Strength Assessment of a Thin Steel Roof Beam

摘要

A new roof beam, which is essentially a flanged 'V' cold-formed of very thin steel, has been tested to establish its load carrying strength for use in low-cost housing. The measured resistance of three different profiles is given, with a report of some interesting observations which were made during testing. When the two open sections were tested with the flanges of the 'V' in compression, the flanges were observed to initially splay apart before failing in a sudden 'snap-through' type mode. Links were placed over the flanges, thus constraining them to prevent splaying and retain their distance apart. This had the effect of reducing the buckling failure load, apparently because both flanges moved laterally together from the outset. It thus appeared that the splaying action increased the elastic stiffness, which restrained strut type flange buckling sufficiently to lead to the increased strength. A finite element model of the section is shown to give good results for certain configurations, but not for other cases where splaying occurs.