Finite Element Modeling of Back-to-Back Built-Up CFS Un-Lipped Channels under Axial Compression

A finite element model is described in this paper, which investigates the behavior of CFS built-up un-lipped channel sections, connected back to back with the help of intermediate web fasteners, subjected to axial load. Finite element package ABAQUS was used to develop the model for built-up columns, which were validated against the test results reported by the authors recently on another paper. Material non-linearity and initial imperfections were included in the FEA model. A parametric study was conducted using the validated FEA model to investigate the effect of screw spacing on axial strength. Axial strengths obtained from the FEA model were compared against the AISI&AS/NZS design strengths; obtained comparisons showed that the AISI&AS/NZS standards were un-conservative for stub and short columns which failed by local buckling whereas the standards were over-conservative for columns failed through overall buckling.