Cross-sectional classification of aluminium beams subjected to fire

The use of aluminium as a construction material has been increasing since its first invention. At present, limited knowledge of the behaviour of aluminium beams in fire gives rise to excessively high insulation demands, decreasing its competitiveness. An explorative study is presented here that aims to assess the potential for improvement in the existing design standards for aluminium in fire conditions. At present, fire design for aluminium alloy beams is performed using the same system of cross-sectional slenderness classes as is employed at room temperature. Identical width-over-thickness ratio limits are used to define the boundaries between the classes. These limits are known (and demonstrated) to be conservative, but may in fact be over-conservative. Especially for tempered alloys, the geometric limits may be relaxed considerably, allowing cross-sections to be upgraded in class for fire design calculations.