Effects of edge-stiffened circular holes on the web crippling strength of cold-formed steel channel sections under one-flange loading conditions

Abstract

Cold-formed steel sections are often used as wall studs or floor joists and such sections often include web holes for ease of installation of services. The holes are normally punched or bored and are unstiffened; when the holes are near to points of concentrated load, web crippling can be the critical design consideration. Recently, a new generation of cold-formed steel channel sections with edge-stiffened circular holes has been developed, for which web crippling may not be so critical. In this paper, a combination of experimental investigation and non-linear elasto-plastic finite element analyses are used to investigate the effect of such edge-stiffened holes under the interior-one-flange (IOF) and end-one-flange (EOF) loading conditions; for comparison, sections without holes and with unstiffened holes are also considered. A total of 90 results comprising 36 tests and 54 finite element analysis results are presented. Owing to manufacturing constraints, in the test programme, the edge-stiffener length was fixed at 13mm. Good agreement between the experimental and finite element results was obtained. For the case of the unstiffened hole, it is shown that the web crippling strength is reduced by up to 12% and 28% for the IOF and EOF loading conditions, respectively. However, with the edge-stiffened circular hole, the web crippling strength is only reduced by 3% for the IOF loading condition and there is no reduction in strength for the EOF loading condition. The finite element model was used for the purposes of a parametric study on the effects of different hole sizes, edge-stiffener length and distances of the web holes to the near edge of the bearing plate. The results indicate that with a suitable edge-stiffener length, the web crippling strength of cold-formed steel channel section with holes can be as high as the one without holes.