Experimental Investigation of the Deformation of Built-up Members of Cold-Formed Steel Profiles

Built-up members of cold-formed steel (CFS) profiles were tested in 4-point bending. CFS profiles (generally thin-walled) deform considerably under load, and the deformed configuration is a result of the superposition of different buckling mode shapes. Local buckling propagates through the profile walls; during distortional buckling parts of the cross-section rotate around a web-flange juncture. Alongside the buckling effects, the overall deformation of the member is considerable. To study these slender and relatively long members, a sufficient number of measuring positions on the specimens is needed. Often, this is not feasible with the conventional measuring techniques. An optical measuring device was used to record the movement of a large number of points per specimen. The obtained results are placed in a 3D coordinate system and can be exported for further data processing. The goal of the measurement campaign was to calibrate a Finite Element model that will simulate the tests. The model will be used for the analysis of composed frame members of CFS profiles, whose design is not entirely covered by the European Standard [1]. After calibration, the FEA predicts the performance of these built-up members well.