COLD-FORMED STEEL LIPPED CHANNEL COLUMNS UNDER LOCAL- DISTORTIONAL-GLOBAL BUCKLING MODE INTERACTION

Resumo

Thin-walled steel cold-formed lipped channel members in axial compression are susceptible
to buckling phenomena in the following modes: Local buckling (L), Distortional buckling (D) and
Global buckling (G). In these cases, the Direct Strength Method (DSM) predicts the ultimate strength.
However, some geometries are affected by the occurrence of coupling phenomena involving two or
three buckling modes interaction. The buckling modes interaction produces additional column strength
reduction if compared to isolated buckling modes occurrence. Furthermore, the design specifications
and codes for cold-formed steel members do not handle properly the ultimate strength for the cases of
L-D, D-G and L-D-G interactions. In this context, the present article is aimed at developing a Direct
Strength Method (DSM) approach to estimate the ultimate strength of lipped channel columns affected
by Local-Distortional-Global buckling mode interaction. To achieve this goal, the investigation is based
on: (i) literature review of experimental columns affected by buckling mode interaction (ii) calibration
of the FEM model based on experimental results; (iii) nonlinear FEM analysis of post-buckling behavior
affected by mode interaction performed with the help of the ANSYS computational program; (iv)
propose a Direct Strength Method (DSM) approach to estimate the ultimate strength of lipped channel
columns affected by Local-Distortional-Global buckling mode interaction.