Research On The Structure Behavior And Ultimate Capacity Design Of Overlap Tubular K-Joints

Tubular structure is frequently applied in all kinds of large span structures in these days. It assorts with structure and architecture in a walk, provided with predominant structural capacity and satisfied ecnomy benefit. Overlap tubular K-joints are common features in tubular structures because of their low steel-consuming, excellent mechnics performance, large bearing capacity and special technics. Before long a new kind of tubular joints,called overlap parallel tubular K-joints, is appeared in Suzhou Internantional Expro Center, which has no theoretics to comply with. So, the mechnics performance study of uniplanar overlap tubular K-joints as a leadoff, a research of the new kind of joints is then presented for the first time. Meanwhile, Hidden weld effection is also analysed ,which is not available in the national investigation.Dearing the study of uniplanar overlap tubular K-joints, using a finite element (FE) study of axially loaded overlap tubular K-joints as a platform, a research on the distribution of the various modes of failure, an extensive, systematic parametric study and an analysis of the hidden weld effection are carried out in turn. The results indicate that the ultimate bearing capacity of overlap K-joints is obviously larger than the gap ones.Comparing with the current codes and design guidances, a equation predicting the strength Pu of overlap K-joints is developed, using nonlinear regression techniques. In the equation, the effection of hidden weld is also considered.Further more, the corresponding study of multiplanar overlap parallel tubular K-joints is proceeded, with the same parameters and ranges as those of uniplanar K-joints.The results of research disclosure the similarity between these two joint-forms. Applying the bearing capacity equation advanced above to multiplanar parallel one, shows a good accurate prediction (nonmember failure) of the FE data. So it is feasible to simplify a multiplanar pallel K-joints to two uniplanar K-joints, when the ultimate bearing capacity is what we want to know.Five full size parellel tubular K-joints model tests are fulfilled. The specimens are come from Suzhou Internantional Expro Center. The test procedure and data anlysis, especially the comparison between absence and presence of the hidden weld, are written up. Nonelinear finite element analysis (FEA) is also used to analyze the tested tubular joints. The coincidence of experiment data and FEA results shows the applicablilty of the finite-element study.From the research, it is found out that different from the tradional gap K-joints, the faliure modes of overlap K-joints include brace local buckling, combined chord wall bending and brace local buckling and weld break. The ultimate bearing capacity predicting fomular of the overlap K-joints in the current codes needs to be modified. When more than 60 percent weld of the overlap K-joints is considered to be absence of hidden weld, it is suggested to be whole welded, else should be reduced the bearing capacity according to the equation adivised above.