AD 440: Fire design of external steelwork

SCI publication P375 Fire resistance design of steel framed buildings gives guidance on (amongst other things) the design of external steelwork when heated by a fire in a building fire compartment. This AD note clarifies which part of the publication should be used for this purpose.

It has been brought to SCI’s attention that some users of P375 are misinterpreting which section of the document is relevant to the design of external steelwork. Section 3.4.2 Compartment fires – external members refers to Annex B of BS EN 1991-1-2¹ for the model describing the compartment fire conditions and the flames emanating from openings. The expressions in Section 3.4.2 are used in the calculation of the relevant radiative and connective heat fluxes. Design of external steelwork using these heat fluxes should be based on Annex B of BS EN 1993-1-2² as described in para. 4.2.5.4. of the same standard.

Section 3.3.2 External fire curve gives the nominal temperature-time curve intended for the outside of separating external walls as defined in para. 1.5.3.5 of BS EN 1991-1-2 and presented in para. 3.2.2 of the same standard. It is not intended for use in the design of external steel members.

Contact: Richard Henderson
Tel: 01344 636555
Email: advisory@steel-sci.com

1. BS EN 1991-1-2:2002 Eurocode 1: Actions on structures Part 1-2: General actions – Actions on structures exposed to fire
2. BS EN 1993-1-2:2005 Eurocode 3: Design of steel structures – Part 1-2: General rules – Structural fire design