Open cross-section beams under pure bending. I. Experimental investigations

An experimental study of open thin-walled section beams subjected to pure bending is presented. The aim of the study was to analyse the post-collapse behaviour of U-sections and Ω-sections. The beams were made of cold-formed steel, the thickness being 0.6 and 1.5 mm and the grades of the steel S275 and S325. Twenty-two specimens were tested in a four-point bending configuration. A special bending outfit was designed and built, taking into account the slenderness of the beams. Accurate moment-rotation graphs were thus obtained up to angles of rotation in the plastic hinges near to 20°, allowing for a complete development of the plastic mechanism after the collapse. In parallel, a finite element analysis methodology was implemented to simulate the post-collapse behaviour. The comparison with the experimental results validated this methodology (explained in Part II. Finite Element Simulation).