Assessment of cellular beams with transverse stiffeners and closely spaced web openings

• Closely spaced cellular beams with double concentric transverse stiffeners.
• Spacing between the web openings, web thicknesses and stiffener thicknesses.
• Study of Vierendeel shearing failure and web-post buckling.
• The transverse stiffeners are very effective for Sd<1.3.
• Stiffened sections formed plastic hinges closer to the mid height of the web-post.

A computational parametric finite element analysis was carried out, investigating closely spaced cellular beams with double concentric transverse stiffeners. An unstiffened perforated beam section was initially designed and validated against existing finite element analysis results found in the literature. Then, thirty-one models were studied, while altering the spacing between the web openings, the web thicknesses, and the stiffener thicknesses. The results showed that Vierendeel shearing failure occurred more frequently for very closely spaced sections. However, as the spacing increased, the contribution of the stiffener to strength of the section was decreased, and out-of-plane buckling failure occurred more often. A maximum distance for the spacing between the openings was suggested in order to optimally use the derived fomulae. At last, a design model was proposed, where for very closely spaced openings the compressive stresses were given by the Vierendeel moment capacity, while for the maximum distance of the spacing between the openings studied, the compressive stresses were given by a strut analogy, as found in BS5950-1.