| Welding, bolting, screwing and riveting are traditionally regarded as the most simple and practical styles of joint in steel construction. Accordingly, these traditional styles of connection are still adopted in the light gauge steel(LGS) structures that is widely applied day by day. To the development of one kind of structure, the significance of joint is self-evident. As cold-formed steel come forth, the farther development of LGS structure calls for the innovation of connection. Cold-formed steel has much unique characteristic as light, thin-wall, high-strength, and diversification of section, that causes bolting and riveting no longer be the most appropriate styles of joint in cold-formed steel structures. Aimed at the practical application of cold-formed steel elements with special section, here conies an originative and more simple joint-Rosette-joint.The Rosette-joint is a completely new joining method for cold-formed steel structures. The Rosette-joint has several advantages over other common joining methods as mentioned before. The joint is formed using the parent metal of the sections to be joined. Thus, there are no additional fixings, nor is there need for heating, which may cause damage to protective coatings. The connecting of joint can finished rapidly and easily on-site using a special assisting tool. Quality is secured with no direct additional cost. Rosette-joint is well sttit for the ideas of LGS structure design.From year 1997-2000, The theoretical and practical research on Rosette-joint was carried on by the Laboratory of Steel Structures of Helsinki University of Technology in Finland, united with many other organizations. However, the present joint is limited to apply in small-gauge members, and has single style and low load capacity. So it can not be effectively popularized in application.On the basis of foreign research achievements, two kinds of domestic cold-formed steel sections are used as the parent materials to design Rosette-joints. Different styles of joint and various influencing factors (including form of hole, aperture, and the edge distance from the center of joint to the edge of the sheet) are taken into account, and four series of test specimens are schemed out. A series of axial-tension tests on all test specimens are carried out to investigate the shear strength of every rosette-joints. The results of this research project show that the Rosette-joint with rounded hole has better performance than those of other forms. Additionally, on the basis of tests, the pessimistic influencing range of various factors are found out and the advice of preliminary design on the forms of Rosette-joint is also given in this paper.For the theoretic analysis of Rosette-joint, foreign specialists chose shell element to simulate the joint, which can not incarnate stress variation along the direction of thickness in Rosette-joint. In this paper, 3-d quadratic solid element is firstly used to simulate relatively large-gauge joint, multi-layer elements are set along the direction of thickness, and a static,axial-tensile, stepped loading nonlinear analysis is carried through to investigate the casrying capacity of Rosette-joint accurately. After the results of FE-analyses and those of the tests are contrasted and the rationality of the model used in FEM is made certain, there are a series of parametric analyses aimed at the influence of aperture. The optimal proportion of aperture to parent metal section is concluded through the analysis and summarization of the FEM solution results.As a completely novel joint style used in cold-formed steel constructions, Rosette-joint has a wide foreground with resort to its particular predominance. The mechanism of load transfer in Rosette-joint is systematically analyzed and preliminary optimization on the form of joint is. given in this article. This work lays a foundation for advanced research and practical application and popularization of Rosette-joint in the future, and has a meaning of innovation in some degree. |
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