified T-stub of beam-column welded joints improved by traditional weld of the access hole liner,an experimental study was carried out.The test results show that the welding quality and processing quality have some influence on the fracture behavior of the specimens.On the premise of guaranteeing the welding quality and processing quality,monotonic tensile loading and loading and unloading cycle loading have little influence on the fracture behavior of the specimens.The stress state and the fracture resistance of T-stub can be effectively improved by changing the traditional single side welding of the access hole liner to tow side welding or four side welding.The research contents can provide reference for engineering application.Compared with single side welding,the ultimate load and fracture displacement of T-stub specimens with tow side welding of unilateral V-shaped cross-weld are increased by about 0.5% and 33.9% respectively.Compared with single side welding,the ultimate load and fracture displacement of T-stub specimens with four side welding of unilateral V-shaped cross-weld are increased by about 1.2% and 54.1% respectively.(2)The simplified T-stub of welded joints of steel frame beams-to-columns was studied by finite element method.Eight T-stubs with different loading systems and welding forms of the access hole liner were numerically simulated by using finite element analysis software ANASYS.Considering the influence of welding residual stress,thermal analysis and structural analysis were carried out.Thermal entity element SOLID87 was used for thermal analysis and tetrahedral entity element SOLID92 was used for structural analysis.The results of welding residual stress and fracture index(stress triaxiality,equivalent plastic strain index,cracking index)of T-stub under specified path were given.It is found that the loading system has little effect on the fracture behavior of the simplified T-stub of beam-to-column welded joints.The welding form of the access hole liner has a significant influence on the fracture behavior of simplified T-stub of beam-to-column welded joints.(3)The fracture behavior of simplified T-stub of Q345 steel,Q460 steel and Q690 steel beam-to-column welded joints were compared and analyzed.It is concluded that under the same dimensions,structure and loading conditions,the possibility of fracture at butt weld of 690 steel T-stub is the greatest,followed by Q460 steel T-stub,and that at butt weld of Q345 steel T-stub is the smallest.