Behaviour of Steel Structures in Fire Conditions

Current design guidelines on the capacity of T/Y-joints in circular hollow sections under out-of-plane moment loading are derived from a database having a limited range of geometric parameters. Although further test results have become available since, certain geometric parameters are still not adequately covered. This paper presents the results of an experimental and numerical study investigating the effects of the various geometric purameters as well as the influence of the tensile strength to yield stress ratio on the ultimate moment capacity. The results of this investigation show that, whilst the effect of the ratio is minimal, the effect of is very significant at the larger a ratios and it has not been accounted for in existing design formulations. The finite element results obtained were used together with existing test data as the database in a statistical regression analysis, and a new capacity estimation equation is proposed. The new equation is found to be more accurate and reliable than those included in current design codes. M.M.K. Lee, E.M. Dexter and M.G. Kirkwood

The problem Over the past 30 years, the cost of plain steel sections in the UK has decreased dramatically relative to the unit cost of labour (Table 1). The labour-related items, or added value (e.g. drawing, fabrication, erection), constitute approximately 50% of the cost of even the simplest steel framed structure. It is evident, therefore, that the lowest cost steel frame will be the one in which the overall labour content is minimised. This is not to be confused with least weight structural solutions, which very rarely produce the most cost-effective designs. C. Gibbons