Closed-Form Equation for Distortional Buckling of Cold-Formed Lipped Channels Subject to Compression
Daniel Carlos Taissum Cardoso1; Guilherme Cardoso de Salles2; Eduardo de Miranda Batista2; Paulo Batista Gonçalves1
1 Pontifical Catholic University of Rio de Janeiro; 2 Federal University of Rio de Janeiro
doi:10.20906/CPS/CILAMCE2017-0258
Resumo
Since 1960's several works presented rational explicit equations to predict the distortional buckling critical stress of cold-formed columns and beams (Sharp 1966, Lau and Hancock 1987, Schafer 1997, Silvestre and Camotim 2004, Zhou et al. 2015). Many of the derived formulae proved to be accurate and rational however they usually demand calculation of several parameters which makes them complex to be employed by structural engineers in design. This paper adopted Rayleigh Quotient method to obtain explicit equations for distortional buckling critical stress of lipped channel columns. Two different models with different assumed buckled shapes (Models 1 and 2) are developed and the proposed expressions are validated with results obtained with generalized beam theory (GBT) for commercially-available sections with distinct geometries. The main difference between Models 1 and 2 is that the former assumes rigid stiffened flange similarly to Lau and Hancock (1987), Schafer (1997) and Zhou et al. (2015) whereas in the latter, transverse wall-bending of the flange is considered. For typical cross section geometries, average ratios of critical stress between the proposed formulae and GBT are 1.062±0.073 and 0.998±0.001 for Models 1 and 2, respectively. Comparisons to methods included in design standards and specifications are also presented. The presented results indicate that expressions derived for Model 1 are useful for design purposes since they are sufficiently accurate and require computation of parameters familiar to engineers. On the other hand, Model 2 is more complex to implement and results in more accurate predictions.
Palavras-chave: Thin-walled Structures; Cold-formed steel columns; Distortional Buckling