Reliability Analysis of Cold-Formed Steel Columns Subjected to Load Combinations Prescribed by Brazilian and North American Structural Codes

Resumo

The structural safety of columns made of cold-formed steel sections, when the wind load is considered in the analysis, requires further studies for a more in-depth understanding, as most reliability studies focus on combinations of actions involving only self-weight and overload. This paper proposes the evaluation of the reliability of columns designed according to the Direct Strength Method (DSM). Using a comprehensive database, a statistical analysis of the variable "model error" was performed, defined as the ratio between the experimentally measured strength and the strength calculated via DSM. Based on this database, a statistical analysis of the test results was carried out to determine the optimal probabilistic distribution that best fits the model error data and its relevant distribution parameters. Variables related to material strength and geometric properties were incorporated into the reliability evaluation. The structural reliability levels were assessed using the FORM (First Order Reliability Method) for bars designed according to the design requirements of the standards NBR 14762 (ABNT, 2010) and AISI S100 (AISI, 2024). The results indicate that both standards provide adequate levels of reliability, with emphasis on the uniformity of the ASCE 7-22 load combinations. The Brazilian standard showed greater sensitivity to variations in loading, especially when wind is the predominant action. Most of the evaluated combinations achieved the target reliability index of β = 2.5, although in some cases, values below this threshold were observed for the Brazilian standard.