2022 Research Reports No R970-R971

Abstract
The paper develops a stiffness reduction factor to be used in geometric nonlinear beam-element type elastic analysis of cold-formed steel structures. The factor accounts for the reduction in flexural and warping torsion rigidities resulting from local and distortional buckling as well as residuals stresses, as particular to cold-formed steel structures. The purpose of applying the factor is to accurately account for the geometric second order effects when predicting the internal distributions of moments of cold-formed steel structural frames. The stiffness reduction factor arising from local and distortional buckling is first determined followed by the stiffness reduction factor caused by residual stresses. Subsequently, the two effects are combined in a single expression is a format suitable for incorporation in the North American specification for cold-formed steel structures, AISI-S100.

Keywords
Cold-formed steel, local buckling, distortional buckling, residual stress, stiffness reduction