Local buckling of highly corroded hot-rolled box-section beams

Abstract

The steel structures of conveyance guiding systems, particularly steel guides used in mine shafts, are commonly made of box-section beams welded from hot-rolled channel sections. Hot-rolled profiles are generally resistant to local buckling; however, long-term exposure to the aggressive environment of a mine shaft leads to high corrosive loss of the material and reduction of the wall thickness. Some industrial regulations on shaft steelwork design and maintenance allow more than 50% corrosion loss for guides; however, they do not require local buckling calculations. This study investigated the buckling resistance of box-section beams welded from hot-rolled channel sections under bending, in terms of uniform corrosion loss. Laboratory bending tests were conducted on five beams for three levels of web thickness reduction achieved by etching and the results were compared with those obtained from finite element (FE) simulations. Linear modal analyses and nonlinear Riks simulations with imperfections were performed. The hot-rolled box-sections, which are generally resistant to local buckling, were found to be susceptible to local buckling at 46 and 60% corrosion losses in the plastic state and at 71% corrosion loss in the elastic state. This study highlights the need to consider local buckling when using hot-rolled closed profile beams at high corrosion loss.