Numerical Modelling and Optimisation of Cold‐Formed Steel Purlins

Abstract

This paper reports a numerical study on the optimization of the lip size of Z‐sections under gravity loads. Numerical models simulating the structural response of cold‐formed steel Z purlins partially restrained by cladding and angle struts and subjected to sagging moment were developed and validated against a total of nine previously reported experimental results on Z‐sections that failed in local or/and distortional buckling. Models of varying levels of complexity were generated and the key parameters affecting the structural response were determined by means of a sensitivity analysis. The investigated parameters included the magnitude, shape and combination of initial geometric imperfections pertinent to local and distortional buckling and the simplified or explicit modelling of test details such as struts and sheeting. Having determined the appropriate modelling strategy that yields the best balance between accuracy and computational cost, parametric studies were conducted to investigate the effect of decreasing or increasing the lip depth on the sections' moment resistance and corresponding failure mode. Based on the parametric study results, the optimal lip size which maximizes the moment/weight ratio for each section was determined.