Improving the local and distortional resistance of CFS trapezoidal self-supporting roof members

• Published in: Thin-walled structures Vol. 201; p. 112054
• Main Authors: Neves, Marcos, Basaglia, Cilmar, Camotim, Dinar, Araujo, Heitor
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.08.2024
• Subjects: Cold-formed steel members; Direct strength method (DSM); Generalised beam theory (GBT); Genetic Algorithm (GA); Local and distortional resistance; Multi-objective optimisation; Self-supporting roofs; Shape improvement; Trapezoidal cross-sections; Trapezoidal cross-sections; Cold-formed steel members; Self-supporting roofs; Shape improvement; Local and distortional resistance; Generalised beam theory (GBT); Genetic Algorithm (GA); Direct strength method (DSM); Multi-objective optimisation
• ISSN: 0263-8231; 1879-3223
• DOI: 10.1016/j.tws.2024.112054

•Optimisation framework for cold-formed steel (CFS) trapezoidal members is developed.•Performance enhancement of CFS trapezoidal members in self-supporting roof systems.•Multi-objective optimisation through addition of intermediate longitudinal stiffeners.•Genetic Algorithm based on Generalised Beam Theory and Direct Strength Method.•Bending resistance against local and distortional failures optimally increased. This paper reports the development, numerical implementation and application of a methodology to perform the multi-objective optimisation, with respect to local and distortional failures, of cold-formed steel (CFS) trapezoidal cross-section shapes used in members belonging to self-supporting roof systems and manufactured by bending the steel sheets with roll-forming machines. Initially, a brute-force approach is adopted to search for optimal unstiffened cross-section shapes of members subjected to positive (sagging) and negative (hogging) bending moments. Next, an optimisation procedure based on a Genetic Algorithm (GA) is employed to find stiffened cross-sections that (i) outperform the original (plain/unstiffened) ones, as far as the resistance against local and distortional failures is concerned, and (ii) can be fabricated with minimal additional cost, through the sole addition of small intermediate stiffeners, whose possible locations are pre-defined in accordance with a map of executable fold-line positions – the original cross-section typology, overall dimensions and wall angles are retained. The design approach adopted to estimate the member ultimate strengths is based on the Direct Strength Method (DSM), and Generalised Beam Theory (GBT) is used to calculate the elastic buckling stresses due to bending. The application and capabilities of the proposed methodology are illustrated, by means of numerical results presented in terms of cross-section families belonging to optimal Pareto Fronts – an excellent performance of the procedure was found in all cases.