Sustainable Design for CFS Structures: Experimental Data and Numerical Models of Hinged Connections

Cold-formed steel structures represent a suitable alternative to classical, by now, structural solutions considering the recycling/reuse tendency worldwide as part of the circular economy paradigm. The paper presents a new design approach for CFS profile joints to accurately predict their realistic behavior, based on experimental and numerical investigation of two types of connectors frequently used in the construction industry for manufacturing joints made of CFS profiles: steel-steel pop-rivets (SSPR) and self-tapping screws (STS). The experiments carried out in the case of T-joints subjected to tensile forces tested both solutions. Another significant parameter of the research was the thickness of the steel sheet used to make the CFS profiles. A number of 20 specimens of T-joints made of Cold-Formed Steel (CFS) profiles in total were tested. These consist of five specimens for each of two types of steel sheet thicknesses. The results are relevant for designers because they provide relevant data concerning the limited axial rigidity of T-joints, which are an important instrument in numerical models for achieving the optimum design of the structural system in terms of strength and overall rigidity. Experimental tests calibrate the numerical model that accounts for the axial stiffness of the hinged joints between the CFS profiles. The main parameters of the research are the thickness of the steel sheet and the connector type. The calibrated numerical model used in a case study highlights the advantages of the new approach compared to the classical design procedure based on a conventional hinged connection. Based on the results, the conclusion is that, besides the geometry of the joint and the connector type, the joint stiffness plays a crucial role in the overall behavior of the structural system and should be accounted for in the design process.