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AD 278: Changes to the Building Regulations and Approved Document A3 Disproportionate Collapse – Interim Guidance on the use of BS 5950-1: 2000

This AD provides interim guidance in dealing with the changes to Section A3 of Approved Document A – Structure (2004 Edition) in connection with the England and Wales Building Regulations. The changes came into effect from 1 December 2004. Section A3 has been completely rewritten and should be studied. The main change is that the regulation now applies to all buildings, including those of less than five storeys. Now, all buildings have to be classified according to one of effectively four  building classes, 1, 2A, 2B and 3. The forthcoming amendment to BS 5950‑1 will revise Section 2.4.5 to be compatible with the changes in Section A3 of Approved Document A – Structure (2004 Edition). However, proposals for the revision of BS 5950‑1 must first be issued for public comment before being accepted and this process may take some time.

In the meantime the SCI recommends that:

  • Hot-rolled-steel framed buildings classified as 1 or 2A should be designed to Clause 2.4.5.2 of BS 5950‑1: 2000
  • Hot-rolled-steel framed buildings classified as 2B should be designed to Clauses 2.4.5.2 and 2.4.5.3 of BS 5950‑1: 2000
  • Hot-rolled-steel framed buildings classified as 3 should be designed to Clauses 2.4.5.2 and 2.4.5.3 of BS 5950‑1: 2000 in addition to resisting the design conditions that can reasonably be foreseen as possible during the life of the buildings, to the extent that collapse is not disproportionate to the cause. Approved Document A requires that these design conditions be identified by a systematic risk analysis of normal and abnormal hazards
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