Structural robustness and fire

Structural robustness is a performance requirement in most structural codes and standards. The consideration of fire in relation to robustness has been prompted by reviews of major fires in buildings, some of which were the result of terrorist attack. This paper examines the issue of robustness from a fire perspective by considering some of these incidents and the findings from research on the robustness of framed construction. This paper considers whether buildings can be considered to be robust under fire conditions if they meet the design criteria of BV2 of the National Construction Code 2016 in addition to the requirements of Section C (fire-resistance) of that code. It is concluded that demonstrating that BV2(a) (loss of column or similarly critical member) can be achieved under ambient conditions is sufficient evidence that loss of one such member under fire conditions will not result in disproportionate collapse provided the connection details are chosen to avoid the shearing of bolts and crippling of the webs of supporting columns as a result of compression forces induced by restraint of expansion. Suggestions are made as to how the robustness of a building can be further improved through improvements to the design of the sprinkler system and possibly also through the provision of fireresistant edge spandrels even though these are not currently required by the prescriptive provisions of the NCC for buildings with an effective height greater than 25m.