Design of cold-formed compression web members with periodically varying section properties

In this paper, a design procedure for cold-formed channels periodically closed on their open face and utilized as joist web members is detailed. The design method for periodically closed sections is based on the representation of the cross-sectional properties using Fourier series introduced in Timoshenko quotients for the determination of the buckling loads about each of the three member axes. Once those loads are computed, they are used in the current framework of the North American Specification for the design of cold-formed structures with appropriate effective length coefficients. The proposed design methodology is compared with test results obtained from 36 stub column samples and 21 full-scale joist specimens, also presented in this paper.Key words: cold-formed struts, periodically varying cross sections, steel joists, flexural–torsional buckling, effective length coefficients.