Bending strength of buil-up cold-formed steel members stiffened by diagonal web beads

The present paper is concerned with the experimental investigations on the load bearing capacity of innovative cold-formed steel members built-up by different steel sheets assembled through mechanical fasteners. The beam is obtained by assembling back to back two special cold-formed C-profiles, so that an I cross-section with hollow flanges is formed. Two reinforcing plates are placed inside the top and bottom hollow flanges of the I-section, providing a flange connection system between the two C-profiles. The shape of the beams is finally characterized by web openings and diagonal beads to prevent early buckling phenomena. The experimental investigations, performed through four-point bending tests on full-scale prototypes whose cross section depth is equal to 400 mm, have been carried out in order to assess the influence of different parameters on the strength, stiffness and ductility of the beams. In particular, the effects of different connection spacing on local buckling of the compression flanges have been evaluated. Finally the influence on the structural performances of diagonal beads placed along the web has been also investigated.