Nonlinear Flange Curling of Wide-flange Sections (No. R850)

Abstract

This report describes the experimental and theoretical analysis of flange curling deformations. Flange curling of two commercially available roof sheeting profiles named Monoclad and Megaclad provided by Stramit Building Industries have been examined. The results show that a true representation of the wide-flange support condition provided by the web is essential to obtain reasonable agreement with experimental tests and that models used in the past are generally inadequate. The iterative theoretical flange curling model which represents the changing geometric and loading conditions shows that a 5-15% reduction in yield moment due to reduced section modulus can occur and this is otherwise ignored by the simplified flange curling models used in the past. Stresses in the wide flange can vary considerably, with the most drastic nonlinear behaviour exhibited by the Megaclad section where the center-pan stress was only 9% of the web/flange junction stresses. The analysis of section stresses shows that yield develops first at the short flanges and webs and that, for the sections considered, the wide flange stresses remain below the yield stress.