Buckling behavior and strength of thin-walled stiffened trapezoidal CFS under flexural bending

Cold formed steel members are widely applied in light roofing systems, mainly with trussed structural solutions. Developed from thin steel sheets (usually of around one millimeter thickness) stiffened trapezoidal CFS can be considered as an alternative for large span roofing, allowing the assembling of an orthotropic roofing system. In order to improve its flexural buckling behavior, these thin-walled sections must be designed with intermediate stiffeners and quite large possibilities can be achieved in order to (i) improve the cross-section strength under bending moment, (ii) simplify and improve the stiffeners arrangement, (iii) maximize the roof covering width, (iv) develop the roofing system for long span bridging and (v) design with as thin as possible steel sheets. Considering all these conditions, the general cross-section shape can be infinitively modified adopting different stiffener geometries, dimensions, distribution, as well as combining distinct stiffeners along the cross-section. Rational systematic choices and buckling results allowed identifying the "best" solutions, taking advantage of the shape grammar contribution combined with finite strip method buckling analysis. The obtained results revealed the key geometric parameters that must be considered to perform effective improvement of roofing trapezoidal CFS.