changes to approved document a - bsi...

Copyright © 2013 BSI & Modulus. All rights reserved.

Changes to Approved Document A Owen Brooker Technical Director, Modulus

07/03/2013

Copyright © 2013 BSI & Modulus All rights reserved. 2

Outline – key changes

• Material and Workmanship

• Design standards are now Eurocodes

• Eurocode

• Eurocode 1

• Eurocode 2

• Eurocode 7

• Published Documents (PDs) are referenced

07/03/2013


Materials and workmanship

• Currently: “Any building work … should … be carried out with proper materials and in a workmanlike manner”

• New AD A: “Any building work … shall be carried out in accordance with regulation 7. Guidance on meeting these requirements on materials and workmanship is contained in Approved Document 7.

• From 1 July 2013: European Construction products regulation requires that products should have CE marking when they are covered by either a

• European product standard

• European Technical Assessment

• A harmonised standard can be identified by it having an Annex ZA

07/03/2013


CE Marking for concrete products

• Precast concrete – 53 hENs

• Aggregates – Are covered by hENs

• Cements – EN 197 has Annex ZA (All UK cements have CE marks)

• Reinforcement – EN 10080 (harmonised version) has been not been completed

• Prestressing steel - EN 10138 (harmonised version) has been not been completed

• Ready mixed concrete – EN 2061-1 is not a harmonised standard (2013/4 revision?)

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Buildings - STR/GEO Combination of actions

Table A1.2(B)

UK NA: Table NA.A1.2(B)

Combination expression reference

Permanent actions Leading variable action

Accompanying variable actions

Unfavourable Favourable Main(if any) Others

Eqn (6.10) γG,j,sup Gk,j,sup γG,j,inf Gk,j,inf γQ,1 Qk,1 γQ,i Ψ0,i Qk,i

Eqn (6.10a) γG,j,sup Gk,j,sup γG,j,inf Gk,j,inf γQ,1Ψ0,1Qk,1 γQ,i Ψ0,i Qk,i

Eqn (6.10b) ξ γG,j,supGk,j,sup γG,j,inf Gk,j,inf γQ,1 Qk,1 γQ,i Ψ0,i Qk,i

Combination expression reference

Permanent actions Leading variable action

Accompanying variable actions

Unfavourable Favourable Main(if any) Others

Eqn (6.10) 1.35 Gk,j,sup 1.0 Gk,j,inf 1.5 Qk,1 1.5 Ψ0,i Qk,i

Eqn (6.10a) 1.35Gk,j,sup 1.0 Gk,j,inf 1.5 Ψ0,1Qk,1 1.5 Ψ0,i Qk,i

Eqn (6.10b) 0.925 x 1.35 = 1.25 Gk,j,sup

1.0 Gk,j,inf 1.5 Qk,1 1.5 Ψ0,i Qk,i

07/03/2013


Buildings - Can it be simplified?

• For a single action: 1.25 Gk + 1.5 Qk

• Except for storage loads and when Gk < 4.5 Qk

07/03/2013


Actions on structures

• Part 1-1 – Densities and Imposed loads (More information, but little significant change)

• Part 1-2 – Fire

• Part 1-3 – Snow (Similar)

• Part 1-4 – Wind (slightly lower wind pressures, but partial factor for wind only has increased)

• Part 1-5 – Thermal (new standard)

• Part 1.6 – Actions during execution (new standard)

• Part 1.7 – Accidental actions (Be aware there are some minor conflicts with AD A)

• Part 3 – Cranes loading

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References for design of concrete structures

• BS EN 1992-1-1:2004 Eurocode 2: Design of concrete structures – Part 1.1: General rules and rules for buildings; with UK National Annex to BS EN 1992-1-1:2004

• BSI PD 6687-1:2010 Published Document – Background paper to the UK National Annexes to BS EN 1992-1 and BS EN 1992-3

• BS EN 13670:2009 Execution of concrete structures

07/03/2013


Eurocode 2 – potential differences to withdrawn BSs

• Designs are to cylinder strengths – be careful when referring to strength (C25/30)

• Flexure design – very little change

• Shear design – EC2 is more efficient – but detailing rules may wipe out gains

• Punching shear design – less efficient

• Deflection – Base standard is more efficient, but UK NA has removed benefits

• Detailing – greater anchorage and lap lengths

• Foundations – see below

• Eurocode 2 is far more thorough than BS 8110

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150

200

250

300

350

400

450

500

550

600

4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0

SLA

B D

EPT

H,

mm

SPAN, m

Cost implications – flat slabs

Based on Economic Concrete Frames Elements The Concrete centre

EC 2 - solid

BS 8110 - dashed

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Concrete foundations

• Compression length (mm)

• Practically apply a factor of 0.7 - see Whittle, R. Are modern pad footings and pile caps too shallow? Concrete May 2011 pp 53- 55, The Concrete Society.

Bar Φ (mm)

Concrete strength, fck (MPa)

25 30 35 40 50

25 1025 912 820 748 646

32 1312 1168 1050 958 827

40 1640 1460 1312 1198 1033

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Bored piles

• ‘In the absence of other provisions’, the design diameter of cast in place piles without permanent casing is less than the nominal diameter Dnom:

Dd = Dnom – 20 mm for Dnom < 400 mm

Dd = 0.95 Dnom for 400 ≤ Dnom ≤ 1000 mm

Dd = Dnom – 50 mm for Dnom > 1000 mm

• German commentary on Eurocode 2 notes that rules given in EN 1526 for execution of bored piles may be considered ‘other provisions’

• The partial factor for concrete, c should be multiplied by a factor, kf, for cast in place pile without permanent casing. kf, = 1.1

• German commentary on Eurocode 2 notes for bored constructed in accordance with EN 1526, kf, = 1.0

07/03/2013


Eurocode 7

• Geotechnics is now limit state design

• Prescriptive methods are still permitted for class 1 foundations (small and relatively simple) e.g. allowable bearing pressures

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Summary

• Two key changes are

• Requirement to use for CE marking for materials (where standards exist)

• Eurocodes are now referenced instead of withdrawn British Standards

• Consequences:

• Loads, especially once combinations have been considered are slightly lower (say 7 to 12%)

• Concrete elements may be either slightly larger or smaller depending on type of loading and critical phenominum

• Pile caps, pad foundations and bored piles are all areas to pay more attention to, especially early in design

07/03/2013