engleski

Experimental study on the buckling resistance of cold-formed steel back-to-back plain and lipped channels in bending

Cold-formed steel profiles are increasingly in demand in the construction market because of their speed of assembly and low material consumption. Thus, it is necessary to investigate their behavior in depth, since in recent years they have been used as the main structural components of buildings. The paper presents an experimental program where several types of built-up section configurations were tested made of lipped or plain channels, such as simple built-up back-to-back (SBB) and back-to-back with spacers (BBS) cross- sections and two types of discrete connections, i.e. bolts and spot welding. The paper is based on a previous parametric numerical investigation performed to identify the influence of several parameters, i.e. the type of the channel section, length of the beam, continuous and discrete connections between channels, the number and the distance between discrete connections along the beam axis and along the beam height. From the parametric study, it was concluded that the capacity of the cold-formed steel back-to-back built-up steel beams is highly affected by the type of connections. The static scheme of the beams used the 4-point bending setup so that the central area is subject only to the bending moment. The length between the loading points was monitored to capture the behavior of the beams from local to distortional and interactive buckling. A total of thirty beams subjected to pure bending with built-up sections were tested. In addition, the out-of-plane displacements were restricted at the loading points to control the failure area. Before the tests were performed, the sectional dimensions and imperfections of the elements were measured, as this represents a critical issue in the behavior of thin-walled cold-formed steel elements. A 3D laser scanner was used to determine the initial imperfections. The records allowed measurement of the initial imperfections in relation to the nominal cross- section.

Back-to back steel beam, Spot welding, Bolts, Experimental tests

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