Evaluation of the erosion of critical buckling load of cold-formed steel members in compression based on Koiter asymptotic analysis

An imperfection sensitivity analysis of thin-walled cold-formed steel members in compression is presented. The members under investigation are perforated steel pallet racks in compression of different lengths. The analysis is based on a finite element implementation of the Koiter method coupled with Monte Carlo simulation. It is based on an intensive experimental study carried out at the Politehnica University of Timisoara, which showed a strong interaction of the buckling mode with a significant reduction in the load carry capacity. Using Koiter's method the limit load is evaluated statistically analysing thousands of geometrical imperfections. Based on this, the worst combination of imperfections is detected and the erosion of the critical buckling load due to imperfections and modal interaction, is evaluated. A critical discussion of the results is presented with reference to some aspects of Koiter's analysis and how to use these in subsequent GMNIA analysis to account for the nonlinear effects of the material due to plasticity.