Structure: Approved Document A

O N L I N E V E R S I O N A3 Section 5: Reducing the sensitivity of the building to disproportionate collapse in the event of an accident 5.1 The requirement will be met by adopting Critical situations for design should be selected the following approach for ensuring that the that reflect the conditions that can reasonably building is sufficiently robust to sustain a limited be foreseen as possible during the life of the extent of damage or failure, depending on the building. The structural form and concept and consequence class of the building, without any protective measures should then be chosen collapse. and the detailed design of the structure and its elements undertaken in accordance with the a. Determine the building’s consequence class recommendations given in the Standards given in from Table 11. paragraph 5.2. b. For Consequence Class 1 buildings – Further guidance is given in Annexes A and Provided the building has been designed B to BS EN 1991-1-7:2006 Eurocode 1: and constructed in accordance with the rules Actions on structures – Part 1.7: General given in this Approved Document, or other actions – Accidental actions; with UK National guidance referenced under Section 1, for Annex to BS EN 1991-1-7:2006 and BS EN meeting compliance with Requirement A1 1990:2002+A1:2005 Eurocode – Basis of and A2 in normal use, no additional measures structural design; with UK National Annex to are likely to be necessary. BS EN 1990:2002+A1:2005. c. For Consequence Class 2a buildings – 5.2 Details of the effective horizontal and In addition to the Consequence Class 1 vertical ties including tie force determination, measures, provide effective horizontal ties, together with the design approaches for or effective anchorage of suspended floors checking the integrity of the building following to walls, as described in the Standards listed the notional removal of vertical members and the under paragraph 5.2 for framed and load- design of key elements, are given in the following bearing wall construction (the latter being Standards: defined in paragraph 5.3 below). BS EN 1990:2002+A1:2005 Eurocode – Basis d. For Consequence Class 2b buildings – of structural design; with UK National Annex to In addition to the Consequence Class 1 BS EN 1990:2002+A1:2005 measures, provide effective horizontal ties, as described in the Standards listed under BS EN 1991-1-7:2006 Eurocode 1: Actions paragraph 5.2 for framed and load-bearing on structures – Part 1.7: General actions – wall construction (the latter being defined in Accidental actions; with UK National Annex to BS paragraph 5.3 below), together with effective EN 1991-1-7: 2006 and BSI PD 6688-1-7: 2009 vertical ties, as defined in the Standards BS EN 1992-1-1:2004 Eurocode 2: Design of listed under paragraph 5.2, in all supporting concrete structures – Part 1.1: General rules and columns and walls. rules for buildings; with UK National Annex to BS Alternatively, check that upon the notional EN 1992-1-1:2004 and BSI PD 6687-1:2010 removal of each supporting column and each BS EN 1993-1-1:2005 Eurocode 3: Design of beam supporting one or more columns, or any steel structures – Part 1.1: General rules and nominal length of load-bearing wall (one at a rules for buildings; with UK National Annex to BS time in each storey of the building), the building EN 1993-1-1:2005 remains stable and that the area of floor at any storey at risk of collapse does not exceed 15% of BS EN 1994-1-1:2004 Eurocode 4: Design of the floor area of that storey or 100m2, whichever composite steel and concrete structures – Part is smaller, and does not extend further than the 1.1: General rules and rules for buildings; with UK immediate adjacent storeys (see Diagram 24). National Annex to BS EN 1994-1-1:2004 Where the notional removal of such columns BS EN 1995-1-1:2004+A1:2008 Eurocode 5: and lengths of walls would result in an extent of Design of timber structures – Part 1.1: General damage in excess of the above limit, then such – Common rules and rules for buildings; elements should be designed as a ‘key element’ with UK National Annex to BS EN 1995-1- as defined in paragraph 5.3 below. 1:2004+A1:2008 and BSI PD 6693-1:2012 e. For Consequence Class 3 buildings – A BS EN 1996-1-1:2005+A1:2012 Eurocode 6: systematic risk assessment of the building Design of masonry structures – Part 1.1: General should be undertaken taking into account rules for reinforced and unreinforced masonry all the normal hazards that may reasonably structures; with UK National Annex to be foreseen, together with any abnormal BS EN 1996-1-1:2005+A1:2012 and BSI PD hazards. 6697:2010 Approved Document A Structure O N L I N E V E R S I O N 43