Disproportionate collapse requirements with British Standard clause references

Building

class

Building type and occupancy Building regulations

requirements

British standard material references and summary outline guidance

BS 5268 – Timber BS 5628 – Masonry BS 5950 – Steel BS 8110 – Concrete

1

Houses not exceeding 4 storeys.

Agricultural buildings.

Buildings into which people rarely go or come

close to.

Basic Requirements

Structures should be constructed so that no collapse should be disproportionate to the cause and reduce the risk of localized damage

spreading – but that permanent deformation of members/connections is acceptable.

C1.6.1.1: suitable geometry,

connections and bracing.

C1.16.3: robustness, interaction of

components and containment of

spread of damage.

C1.2.1.1.1 and C1.2.4.5.2: effective

horizontal ties as Class 2 A Option 2.

C1.2.2.2.2: effective horizontal

ties AND designed resistance to

notional lateral load of 1.5% design

dead load.

2A

5 storey single occupancy house.

Hotels not exceeding 4 storeys.

Flats, apartments and other residential buildings

not exceeding 4 storeys.

Offi ces not exceeding 4 storeys.

Industrial buildings not exceeding 3 storeys.

Retailing premises not exceeding 3 storeys and

less than 2000 m 2 at each storey.

Option 1:

Effective anchorage of suspended

fl oors to walls

C1.1.6.3.2: Figure M.3 or details in

BS 5628-1 Annex D.

As for Class 1 plus C1.33.4: details in

BS 5628-1 Annex D or BS 8103-1.

Generally N/A but C1.2.4.5.2:

bearing details of precast concrete

units to conform to C1.5.2.3 of

BS 8110-1.

C1.5.2.3: precast bearings not less

than 90 mm or half load bearing

wall/leaf thickness.

Option 2:

Provision of horizontal ties

C1.1.6.3.3 and Figure M.1. As for Class 1 plus C1.33.4 and

Table 12.

C1.2.1.1.1 and C1.2.4.5.2. As Class 1 plus C1.2.2.2.2 and

C1.3.12.3.6 .

2B

Hotels, fl ats, apartments and other residential

buildings greater than 4 storeys but not exceeding

15 storeys.

Educational buildings greater than 1 storey but less

than 15 storeys.

Retailing premises greater than 3 storeys but less

than 15 storeys.

Hospitals not exceeding 3 storeys.

Offi ces greater than 4 storeys but less than

15 storeys.

All buildings to which members of the public are

admitted which contain fl oor areas exceeding

2000 m 2 but are less than 5000 m 2 at each storey.

Car parking not exceeding 6 storeys.

Option 1:

Provision of horizontal and

vertical ties

As Class 2A Option 2 plus

C1.1.6.3.4.

As Class 2A Option 2 plus C1.33.5

and Table 13.

As Class 2A Option 2 plus

C1.2.4.5.3.

As Class 2A Option 2 plus C1.2.2.2.2

and C1.3.12.3.7.

Option 2:

Check notional removal of load

bearing elements

C1.1.6.3.5 .

As for Class 1 plus Table 11:

‘without collapse ’ rather than

limited areas.

C1.2.4.5.3 if Class 2B Option 1

cannot be satisfi ed.

C1.2.6.3 of BS 8110-2.

Check notional removal of load bearing elements such that for removal of any element the building remains stable and that the area of fl oor at any storey

at risk of collapse is less than the lesser of 70 m 2 or 15% of the fl oor area of that storey. The nominal length of load bearing wall should be the distance

between vertical lateral restraints (not exceeding 2.25H for reinforced concrete walls or internal walls of masonry, timber or steel stud). If catenary action is

assumed allowance should be made for the necessary horizontal reactions.

Option 3:

Key element design

C1.1.6.3.6 .

As for Class 1 plus C1.33.2 .

C1.2.4.5.4 if Class 2B Options 1 and

2 cannot be satisfi ed.

C1.2.6.2 of BS 8110-2.

Design of key elements to be capable of withstanding 34 kN/m 2 applied one direction at a time to the member and attached components subject to the

limitations of their strength and connections, such accidental loading should be considered to act simultaneously with full dead loading and 1/3 of all

normal wind/imposed loadings unless permanent storage loads etc. Where relevant, partial load factors of 1.05 or 0.9 should be applied for overturning and

restoring loads respectively. Elements providing stability to key elements should be designed as key elements themselves.

3

All buildings defi ned above as Class 2A and 2B that

exceed the limits of area or number of storeys.

Grandstands accommodating more than 5000

spectators.

Buildings containing hazardous substances and/or

processes.

Systematic risk assessment of the

building should be undertaken

taking into account all the normal

hazards that may be reasonably

forseen, together with any abnormal

hazards.

Lack of clear guidance . Lack of clear guidance. C1.2.4.5.1: Class 2B required as

a minimum.

Class 2B required as a minimum.

NOTES:

1. Refer to the detailed British Standard clauses for full details of design and detailing requirements.

2. Where provided, horizontal and vertical ties should be safeguarded against damage and corrosion.

3. Key elements may be present in any class of structure and should be designed accordingly.

4. The construction details required by Class 2B can make buildings with load bearing walls diffi cult to justify economically.

5. In Class 2B and 3 buildings, precast concrete elements not acting as ties should be effectively anchored (C1.5.1.8.3), such anchorage being capable of carrying the dead weight of the member.

Source: Adapted from Table 11, Part A3 Approved Document A, HMSO.

29