An experimental study on the flexural behavior of cold-formed steel composite beams

Abstract

Local buckling instability under compressive stresses is common in cold-formed steel (CFS) members and generally occurs well before the material has reached its yield strength. This results in under-utilization of the cross-section, compared to its full capacity governed by strength failure. Under flexural loading these CFS members possess sufficient inelastic reserve strength up to the ultimate stage. A recent study indicated that plate girders with tubular flanges offer higher flexural and torsional strengths compared to the ones with flat flanges. Upon packing of the tubular compression flange of CFS beams with hard materials like concrete/ timber etc., there will be a substantial delay in early local buckling instabilities, thus improving their load carrying capacity considerably. Although, numerous CFS composite sections have been developed recently, very limited lightweight packing materials have been adopted. The current study presents an experimental investigation carried out on CFS beams with flanges and webs possessing rectangular box geometry, packed with suitable low-cost lightweight packing materials, resulting in novel light-weight CFS composite beams. Four point flexural tests were conducted on these beams with simply supported end conditions. The ultimate strengths, modes of failure, load vs. displacement plots were obtained to study their flexural behavior, in order to evaluate the structural efficiency of the different packing materials. Lastly, the North American Specifications and Australian New Zealand Standard for CFS structures were also used for determining the design strengths of the specimens for comparison sake. This study proved that these novel CFS composite beams have shown better performance considerably.