Section B5 of the AISI Specification, covering stiffened elements with multiple intermediate Stiffeners and edge stiffened elements with intermediate Stiffeners, has been entirely replaced in the latest edition of the Cold-Formed Steel Specification (NAS 2001). The new design rules are based primarily on the work of Schafer and Pekoez (1998); however, subsequent to that work and prior to adoption by AISI, additional work was also completed. For elements with multiple intermediate Stiffeners consideration of web/flange interaction was added. The resulting expressions are shown to agree well with both experimental and numerical data. New provisions for edge stiffened elements with intermediate Stiffeners have also recently been adopted. The logic behind the development of these provisions is discussed herein. Compared with previously used procedures (AISI 1996) the new methods provide a more robust and reliable method for the design of these unique elements.
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