Structural hollow sections (SHS) offer a number of structural and architectural advantages over open section profiles. They possess a high strength to weight ratio and high torsional and minor axis stiffnesses. As such, they are very efficient in resisting lateral torsional instability and compressive forces. SHS are favoured by architects due to their aesthetic appeal and versatility.
SHS offer, for a given volume of steel, an exposed surface area appreciably smaller than open sections, leading to improved performance in fire.
The fire resistance of SHS can be enhanced by the application of external insulating materials and/or filling the section with concrete or water. External protection to SHS takes one of a number of forms; sprays ( vermiculite or mineral fibre based ), boards, pre-formed casings, intumescent coatings, concrete and brick or block protection are all used. Internal protection is particular to SHS and takes the form of concrete filling (which also enhances structural performance) or water filling.
BS 5950: Part 8 sets out a methodology for determining fire resistance based on fire tests and analytical methods.. The purpose of this article is to describe ways of achieving fire resistance for SHS in accordance with BS 5950: Part 8, provide design guidance for each of the methods described in the Code and act as a commentary to the Code. Where additional information is available, the article expands on the Code methods. 16 refs.