DSM versus design codes predictions on Z-section members having different flange stiffening configurations under web crippling loadings

• Published in: Thin-walled structures Vol. 215; p. 113409
• Main Authors: He, Jun, Ellobody, Ehab
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2025
• Subjects: Cold-formed steel; Design predictions; Numerical modelling; Web crippling; Z-sections; Z-sections; Web crippling; Cold-formed steel; Design predictions; Numerical modelling
• ISSN: 0263-8231
• DOI: 10.1016/j.tws.2025.113409

•DSM and design codes predictions were compared on Z-section members under web crippling loading conditions.•Parametric studies were performed using developed and validated FE models.•Web crippling strengths, load-displacement relationships and failure modes of Z-section members were investigated.•A DSM-based design equation was proposed.•Reliability analyses were performed to assess the proposed DSM-based and design equations. Direct Strength Method (DSM) and design codes predictions are compared, analysed and presented in this paper on Z-section members having different flange stiffening configurations subjected to End-Two-Flange (ETF) and Interior-Two-Flange (ITF) web crippling loading conditions. The paper highlights a robust and comprehensive approach combining design with finite element modelling augmented with an extensive testing program previously reported by the authors on the members. The Z-sections members were of high strength brake-pressed from zinc-coated grades G450-G550 having unstiffened and stiffened flanges. The paper highlights, in extensive detailed parametric studies, the behaviour of the members considering key affecting variables and investigates. Using developed and validated FE models, the Z-section members’ web crippling strengths, stress and strain contours, plastic model, load-displacement relationships and failure modes were predicted. The members’ behaviour is studied over wide ranges of web slenderness (flat height-to-thickness h/t), bearing length-to-thickness (N/t) and inner radius-to-thickness (ri/t) ratios varying (from 36 to 233), (from 16.7 to 145.9) and (from 1 to 2.5), respectively. It is shown that different flange stiffening configurations with minimum practical production requirements have a considerable effect on the overall web crippling performance of the Z-section members. The paper proposes a DSM-based design equation, which was assessed together with the North American Specification and Eurocode design rules, using reliability analyses. It is shown that the proposed DSM-based design equation is reliable and accurate, compared with the design predictions, and should be adopted for designing Z-section members having different flange stiffening configurations investigated in this study under ETF and ITF web crippling loadings.