Web shear buckling capacity of a stiffened Z-purlin: reporting of experimental tests

Resumo

Over the last few years there was a growing demand for structural solutions with lower steel consumption in the design of portal frames. It is considered that cold-formed steel (CFS) represents a consumption of 30 to 40% of steel in the entire structure, due to its great applicability in roof systems. Purlins with Z-sections have capabilities to achieve greater spans than other sections due to the continuity provided by overlapping connections. Greater spans require higher sections, thus increasing the susceptibility to local buckling of the web when the purlin is subjected to bending. Therefore, there is the need to introduce web stiffeners with complex geometry, providing better structural performance to local buckling strength. However, this also introduces complex web behaviour in the presence of shear, as result it requires advanced analytical, experimental and numerical studies to assess the web shear buckling mode of failure of such sections. In this context, as a first incursion in this field, the authors report in this paper some experimental tests of a new stiffened web cold-formed Z-section in the Brazilian market aiming the web shear buckling mode of failure. Consequently, an experimental setup of simply-supported purlins with short spans under 3-point bending are carried out. The flanges were locked to investigate the structural behaviour of CFS under predominantly shear. The resistances are compared between experimental data and direct strength method (DSM) as prescribed in the AISI S100. The results were evaluated providing a rich understanding of the structural behaviour of the CFS Z-sections with stiffened web and complex geometry.