Experimental and Numerical Investigation on Stiffened Rectangular Hollow Flange Beam

Cold-formed thin-walled steel hollow flange beam (HFB) has been emerged and utilised structurally. It is composed of one or two closed flanges with high torsional stiffness and relatively flexible web. Hence, the global stability of such beam has greatly been improved compared with conventional I-beams with flat flanges, due to their superior torsional stiffness and stability. However, under concentrated loading, local flange deformation occurs easily at the load-action-region, because the tubular flange is hollow even if stiffeners are attached to the webs. Up-to-date, rather than filling the tubular flange with concrete, there is not any relevant literature or reports on how to improve the local buckling state of the hollow flange I-beams. Accordingly, in this paper, a stiffened compression rectangular hollow flange beam (SCHFB) is presented, from which the web penetrates the bottom wall of the top tubular flange until it reaches its top wall. By doing so, several concentrated loads may be applied safely on the beams or the segmental lunching technique may successfully be used to erect the beam in its place. This paper examines experimentally this stiffened beam and then extends to use the finite element modelling to replicate the actual behaviour of the beam. A numerical comparison between the SCHFB, conventional CHFB and I-beam shows that the ultimate bearing capacity and ductility are significantly enhanced in the case of SCHFB compared with the other two beams. Additionally, the SCHFB has been found to own better local deformation performance than that of the CHFB. However, with the span increase, the vertical concave deformation, lateral deformations at top flange and vertical deformations of top flange plate of the tubes of the SCHFB and CHFB may approach each other. So, the SCHFB becomes the best choice for short-span beams under either concentrated or distributed loading.