Experimental and numerical investigation of the structural behavior of cold formed steel built-up box sections

In Cold-Formed Steel (CFS) construction, built-up box sections are becoming more and more common for beam members. This paper presents a thorough analysis of the experimental and numerical aspects of the innovative faceto- face joined built-up cold-formed steel beams. It is done by finding buckling-moment resistance capacity under fourpoint bending. Two press-braked channel pieces are used to build these built-up beams, and bolted connections hold them together. The two different cross sections examined in the research work are namely HT (face-to-face connected hollow CFS channel section having screws only at the top) and HTB (face-to-face connected Hollow CFS channel section having screws both at the top and the bottom). The beam is square in cross-section and contains stiffener only at the web portion. The study took into account three distinct parameters: (1) screw spacing; (2) the screw’s placement; and (3) the thickness of the section. A total of 8 specimens were tested using the experimental method. Here, the load-displacement relationship and the failure mechanism are covered in detail. Using Finite-Element (FE) models produced with the commercial software ABAQUS, numerical analysis was performed. Regarding ultimate moment capacities and buckling modes, the findings of the actual tests and the FE agreed rather well. The FE models were therefore confirmed. The design strengths computed concerning the American Iron and Steel Institute (AISI) were compared with the design strengths found through experimental and FE method. Also, a detailed discussion is provided on how the parameters as mentioned earlier affect stiffness, buckling resistance behavior, flexural strength, and the failure mode. After a discussion of the experimental, theoretical, and FE results, the ideal screw spacing, location, and specimen thickness are suggested.