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FOURTH EDITION
Standard method of
detailing structural
concrete
FOURTH EDITION
Standard method of
detailing structural
concrete
Production supported by:
ii
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
Task Group
L Brankley
O Brooker
A Gardner
M Gilliver
C Goodchild
E Halliwell
D Keogh
S Mahmood
S Nadarajah
R Vollum
R Whittle
BSc MSc MBA MCQI CQP (CARES – UK Certification Authority for Reinforcing Steels)
BEng CEng MICE MIStructE MCS (Modulus) Chair
CEng MIStructE (Arup)
BEng MEng (CCL)
BSc CEng MIStructE MCIOB (MPA The Concrete Centre)
MA(Cantab) MEng CEng MICE (MPA The Concrete Centre)
(Laing O’Rourke)
BSc CEng MIStructE (Consultant)
CEng, MIStructE (Praeter Engineering)
MSc PhD (Imperial College London)
MA(Cantab) CEng MICE (Arup Research and Development)
Publishing
L Baldwin
BA(Hons) DipPub (The Institution of Structural Engineers)
Acknowledgements
Permission to reproduce extracts from British Standards is granted by BSI. British Standards can be obtained in PDF
or hard copy formats from the BSI online shop: www.bsigroup.com/Shop
Permission to reproduce the following has been obtained, courtesy of these individuals/organisations:
Figures 2.1, 6.2, 6.8 and 6.16: MPA The Concrete Centre
Figure 2.2: Laing O’Rourke
Figures 2.3–2.6, 5.3–5.12, 6.1, 6.3–6.7, 6.9–6.11, 6.14, 6.17–6.23, 6.27–6.32, 6.36–6.39, 6.42, 7.17–7.21, 8.1, D1–3: Arup
Figures 4.5 and 4.6: The Concrete Society
Figures 4.7, 4.8 and 7.9 (left): BSI
Figures 5.1 and 5.2: CARES (UK Certification Authority for Reinforcing Steels)
Figures 6.12, 6.13, 6.15, 6.24–6.26, 6.33–6.35: Arup/CADS
Figures 6.40, 6.41, 6.43 and 6.44: CADS
Figures 7.1–7.6, 7.8, 7.9 (right), 7.10, 7.13–7.16: CCL (GB) Ltd
Figures 7.7a and 7.12b: Praeter Engineering
Tables 5.2, 5.4, 5.6–5.10, 7.1, A5, A7, A8, B1, C1–C3, J1: BSI
Tables 6.1–6.6: Modulus
Table E1: MPA The Concrete Centre
The Institution would also like to acknowledge its appreciation of CADS for their support in the production of all the
Model Details.
Published by The Institution of Structural Engineers
International HQ, 47–58 Bastwick Street, London EC1V 3PS, United Kingdom
T: +44(0)20 7235 4535
E: mail@istructe.org
W: www.istructe.org
First published (version 1.0) January 2021
978-1-906335-48-9 (print)
978-1-906335-49-6 (pdf )
© 2021 The Institution of Structural Engineers
The Institution of Structural Engineers and the members who served on the Task Group which produced this Manual have endeavoured to ensure the
accuracy of its contents. However, the guidance and recommendations given should always be reviewed by those using the Manual in light of the facts
of their particular case and any specialist advice. No liability for negligence or otherwise in relation to this Manual and its contents is accepted by the
Institution, its servants or agents. Any person using this Manual should pay particular attention to the provisions of this Condition.
No part of this publication may be reproduced or stored in a retrieval system without prior permission of The Institution of Structural Engineers,
who may be contacted at: 47–58 Bastwick Street, London EC1V 3PS, United Kingdom.
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
| iii
Contents
Foreword
viii
1
Introduction and scope
1
2
2.1
Communication of information
General
3
3
2.2
The reinforcement process
4
2.3
2.4
Designer detailing
Contractor detailing
8
9
2.5
2.6
BIM and 3D detailing
Electronic data interchange (EDI)
9
10
2.7
Typical methods of providing required information for detailing
11
2.7.1
Flat slabs
11
2.7.2
Beams
12
2.7.3
Pile caps
14
2.7.4
Pro formas
15
3
Drawings
16
3.1
General
16
3.2
Types of drawings
16
3.2.1
Structural drawings
16
3.2.2
Reinforcement drawings
16
3.2.3
Standard details
17
3.2.4
Diagrams
17
3.2.5
Record drawings
17
3.3
Photocopying and reduction
17
3.4
Abbreviations
17
3.5
Dimensions of drawing sheets
18
3.6
Borders
18
3.7
Title and information panels
18
3.8
Key
19
3.9
Orientation
19
3.9.1
Site plans
19
3.9.2
All other drawings
19
3.10
Thickness of lines
19
3.11
Lettering
20
3.12
Spelling
20
3.13
Dimensions
20
3.14
Levels
20
3.14.1
Datum
20
3.14.2
Levels on plan
21
3.14.3
Levels on section and elevation
21
iv
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
3.15
Scales
21
3.16
Plans
21
3.17
Elevations
21
3.18
Sections
22
3.19
Gridlines and a recommended reference system
22
3.20
Layout of slabs
23
3.20.1
Methods of preparing GA drawings for concrete structures
23
3.20.2
Information shown on GA drawings for concrete structures
23
3.20.3
Fixing in concrete
27
3.20.4
GA drawing for concrete structures
27
3.21
Layout of foundations
27
3.22
Layout of stairs
29
4
Detailing and scheduling
30
4.1
Detailing techniques
30
4.1.1
Tabular method of detailing
30
4.1.2
Template drawings/typical details
31
4.1.3
Overlay drawings
31
4.2
Detailing reinforcement
31
4.2.1
General
31
4.2.2
Intersection and layering of reinforcement
33
4.2.3
Preformed cages
35
4.2.4
Straight bars
36
4.2.5
Welded fabric
36
4.2.6
Chairs
36
4.3
Precast concrete
36
4.4
Checklist for detailer
37
4.5
Schedules and scheduling
37
4.5.1
General
37
4.5.2
Allowances for tolerances/deviations
40
4.5.3
Out-of-plane deviations
40
4.6
Procedure for checking reinforcement drawings and schedules
41
5
Technical information and requirements
42
5.1
Reinforcement
42
5.1.1
General
42
5.1.2
Strength/ductility properties
42
5.1.3
Bar identification
42
5.1.4
Notation
44
5.1.5
Specifying stainless steel
44
5.1.6
Sizes of reinforcing bars
44
5.1.7
Length and overall dimensions of reinforcing bars
46
5.1.8
Rebending bars
46
5.1.9
Large diameter bends
46
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
5.2
|v
5.1.10
Structural tying reinforcement to ensure robustness
46
5.1.11
Fabric reinforcement
47
Cover to reinforcement
48
5.2.1
General
48
5.2.2
Cover for durability
49
5.2.3
Cover for fire resistance
49
5.2.4
Fixing reinforcement to obtain correct cover
49
5.2.5
Minimum spacing of reinforcement
50
5.3
Cutting and bending tolerances
50
5.4
Anchorage and lap lengths
52
5.4.1
General
52
5.4.2
Laps in reinforcement
52
5.4.3
Additional rules for large bars
53
5.4.4
Bundled bars
54
5.4.5
Laps in welded fabric
56
5.5
Welding of reinforcement
57
5.5.1
General
57
5.5.2
Semi-structural welding
57
5.5.3
Tack welding
57
6
Common structural elements
58
6.1
Introduction
58
6.2
Slabs
58
6.3
6.4
6.5
6.2.1
Scope
58
6.2.2
Design and detailing notes
58
6.2.3
Detailing information
74
6.2.4
Presentation of working drawings
75
Beams
91
6.3.1
Introduction
91
6.3.2
Design and detailing notes
91
6.3.3
Detailing information
97
6.3.4
Presentation of working drawings
97
Columns
104
6.4.1
Introduction
104
6.4.2
Design and detailing notes
104
6.4.3
Detailing information
107
6.4.4
Presentation of working drawings
108
Walls
118
6.5.1
Introduction
118
6.5.2
Design and detailing notes
118
6.5.3
Detailing information
121
6.5.4
Presentation of working drawing
121
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Institution of Structural Engineers
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Standard method of detailing structural concrete (4th edition)
6.6
6.7
6.8
6.9
6.10
Retaining walls
127
6.6.1
Introduction
127
6.6.2
Design and detailing notes
127
6.6.3
Detailing information
128
6.6.4
Presentation of working drawings
128
Foundations
134
6.7.1
Introduction
134
6.7.2
Design and detailing notes
134
6.7.3
Detailing information
137
6.7.4
Presentation of working drawings
137
Staircases
145
6.8.1
Introduction
145
6.8.2
Design and detailing notes
145
6.8.3
Detailing information
146
6.8.4
Presentation of working drawings
146
Corbels, half-joints and nibs
151
6.9.1
Introduction
151
6.9.2
Design and detailing notes
151
6.9.3
Detailing information
152
Composite slabs
156
6.10.1
Introduction
156
6.10.2
Design and detailing notes
156
6.10.3
Detailing information
156
7
Prestressed concrete
157
7.1
General
157
7.2
Prestressing strand
157
7.3
Post-tensioning
158
7.3.1
Anchorage and tendons
158
7.3.2
Anchor cover and spacing
160
7.3.3
Anchor pockets and stressing access
161
7.3.4
Tendon ducts
164
7.3.5
Anti-bursting reinforcement
166
7.3.6
Tendon profile detailing
167
7.4
7.5
Pre-tensioning
170
7.4.1
Anchorage and debonding
170
7.4.2
Transmission zones
170
7.4.3
Strand cover and spacing
171
7.4.4
Supports and bearings
171
7.4.5
Tendon profiles
172
Exchange of information
172
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Standard method of detailing structural concrete (4th edition)
| vii
8
Precast concrete
175
8.1
Introduction
175
8.2
Particular durability problems
176
Appendix A: Changes to reinforcement since 1948
177
Appendix B: Bar shapes (BS 8666:2020)
187
Appendix C: Scheduling radii
194
Appendix D: Mechanical couplers for bars
197
Type 1: Couplers with parallel threads
197
Type 2: Couplers with taper-cut threads
198
Type 3: Couplers with integral threads over full length bar
199
Type 4: Metal sleeves swaged onto bars
199
Type 5: Threaded couplers swaged onto ends of reinforcing bars
199
Type 6: Wedge locking sleeves
200
Type 7: Couplers with shear bolts and serrated saddles
200
Appendix E: Lap and anchorage lengths
201
Appendix F: Effective anchorage length
205
Appendix G: Minimum overall depth of various U-bars
207
Appendix H: Large diameter bends
208
Appendix I: Abbreviations
214
Appendix J: Fabric types
215
References
216
Appendix K: Bar areas/weights
Inside back cover
viii
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
Foreword
Standard method of detailing reinforced concrete was published in 1970 and followed in 1973 by the Concrete
Society’s publication on Standard reinforced concrete details. This was updated in 1989 to incorporate a section on
prestressed concrete and the title was amended to Standard method of detailing structural concrete. A steering
group from across the concrete industry was formed to present guidance consistent with BS EN 1992
(‘Eurocode 2’/‘EC2’) which was published in 2006 as the third edition.
The third edition was produced to prepare the concrete industry for the implementation of BS EN 1992. It is fair to
say that while the Eurocode is less prescriptive than BS 8110, it also contains some ambiguities and variations from
previous practice. It was therefore deemed necessary to produce this fourth edition. The primary aim is to clarify the
application of BS EN 1992 to UK detailing practice, and to provide a consistent approach that can be applied by all
members of the construction project team.
Guidance in BS 8110 was reasonably prescriptive and could often be implemented by a detailer without in-depth
knowledge of the design of an element. The Eurocode, being less prescriptive, does require more information to be
provided by the designer to the detailer. This edition clarifies where these situations occur, so that information is
conveyed at the outset of the detailing phase.
There have been many welcome contributions to this new edition, but one I must mention is that of CADS
(Computer and Design Services Ltd.) who have redrawn and updated all the Model Details in Chapter 6.
A new version of the Eurocode is currently being prepared but in the interim, the fourth edition of this Manual is
expected to continue to be widely used, and provides useful new tables, guidance and details to assist in the
detailing of reinforcement.
Owen Brooker
Chair
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
|1
1 Introduction and scope
This Manual is a working document for concrete reinforcement that can be used to interpret the designer’s
instructions in the form of drawings and schedules for communication to the construction site.
The information given is essential for both the designer and detailer — and both parties are responsible for ensuring
that they are working with correct information, particularly as the designer is likely to be just one component of a
wider project team.
The information and guidance is based on Eurocodes and UK practice but considered relevant for use in most parts
of the world with only minor adjustment.
The purpose of this Manual is to provide a standard reference that can be used by practising designers and
detailers, as well as being a valuable teaching aid for more junior engineers. It uses ‘Model Details’ (MDs) to illustrate
the preferred method of detailing for each type of structural element (Chapter 6).
It is assumed that it is the designer’s responsibility to specify design requirements clearly to the detailer — and the
detailer’s responsibility to implement these requirements in a consistent, unambiguous and complete way, for the
end user. Certain details have design implications, and this guidance does not attribute a lesser degree of
responsibility to the designer. In detailing reinforcement for structural concrete, the impact on the entire project team
should be borne in mind; poor detailing can lead to other issues/additional costs at a later stage.
The term ‘standard method’ should also be clarified. It is not intended that any one detail should be copied verbatim
for all situations, but all the principles should be followed. Details can be prepared with different objectives in mind,
e.g. to reduce labour on site by allowing off-site prefabrication of reinforcement into cages, or to utilise the materials
most readily available in a particular location — the principles covered in this Manual apply to almost any objective.
The details have been prepared with the following priorities in mind:
• technical correctness and safety
• buildability and speed of construction
• labour and material costs
The previous (third) edition of this Manual (2006–20) introduced detailing rules that conformed to the current version
of principal standards at that time, which remains the case for this edition:
BS EN 1992-1-1. Eurocode 2. Design of concrete structures. General rules and rules for buildings 1
BS EN 1992-1-2. Eurocode 2. Design of concrete structures. General rules. Structural fire design 2
BS EN 1992-2. Eurocode 2. Design of concrete structures. Concrete bridges. Design and detailing rules 3
BS EN 1992-3. Eurocode 2. Design of concrete structures. Liquid retaining and containing structures 4
It should be noted that UK National Annex values are embedded in the equations and tables.
In general, the conventional use of materials covered by European Standards or British Standards is assumed.
Where other authoritative documents exist, this Manual refers to them rather than repeating them in full. It refers to
generic rather than particular proprietary systems — and any proprietary systems shown are for general illustrative
purposes only and are not specifically endorsed.
2
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
The third edition also placed more emphasis on the communication of information and the responsibility for
detailing — the use of ‘contractor detailing’ was recognised. This edition builds on that with a checklist of information
that should be provided by the designer to the detailer; and decisions that should be coordinated between the
contractor, detailer and designer.
Within the UK, the use of mild steel reinforcement is no longer common practice. Class B or C high yield
reinforcement is considered to provide the required ductility for specific situations where mild steel was considered
necessary. Accordingly, reference to mild steel has been removed. In deriving details and standards it is good
practice that reinforcement will be supplied by a company holding a valid certificate of approval from a recognised
third party product certification body, e.g. CARES – UK Certification Authority for Reinforcing Steels5.
There is growing use of stainless steel for reinforcement in situations where greater durability is required. BS 67446
provides details on its use and testing.
The principles covered by BS 8666:20207 have been adopted. BS 8666 defines a standard method of scheduling,
and a set of bar shapes that, in suitable combination, are normally sufficient for any detailing situation; it is
considered to be an essential companion document to this Manual.
The division between civil and structural engineering is somewhat arbitrary, and it follows that good practice is
common to both structural engineering and civil engineering. There are, however, a number of factors that occur in
large-scale works of which account should be taken when detailing reinforcement. These include:
•
•
•
•
provision of access for concrete to be safely placed in massive concrete sections such as raft foundations
adjustments of reinforcement to take account of the effects in large pours of concrete8,9
suitable reinforcement arrangements to suit long-strip methods of laying ground slabs
recognition of the likely positioning of construction joints and their effect on reinforcement arrangements
(also important for building slabs)
• recognition of the effects of different concrete mixes and aggregates
Note: this Manual does not cover:
•
•
•
•
•
•
detailing of structures designed for seismic situations10
detailing of joints and reinforcement for ground slabs11
water-resistance of wall and slab elements in contact with the ground9,12
detailing of marine structures13
use of lightweight aggregate concrete1
temporary stability of reinforcement cages
The temporary stability of reinforcement cages is an important consideration as collapses have occurred. Guidance
on good management practice and technical aspects of cages in the temporary condition is available from the
Temporary Works forum website at: www.twforum.org.uk.
This edition has been published as an interim update, pending publication of a second generation of Eurocodes,
expected to be available during the early/mid 2020s. It is believed that sufficient knowledge in the use of BS EN 1992
makes dissemination of the current understanding of how to apply its detailing requirements, worthwhile. In the
process of reviewing the details, it also became apparent that some of the standard details no longer reflected
current practice and this opportunity has been taken to bring them up to date.
This edition has also placed an emphasis on providing figures and tables with recommended values to use, rather
than detailed design equations. However, it should be recognised that BS EN 1992 has fewer “deemed to satisfy”
rules, and there are more situations where the designer should provide information to the detailer; and this edition
places more emphasis on noting where these situations occur. In particular, Chapter 2 now includes a detailed list of
information that should be provided to the detailer.
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
|3
2 Communication of information
2.1 General
Accurate detailing has an important role in the procurement and durability of reinforced concrete (RC) structures.
The actual process of detailing normally comes relatively late in the procurement process. Concepts and working
details can be confirmed during the early design phases but the preparation of final reinforcement drawings and
schedules is generally squeezed into a period between completion of final design and the start of construction on
site. Detailing very often becomes a critical process in the construction programme. Figure 2.1 illustrates the process
between completion of the RC design and the final reinforcement drawings and schedules.
Figure 2.1: From RC design to contract drawings and schedules
DETAILER1
CONTRACT
ADMINISTRATOR
DESIGNER
MAIN
CONTRACTOR
SPECIALIST
CONCRETE
SUBCONTRACTOR
RC design2
Agree detailing specification
Preferred methods of construction
Provide GAs
Provide design3
Detail and
schedule
Y
Comments
from checks?
Comments
from checks?
Issue drawings
and schedules
to designer
Key
Design
issues?
N
Y
1.
N
Issue drawings
and schedules
to CA
Receive and issue
drawings and
schedues to
design team and
main contractor
2.
3.
Process
Link.
As contract conditions.
Extent of traditional areas of responsibility.
The detailer is shown here as being responsible
to the designer. In less traditional arrangements
the detailing may be in the main or specialist
concrete subcontractor’s domain.
RC design includes early and final structural
concrete design and changes to design.
RC design may by agreement be provided in the
form of calculations, marked up GA drawings,
design intent drawings, models, etc.
Contract RC drawings and schedules
There are various forms of procuring detailing services. Traditionally, detailing is the responsibility of the structural
designer. Other lines of responsibility may exist with non-traditional forms of contract such as contractor detailing,
design-and-build, management contracting etc. In each case, the aim is to produce accurate contract RC drawings
and schedules in a timely manner.
The contract RC drawings and schedules are used to procure the reinforcement, programme reinforcement works on
site, call-off deliveries, fix the reinforcement, and to check the reinforcement at various stages. Schedules are often
used for costing purposes.
In the UK, pressure on construction timescales and moves toward non-traditional forms of construction has made
detailing an even more critical and pressured activity.
4
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
2.2 The reinforcement process
Detailing can only really begin once the final design is available. The design requirements are normally given to the
detailer in the form of design calculations, marked-up general arrangement (GA) drawings, design intent drawings,
beam schedules or completed pro forma or similar.
It is important that detailing is carried out with responsibilities and adequate timescales clearly defined. Issues such
as site constraints, relevant standards, laps, covers, concrete grades, holes, detailing preferences, etc. must all be
covered. These requirements should be formalised into a detailing specification — whether detailing is carried out
in-house or outsourced. Ideally the contractor’s preferred methods and sequence of construction should be made
available and accommodated for.
The requirements for the whole structure should be handed over and explained to the detailer at a single point in
time. Packages of information that need to be provided to match the construction sequence or phasing must be
defined. For instance, sufficient information for the detailing of foundations and (wall and column) starter bars may be
the first package required to be delivered.
Designers and detailers should be aware that BS EN 1992 has fewer “deemed-to-satisfy” rules than previous
standards and that there are situations where it is necessary for the designer to undertake calculations based on the
proposed design and then convey the required information to the detailer. Notes are included in the Model Details to
highlight where this is necessary. There will be fewer queries between parties if the designer is familiar with these
requirements and provides the information at the outset. Drawings and schedules can then be prepared by the
detailer.
Once drawings and schedules have been completed, they are usually checked by the detailers themselves, checked
by the designer for design intent and compliance with standards, and where appropriate, checked by contractors
for buildability and completeness, all in accordance with the relevant contracts, specifications and quality assurance
(QA) procedures.
Once detailing is underway, design changes should be avoided unless absolutely necessary. Any changes
significantly disrupt workflows, increase workloads and greatly increase the risk of errors. However, there are often
situations where final design information is not available, and design developments and checks will result in changes
being required. While not ideal, changes are almost inevitable, and should be controlled. An agreed system of
‘design freezes’ is most beneficial.
Once the reinforcement drawings and schedules gain the status of ‘construction drawings’ they are distributed to the
relevant parties. In traditional contracts, these will be issued physically or electronically to the contract administrator
and to the main contractor, client’s quantity surveyor, etc. The main contractor normally distributes the information to
site staff, quantity surveyors, buyers etc. and to specialist subcontractors. The schedules will be sent to the
reinforcement fabricator/supplier.
The reinforcement is usually ‘called-off’ from site. As the work proceeds and reinforcement is required, the site will
ask for reinforcement from certain schedules to be delivered. Again, depending on circumstances, these may be
bulk deliveries, individual pages of schedules or schedules reconfigured by site into work packages. On site,
deliveries of reinforcement call for inspection, craneage, sorting, storage, and document processing. Unless just-intime deliveries are feasible or suitable storage areas are available adjacent to the work area, the reinforcement may
need to be sorted and moved again immediately prior to fixing. Prefabrication, e.g. prefabricated pile, column and
beam cages, may be undertaken either on or off site.
The reinforcement supplier or fabricator has to predict call-offs so that sufficient stock and labour is available to meet
customer requirements. The cutting and bending process is well documented but of most concern are issues such
as price changes, clarity of information, off-cuts, non-standard shapes, full deliveries and delivery timescales.
Deliveries required within 48hrs of receipt of a call-off usually attract a premium.
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
|5
Reinforcement is placed and fixed by steel fixers then checked in situ. Responsibility for checking reinforcement
should be covered in the specification. Formal pre-concreting checks should include checks of the reinforcement,
covers, inserts and specialist items. The reinforcement should be checked again during concreting for position, and
dowels and starter bars should be treated and/or protected. The specification may also require a cover meter survey
after concreting.
Through all these processes, correct and current reinforcement drawings and schedules play a vital role. The schedules
also form the basis for payments to suppliers and contractors.
The communication of reinforcement detailing information from design office to site must be as efficient as possible.
Traditionally, the designer has also been responsible for preparing the reinforcement detail drawings and schedules
(designer detailing). The emergence of specialist concrete contractors has provided an alternative means of
producing the information through contractor detailing. Both systems have advantages and disadvantages
because although both parties handle the same technical information, the timing and way in which they are
produced, differs:
Advantages of designer detailing
• Details are produced as an integral part of the design and can be more easily tailored.
• Production of reinforcement details can take place while the design is still being finalised, saving time
(e.g. in the design of foundations).
Disadvantages of designer detailing
• Work may require revision to take into account the contractor’s preferred construction methods.
Advantages of contractor detailing
• Details can more readily take account of the contractor’s preferred method of working.
• Reinforcement detailing will take account of the contractor’s preferred construction methods and final material
selection.
Disadvantages of contractor detailing
• Preparing design information takes longer (reducing checking time) and is likely to be at a later stage in the
process (possibly requiring further checking/changes).
• Approval process can take longer due to likely rechecking.
Irrespective of the system chosen, it is essential that all the design information is provided. If different designers on
the same project are producing calculations (and thus detailing instructions) in a non-standard way, the format and
content differences can result in:
• making the checking of calculations and instructions time-consuming and laborious. In addition, the communication
of design information to external checking authorities can be unnecessarily confused and protracted
• it taking longer for the detailer to absorb the reinforcement information supplied, and increases the possible need
for clarification. It can also lead to a degree of abortive work and misunderstanding between designer and detailer
Although it is clearly more efficient to invoke a time freeze on the provision of new or altered information (e.g. mechanical
and electrical information) this may not always be in the interests of the client, who is looking for the optimum solution.
The use of BIM and 3D detailing is becoming increasingly widespread in RC construction, certainly on major projects.
Indeed, their use may be part of the employer’s requirements. The principles and rules of detailing in these
environments should be the same as those used in producing traditional 2D drawings and schedules. For detailing,
this may mean a degree of upskilling from a 2D CAD/Excel environment.
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Box 1 provides a checklist of information normally required by the detailer (see Section 2.7 for examples of methods
for conveying reinforcement requirements).
Box 2 notes information required by the detailer, but which affects the construction process. It is usually necessary to
discuss and agree these aspects with the contractor.
Box 1: Checklist of information to be provided by designer:
1) General arrangement (GA) drawings showing:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
column plan dimension including any chamfers
floor levels — sufficient to enable all column heights to be determined
beam sizes including details of any chamfers and nibs
level of beams in relation to slabs/columns/other interfaces
slab thicknesses (and ribbed details where appropriate)
landing levels and thickness, going and tread dimension, waist thickness for stairs
plan dimensions for pile caps and pad foundations, pile and column locations in relation to caps/bases
wall thicknesses and any requirements for links
full section details for retaining walls, including any large radius bend sizes
depths, wall thicknesses, sump size and location, and cover recess sizes for trenches and manholes
full section details for corbels
movement joint locations, including details of joint
concrete classes for each element (consider using a tabular format)
details for all necessary service holes, including sizes and location
full details of any conduits, cladding fixings, puddle flanges and gullies
provisions for ducts and cast-in fittings etc.
2) Project specification including:
•
•
•
•
•
•
•
•
lap/anchorage lengths or concrete classes
reinforcement class (i.e. H, A, B, C or S)
stainless steel specification (to BS 67446 if required)
proprietary systems to be used/permitted/excluded e.g. wall pull-out bars, shear studs or couplers
tolerances
cover requirements for all elements, including foundations
any tying requirements for robustness
any special requirements e.g. seismic
3) Design requirements in one of the following forms:
•
•
•
•
structural design calculations
marked-up GAs (common practice for small-scale, simple projects)
element schedules: sketches of the required reinforcement by element
pre-printed drawings (completed pro formas), sketches and tables incorporated with CAD. They should
provide:
– bar size and pitch
– link size, pitch and number of legs
4) Specific detailing requirements:
• lap and anchorage lengths
• layering directions (T1, T2 etc.) and layering at cross-over of elements
• stress in bar and crack width size limit, or max. bar spacing/max. bar size
• curtailment of reinforcement — if slab arrangement and load limits are outside the limitations of simplified
rules in Figures 6.3 or 6.14
• effective width of flange for distribution of tension reinforcement in T-beams and L-beams
• any requirement for additional distribution reinforcement in a flanged beam to meet requirements of
Clause 6.2.4 of BS EN 1992-1-1
• curtailment of reinforcement for cantilevers
• punching shear requirements under large concentrated loads
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
details for moment connections
for columns, determine if 0.10 NEd/fyd is greater than 0.002Ac and advise accordingly
increase in link requirements due to shear in column section
requirements for shear enhancement in column at moment connection (Figure 6.30)
requirements to restrain bursting action in columns where column section changes size
details of lapping requirements for bundled bars
details of any column links within slab depth
details for construction joints
minimum reinforcement for water-resisting retaining walls
details for handrail supports for slab edges on stairs
when θ is greater than 21.8° in beam shear calculations, designer should inform detailer of curtailment
length (MD B1)
where a beam is resisting torsion, the torsion link shape should be specified — Clause 9.2.3(1) of
BS EN 1992-1-1
fully dimensioned bearing and reinforcement details for corbels and nibs — Clause 10.9.5.2 of
BS EN 1992-1-1
requirements for water-resisting concrete
large radius bends where required (e.g. retaining walls, corbels, pile caps)
requirement to use Detail B or C in MD S2
spacing of links for columns in concrete with a strength greater than fck = 50MPa
for composite slabs, U-bar sizes, reinforcements sizes, shear stud spacing, slabs edge locations —
check reinforcement can fit in slab depth, e.g. for 130mm thick slab, max. recommended U-bar size is 10mm
advise which beams are ‘deep beams’ (Section 6.3.2)
links requirements for walls where the area of reinforcement in one face is greater than 0.02Ac
fastenings designed in accordance with BS EN 1992-414
if small circular columns can be detailed with less than 6No. bars
The efficient communication of information from designer to detailer is important.
Box 2: Construction information to be coordinated between designer, contractor and detailer
•
•
•
•
•
•
•
•
•
•
•
•
location of construction joints for slabs and walls, pour sizes
use of kickers (and height), or kickerless construction
use of wall pull-out bars
use of shear studs
use of other proprietary systems
value of Δcdev , deviation to adopt, in particular if a quality control system is to be used
type of chairs to be used if they are to be scheduled on reinforcement drawings
max. pitch of top reinforcement in slabs to safely walk over
aggregate size unless 20mm is to be used
proprietary systems to be used for retaining wall construction joints
preferred punching shear link shape (MD S6)
elements to be pre-fabricated (e.g. columns), including how column/slab interface is to be detailed,
responsibilities for various components. Impact on design of slab is not considered here.
Note that it may be necessary to revise slab design to accommodate precast column
• reinforcement cages to be pre-fabricated
However, it is not suggested that a rigorous format for calculations be adopted throughout the industry. It is
preferred that the designer should recognise and tailor the guidelines given in this Manual to suit different situations
that arise.
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The following should be considered when preparing instructions to the detailer:
• Instructions should be indexed. An edited calculation index is normally sufficient. Any special requirements should
be noted on individual calculation/instruction pages.
• Detailing instructions should comprise only the calculation sheets describing the geometric and reinforcement
requirements of a particular structural element. Information concerning general analysis of the structure,
e.g. stability analysis, computer listings etc. is not required.
• Instructions should include clear diagrams of the reinforcement, consistent with the design calculations.
• Where appropriate and/or where alternative sketches are supplied, reference should be made to the Model Details
in this Manual.
• Detailing information should normally be given in the right-hand margin of the calculation sheet. Where the
calculations for an element or series of elements are lengthy or complex, the relevant reinforcement information
should be extracted and presented in a summary sheet.
• The use of marked-up outline drawings as a summary should be accompanied by calculations for congested
areas or where the section is small.
• Sketch details: all instructions should explicitly address the curtailment of reinforcement including the angle of strut
assumed in shear design (Section 6.3.2). Where conditions permit the use of standard arrangements these should
be adopted. The instructions should also note where the standard curtailments may still be used where the
elements fall outside the conditions for their use.
• Where only bending moment and shear force diagrams are provided these should be accompanied with clear
instructions concerning curtailment. This method can be inefficient for detailing unless the designer has given
thought to the rationalisation of the layout (e.g. beam cages).
• Where reinforcement is congested or there are particularly complex connections e.g. corbels, nibs, deep beams
to thin cross-section walls or columns, details should be sketched at a large size, even full-size, to confirm
buildability. The sequence of installation must be considered to ensure beams can be lifted and placed.
• Each particular structural element requires specific design and geometric information. The list of information
required is given in the ‘Detailing information’ sub-section of Chapter 6 for each element.
• Always provide the detailer with the latest revision of relevant GAs and sections to avoid abortive work and the
possibility of incorrect details. Drawings and details should be made available in CAD formats (DWG/DGN) as well
as PDF. Where 3D detailing is to be used, the relevant Industry Foundation Class (IFC) should be made available.
• The designer should seek to maintain regular direct contact with the detailer during the detailing process.
• It is recommended that in the absence of an instruction from the designer for a particular detail, or for
nominal reinforcement, the detailer should assume that the standards described in this Manual are to be applied.
The designer should take responsibility for ensuring that critical details are provided to the detailer.
• Where Model Details given in this Manual are not applicable to the geometric configuration, the detailer should
provide suitable alternatives based on similar principles.
2.3 Designer detailing
To ensure efficient detailing, the designer should understand the contractor’s preferred methods and agree a sensible
programme and sequence of work eliminating any unrealistic demands. Where the construction sequence is
dependent on the design, the designer should provide a description of the design philosophy and constraints in
addition to the information listed in Section 2.2.
Provide a description of the design intent and the form of construction assumed in design.
All sketches and reinforcement correspondence should be given a unique identification sketch or instruction number.
‘Nominal’ reinforcement should be assumed to be in accordance with the relevant element in Chapter 6 unless
clearly stated by the designer.
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Standard method of detailing structural concrete (4th edition)
|9
2.4 Contractor detailing
Where detailing is commissioned through the contractor under the contract for a project, the following managerial
points should be noted:
• The sub-contract should clearly state and define the responsibilities of each party.
• Legal advice should be sought, where necessary, to remove any ambiguity over contractual liabilities.
• The specialist concrete contractor should be satisfied with the obligations and duties imposed by the contract
and any warranties.
• The specialist concrete contractor should have insurance cover commensurate with the exposure to the relevant
risks and liabilities.
2.5 BIM and 3D detailing
BIM and 3D detailing are becoming increasingly prevalent. The software provides users with diverse tools for solid
modelling, reinforcement modelling, detailing and scheduling. With clear understanding and practice, reinforcement
detailers can automate many of the more tedious parts of their work including: the creation of bending schedules,
annotation of rebar, 2D RC drawings, plans and sections, representation of complicated details by using 3D views, etc.
3D RC details are often built up from the base BIM model and other design inputs, such as separate calculations,
design intent drawings, marked up GAs, construction methodology, BIM protocols, detailing specification, etc. The
detailer’s skill is in aggregating these inputs into complete RC models and details that satisfy the structural design
and detailing rules, yet afford best constructability. Figure 2.2 illustrates a possible workflow that may include
collaborative reviews, checks and approvals.
Figure 2.2: 3D RC detailing — summarised workflow
Utilise 3D model for
onsite activities
(construction,
inspection, records etc.)
RFI
BIM execution plan
including data
specification
GA and
design intent
3D modelling/
RC detailing
3D model issued
for collaborative
review
3D model issued
for approval
Approved 3D
model issued
Annotate and
dimension model
Construction
methods
Temporary
works design
Comments
Comments
Call off rebar
from model
Digital bar schedule
(csv, BVBS or similar)
3D RC detailing should be a tool that supports improved collaboration — allowing the designer, contractor and
specialist trades to have input and review with a target of promoting efficiency and reducing risk. 2D drawings and
bar schedules should be representations of data within the 3D model, to ensure that all the information contained
within each is consistent. This allows some/all information formats to be utilised — to best suit project and user
requirements. With the progression of technology, consideration should be given to effective use of the 3D model at
all stages of the RC detailing process, with an evolution towards the model becoming the primary deliverable and
source of construction information as illustrated (Fig. 2.2).
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3D RC detailing can provide further enhancement to the construction process. All the bars are represented within the
3D model (but still collated into bar marks to bundle common bars), whereas in 2D only a range is indicated on the
drawing. With the model detailing every individual bar, processes further downstream can be linked to the model
data, enhancing quality and traceability. Such processes may include: materials management, quality inspection
sign-off, end-to-end traceability and records.
The file formats utilised in the 3D RC detailing process should allow information to be shared, reviewed and
commented on, without a need for a licence of the authoring software. An example would be the export of an
IFC file format model (other sharing formats can be utilised).
Reinforcement is a variable material, and issues such as out-of-plane bending and ‘springback’ may, in practice,
render bars not quite as accurate as 3D models might suggest.
2.6 Electronic data interchange (EDI)
The widespread adoption of electronic data interchange (EDI) necessitates careful and consistent schedule formats
complying with BS 86667. This allows the data to be transferred throughout the entire supply chain.
Minimum requirements
• Use of consistent nomenclature for drawing and revision numbers or letters, i.e.:
○ Revisions 1 and 2 should never be succeeded by Revisions C and D.
○ The number 0 should never be interchanged with the letter O.
○ A revision at bar mark level should be consistent with the drawing level, e.g. if a bar mark revision is
marked ‘2’ the drawing and schedule revision should be marked ‘2’ (although lower revisions can be displayed
against the appropriate bar mark, if they were not changed in the new revision).
• Member names must remain consistent through a schedule. The name itself is not important but a member
called, for example ‘garage-1’ in one part of a schedule and later abbreviated to ‘grge-1’ in another part will be
recognised by software as two different members.
• The same bar mark must never repeat within the same member name.
• When a library of Shape Code 99s is created (e.g. 99-01, 99-02 etc.) the shapes should be defined graphically
and remain consistent for the duration of the contract.
Recommended procedures
• When a revision is issued, each schedule page should display this revision, regardless of whether any bar marks
have changed on that page.
• Where bar marks are revised, this should be indicated in the appropriate column of the schedule, with the revision
number or letter. This column should be left blank for any bar marks which have not been altered since the
previous revision.
• When schedules are produced, a naming convention of drawing number revision, e.g. 213_02 is suggested.
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Standard method of detailing structural concrete (4th edition)
| 11
2.7 Typical methods of providing required information for detailing
2.7.1 Flat slabs
Figure 2.3 is an example of a marked-up GA for a flat slab. Notes on the drawing should include concrete grade or
cover (or at least a reference to these). GA drawings should also be provided.
Figure 2.3: General arrangement drawing (flat slab)
B
C
D
565mm2
565mm2
A
565mm2
1795mm2
565mm2
565mm2
565mm2
1795mm2
565mm2
565mm2
565mm2
565mm2
2094
mm2
565mm2
2805mm2
1795mm2
565mm2
2094
mm2
646mm2
565mm2
1795mm2
1796mm2
565mm2
2094
mm2
1795mm2
1005
mm2
2094
mm2
565mm2
565mm2
565mm2
565mm2
565mm2
2094
mm2
4
1795mm2
565mm2
A
1796mm2
565mm2
565mm2
3
565mm2
1796mm2
1795mm2
565mm2
565mm2
565mm2
565mm2
2094
mm2
565mm2
1796mm2
2
646mm2
565mm2
565mm2
565mm2
1796mm2
565mm2
2094
mm2
1
565mm2
646mm2
1005mm2
565mm2
1005mm2
1005mm2
565mm2
5
Where contour plots from proprietary systems are provided, the level of rationalisation to be applied should be
agreed between designer and detailer. Alternatively, where crack control is important, a schematic layout of bars
should be given. The method used for indicating holes, and the associated reinforcement trimming details required,
must be clearly stated (Section 6.2.2).
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2.7.2 Beams
Figure 2.4 is an example of a calculation sheet for beams.
Figure 2.4: Calculation sheet (beams)
Job No.
Calculation
sheet
Sheet No.
Rev.
56789
FB.3
Beam, Level 2, Grid 4, B-C
LO2
Date
AB
Nov 2019 Chd CD
Member/Location
Job Title.
EC2
Org. Ref
Euro House
Made by
Beam, Level 2, Grid 4, B-C
fck = 30 MPa
Beam, Level 2
fy = 500 MPa
Grid 4, B-C
Supports B & C
Supports B & C
MEd = 645 kNm
h = 500, bN = 400
40 cover
20 allowance
for slab steel
12 link
d = 500 – 40 – 20 – 20
= 420
dc = 40 + 20 + 13
= 65
For x/d = 0.5, max. moment without comprssn
3.1.7(3) steel, Mu = 0.32 bd2fcd
∴ Mu = 0.32 x 0.4 x 0.422 x 0.85 x 30 x 103
1.5
= 384 kNm
ASC = MEd – Mu = (645 – 384) x 103
fyd (d – dc)
500 (0.42 – 0.065)
1.15
Use 4H25 bottom
= 1691 mm2
AS = ASC +
Mu
= 1691 +
fyd 0.8d
384 x 103
500
x 0.8 x 0.42
1.15
= 4320mm
2
(1963mm2)
1.2%
Use 4H40 top
(5027mm2)
3.0%
Span
Span
MEd = 615 kNm
h = 500, beff = 3340
40 cover
12 link
d = 500 – 40 – 12 – 20
= 428
5.3.2.1(3) beff = 400 + 2 x 1470 = 3340mm
x = 1.25d – 1.56d2 – M/(0.32befffcd)
= 1.25 x 0.428 –
1.56 x 0.4282 –
= 33mm (within slab)
ASC =
MEd
fyd (d – 0.4x)
=
0.615
0.85 x 30
0.32 x 3.34 x
1.5
615 x 103
500
(0.428 – 0.4 x 0.033)
1.15
= 3400mm2
Use 4H40 bottom
(5027mm2)
2.9%
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
Figure 2.4: Continued
Job No.
Calculation
sheet
Sheet No.
Rev.
56789
FB.4
Beam, Level 2, Grid 4, B-C
LO2
Date
AB
Nov 2019 Chd CD
Member/Location
Job Title.
Org. Ref
Euro House
Made by
Shear at supports
Shear at supports
VEd
Zsupport
Z = 343, bw = 400
=
=
512kN
645 x 106
= 343mm
4320 x 500
1.15
6.2.3(3) Calculate maximum value of cot θ
VEd < VRd, max = αcw bw z y1 fcd / (cot θ + tan θ)
∴ cot θ + tan θ < 1 x 0.4 x 0.343 x 0.6 (1 – 30) x 1 x 30
250
1.5
0.512
< 2.83
∴ cot θ
= 2.42 (< 2.50)
512 x 103
∴ As =
VEd
.
=
S
zfywd . cot θ
0.343 x 500 x 2.42
1.15
= 1419mm/mm
9.2.13
Shift rule
al = z cot θ = 343 x 2.42 = 415mm
2
2
Use 2legsH12@150
(1508mm2/m)
Shift rule
al = 415mm
| 13
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2.7.3 Pile caps
Figure 2.5 is an example of a sketch on a calculation sheet.
Figure 2.5: Calculation sheet sketch (pile cap)
Pile cap: Core 6.
GL. A13, B2
Type/Size
H16
H40
H16
H16
H40
H16
Spacing
250
–
–
@ same spacing as 08
–
–
4
6
13
No.
–
4
4
–
5
–
628 band
width
A
Mark
6
7
8
9
10
11
11
B2
695 band width
08
07
06
10
09
6
11
11
11
11
10
10
10
10
10
6–6
8
8
8
9
9
9
13
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
2.7.4 Pro formas
Figure 2.6 contains example pro formas.
Figure 2.6: Sample pro formas
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3 Drawings
3.1 General
Drawings are prepared so that designers can communicate their requirements clearly and concisely. It is important to
ensure that drawings are not unnecessarily congested or complicated. Original drawings will almost certainly be
supplied to the detailer digitally — and the clarity of these originals is important because reproductions used on site
are likely to suffer wear and tear.
It is recommended that A1 size drawings are generally used for GAs, larger sized drawings being used only when
unavoidable. A3 and A4 are recommended for details. For each task, the chosen drawing size should be used
consistently. Annotations should be as brief as possible, consistent with completeness, and if hand-written,
clearly legible. Any instructions on drawings should be positive; they should be written in the imperative.
Each drawing should give all the information necessary (together with reference to associated drawings) for the
construction of the portion of the work shown, omitting irrelevant detail. Details of materials to be used will normally
be given in a separate specification, and reference to the concrete or other types of material on drawings will be in
an abbreviated form.
Reference to any special items concerned with construction details should be made on the GA drawings and not via
separate correspondence. Special requirements of the designer, e.g. details of cambers, chamfers, sequence of
construction, position and type of joints etc., should all be described on the GA drawings.
3.2 Types of drawings
The main purpose of preparing structural drawings is to explain the shape and position of all the parts of the
structure. Such drawings are used to progress the architect’s concept and then to enable construction of
the structure on site. Structural drawings are also necessary for the preparation of the reinforcement drawings.
3.2.1 Structural drawings
Drawings for concrete structures consist of dimensional data necessary for the setting-out and construction of the
concrete formwork, e.g.:
• setting-out of the concrete structure on site
• plans, sections and elevations (where appropriate) showing layout, dimensions and levels of all concrete members
within the structure
• location of all holes, chases, pockets, fixings and items affecting the concrete work
• north point
• notes on specifications, finishes and cross-references of the construction
They also provide the detailer with the layout and sectional information required to specify the length, shape and
number of each type of reinforcing bar. All these matters should be considered at the outset of every drawing
programme. Detailed examples of structural layout drawings and guidance notes are illustrated in Section 3.20.
3.2.2 Reinforcement drawings
Reinforcement drawings describe and locate the reinforcement in relation to the outline of the concrete work, and to
relevant holes and fixings.
Generally, circular holes ⩽150mm diameter and rectangular holes up to 150 × 150mm in slabs or walls need not be
indicated on the reinforcement drawings. All other holes should be indicated and should be trimmed, where
necessary, by suitable reinforcing bars.
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Separate drawings or plans for top and bottom layers of reinforcement should be used only for fabric and in
exceptional cases, e.g. voided bridge decks and box girders with four layers of reinforcement.
Reinforcement drawings are primarily for the use of the steel fixers. It is preferable that GA and reinforcement
drawings be kept separate, but for simple structures a combined drawing may be appropriate.
3.2.3 Standard details
‘Standard details’ are details used on a repetitive basis. They must be carefully worked out, fully detailed and totally
applicable to each location where they are to be specified. Standard details may apply to concrete profiles or
reinforcement arrangements, and they should be drawn to a large scale.
3.2.4 Diagrams
Diagrams may be used as a means of communicating design ideas, both pre- and post-contract. Diagrams may be
formally presented or sketched, provided they convey information clearly and in detail. The information contained in
diagrams should be drawn to scale.
3.2.5 Record drawings
When the RC structure has been constructed, the original drawings used for the construction process should be
amended to indicate any changes in detail that were made during construction. A suffix reference should be added
to the drawing number to indicate the drawing is a ‘record’ drawing. The amendments should be described verbally
against the appropriate suffix reference. A register of drawings should be kept; listing reference numbers, titles and
recipients of drawings. The record drawings should be included in the Construction Phase Plan compiled under
Construction (Design and Management) Regulations 2015 (CDM 2015)15 and submitted to the client for safekeeping
at handover of the project.
3.3 Photocopying and reduction
There are a number of considerations if photographically reduced drawings are to be fully understandable
(Section 3.15). These include:
•
•
•
•
•
chosen range of line thickness
size and nature of annotations
arrangement of information on drawings, avoiding congestion
ensuring that graphical and verbal information is, as far as possible, kept separate
awareness that solid black areas may not print properly
Since many drawings will be reduced for archive storage on completion of the construction, these aspects should be
considered at the outset of every drawing programme. It is recommended that checking of reinforcement is
undertaken on full-size prints. Errors can easily occur if reduced-sized prints are used, e.g. from A1 to A3.
3.4 Abbreviations
Standard abbreviations are recommended, but if there is any risk of confusion or ambiguity with their use in any
particular circumstances, then the words should be written in full. No other abbreviations should be used unless
clearly defined on all the drawings on which they appear.
Particular attention is drawn to the use of lowercase and capital letters. All abbreviations are the same in the plural as
in the singular. Appendix I provides a list of common abbreviations.
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3.5 Dimensions of drawing sheets
The recommended dimensions of drawing sheets are given in Table 3.1. Figure 3.1 shows the relative sizes.
Table 3.1: Size of drawing sheets
BS reference
Dimensions mm × mm
A0
841 × 1189
A1
594 × 841
A2
420 × 594
A3
297 × 420
A4
210 × 297
Note: Margins and information panels are contained within these dimensions.
Figure 3.1: Relative size of recommended drawings
A0
A2
A1
A4
A3
3.6 Borders
Borders should be 20mm (min.) for A0 and A1 and 10mm (min.) for A2, A3 and A4. The border margin line should
be at least 0.5mm thick.
3.7 Title and information panels
Key information relating to the task and drawings should be placed in the bottom right-hand corner of the drawing
sheet (panel A in Figure 3.2).
Figure 3.2: Layout of key information
0.5mm min.
20mm
min.
B
A
20mm min.
A0 – A1
10mm min.
A2 – A3 – A4
180
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Panel A should include at least the following information:
•
•
•
•
•
•
•
•
•
office project number
project title
drawing number with provision for revision suffix
drawing title
office of origin
scales
drawn by (name)
checked by (name)
date of drawing
A box should be provided immediately above panel A to contain the necessary reference to relevant bar and fabric
schedule page numbers. Panel B may be developed vertically from panel A to include such information as revisions
working up from panel A and notes (working down from the top of panel B). Notes on reinforcement drawings
should include cross-references to GAs, a list of abbreviations, the grade of concrete, specified covers and the
relevant ‘schedule refs’.
3.8 Key
For tasks where a portion of the work has to be divided into several drawings, it is useful to have a small
diagrammatic key on each drawing, with the portion covered by that drawing clearly defined, and adjacent panels
identified with a given drawing number.
3.9 Orientation
3.9.1 Site plans
The direction of the north point should be clearly shown.
3.9.2 All other drawings
All other drawings relating to particular buildings or major subdivision of a task should have consistent orientation,
which should preferably be as close as possible to the site-plan orientation.
3.10 Thickness of lines
The objective of using varying line thicknesses is to improve clarity by differentiation. The scale of drawing and the
need for clear prints to be taken from the original should be borne in mind. The following suggested line thicknesses
are considered suitable for RC drawings:
Concrete outlines generally and GA drawings 0.35mm
Concrete outlines on reinforcement
0.35mm
Main reinforcing bar
0.70mm
Links
0.35–0.70mm
Dimension lines and centrelines
0.25mm
Cross-sections of reinforcement should be drawn approximately to scale.
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3.11 Lettering
Distinct and uniform letters and figures ensure the production of good, legible prints; the style should be simple.
Capital letters should be used for all titles and subtitles. Lowercase letters may be used in notes.
3.12 Spelling
The spelling of all words should be in accordance with BS 6100-916.
3.13 Dimensions
The GA drawing should show all setting-out dimensions and sizes of members. The reinforcement drawings should
contain only those dimensions necessary for the correct location of reinforcement. Figure 3.3 shows the points to
which the dimension lines should relate.
Figure 3.3: Dimension lines
1104
1800
Dimensions should be written in such a way that they may be read when viewed from the bottom or the right-hand
side of the drawing. They should, where possible, be kept clear of structural detail and placed near to and above the
line, not through the line.
For site layouts and levels, the recommended unit is the metre. For detailing reinforcement and the specification of
small sections, the recommended unit is the millimetre. It is not necessary to write ‘mm’.
Dimensions should normally be to the nearest whole millimetre. Thus:
4.250
114.200
6.210m
5
15
1725
3.14 Levels
3.14.1 Datum
On civil engineering and major building works it is usually necessary to relate the task datum — a temporary
benchmark (TBM) or transferred Ordnance Survey benchmark — to the Ordnance Survey datum. On other works,
a suitable fixed point should be taken as task datum, such that all other levels are positive. This datum should be
clearly indicated or described on the drawings, and all levels and vertical dimensions should be related to it.
Levels should be expressed in metres.
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3.14.2 Levels on plan
It is important to differentiate between existing levels and intended levels on site layout drawings (Table 3.2, row n).
3.14.3 Levels on section and elevation
The same method for levels on plan should be used, except that the level should be projected beyond the drawing
with a closed arrowhead indicating the appropriate line. When developing a structure, it is the level of the structure
that is important. If it is necessary to refer to the finished floor level, this should be a reference in addition to the
structural floor level (Figure 3.4).
Figure 3.4: Levels on sections
40
FFL
SSL
12.000
3.15 Scales
Scales should be expressed as ratios e.g. 1 :10 (one to ten). The following scales are recommended as suitable for
concrete work:
GAs
wall and slab detail
beam and column elevations
beam and column sections
1 :100
1 :50
1 :50
1 :20
Where larger scales are required, 1 : 10, 1 : 5, 1:2 or full-size are preferred. It is quite common for a drawing to be
printed at a different scale than that for which it was drawn. For this reason, further information should be added
indicating the original size of drawing (e.g. 1 :100 for A1).
3.16 Plans
Plans should be drawn in such a way as to illustrate the method of support below, which should be shown as
dashed lines. This is achieved if one assumes a horizontal section drawn immediately above the surface of the
structural arrangement or component. Dimension lines should be kept clear of the structural details and information.
3.17 Elevations
An elevation on a portion of a structure will normally be taken as a vertical cut immediately adjacent to the element
under consideration. Structural members cut by the section should be shown in continuous lines. Other connecting
members behind the member being detailed should be identified by dashed lines.
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3.18 Sections
Where sections are taken through structural elements, only the material in the cutting plane is shown on a section;
in general a cut showing features beyond should not be used. For clarity, the cut member may be shaded.
The directions of sections should be taken looking consistently in the same direction, looking towards the left for
beams and downwards for columns. A section should be drawn as near as possible to the detail to which it relates.
3.19 Gridlines and a recommended reference system
A grid system provides a convenient way to locate and reference members, since columns are usually placed at or
near the intersection of gridlines (Figure 3.5).
Figure 3.5: Framing plan
1
2
3
2:5
C22
C12
C
Ba2:52
B31
B25
B21
B11
Ba
B23
B24
B12
B
B22
A
A12
A31
A14
A15
A21
A13
A11
A16
2A2
Grid notation should be agreed with the architect and would normally be numbered 1, 2, 3 etc., in one direction, and
lettered A, B, C, … X, Y, Z, AA, AB, etc. (omitting I and O) in the other direction. These sequences should start at
the lower left corner of the grid system. Supplementary grids, if required, can be incorporated within the system and
identified as follows: Aa, Ab, Ac, Ba, 2.5, 4.2, etc.
Referring to Fig. 3.5:
• All beams within a floor panel are referenced from the column situated in the lower left corner of that panel,
e.g. column reference B2 occurs at the intersection of grids B and 2.
• Each beam reference includes the column reference plus a suffix number, e.g. B21, B23, etc. for beams spanning
up the panel, and B22, B24, etc. for beams across the panel.
• similarly for supplementary column Ba2:52
This format is similar to the system used successfully for structural steelwork. Beams should be labelled on the
GA drawing, particularly off-grid members. Beams on gridlines may have their labels omitted, in which case strings of
beams should be described as: ‘beams along gridline B/1 to 3’.
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3.20 Layout of slabs
GAs are developed over a period of time and coordinated from dimensional information provided by the architect,
engineer and specialists. The dimensions should be checked and approved before commencing the detailing of
reinforcement.
3.20.1 Methods of preparing GA drawings for concrete structures
As projects vary in size and complexity, it is important to select a scale that will enable the final drawing to be read
with clarity. Large floor areas can be spread over several drawings and linked and referenced by means of key plans.
Local complexities, such as staircases, can be isolated and referenced to a larger-scale drawing.
3.20.2 Information shown on GA drawings for concrete structures
On plan (Table 3.2)
Table 3.2: GA drawings: information shown on plan
(a) Gridlines
2
These form a network across the job and provide a convenient way of
dimensioning and referencing elements (Section 3.19). Grids usually coincide
with the centrelines of columns; clarify if they do not.
D
(b) Centrelines
C
These often coincide with gridlines. Otherwise notate and locate by offset
dimensions from nearest grid. It is useful to locate groups of holes, pockets,
isolated bases, plinths, machinery, plant, etc.
3050
50
CL
(c) Columns
150
CL
COL.
CL BASE
MILL
100
200
300
State overall concrete size (with clear indication of orientation) and locate
relative to the nearest gridlines. If the size of the column is greater below
floor, show the lower profile dashed; its size will be indicated on the lower
floor plan.
Where repetition occurs it may be convenient to add an explanatory note,
e.g. ‘all columns 300 × 300 and centred on gridlines unless noted’.
col.
500 × 300
(d) Nibs on columns
80
50 80
200
Where the profile becomes more complex it may be necessary to refer to an
enlarged detail for dimensions. Elevations will be required if the vertical
extent of the nibs is not obvious from the plan.
300 200
Dimension on plan.
90
100
200
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Table 3.2: Continued
h
(e) Downstand beams
State beam reference (Section 3.19) and overall concrete size (h × b), both
preferably at the centre of span. The dashed line plots the profile of the
lowest beam soffit.
b
200
Where repetition occurs it may be convenient to add an explanatory note,
e.g. ‘all internal beams 600 × 300 unless noted’.
4B1
h
h
(f ) Upstand beams
500 × 300
550 × 300
3B4
State beam reference and overall concrete size (h × b). Add level to top of
beam and/or draw section to clarify.
b
b
3C2
2.570
800 × 350
(g) Nibs and kerbs on beams
NIB
Locate extent of projection on plan and notate, indicating depth. Clarify with
section and/or add levels to top.
200 deep
2.150
425
1575
150
600
150
KERB
150 high
(h) Bases and ground slabs
(150)
GROUND
SLAB
Notate and indicate thickness.
(500)
BASE
Type ‘A’
(j) Suspended slabs
Show direction of span and indicate thickness of slab, preferably near the
centre of the panel.
• one-way spanning
160
175
• two-way spanning
• cantilever
150
CANTILEVER
• tapered cantilever (add section and indicate direction of taper)
150 to 200
CANTILEVER
175
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Table 3.2: Continued
(k) Walls
150
95
State wall thickness and its location relative to the nearest datum. If the
wall size under is different, show its profile dashed; its thickness will be
indicated on the lower floor plan.
105
150
WALL
(l) Dwarf walls and parapets
350
150
105
95
These walls are viewed just above their top and notated. Sections and/or
levels are added for clarity.
150
PARAPET
31.100
32.500
(m) Loadbearing walls
450
475
• Indicate wall material and thickness and its location relative to the nearest
datum. Supporting walls under to be shown dashed and notated on the
lower floor plan.
225 Block
WALL
• Locate and identify walls above floors that are not continuously supported
by walls below.
225 Brick WALL
425
above slab only
Non-loadbearing partitions are not generally shown on structural drawings.
(n) Levels
These provide a vertical datum and should be displayed prominently at each
level as appropriate, thus:
• top level of concrete, e.g. foundation base
125.000
• top of structural slab level
SSL
150.050
• top of finished floor level
FFL
150.075
• top of existing level
EL
150.075
50 FALL
• arrow indicates direction of down-slopes and falls, and up-slopes
• arrow indicates level to top surface as noted
UP
LEDGE
245.750
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50 STEP
Table 3.2: Continued
(p) Steps in level
Lines at a change in level can be quickly identified by adding sectional
hatching to the plan as follows:
• step on top surface
• splay on slab soffit shown dashed
• locate steps to nearest datum appropriate
150.050
150.000
150
45º splay under
2000
(q) Joints
100
Description of
Any special joint required by the designer should be located and notated on
plan with a bold chain-dashed line and supported by a section if required for
clarification.
JOINT
5250
(r) Stairwells
STAIR
See drg..
(s) Holes
C
L group
All should be drawn to scale, sized and located to the nearest datum
(circular holes ⩽150mm diameter and rectangular holes up to 150 × 150mm
may not be shown):
175
75
C
L
300 × 200
C
L
175 x 100
2 no HOLES
100 x 100
80 160
• holes through beams or walls
Indicate level to bottom of hole, e.g. window sill. Show cross dashed
if below the section, e.g. downstand beam. An elevation will be required if
holes are too complicated to show on plan.
200
C
L
170 175
• hole through slab
• groups of holes
Identify holes with a cross.
450
250
350
On floor plans, complicated areas such as stairwells are often referred to an
enlarged layout drawing. The direction of stair flights should be indicated
with an arrow pointing in the relevant direction.
1250
× 500
350
9.750
500
500
175 200
• similar to holes but identify area with diagonal only and notate.
• small pockets such as those used for anchor bolts are usually identified by
a large dot and notated.
pkt
25 deep
170 275
4 no pkt
125 × 125
100 deep
350 325
75
(t) Pockets and recesses
350
OPENING
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On section
Sections are drawn to clarify the plan and provide mainly vertical information (Table 3.3)
Table 3.3: GA drawings: information shown on section
(a) General cross-sections
175
75
SFL
1.500
600
(b) Local sections
200
200
These provide a general impression of the entire vertical structure. Major dimensions
and levels shown. Complicated profiles etc. may remain undimensioned; these are
shown by local section prepared with the floor layouts. The elevation of background
walls and columns are often included to increase impression.
Show all vertical dimensions and levels. Adding some horizontal dimensions will help to
tie in with the plan. It is preferable for local sections to be placed alongside the plan.
3.20.3 Fixing in concrete
Where ancillary fixings are likely to affect the proper location of the reinforcement, they should be located on the
drawings. Where extensive, these fixings may be indicated only, and refer to other drawings for location etc.
Consideration should also be given to any extra reinforcement required.
3.20.4 GA drawing for concrete structures
Figure 3.6 is an example GA drawing.
3.21 Layout of foundations
The position of each foundation should be given relative to the gridlines. The width, length and depth should be
given and the level of the bottom of the foundation should be supplied relative to a given datum. This information is
often supplied in tabular form. Each foundation should be given a distinguishing letter that will serve as a
cross-reference for the foundation details given elsewhere.
The maximum allowable safe ground bearing pressure should be shown in note form on the drawing. The blinding
thickness and type should be noted.
When piling is employed it is usual to have a separate GA or piling plan. This shows the position of piles relative to
gridlines, and contains a schedule and notes which include the following relevant items depending on the project:
•
•
•
•
•
•
•
•
•
pile reference number
diameter
safe working load of pile
imposed moment
imposed horizontal force
cut-off level
minimum toe level
angle of rake
pile positional tolerances
The horizontal dimensional permissible deviation is normally stated in the piling specification, but it should also be
repeated on the piling plan.
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Figure 3.6: GA drawing: example for concrete structure
4
5
6
4250
3750
150
150
N
KERB
150 high
H52
600 × 300
250
150
H42
450 × 300
125
150
WALL
G53
SSL
112.000
400 × 300
1650
125
PLINTH
1500 × 750 × 300 high
with 4 no pkt
75 × 75 × 75 deep
G61
G51
G54
STAIR
See
drg....
3450
G41
450 × 300
150
7000
600 × 300
250
SSL
600 × 300
150
150 STEP
300 × 250
550
250
500
H
NIB
200 deep
112.150
175
1100
G42
500 × 300
125
G52
G
500 500
F61
600 × 300
150
600 × 300
F51
CL
150 STEP
150
F42
F52
500
1800
1
COL.
500 × 300
400 × 300
CL
175 175
F41
450 × 300
3000
1350
450 × 300
600 × 300
250
150
F
7TH FLOOR LAYOUT
All columns 300 × 300 and centred on grids, unless noted.
5
6
200
125
300
600
600
SSL
112.150
150
150
300
450 150
4
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3.22 Layout of stairs
The stair GA drawing should indicate all the dimensions required to set out the concrete profile (Figure 3.7).
Figure 3.7: Typical stair notation
Flight
9 equal treads
20
18
Flight
Architectural
finishes shown
16
FFL
19
17
Soffit
14
Pitch
10
9
8
7
Tread or going
Flight
6
5
20 equal risers
12
11
Landing
FFL
Storey height
13
Riser
4
3
Pitch
Pitch line
2
1
FFL
The architect will normally locate the stair between floors using the top of the finishes as the vertical datum. The height
of risers will be equal but the thickness of finish may vary, particularly at floors and landings. It follows that structural
risers may vary in height. Treads may require sloping risers to provide a nosing, and fillets may be needed to maintain a
constant waist thickness (Figure 3.8).
Figure 3.8: Typical stair shapes
Finished risers equal
Structural tread
or going
Riser
Going
Structural risers vary to
suit thickness of finish
Nosing
Finishes
Fillet
Structural SFL
waist
Finishes
Vertical risers
Structural waist
Sloping risers with fillets
Finishes to treads
of each flight align
Finishes to soffit
junction align
It is often devised such that the finishes to nosings of adjacent flights will align across the stair. Sometimes the
junctions of all soffits are made to align.
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4 Detailing and scheduling
4.1 Detailing techniques
The majority of detailing examples contained in this guidance are based on a manual detailing system, that fully
describes all aspects of each element. This is the traditional method of detailing in the UK, and tends to be simpler
to plan and operate than the other methods listed here — but in certain circumstances can take longer to produce.
4.1.1 Tabular method of detailing
The tabular method may be adopted where a number of concrete elements have a similar profile and reinforcement
arrangement but have differing dimensions and quantity of reinforcement. A typical element is drawn, usually not to
scale, but visually representative of its shape, with the dimensions and reinforcement given as code letters. A table is
given to show the actual values of these code letters for each individual element (Table 4.1).
Table 4.1: Tabular method of detailing — examples
Plan
Elevation
Y
Z
B1
Level C
75 Blinding
conc.
B2
X
B2
B1
Column bases
Base
No. off
X
Y
Z
Level — C
Reinforcement
B1
B2
7A, 7B, 7C
3
1800
1800
400
12 H20-1-150
12 H20-1-150
19.000
8A, 8B, 8C
3
1800
1350
400
9 H16-2-150
12 H20-1-150
19.000
Level D
A
E
Lap
length
E
75 Kicker
E
E
F
B
F
A
E
E
B
F
Level C
E
A–A
E
1–1
E
E
E
2–2
Column starters
Col
No. off Level
C
Reinforcement
D
E
Sect Elev Column dims
F
A
B
7A, 7B, 7C, 7D
3
19.000 19.400 4 H32-3 3 H10-4-150
1-1
A-A
350
550
8C
3
19.500 19.950 6 H25-5 6 H10-6-150 + 6 H10-7-150
2-2
A-A
575
575
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Advantages
• a large number of similar elements may be detailed on a few drawings
• quicker to produce and thus saves detailing time
Disadvantages
• elements are not drawn to scale
• checking of drawings and schedules tends to take longer and is more prone to error
• once alterations or additions are made, special details may be required to which the initial tables have to refer,
this complicates the system and can lead to errors
• visual checks of drawings may be misleading
4.1.2 Template drawings/typical details
These are used where a library of typical elements and details have been set up. The advantage of these drawings
is obvious, but care must be taken to ensure that the details given do, in fact, apply to the condition required.
A check should also be made to ensure that they reflect the requirements of the client and architect.
4.1.3 Overlay drawings
These are layers of information brought together to form a single drawing.
4.2 Detailing reinforcement
4.2.1 General
Reinforcement detailing should be kept as simple as possible, consistent with showing its shape and exact location
(a list of standard shapes is given in Appendix B). The information given on a drawing should be in accordance with
BS 86667. The standard sequence of description is as follows:
1.
2.
3.
4.
5.
6.
Number
Type and grade
Size
Mark
Bar centres
Location or comment
For example, a slab described as ‘20H16-63-150B1’ contains 20No. high yield deformed bars of 16mm nominal size
at a pitch of 150mm in the bottom outer layer. The bar mark is -63-.
The bar centres, location or comment, are not usually required for beams and columns (Sections 6.3 and 6.4).
To avoid confusion when totalling quantities for entry on the schedule, the number of bars in a group should be
stated only once on the drawing.
The comment is usually used to indicate the position, arrangement or orientation of the reinforcement. A number of
abbreviations are used to keep the description brief (Appendix I). It is good practice to include the abbreviations in
the drawing notes. Since the contractor may not be familiar with this notation it should be illustrated by a sketch
on the relevant drawings.
All reinforcement must be fixed prior to concreting. Bar bending schedules must include all relevant elements relating
to the pour, e.g. wall starters, column starters and shear rebar/studs. Although the elements of a structure, such as
beam, slabs and columns, are detailed separately, the designer and the detailer should always consider each
element as a part of the entire structure. Frequently, the arrangement for reinforcement in an element will affect the
arrangement in the adjacent elements, and the following cases often arise:
• at beam-to-column intersections where the beam reinforcement must avoid the column reinforcement, which is
likely to be cast into the concrete before the beam reinforcement is fixed
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• at beam-to-beam intersections where levels of several layers of reinforcement in each beam must be such that
they will pass over each other and give the correct cover to the upper and lower layers
• at slab-to-beam intersections the cover over the reinforcement in the beam must be sufficient for the top steel in
the slab to pass over the beam with the correct cover
Generally, it is advisable early in the design to establish a system for achieving this, particularly in projects on which
several detailers may be working simultaneously on adjacent structural elements.
Flexible detailing should be carried out so that reinforcement cages can be prefabricated or fixed in situ. Figure 4.1
shows a typical layout to achieve this. The decision to preassemble the reinforcement will normally be taken by the
contractor. However, the designer and detailer should keep the possibility in mind.
Figure 4.1: Internal beam/column intersection — flexible detailing of reinforcement
Column bars
straight through
junction
Link hanger bars stop
short of column face
Top support bars and
primary beam bars placed
above secondary beam bars
Secondary
beam
Primary
beam
Bottom
support bars
Bottom span bars
stop short of
column face
Bottom span bars stop
short of column face
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4.2.2 Intersection and layering of reinforcement
The physical size and shape of bars affects how the intersection and layering of bars is arranged. Figures 4.2–4.4
show the intersection of a complex beam and column intersection (and the following notes provide guidance to the
detailer):
1. Every column bar must be retained by a link except where the distance between column bars is ⩽150mm,
in which case every other bar should be retained by a link.
2. Where column reinforcement is bent out, e.g. top-lift of column, the position should be clearly shown in order to
maintain the correct concrete cover and clearance for slab and beam reinforcement. This may be in layer three for
ease of fixing and to avoid clashing.
3. Where the secondary-beam reinforcement has increased top cover, check that the resulting reduction in lever arm
is satisfactory (Section 5.1.6).
Figure 4.2: Elevation of reinforcement at beam/column intersection
Column reinforcement
from above
cranked inside
Crank 1:12
Check that when column
bars are cranked in they
do not foul any other
reinforcement
1
Compression or tension
lap depending on design
50
12
Kicker
Hole for vibrator, allow
75mm space for every
300mm of beam width
See note 3
See note 2
Check sufficient space for slab
reinforcement at correct cover
Nominal longitudinal lacing bar
Cross ties at 1000 crs to limit
free height of link to 400mm
Check concrete cover
is maintained to link
Spacer bars
See enlarged detail
Check whether chamfers/fillets
are required (they may affect
cover to reinforcement)
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Figure 4.3: Detail of beam corner
See Section 5.2.5
If corner bar has to move to
the right use smaller diameter
to fit into radius of link.
Check with designer
Link
Spacer bars at 1000
Link
Check that if main bar is
displaced it will not foul
any other bar
Check that standard radius for both links and secondary beam
reinforcement will pass between main reinforcement
Figure 4.4: Plan of reinforcement at beam/column intersection
Check there is sufficient space between links to
allow concrete and a vibrator to pass through.
When calculating actual space between links
remember to add thickness of returned legs of link
Returned leg of link
With large columns it is
advisable to keep central area
free of links to allow access
for cleaning out formwork
prior to concreting
Check minimum spacing
(see Sections 6.3.2.2 and 6.4.2)
Check whether chamfers/fillets are
required (they may affect cover
to reinforcement)
Denotes column bars from below
Beam bar
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4.2.3 Preformed cages
The use of preformed cages can improve the speed and efficiency of work on site (assuming adequate storage,
craneage and correct handling). It allows the contractor to assemble a large proportion of the reinforcement in one
place, and from there to lift the cages into position using cranes. Prefabrication of reinforcement cages in either a
designated site or off site, may have site safety benefits.
Flexible detailing
The term ‘flexible detailing’ is used to describe the method of detailing end bars (as separate from the main
longitudinal bars of an element). This method ensures that the correct end cover can be achieved by a limited
amount of telescoping at the splice. It also encourages the detailing of preformed cages. A typical example is the
detail of separate bottom splice bars at the supports of continuous beams which lap on to the main span bars.
Internal beam/column intersection
The beam/column intersection (Fig. 4.1) demonstrates some basic rules in the preferred method of detailing such
cages, namely:
• neither the bottom span bars nor the link hanger bars extend into the column
• continuity through the column is provided by the main support bars and by bottom support bars of appropriate sizes
This arrangement of steel has two major advantages. Firstly, the links, bottom span bars and link hanger bars can be
completely prefabricated. Secondly, since the support bars do not have to be positioned in the corners of the links,
there is considerable scope, without resorting to cranking, for them to be positioned to avoid column or intersecting
beam reinforcement.
External beam/column intersection
The method of connecting a beam with an edge column (Figure 4.5) should take account of the construction
sequence. U-bars may be placed into the column reinforcement. These can be fitted after the column below has
been cast and before the prefabricated beam cage is fixed in position.
Note: U-bars must be positioned as close to the far face of the column as possible.
Figure 4.5: External beam/column intersection — flexible detailing of reinforcement
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Where the design requires L-bars with the vertical leg to be fixed into the lower column (MD S2), their position should
be clearly shown on the drawings. The beam L-bars are cast into the lower column before the prefabricated beam
cage is placed in position (Figure 4.6). It should be noted that this detail can delay construction if the reinforcement
is not fixed in the correct position.
Figure 4.6: External beam/column intersection — main top-beam bars bent down into column
4.2.4 Straight bars
Straight bars are easier to detail, supply, transport and fix than bars with bends. They should be used wherever
possible.
4.2.5 Welded fabric
Where the same fabric is used throughout, it is good practice to identify the perimeter and note the type of fabric
(including orientation), layers, laps, etc. Where the fabric type varies, individual locations should be shown.
The number of fabric sheets in a set should be stated only once on the drawing.
Layering of fabric sheets can be avoided by clearly stating/scheduling the use of ‘flying end’ fabrics, or by suitable
detailing of purpose-made fabrics.
Where complicated detailing of fabric sheets is required e.g. for voided slab construction, manufacturers will often
be able to assist.
Also see Sections 5.1.11 and 6.2.2.14.
4.2.6 Chairs
BS 797317,18 provides the specification for proprietary chairs. In general, this Manual does not include the detailing of
top steel support chairs since this is considered to be the contractor’s responsibility. An exception to this concerns
multi-column foundations and rafts (Section 6.7.2).
4.3 Precast concrete
Where congestion of reinforcement occurs in precast concrete it may be necessary to fabricate a prototype before
finalising the details. It is essential to check:
• cover shown on drawing with that assumed in the calculation
• cover to reinforcement actually achieved on site
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Standard method of detailing structural concrete (4th edition)
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4.4 Checklist for detailer
• Study and be familiar with what is to be detailed. Check that calculations, setting-out details, concrete profiles,
services, concrete covers, type of reinforcement, and the concrete grade required, are known.
• Decide which scales are to be used.
• Plan out the contents of the drawings and therefore the number required.
• Determine which are secondary and which are main beams from calculations and GA drawings;
check direction of slab spans and layering of slab reinforcement.
• Determine setting-out of column reinforcement.
• Consider any difficult junctions and draw sketch details to a scale of 1: 10 or larger to clarify.
• Check that beam reinforcement will pass column reinforcement.
• Check beam-to-beam connections and ensure layers of reinforcement do not clash.
• Check location of laps, remembering maximum lengths of bar available.
• Detail all beams in one direction, then all beams in the other direction.
• Draw sufficient sections or details to show reinforcement arrangement — not only in simple areas but particularly
in congested areas of reinforcement.
• Check wording required for title boxes, notes, job number and drawing number.
• Produce bar or fabric schedules, using a print of the drawing and mark off bars as they are listed;
update drawing with errors found during scheduling.
• Provide copies of both drawing and schedules for checking by another competent person.
4.5 Schedules and scheduling
4.5.1 General
Scheduling is the operation of listing the location, mark, type and size, quantity, length and bending details of each bar
or sheet of fabric. When dealing with bars, the completed lists are called ‘bar schedules’ (Figure 4.7). The bars should
be grouped together for each structural unit, e.g. beam, column, etc. In a building the bars should be listed pour by
pour, element by element, level by level, floor by floor, to allow the reinforcement to be called-off without error.
Separate schedules should be prepared for fabric reinforcement using a form fabric schedule (Figure 4.8).
Fabrics should be grouped together according to their BS reference number and sheet size. For cutting and bending
purposes, schedules should be provided separately (A4 size) and not as part of the detailed reinforcement drawings.
Each schedule should be a document complete in itself, and reference to earlier schedules by the use of terms such
as ‘as before’ or ‘repeat as 1st floor’ should not be made. Schedules and drawings should have the same revision to
ensure the latest schedule and drawing is used.
Schedules are used by the:
•
•
•
•
•
•
•
detailer
person checking the drawing
contractor who orders the reinforcement
organisation responsible for fabricating the reinforcement
steel fixer
clerk of works or other inspector
quantity surveyor
The schedules should have simple consecutive reference numbers not exceeding six characters, and should be
cross-referenced to the relevant drawing number. A convenient way of achieving this is to use the first three
characters to refer to the drawing number (implying that the task will be divided into units with a maximum number of
999 drawings per unit), to use the next two characters to describe the schedule number (starting at 01 and not
exceeding 99 schedules per drawing), and to reserve the last character for revision letters. If an internal job number
or other internal reference number is used, it is suggested that this should be incorporated in the site reference,
rather than extending the reinforcement schedule reference. Drawing and schedule numbers may be determined
using the numbering systems found within collaborative tools.
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Figure 4.7: Typical bar schedule
Paper width 210mm or 297mm (landscape, columns in same order, widths pro rata)
5
25
9
9
9
9
9
13
13
12
35
Consultant/Detailer name/logo
Project:
Member:
Level:
Pour No:
Beam 18
12
Job No:
New Library Surbridge
Ring Beam
Level 2
Pour 4
Drawing No:
Date Prepared:
Prepared By:
Bar Type No. No. Total Length Shape
mark and
of
in
no. of each Code
size mbrs each
bar†
mm
12
16-01-20
SSK
C*
mm
D*
mm
(160)
(160)
B12
1
80
80
2200
51
500
500
02
B20
1
48
48
3000
11
190
(2850)
03
B16
1
80
80
3075
21
1450
225
E04
B16
1
20
20
775
99-xxx 500
12
12
Page No:
Rev:
Date Revised:
Checked By
Status:
2200-41983
B*
mm
01
12
50200796
A*
mm
E*
mm
F*
mm
R*
mm
(1450)
(300)
13
6
1 of 4
01
31-01-20
AMB
C
Weight Rev
(kg)
156
01
355
01
388
01
24
01
47
01
682
01
197
01
COUPLER MANUFACTURER AND TYPE
TO BE ADDED TO THE NOTATION
STANDARD FEMALE
COUPLER
(B)
A
E05
B16
1
20
20
1500
99-xxx 1500
COUPLER MANUFACTURER AND TYPE
TO BE ADDED TO THE NOTATION
21 × 10 = 210
Paper length 297mm or 210mm (landscape, columns in same order, lengths pro rata)
10
15
Member
12
A
STANDARD MALE
THREADED COUPLER
06
B32
1
12
12
9000
00
9000
07
S16
1
25
25
5000
00
5000
08
D16
1
160
160
1600
00
1600
404
01
09
B16
1
50
50
2000
99-xxx 2000
158
01
Austenitic Ferritic (Duplex) 1.4501
COUPLER MANUFACTURER AND TYPE
TO BE ADDED TO THE NOTATION
A
B
C
THREADED END WITH
HEADED END
This schedule conforms to BS 8666:2020
Page Total 2411 kgs
37
* Specified in multiples of 5mm. † Specified in multiples of 25mm
Page 1 of 4
Derived/adapted from BS 8666:2020
Status:
P Preliminary
T Tender
C Construction
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Figure 4.8: Typical fabric schedule
Consultant/Detailer name/logo
Project:
Member:
Level:
Pour No:
Job No:
New Library Surbridge
Ring Beam
Level 2
Pour 4
Drawing No:
Date Prepared:
Prepared By:
BS reference or sheet details
Fabric
mark
Type
No. and Pitch
†
of size
wires mm mm
Length
†
mm
Overhangs
O2
O1
O3
O4
mm mm
Page No:
Rev:
Date Revised:
Checked By
Status:
50200796
2200-41984
16-01-20
SSK
1 of 4
01
31-01-20
AMB
C
Special details and/or bending dimensions
Sheet
length
“L”†
m
Sheet
width
“B”†
m
No.
of
sheets
Shape
Code
Bending
instruction
A*
B*
C*
D*
EIR*
mm
mm
mm
mm
mm
Rev
letter
Purpose-made fabric example
20 H10 125 6600 300 300 6.6
12
38
04
25 H8 250 2450
25 50
150 6300
L
2.45
Standard fabric example
05
B 785
6.2
2.2 12
37
500
B
L
This schedule conforms to BS 8666:2020
* Specified in multiples of 5mm. † Specified in multiples of 25mm
Status:
P Preliminary
T Tender
C Construction
Derived/adapted from BS 8666:2020
The form of bar and fabric schedule and the shapes of bar used should be in accordance with BS 8666.
The preferred shapes account for more than 95% of the reinforcement used. It is preferable that bars should be
listed in the schedule in numerical order.
It is essential that the bar mark reference on the label attached to a bundle of bars refers uniquely to a particular
group or set of bars of defined length, size, shape and type used for the project. This unique reference is achieved
by a combination of the bar schedule reference number and the bar mark number. To comply with BS 8666, both
the schedule reference number and the bar mark must appear on the label attached to the bundle of bars.
Thus, the bar schedule reference number 046 02A in the example that follows (note the importance of the zeros)
and the bar mark are associated, and the bar-marking system that follows is based on the assumption that the
bar schedule reference numbering system set out in BS 8666 is used precisely as described with no variations.
Each schedule must have a different reference number and must refer only to one drawing. Such terms as
sheet number, page number, 1 of 8, 2 of 8, etc. and such practices as including the date, the year, the
detailer’s initials, the job number or other internal reference as part of the reference number must not be used
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with this combined system of bar marking and schedule numbering. Each of these practices may have intrinsic
merits, but they should be abandoned in favour of a system that is universally applicable and universally
understood.
Correct scheduling in the UK is not possible without a thorough knowledge of BS 8666.
The bar size is not part of the bar mark, and prefixes or suffixes of letters or other characters to describe the location
of the bars should not be included. The exception is when bars of varying shape or length are used and are
described on the drawing thus:
8H20-1(a to h)-150
Note this may appear to be one bar mark, but in effect it is delivered as eight bars collected together that have to be
sorted on site. This should generally be avoided where possible (or bars should be grouped to reduce the number of
varying bars). It is good practice to discuss with the contractor prior to implementation.
The bar mark given on the schedule is therefore 1a, 1b, 1c.
On a small project with only a few drawings it may be convenient to start at bar mark 1 and carry on through the
whole task in a consecutive sequence. On larger projects it may be more convenient to start scheduling each
drawing with bar mark 1, relying on the site to distinguish between mark 1 on drawing 1 and mark 1 on drawing 2.
When top and bottom reinforcement are detailed on separate drawings it is advisable to allocate a group of
bar marks for each drawing, e.g. bottom reinforcement bar marks 1–99, top reinforcement bar marks 100–199.
When it becomes necessary to revise a bar item on the schedule or drawing, both the drawing and schedules
should be re-issued.
4.5.2 Allowances for tolerances/deviations
Cover to reinforcement is liable to variation on account of the cumulative effect of inevitable small errors in the
dimensions of formwork; and the cutting, bending and fixing of the reinforcement.
All reinforcement should be fixed to the nominal cover shown on the drawings; using spacers of the same nominal
size as the nominal cover (Section 5.2.1) and the correct size of chairs to achieve the nominal cover.
Where a reinforcing bar is to fit between two concrete faces (e.g. a single rectangular link in a beam), the dimensions
on the schedule should be determined as the nominal dimension of the concrete, less the nominal cover on each
face, and less an allowance for all other errors (Table 5.6).
It should be noted that the actual size of the bar is larger than the nominal size (Section 5.1.6).
4.5.3 Out-of-plane deviations
Due to the inherent properties of the reinforcement, bars with two or more bends may (albeit rarely) deviate
out-of-plane. For 16mm bars and smaller this does not normally cause difficulties with fixing bars on site.
For bars larger than 16mm the issue may be more significant and where critical, consideration should be given to
specifying the bars using a Shape Code 99 with a limit on out-of-plane deviations. This limit should be agreed
with the fabricator. Alternatively, the number of bends in a bar could be restricted e.g. specifying L-bars rather
than U-bars.
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4.6 Procedure for checking reinforcement drawings and schedules
The checking of drawings comprises three stages (detailed in Box 3).
Box 3: Checking of reinforcement drawings
Stage 1: Design check
• Do the drawings correctly interpret the design as described in (and supported by) the checked calculations?
Stage 2: Detailing check
• Has the drawing been prepared in accordance with current standards and does it meet the requirements of
the particular task?
• Does the information agree with the GA and other associated drawings, and bar and fabric schedules — with
particular reference to dimensions, termination of reinforcement, construction details, notes, etc?
• Can the details provided be constructed in practice?
Where standard drawings are used they should be checked to ensure they represent the actual structure correctly.
When alterations are made, they should be checked to ensure original design intentions have not been lost.
Stage 3: Overall check
• Is the drawing, in all general aspects, suitable for its purpose and truly reflective of the project’s
requirements?
• Does each drawing have a ‘box’ containing the name of the detailer and checker?
Specific checks (note this list is unlikely to be fully comprehensive):
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Is general presentation and orientation correct?
Are title, scales and drawing numbers correct?
Are revision letters correct and their location shown?
Are sufficient sections and details given?
Are general notes complete and can they be understood?
Is spelling correct?
Have all standards and codes of practice been complied with?
Are setting-out dimensions correct?
Have check dimensions been included?
Do running dimensions agree with overall dimensions?
Can materials specified be obtained?
Do numbers, sizes and reinforcement agree with the relevant calculations and other drawings?
Has cross-referencing to other drawings and bar and fabric schedules been provided?
Where applicable, is quantity correct?
Are chamfers, fillets and drips, and other similar features shown?
Are all projections reinforced?
Is the cover specified and correct?
Are splices and laps in correct position?
Do splices suit construction joints?
Is there congestion of reinforcement?
Are large-scale details required?
Are cranks required where bars cross?
Is spacing of reinforcement correct both on plan and section?
Is reinforcement required for anti-crack or fire resistance?
Do hooks foul other reinforcement?
Are schedules correct?
Have drawings been signed by the detailer and checker?
Where required, are the spacers and chairs shown/specified?
Have transverse bars been provided where change in direction of longitudinal reinforcement is greater than 1 in 12?
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5 Technical information and
requirements
5.1 Reinforcement
5.1.1 General
BS 444919 specifies the requirements for weldable reinforcing steel manufactured from bar, coil and decoiled product
in accordance with Annex C of BS EN 1992. BS 4449 meets the requirements of BS EN 1008020.
BS 448321 specifies the requirements for factory-made machine-welded steel fabric manufactured from deformed
wires conforming to BS 4449 and Annex C of BS EN 1992. BS 4483 meets the requirements of BS EN 10080.
BS 448222 contains provisions for plain, indented and ribbed wire. The characteristic strength and ductility
requirements are aligned with Grade B500A of BS 4449. This standard is complementary to the requirements of
BS EN 10080 and Annex C of BS EN 1992, except that no fatigue performance is specified and the Eurocode only
relates to ribbed and not plain or indented steel.
In the UK, CARES5 is the certification body that ensures reinforcement is correctly produced, processed and
handled. It covers steel production and billet casting, and the rolling, cutting, bending, fabrication and welding of
reinforcement. CARES also operates a Technical Approval scheme, relevant for products derived of reinforcement,
e.g. reinforcement continuity systems, punching shear reinforcement systems and couplers.
5.1.2 Strength/ductility properties
BS 4449 and Annex C of BS EN 1992 specify the strength and ductility requirements for three grades of ductility:
Grade A, Grade B and Grade C. The tensile properties are given in Table 5.1. Grade 250 (mild steel) plain bars are
no longer commonly available. Where available they may be found in sizes 8, 10, 12 and 16mm to BS EN 13877-323.
Other bar types are as defined in the project specification.
Table 5.1: Tensile properties of reinforcement
Grade
Yield strength Re (MPa)
Stress ratio Rm/Re
Total elongation at max. force Agt (%)
B500A
500
⩾1.05
⩾2.5
B500B
500
⩾1.08
⩾5.0
B500C
500
⩾1.15 <1.35
⩾7.5
Notes:
Rm = tensile strength.
Re = yield strength.
Derived/adapted from Table 4 of BS 4449.
5.1.3 Bar identification
Reinforcement can be identified by the arrangement of ribs with dots or spaces between them. For Grade A steel,
the bars have two or more series of parallel transverse ribs with the same angle of inclination and the same direction
for each series. For Grade B steel, the bars have two or more series of parallel transverse ribs. For bars with two or
three rib series, one of the series is at a contrary angle to the remainder; and for bars with four rib series, two of the
series are at a contrary angle to the remainder. For Grade C steel, the bars have the same rib series as Grade B.
However, in each rib series, the ribs shall alternate between a higher and lower angle with respect to the bar axis
(differing by at least 10°).
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The identification of country of origin is as follows:
UK, Ireland, Iceland:
Austria, Czech Republic, Germany, Poland, Slovakia:
Belgium, Luxembourg, Netherlands, Switzerland:
France, Hungary:
Italy, Malta, Slovenia:
Denmark, Estonia, Finland, Latvia, Lithuania, Norway, Sweden:
Portugal, Spain:
Cyprus, Greece:
Other (non-European) countries incl. China, Egypt, Nigeria, Russia, Saudi Arabia and Ukraine:
5
1
2
3
4
6
7
8
9
ribs
rib
ribs
ribs
ribs
ribs
ribs
ribs
ribs
All CARES-approved reinforcing steel is identified by rolling marks on the surface of the bar at intervals of ⩽1.5m
(Figure 5.1).
Figure 5.1: Rib patterns identifying ductility grades
Example rib pattern for Grade B500A
Example rib pattern for Grade B500B
Example rib pattern for Grade B500C
The rolling mark comprises:
• the CARES certification mark
• the country
• the mill
Figure 5.2 shows the CARES certification mark and indicates that the product is CARES-approved.
The CARES Approved Company tool at: www.ukcares.com/approved-companies may be used to source the country
and mill that produced the reinforcement.
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Figure 5.2: Manufacturer’s identification mark using CARES’ product marking system
Bar mark 5-25 is shown below:
The
CARES
mark
5 ribs
2 ribs
5 ribs
Notes:
‘Dot-dash-dot’ denotes CARES-approved steel.
Number of ribs between next two dots after CARES certification mark, indicate country of origin
(in this example, country = 5).
Number of ribs between next two dots indicates steel mill number (in this example, mill number = 25).
Dash denotes Grade 500.
5.1.4 Notation
The notation (Table 5.2) should appear before the bar diameter, so if a Grade B bar of 20mm diameter is required,
B20 should be used. Note that Grade A bars are only available in diameters of ⩽12mm. Also, the majority of
reinforcement supplied in the UK is Class B or C, so Class B reinforcement should generally be specified.
Table 5.2: Notation of steel reinforcement
Type of reinforcement/fabric (in accordance with BS 4449)
Notation
Strength (MPa)
For diameters ⩽12mm, Grade B500A, Grade B500B or Grade B500C
For diameters >12mm, Grade B500B or Grade B500C
H
500
Reinforcement Grade B500A
A
500
Reinforcement Grade B500B
or B500C
B
500
Reinforcement Grade B500C
C
500
Smooth plain round bar, straight Shape Code 00, for dowel bars only
conforming to BS EN 13877-3
D
The specific grade/s and steel designation number/s of ribbed stainless steel
conforming to BS 67446 and BS EN 1008824 shall be stated on each relevant
bending schedule
S
Reinforcement of a type not listed in this table, having material properties that
are defined in the design or contract specification
X
Derived/adapted from Table 1 of BS 8666.
5.1.5 Specifying stainless steel
The grade and type of stainless steel reinforcement should be specified by the designer in accordance with BS 67446.
The detailer should identify the stainless steel reinforcement on the bar schedule by using the ‘S’ notation in
accordance with Table 1 of BS 8666 and should communicate the grade and type of stainless steel reinforcement
specified by the designer. The detailer should be aware of potentially longer lead times for stainless steel
reinforcement compared to plain carbon steel reinforcement.
5.1.6 Sizes of reinforcing bars
Design and detailing of reinforcement is based on ‘nominal sizes’ of bars and wires. The nominal size is the diameter
of a circle with an area equal to the effective cross-sectional area of the bar or wire.
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The word ‘size’ rather than ‘diameter’ is used to describe the nominal size of bars. For example, on a nominal size
20 bar, the maximum diameter measures 23mm because of the surface deformations. Most deformed bars can be
contained in a circumscribing circle 10% larger than the nominal size of bar. However, because of variations in rib
size, individual sections can measure 13 or 14% more than the nominal size at the largest cross-dimension
(Table 5.3). Examples where special care is required are given in Section 5.3.
Table 5.3: Comparison between nominal size of bar and the actual max. size (mm)
Nominal size
61
82
10
12
16
20
25
32
40
501
Actual max. size
8
11
13
14
19
23
29
37
46
57
1. Not a preferred size of bar.
2. Check availability in UK.
Preferred sizes of high yield reinforcing bars in the UK are 8, 10, 12, 16, 20, 25, 32 and 40mm. Size 6 is not
commonly available owing to low demand and infrequent rollings. Size 50 is not generally stocked by fabricators but
can be available to order and is dependent on rolling programmes. Since off-cuts of 50mm are useless, the size
tends to be ordered cut-to-length from the mill and requires careful planning. Consideration should be given to using
the commonly available size 40mm in bundles instead of using 50mm. In the UK some of the larger steel suppliers
choose not to stock size 8 bars, so availability should be checked before specifying.
Note that large bar sizes may be difficult to handle and may require suitable cranage in accordance with Health and
Safety regulations. Table 5.4 gives the cross-sectional area and mass per metre of the bars.
Table 5.4: Actual area and mass of bars
Bar size (mm)
Cross-section (mm2)
Mass per metre run (kg/m)
6
28.3
0.222
8
50.3
0.395
10
78.5
0.616
12
113.1
0.888
16
201.1
1.579
20
314.2
2.466
25
490.9
3.854
32
804.2
6.313
40
1256.6
9.864
50
1963.5
15.413
Derived/adapted from Table 7 of BS 4449.
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5.1.7 Length and overall dimensions of reinforcing bars
Maximum bar lengths need to align with good practice, site pour layouts and site requirements/restrictions.
Table 5.5 provides guidance.
Table 5.5: Recommended maximum straight bar lengths
Bar size
Length
10–16mm
Approx. 6–9m
20–40mm
Approx. 12m
Note: Approx. 12m may be used for size 16mm bars depending on pour locations and layouts.
The stock length of bar is 12m, and the maximum length of bar available and transportable is 18m, but extra cost
and delays may be involved if 12m lengths are exceeded.
For a bent bar to be transportable the shape should be contained by an imaginary rectangle where the shortest side
does not exceed 2.75m.
5.1.8 Rebending bars
The minimum mandrel diameter for bending of bars for sizes ⩽16mm is 4∅ and for bar sizes >16mm is 7∅.
Generally, rebending bars on site should not be permitted. Where it can be shown that the bars are sufficiently
ductile (e.g. Class B or Class C steel), bars ⩽12mm size may be rebent provided that care is taken not to reduce
the mandrel size below 4× the bar size. Larger bar sizes may be rebent only where they are within a proprietary
reinforcement continuity system which holds a Technical Approval issued by a suitably accredited product
certification body (e.g. CARES) and it has been shown by regular testing that no damage to the properties of the
bar occur. Note that where rebending of bars is undertaken it can cause damage to the concrete surface.
5.1.9 Large diameter bends
The designer will normally be responsible for the calculation of large diameter bends, but the detailer should be
aware of their existence and should be able to recognise when a large radius bend is required vs. a standard bend.
Tables in Appendix H give values of mandrel size for various concrete grades for a given steel design stress.
Examples of where larger diameter bends are required include:
•
•
•
•
end of column and wall connections to beams or slabs
cantilever retaining walls
corbels
bottom bars for pile caps
5.1.10 Structural tying reinforcement to ensure
Tying reinforcement is not intended to be additional
minimum to ensure the robustness of the structure.
sufficiently ductile, and Class A reinforcement is not
robustness
reinforcement to that required by the design, but is required as a
It should be noted that reinforcement used for tying should be
considered suitable for tying purposes.
Refer to Clause 9.10 of BS EN 1992-1 for further information.
Peripheral ties
At each floor and roof level there should be an effective continuous peripheral tie within 1.2m of the edge of the
structure. The peripheral tie should be able to resist a design tensile force equal to (20 + 4no ) ⩽ 60kN where no is the
number of storeys. While this contradicts what is stated in the UK National Annex, it is considered that this reflects
the intention of the UK BSI Committee.
Internal ties
At each floor and roof level there should be internal ties in two directions approximately at right angles. They should
be effectively continuous throughout their length and should be anchored to the peripheral ties at each end, unless
continuing as horizontal ties to columns or walls. They may, in whole or in part, be spread evenly in the slabs or
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Standard method of detailing structural concrete (4th edition)
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may be grouped at or in beams, walls or other appropriate positions. In walls they should be within 0.5m of the top
or bottom of floor slabs. In each direction, internal ties should be capable of resisting a design tensile force of:
Ftie,int = [(gk + qk )/7.5](lr/5)(F1 ) ⩾ Ft kN/m
Where:
(gk + qk ) = sum of average permanent and variable floor loads (kN/m2)
= greater of distances (m) between centres of columns, frames or walls supporting any two adjacent
lr
floor spans in direction of tie under consideration
Ft
= (20 + 4no ) ⩽ 60kN/m
Maximum spacing of internal ties = 1.5lr
Horizontal ties to columns and/or walls
Edge columns and walls should be tied horizontally to the structure at each floor and roof level. Such ties should be
capable of resisting a design tensile force which is the greater of:
2Ft ⩽ ls/2.5Ft
or
3% of total design ultimate vertical load carried by column or wall at that level
Where:
ls = floor-to-ceiling height (m)
Note: Force is in kN per metre run of wall and kN per column
Tying of external walls is only required if the peripheral tie is not located within the wall. Corner columns should be
tied in two directions. Steel provided for the peripheral tie may be used as the horizontal tie in this case.
All precast floor, roof and stair members should be effectively anchored, irrespective of whether members are used
to provide other ties. Such anchorages should be capable of carrying the permanent action of the member to that
part of the structure containing the ties.
Vertical ties
Each column and each wall carrying vertical load should be tied continuously from the lowest to the highest level. The tie
should be capable of carrying a tensile force equal to the design load likely to be received by the column or wall from
any one storey under accidental design situation (i.e. loading calculated using Expression 6.11b of BS EN 199025).
Continuity and anchorage of ties
Ties in two horizontal directions shall be effectively continuous and anchored at the perimeter of the structure.
They may be provided wholly within the in situ concrete topping or at connections of precast members. Where ties
are not continuous in one plane, the bending effects resulting from the eccentricities should be considered.
Ties should not normally be lapped in narrow joints between precast units. Mechanical anchorage should be used
in these cases.
5.1.11 Fabric reinforcement
There are two classifications of fabric reinforcement; standard and purpose-made. For detailing and scheduling of
fabric see Section 4.2.5. For British Standard fabrics see Appendix J.
Standard fabric
These are categorised by BS 4483, and have distinct classifications according to the wire orientation and the
cross-sectional steel area. Standard sheet size is 4.8m × 2.4m, with the edge overhangs being 0.5× wire centres.
There are three main types:
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• ‘A’ or ‘square’ fabrics have wires of equal size at 200mm centres in both directions. Wire sizes are 5–10mm,
but exclude 9mm.
• ‘B’ or ‘structural’ fabrics have the main reinforcement in the long direction at 100mm centres, with transverse
reinforcement at 200mm centres. Main wire sizes are 5–12mm, excluding 9 and 11mm.
• ‘C’ or ‘long’ fabrics have the main wires at 100mm, with the transverse steel being nominal size at 400mm
centres. Main wire sizes are 6–10mm.
In addition, there is a lightweight fabric (D49), which is often used for crack control. ‘Flying end’ fabrics are also
available as a standard product from most manufacturers. These have extended overhangs, designed to eliminate
the build-up of layers that occur at lapping points with standard fabric. Sheet sizes and overhangs may vary between
manufacturers.
Purpose-made fabric
Purpose-made sheets can be specified using standard reinforcing bars. These bars can be set at varying pitches
and edge projections. Sheet sizes can vary, with due consideration given to handling and transportation.
Bending of fabric
Generally, all fabrics can be cut to size, and bent to most BS shapes. Manufacturers will normally be able to offer
guidance. Bending of wire sizes >12mm may not be possible by standard machine manufacture.
Laps in fabric
Layering of fabric sheets can be avoided by using flying end fabrics, or by suitable detailing of purpose-made fabrics
(Section 6.2.2.14).
5.2 Cover to reinforcement
5.2.1 General
The required nominal cover should be specified by the designer. Cover to reinforcement is required to ensure:
• the safe transmission of bond forces. The minimum cover should not be less than the bar size (or equivalent
bar size for bundles of bars)
• the protection of the steel against corrosion
• adequate fire resistance (BS EN 1992-1-22 refers to ‘axis distance’ for cover). This is the distance from the centre
of reinforcing bar to the surface of concrete
The importance of achieving cover cannot be overstated since it often determines the structure’s durability.
Further guidance on determining concrete cover can be found in Manual for the design of concrete building
structures to Eurocode 2 26 and How to design concrete structures to Eurocode 2 27.
Refer to Sections 4 and 5 of BS EN 1992-1 for further information.
Nominal cover
Nominal cover is the cover specified by the designer and shown on the structural drawings. Nominal cover is defined
as the minimum cover cmin plus an allowance in design for deviation to all steel reinforcement Δcdev . It should be
specified to the reinforcement nearest to the surface of the concrete (e.g. links in a beam).
The nominal cover to a link should be such that the resulting cover to the main bar is at least equal to the size of
the main bar (or to a bar of equivalent size in the case of pairs or bundles of three or more bars) plus Δcdev .
Where no links are present, the nominal cover should be at least equal to this size of the bar plus Δcdev .
Where special surface treatments are used (e.g. bush hammering), the expected depth of treatment should be added
to the nominal cover.
Nominal covers should not be less than the maximum (nominal) aggregate size.
Refer to Clause 4.4.1.1 of BS EN 1992-1 for further information.
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Deviation, Δcdev
The recommended value for Δcdev = 10mm. Where it is specified that only a contractor with a recognised quality
system shall do the work, Δcdev may be reduced to 5mm. The designer should confirm the value to be used and
whether this is to be specified on the reinforcement drawings.
Refer to Clause 4.4.1.3 of BS EN 1992-1 for further information.
Limit to positive tolerance, Δc(plus)
In addition to the negative tolerance given in BS EN 1992, BS EN 1367028 advises on a max. positive tolerance to
avoid excessive cover and a reduction in the section strength. Δc(plus) varies with the size of the member (Table 5.6).
Table 5.6: Positive and negative tolerance
∆c(plus)
cnom
∆c(minus)
cmin
Overall section depth h (mm)
Δc(plus) , mm
⩽150
10
400
15
⩾2500
25
Notes:
Linear interpolation for intermediate values may be used.
Values for Δc(plus) are for Class 1 tolerances. Where Class 2 tolerances are required, refer to BS EN 13670.
Derived/adapted from Figure 4 of BS EN 13670.
5.2.2 Cover for durability
The exposure conditions to which the structure may be subjected determine the required cover to the reinforcement
and should be specified by the designer.
Refer to Clause 4.2 of BS EN 1992-1 for further information.
5.2.3 Cover for fire resistance
The size of structural members and cover (axis distance) required for fire resistance should be specified by the
designer.
5.2.4 Fixing reinforcement to obtain correct cover
Non-structural connections for the positioning of reinforcement should be made with steel wire tying devices (e.g. No.16
gauge annealed soft iron wire) or by welding (Section 5.5). It is not necessary to tie every bar intersection, provided that
rigidity of the cage or mat can be achieved while the concrete is being placed and vibrated.
The most common method of maintaining cover is the use of spacers and chairs. A wide range of plastic and
cementitious spacers and steel wire chairs are available. BS 797317,18 provides information concerning spacers and
their use. Layers of bars in beams can be separated by means of short lengths of bar. The spacing along the beam
should be specified on the drawings (usually 1m), and the bar spacers should be detailed on the schedules.
Normally, the method of achieving cover and position is left entirely to the contractor. However, where the detailing is
complex the designer may specify spacers and detail chairs, which should be in accordance with the requirements
of BS 7973.
Note that the weight of reinforcement can damage inserts (e.g. Styrofoam™ inserts) if not properly supported.
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5.2.5 Minimum spacing of reinforcement
The minimum clear distance between bars (horizontal or vertical) should not be less than the bar size, b (dg + 5mm),
or 20mm, where dg is the maximum size of aggregate (denoted as Dupper in BS 850029).
Where bars are positioned in separate horizontal layers, the bars in each layer should be located vertically above
each other. There should be sufficient space between the resulting columns of bars to allow access for vibrators and
good compaction of the concrete.
Note that the distance between bars is stated as a minimum, and consideration should be given to placing
tolerances — particularly when spacing for the scheduled bars is close to the minimum allowable. It may be
necessary to consider providing tolerances for critical areas.
Refer to Clause 8.2 of BS EN 1992-1 for further information.
5.3 Cutting and bending tolerances
Dimensions of reinforcement should take account of cutting and bending tolerances, which are detailed in BS 8666.
Where close-fit conditions exist, these should be considered at an early stage, otherwise increases in member size
may occur at a much later and more expensive stage in the project. Large-scale sketches may help to highlight any
problems. Where an overall/internal dimension of a bent bar is specified, the tolerance unless otherwise stated, is
given in Table 5.7. The cutting length is the sum of the bending dimensions and allowances specified, rounded up to
the nearest 25mm.
Table 5.7: Cutting and bending tolerances
Bar dimension
Tolerance (mm)
Straight bars, all lengths including bars to be bent
±25
Bending dimensions <1m
±5
Bending dimensions 1–2m
+5 to −10
Bending dimensions >2m
+5 to −25
Wires in fabric
Greater of ±25 or ±0.5% length of bar
Derived/adapted from Table 7 of BS 8666.
Bending dimension
For practical reasons there is a minimum end dimension P to allow for cutting and bending bars (Table C.1 in
Appendix C). Note that for shear links where the bend is <150° the end dimension is increased.
For shapes with two or more bends in the same or opposite directions (whether in the same plane or not), the
overall dimension given on the schedule shall include a minimum straight of 4∅ between the curved portion of the
bends. The minimum requirements are given in Table C.2 (Appendix C).
For hooks, the anticipated actual hook diameter q is given in Table C.1 and is calculated as 3∅ + 2r and rounded
up to the nearest whole 5mm increment. The values provided are based on the minimum radius for scheduling and
include an allowance of 1∅ for ‘springback’, which occurs when the bar tries to return to its original shape after
being bent. For mandrel diameters larger than the minimum, the value of q may be calculated as described
previously.
‘Closed’ detailing tolerances
Where a closed system of detailing has been used and the reinforcement is required to fit between two concrete
faces (e.g. links in beams and columns), a deduction on the scheduled length should be made to allow for member
dimensional tolerances (Table 5.8). An additional 10mm should be deducted when determining the cutting length of
straight bars when their ends are placed between two concrete faces.
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Table 5.8: Standard deductions between two concrete faces
Distance between concrete faces (mm)
Deduction (mm)
⩽200
5
⩽400
10
⩽1,000
15
⩽2,000
20
>2,000
30
Derived/adapted from Table 3 of BS 8666.
Figures 5.3–5.5 illustrate typical situations. The fitting of the whole arrangement can affect the actual position of a bar
and can sometimes make compliance difficult. It is important to consider that the maximum bar diameter exceeds
the notional bar ‘size’ (Section 5.1.6).
Figure 5.3: Beam corner detail
H16
44
13
H40
B
A
Notes:
Actual size of H16 may be 18mm (+10%).
Curve in H16 link causes further increase of cover to main bar (H32).
Main bar in position A has increased cover to one of the faces of 48mm.
Main bar in position B has increased cover to both faces of 14mm.
Position of bar will affect both crack-width and fire resistance. It may also cause problems at
column intersection where clashes of reinforcement may occur.
40
Figure 5.4: Beam/column junction
Column link
H12
40
40
H32
H32
H32
H32
H32
Beam bars
275
Notes:
Since tolerance deduction is 10mm for bending dimensions it is possible that space
inside link (H12) could be 275 – 80 – 2(12 + 1) – 10 = 159mm.
This is just under 5 × H32. Unfortunately it does not take into account actual bar size
(+10%). Actual space required by these bars is 176mm.
Hence, they won’t fit.
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Figure 5.5: Flanged beam
20
B
A
H16
H25
H25
H25
150
H16
20
Notes:
Without taking tolerances into account the gap between bars A and B is 3mm.
However with link tolerance of 5mm and effect of actual size of bar, position of
bar A could be 12mm lower.
Weight of cage is likely to cause the tolerance to be taken out at top, and
cover to bar B could finish up less than 10mm if level of slab formwork was
2 or 3mm out.
5.4 Anchorage and lap lengths
5.4.1 General
The bond between concrete and reinforcement determines the anchorage and lap lengths. The designer should
ascertain these based on guidance in BS EN 1992. Where the designer has not provided anchorage and lap lengths,
values given in the Tables in Appendix E of this Manual may safely be used. The description of bond conditions for
different positions of the reinforcement in the concrete are indicated in Figure 5.6.
Figure 5.6: Description of bond conditions
h
‘Good’ bond conditions
‘Poor’ bond conditions
h
(a) Vertical bars
(b) h #250mm
(c) h >250mm
5.4.2 Laps in reinforcement
BS EN 1992 recommends that under normal circumstances, laps between bars should be staggered and not located
in areas of high moments/forces (e.g. plastic hinges). They should be arranged symmetrically in any section. The
arrangement of lapped bars should comply with Figure 5.7.
Figure 5.7: Adjacent laps
>0.3l0
l0
Fs
<50mm
<4ø
Fs
a
>2ø
>20mm
ø
Fs
Fs
Fs
Fs
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When the following provisions are met, the permissible percentage of lapped bars in tension may be 100%
(i.e. not staggered) where all bars are in one layer:
• The clear distance between lapped bars should not be >4∅ or 50mm, otherwise the lap length should be
increased by a length equal to the clear space where it exceeds 4∅ or 50mm.
• In adjacent laps, the clear distance between adjacent bars should not be <2∅ or 20mm, where the transverse
reinforcement is formed by links or U-bars anchored into the body of the section.
• The distance a between adjacent laps at a section is ⩽10∅ where the transverse reinforcement is not formed
by links or U-bars anchored into the body of the section.
However, it is considered that the principles of Clause 8.7.2(1)P of BS EN 1992-1-1 will be met where the laps
are not staggered and the bars size is ⩽25mm, provided the laps are detailed to occur at points of low stress
(e.g. one third/quarter of the span).
Transverse reinforcement for bars in tension
Transverse reinforcement is required in the lap zone to resist transverse tension forces. Where the diameter b of the
lapped bars is <20mm, or the percentage of lapped bars in any section is <25%, any transverse reinforcement or
links necessary for other reasons may be assumed sufficient for the transverse tensile forces without further
justification.
Where the diameter b of the lapped bars is ⩾20mm, the transverse reinforcement should have a total area Ast
(sum of all legs parallel to the layer of the spliced reinforcement) of not less than the area As of one lapped bar
(ΣAst ⩾ 1.0As ). The transverse bar should be placed perpendicular to the direction of the lapped reinforcement.
If >50% of the reinforcement is lapped at one point and the distance a between adjacent laps at a section is ⩽10∅
(Fig. 5.7) transverse reinforcement should be formed by links or U-bars anchored into the body of the section.
The transverse reinforcement provided for this should be positioned at the outer sections of the lap (Figure 5.8a).
Transverse reinforcement for bars permanently in compression
In addition to the rules for bars in tension, one bar of the transverse reinforcement should be placed outside each
end of the lap length and within 4∅ of the ends of the lap length (Figure 5.8b).
Figure 5.8: Transverse reinforcement for lapped splices
Σ Ast/2
Σ Ast/2
l0 l3
l0 l3
ΣAst/2
<150mm
Fs
Fs
<150mm
Fs
Fs
l0
l0
4ø
a) bars in tension
Σ Ast/2
l0 l3
l0 l3
4ø
b) bars in compression
5.4.3 Additional rules for large bars
Additional rules should be applied to bar sizes >40mm. Splitting forces are higher and dowel action is greater for
such sizes. They should preferably be anchored with mechanical devices. However, where anchored as straight bars,
links should be provided as confining reinforcement in the anchorage zone. These links (Figure 5.9) should be in
addition to those provided for shear where transverse compression is not present.
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Figure 5.9: Additional reinforcement in anchorage for large diameter bars (no transverse compression)
Σ Asv > 0.5 As1
Σ Asv > 0.5 As1
Anchored bar
Continuing bar
As1
As1
Σ Asv > 0.25As1
Example:
In the left hand case
n1 = 1, n2 = 2
Σ Asv > 0.5 As1
and in the right hand case
n1 = 2, n2 = 2
The area of these should not be less than:
• Ash = 0.25Asn1 (in direction parallel to tension face)
• Asv = 0.25Asn2 (in direction perpendicular to tension face)
Where:
As = cross-sectional area of anchored bar
n1 = number of layers with bars anchored at same point in member
n2 = number of bars anchored in each layer
The additional transverse reinforcement should be uniformly distributed in the anchorage zone, and the spacing of
bars should not exceed 5× the diameter of the longitudinal reinforcement.
Large bars should not be lapped, except for sections with a minimum dimension of ⩾1m or where the stress is not
greater than 80% of the design ultimate strength.
Surface reinforcement may be required for crack control (Clauses 7.3.4, 8.8 and 9.2.4 of BS EN 1992).
Refer to Clause 8.8 of BS EN 1992 for further information.
5.4.4 Bundled bars
General
It is sometimes preferable to bundle bars to provide better compaction of concrete in heavily reinforced members.
Generally, the rules for individual bars also apply for bundles using the equivalent diameter. In a bundle, all the bars
should have the same characteristics (type and grade). Bars of different sizes may be bundled provided the ratio of
diameters does not exceed 1 :7.
In design, the bundle is replaced by a notional bar having the same sectional area and the same centre of gravity as
the bundle. The equivalent diameter ∅n of this notional bar is such that:
∅n = ∅√nb ⩽55mm
Where:
nb = number of bars in bundle
Which is limited to:
nb ⩽4 for vertical bars in compression and for bars in a lapped joint
nb ⩽3 for all other cases.
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The clear distance between bundles should be measured from the actual external contour of the bundle. The
concrete cover should be measured from the actual external contour of the bundles and should not be less than ∅n .
Where two touching bars are positioned one above the other, and where the bond conditions are good, such bars
need not be treated as a bundle.
Anchorage of bundles of bars
Bundles of bars in tension may be curtailed over end and intermediate supports. Bundles with an equivalent
diameter <32mm may be curtailed near a support without the need for staggering bars. Bundles with an
equivalent diameter ⩾32mm which are anchored near a support should be staggered in the longitudinal direction
(Figure 5.10).
Figure 5.10: Anchorage of widely staggered bars in bundle
>lb
>1.3lb
A
Fs
A–A
A
Where individual bars are anchored with a staggered distance greater than 1.3lb,rqd (where lb,rqd is based on the
bar diameter), the diameter of the bar may be used in assessing lbd . Otherwise the equivalent diameter of the bundle
∅n should be used.
For compression anchorages, bundled bars need not be staggered. For bundles with an equivalent diameter
⩾32mm, at least four links having a diameter ⩾12mm should be provided at the ends of the bundle. A further link
should be provided just beyond the end of the curtailed bar.
Lapping bundles of bars
The lap length should be calculated as for individual bars using ∅n as the equivalent diameter of bar.
For bundles consisting of two bars with an equivalent diameter <32mm, the bars may be lapped without staggering
individual bars. In this case the equivalent bar size should be used to calculate l0 .
For bundles consisting of two bars with an equivalent diameter ⩾ 32mm or of three bars, individual bars should be
staggered in the longitudinal direction by at least 1.3l0 (Figure 5.11), where l0 is based on a single bar. For this case
bar No.4 is used as the lapping bar. Care should be taken to ensure that there are not more than four bars in any
lap cross-section. Bundles of more than three bars should not be lapped.
Figure 5.11: Lap joint in tension, including a fourth bar
1
1
3
Fs
3
Fs
1.3l0
1.3l0
1.3l0
1.3l0
4
2
4
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5.4.5 Laps in welded fabric
Laps of the main reinforcement
Laps may be made either by intermeshing (nesting) or by layering of the fabrics (Figure 5.12).
Figure 5.12: Lapping of welded fabric
Fs
Fs
l0
a) intermeshed fabric (longitudinal section)
Fs
Fs
l0
b) layered fabric (longitudinal section)
Fs
Fs
l0
‘flying end’
c) fabric with ‘flying ends’ (longitudinal section)
For intermeshed fabric, lapping arrangements for the main longitudinal bars should conform to Section 6.2.2.14.
Any favourable effects of the transverse bars should be ignored: thus taking α3 = 1.0.
For layered fabric, the laps of the main reinforcement should generally be situated in zones where the calculated
stress in the reinforcement at ultimate limit state is not more than 80% of the meshed fabric (longitudinal section)
design strength.
The percentage of the main reinforcement, which may be lapped in any one section, should comply with the following:
• For intermeshed fabric, the values given in Table 5.9 are applicable.
• For layered fabric the permissible percentage of the main reinforcement that may be spliced by lapping in any
section, depends on the specific cross-section area of the welded fabric provided (As/s)prov, where s is the
spacing of wires:
• 100% if (As/s)prov ⩽1200mm2/m
• 60% if (As/s)prov >1200mm2/m
The joints of the multiple layers should be staggered by at least 1.3l0 .
Table 5.9: Values of the coefficient α6
Percentage of lapped bars relative to the total cross-section area
α6
<25%
33%
50%
>50%
1
1.15
1.4
1.5
Note: Intermediate values may be determined by interpolation.
Derived/adapted from Table 8.3 of BS EN 1992-1-1.
All secondary reinforcement may be lapped at the same location. The minimum values of the lap length l are given in
Table 5.10. The lap length of two secondary bars should cover two main bars.
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Table 5.10: Required lap lengths for secondary wires of fabrics
Size of secondary wires (mm)
Lap lengths
∅⩽6
⩾150mm; at least 1 wire pitch within lap length
6 < ∅ ⩽ 8.5
⩾250mm; at least 2 wire pitches
8.5 < ∅ ⩽ 12
⩾350mm; at least 2 wire pitches
5.5 Welding of reinforcement
5.5.1 General
On-site welding of reinforcement should be avoided wherever possible. However, where it is deemed necessary,
the technical guidance described in BS 854830 should be satisfied in order to produce acceptable welds. The contract
administrator should be responsible for ensuring the qualification of weld test procedures and the qualification and
testing of welders. The contract administrator should clearly identify any design requirement, including temporary works
design, and who is responsible for the design.
5.5.2 Semi-structural welding
In the UK, semi-structural welding of reinforcement should only be carried out by firms that have achieved
certification to CARES’ Steel for the Reinforcement of Concrete scheme.
5.5.3 Tack welding
Tack welding on site should not be permitted, other than in particular circumstances for which special approval must
be sought (Section 5.5.1). Tack welding of reinforcement should only be carried out by firms that have achieved
certification to CARES’ Steel for the Reinforcement of Concrete scheme.
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6 Common structural elements
6.1 Introduction
Nationally Determined Parameters (NDPs) are based on the UK National Annex to BS EN 199231. Common values of
cover are given. However, the designer should review and adjust for the specific cover requirements of the element
being considered. The information given in the Model Details (MDs) has been developed over many decades. It is
considered good practice and combines a mix of code-based rules plus experience. The detailer is expected to
follow the MDs unless the designer has given specific alternative instructions. The designer should always check that
where minimum reinforcements are provided, they meet the design requirements. The recommendations given in this
chapter assume that the contractor has a recognised quality system in place (Section 5.2.1) and as a consequence,
the value of Δcdev assumed in the MDs is 5mm.
6.2 Slabs
6.2.1 Scope
The guidance relates to:
•
•
•
•
•
single and two-way orthogonal slabs
cantilever slabs
orthogonal flat slabs
trough and coffered slabs
composite slabs using permanent metal formwork
Slabs of irregular shape may often be detailed using the same principles. However, six or more layers of
reinforcement may be required for skew reinforcement, and allowance should be made for this in design. For ribbed
and coffered slabs the ribs should be detailed as beams. For fire ratings greater than 2hrs the need to provide
supplementary reinforcement should be considered. For prestressed slabs, the rules in this section are supplemented
by those in Chapter 7, which take precedence if contradictory. Ground slabs are not covered, and reference should
be made to TR34: Concrete industrial ground floors 11. Special care is required to ensure adequate cover is specified
where drainage channels with ‘falls’, run along the surface of the slab. In addition, where the surface finish effects the
cover this should be stated on the drawings.
6.2.2 Design and detailing notes
6.2.2.1 Minimum area of reinforcement
Solid slabs
• Tension reinforcement:
As,min = 0.26btd fctm/fyk and not less than 0.0013btd
Where:
bt
d
fctm
fyk
= mean width of tension zone
= effective depth
= mean tensile strength of concrete (Table 6.1)
= characteristic yield strength (500MPa in UK)
• For common solid slab thicknesses see Tables 6.1 and 6.2 for calculated minimum areas and suggested
reinforcement.
• Minimum reinforcement also applies for nominal reinforcement.
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Table 6.1: Minimum area of steel As,min for various solid slab thicknesses (mm2/m)
fck
fctm
Min. %a
Slab thickness (mm)
125
150
175
200
225
250
275
300
325
350
375
400
⩽25
2.6
0.13
157
191
223
253
287
320
353
387
417
453
487
157
28
2.8
0.14
170
204
240
273
309
345
381
414
453
489
525
170
30
2.9
0.15
178
214
252
286
324
361
396
434
474
512
547
178
32
3.0
0.16
186
223
259
299
338
377
414
456
495
531
574
186
35
3.2
0.17
195
237
275
317
359
397
439
484
526
568
609
195
40
3.5
0.18
213
255
301
347
392
434
484
525
575
620
662
213
45
3.8
0.20
231
276
326
375
420
474
523
572
622
667
716
231
50
4.1
0.21
248
296
349
398
455
508
557
614
663
716
760
248
Notes:
a
Where area of concrete is btd.
bt = mean width of tension flange (i.e. slab width, flange width for top reinforcement in T-beam, or web width for bottom
reinforcement in beam).
d = effective depth (distance from top of section to centre of reinforcing bar).
Values have been determined using a nominal cover of 25mm and an appropriate bar diameter to provide minimum area
of reinforcement.
Table 6.2: Suggested minimum reinforcement for various solid slab thicknesses
fck
Slab thickness (mm)
125
150
200
250
300
350
400
⩽25
A142 fabric
A193 fabric
A252 fabric
10 @ 250
10 @ 200
12 @ 250
10 @ 150
28
A142 fabric
A193 fabric
A252 fabric
10 @ 250
10 @ 200
10 @ 150
12 @ 200
30
A142 fabric
A193 fabric
A252 fabric
10 @ 200
12 @ 250
10 @ 150
12 @ 200
32
A193 fabric
A193 fabric
10 @ 250
10 @ 200
12 @ 250
10 @ 150
10 @ 125
35
A193 fabric
A252 fabric
10 @ 250
10 @ 200
12 @ 250
12 @ 200
10 @ 125
40
A193 fabric
A252 fabric
10 @ 250
10 @ 200
10 @ 150
10 @ 125
12 @ 150
45
A193 fabric
A252 fabric
10 @ 200
12 @ 250
12 @ 200
10 @ 125
12 @ 150
50
A252 fabric
A252 fabric
10 @ 200
10 @ 150
12 @ 200
12 @ 150
16 @ 250
Cantilever slabs
• For exposed cantilevers where shrinkage and temperature significantly impact the deflection, the area of bottom
reinforcement in the direction of span should relate to the top reinforcement (e.g. 50%).
Ribbed slabs
• Minimum bar diameter in rib as for beams
• Minimum reinforcement in flange as for single-way slabs
• If fabric is used, spacing of wires should not exceed half the pitch of ribs
Refer to Clauses 9.2.1.1, 9.3.1.1 and 9.3.1.2 of BS EN 1992-1-1 for further information.
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6.2.2.2 Bar spacing
Recommended minimum pitch of bars to allow for placing and compaction of concrete are given in Table 6.3.
Table 6.3: Recommended minimum pitch of bars in slabs
Bar size ∅
No laps occurring
Where laps occur
⩽20
75
75
25
75
100
32
75
125
40
100
150
Maximum pitch of bars
• Main bars: 3h ⩽ 400mm (in areas of concentrated loads 2h ⩽ 250mm)
• Secondary bars: 3.5h ⩽ 450mm (in areas of concentrated loads 3h ⩽ 400mm)
These criteria set out the theoretical maxima for strength design. However, making the reinforcement safe for site
operatives plus achieving serviceability requirements, can often lead to more onerous limits.
Refer to Clauses 8.2 and 9.3.1.1 of BS EN 1992-1-1 for further information.
6.2.2.3 Anchorage and lapping of bars
Typical anchorage and lap lengths for ‘good’ and ‘poor’ bond conditions (Fig. 5.6) are given in Appendix E. For slab
ends that are on ‘direct supports’ (Figure 6.1) the anchorage length beyond the face of the support may be reduced
to d but not less than the greater of 0.3lb,rqd , 10∅ or 100mm.
Figure 6.1: Anchorage of bottom reinforcement at end supports
lbd
lbd
b
a) Direct support
Supported by wall/column
b) Indirect support
Supported by another beam
Where a slab supports a high point load, such as a column, the designer should advise the detailer on the specific
anchorage or lapping requirements.
Lap lengths provided (for nominal bars etc.) should not be less than 15× the bar size or 200mm, whichever is
greater. The arrangement of lapped bars should comply with Fig. 5.7.
Refer to Clauses 8.4 and 8.7 of BS EN 1992-1-1 for further information.
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6.2.2.4 Simplified rules for the curtailment of reinforcement
Figure 6.2 provides guidance on the curtailment of reinforcement for slabs to meet the requirements of
Clauses 9.2.1.3 and 9.3.1.2 of BS EN 1992-1-1 and UK National Annex recommendations for load combinations.
• Minimum bottom reinforcement in direction of span:
40% of max. required reinforcement
• Minimum top reinforcement at support (e.g. where partial fixity exists):
25% of maximum required reinforcement in span, but not less than As,min .
• This may be reduced to 15% for an end support
Figure 6.2: Curtailment of reinforcement for slabs
Face of support
100%
Reinforcement for
maximum hogging moment
0.15l > lbd
40%
50%
0.2l
Position of
effective
support
0.30l
a) Continuous member, top reinforcement
100%
Reinforcement for
maximum sagging moment
b) Continuous member, bottom reinforcement
25%
15%
lbd
Face of
support
100%
c) Simple support, bottom reinforcement
Notes:
l = effective length
lbd = design anchorage length
Qk < 1.25Gk and qk < 5kN/m2
Minimum of two spans required
Applies to uniformly distributed loads only
Shortest span must be >0.85× longest span
Applies where 20% redistribution has been used
Secondary transverse reinforcement:
• 20% of main reinforcement except where there is no transverse bending (e.g. near continuous wall supports).
• The area of reinforcement provided at supports with little or no end fixity assumed in design should be at least
0.25 of that provided in the span.
Curtailment should not reduce the percentage of reinforcement at any section below the minimum percentage except
where no tension occurs. Where minimum tension bottom reinforcement is used at the supports or curtailment points
of simply supported slabs or beams, the anchorage length may be taken as lb,min , (i.e. maximum of 0.3× anchorage
length from Tables in Appendix E, 10∅ or 100mm).
6.2.2.5 Notation for the locating layers of reinforcement
Reinforcement is fixed in layers starting from the bottom of the slab upwards, and bar marks should preferably follow
a similar sequence of numbering. Notation is as follows:
•
•
•
•
abbreviation
abbreviation
abbreviation
abbreviation
for
for
for
for
top outer layer
top second layer
bottom second layer
bottom outer layer
T1
T2
B2
B1
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The sketch and notation should be stated on each drawing.
T2
T1
T2
B1
B2
B1
6.2.2.6 Typical bar and indicator lines
Generally, each bar mark is represented on plan by a typical bar drawn to scale, using a thick line. The bar is
positioned approximately midway along its indicator line, the junction highlighted by a large dot. The first and
last bars in a zone of several bars are represented by short thick lines, their extent indicated by arrowheads.
Bends or hooks, when they occur at either end of the typical bar, are represented by a medium dot or similar.
• one bar only
1H10-63-T1
• two bars
2H10-63-150T1
• a zone of three or more bars
20H10-63-150T1
• multiple zones, showing similar marks in each zone, with quantities indicated in brackets
20H10-63-150T1
(12)
(8)
• multiple zones, showing dissimilar marks in each zone
12H10-63-150T1
8H20-64-200T1
63
64
Generally, the ‘calling up’ of bars is located at the periphery of the detail or as an extension of the indicator line:
• when space is restricted ‘calling up’ can be written within the zone of the indicator line
20H10-63
150T1
• or in extreme cases, written along the bar itself
20H10-63
150T1
• instructions to stagger bars of same mark
Stg.
• instructions to alternate bars of different mark
63
64
Alt.
Bars detailed ‘elsewhere’
These are shown as a thick dashed line.
SEE DRG
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0
125
3
0- 6
H1
0
1
2
0T
15
750
Bars set out from a radius in a ‘fan’ zone
The indicator line can be located on a datum radius for measuring the pitch of the bars. Locate end of bars to datum.
s.o.p
Bars of varying length in a zone
Each bar in the zone is given the same bar mark but a different suffix, beginning with ‘a’. The bar schedule will
allocate different bar lengths to each suffix as appropriate.
a
f
v
20H10-65 (a to v)-150 T1
Bars in long panels
To simplify the ‘calling up’ of strings of bars in very long panels, e.g. distribution bars in one-way slabs, identical bars
of a convenient length can be lapped from end to end of the panel. State minimum lap. The use of random length
bars is not recommended.
3 × 8H10-63- 150 B2
min. lap
300
Cranked and bent bars
For convenience, these can be drawn on plan as though laid flat. However, confusion on site can result if some of
these bars are required to be fixed flat and some upright. Sections and notes should be provided to clarify this
method if used.
63
64 Alt.
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Fixing dimensions
Dimensions (mm) are restricted to those required by the steel-fixer to locate bars not already controlled by end
covers. Dimension lines are thin, terminated by short obliques.
1750
Bars in elevation
Bars in elevation are represented by a thick line with mark indicators. First and last bars in a zone are indicated by a
dot in section with appropriate mark.
64
63
Curtailed bars
Curtailed bars are identified by short 30° obliques with appropriate mark. If the bars are congested the ends should
be clarified with pointers.
2
3
2
6.2.2.7 Two-way slabs
Figure 6.3 shows the recommended arrangement of reinforcement into strips and areas.
Bars in the edge strips should be the same length and diameter as those in the middle strips, but the pitch may be
increased to give the minimum reinforcement permitted.
Figure 6.3: Arrangement for reinforcement strips for two-way slabs
Ly
Edge strip
Edge strip
Edge strips.
Nominal bars spanning
in direction of arrows
Ly/8
Middle strip
Lx/8
Lx/8
Ly/8
Edge strip
Lx
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6.2.2.8 Flat slabs
Detailing strips (Figure 6.4) are for analysis by an equivalent frame method or by the use of coefficients.
Figure 6.4: Division of reinforcement strips for flat slabs
Lx
Ly/4
3Ly/4
Ly/4
Ly
Middle
strip
Ly/2
Column
strip
Column
strip
Middle
strip
Nominal
strip (one way)
6.2.2.9 Internal panels
Each bay is divided into column and middle strips as shown in Fig. 6.4. The width of column strip in both directions
is normally half the shorter panel dimension. Where column drops are used, the column strip is set equal to their
width. For aspect ratios greater than 2, the centre of the panel behaves as if spanning one way. Distribution
reinforcement should be placed in this strip, parallel to the short side. Otherwise, Table 6.2 indicates the proportion
of reinforcement which should be placed in each strip. In general, two thirds of the amount of reinforcement required
to resist negative moment in the column strip should be placed in a width equal to half that of the column strip, and
central with the column. At least two bottom bars should pass through the column.
Note: These rules comply with Clause 9.4.1(2) of BS EN 1992-1-1.
6.2.2.10 Slab at edge and corner columns
The reinforcement perpendicular to a free edge which is required to transmit moments from the slab to an edge or
corner column should be placed within the effective width (Figure 6.5). Nominal reinforcement should be placed along
the remainder of the edge.
Figure 6.5: Effective width be of flat slab
cz
cz
Slab edge
Slab edge
cy
cy
y
y
z
Slab edge
be = cx + 2y
be = cz + y
a) Edge column
b) Corner column
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6.2.2.11 Edge reinforcement
Reinforcement should be placed along free (unsupported) edges of slabs and at corners that are supported on both
sides. This allows the distribution of local loads which helps to prevent unacceptable cracking. This reinforcement
may be supplied in the form of U-bars (Figure 6.6).
Figure 6.6: Edge reinforcement for slab
h
>2h
Where the corners of slabs are held down, the bars should extend into the slab a minimum distance of at least one
fifth of the shorter span (Figure 6.7). The area of this torsion reinforcement required in each leg should be at least
three quarters of the area required for the maximum mid-span design moments in the slab. Only half this area is
required at a corner with only one discontinuous edge.
Figure 6.7: Torsion reinforcement at slab corners
Torsion mat at a
corner with two
discontinuous edges
Torsion mat at a
corner with one
discontinuous edge
Torsion mat at a corner
with one discontinuous
edge and no torsion
mat required in
adjacent bay
Edge strip
Refer to Clauses 9.3.1.3 and 9.3.1.4 of BS EN 1992-1-1 for further information.
6.2.2.12 Trimming holes in a slab
• Where holes, or groups of holes are considered to be of structural significance (e.g. in flat slabs), the design data
should indicate any special reinforcement.
• Where holes or groups of holes are considered to be structurally insignificant, the following rules apply:
○ minimum unsupported edge distance = width of hole w1
○ maximum width of isolated opening measured at right-angles to span = 1000mm
○ maximum length of isolated opening measured parallel to span = 0.25 span lx.
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Maximum total width (w1 + w2 + w3 ) of multiple holes measured at right-angles to span lx = 0.25 span ly
w1
w1
w2
w3
span lx
○
○
small isolated holes with sides ⩽150mm can generally be ignored. Significant holes should be drawn to scale
and shown on the reinforcement drawing
for larger isolated holes with sides ⩽500mm, either displace affected bars equally either side of hole
(see MD S1 for spacing details)
or:
cut or slide back affected bars to face of hole. Compensating bars of equal area should be provided to trim
all sides. Trimmers should extend a minimum 45∅ (nominal anchorage length) beyond the hole
45ø
45ø
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○
large isolated holes with sides 500–1000mm: treat as ⩽500mm but in addition trim top of holes with similar
bars. If depth of slab exceeds 250mm, where practical provide diagonal reinforcement of similar area in top
and bottom, but consideration should be given to the congestion of multiple layers
○
groups of holes within boundary of 500mm or less: trim as single hole using methods described for ⩽500mm.
Bars should pass alongside holes where possible
45
m ø
in
68
45ø
min
45ø
min
Trimmers
○
groups of holes within boundary of 500–1000mm: trim as single hole using methods described for
⩽500mm/500–1000mm
Standard details for openings are shown in MD OP1.
6.2.2.13 Secondary reinforcement
Distribution reinforcement is provided at right angles to the main tensile reinforcement in all circumstances where
other main reinforcement is not already included.
Fabric reinforcement (either as loose bars or a welded mat) may be required to control cracking due to shrinkage
and temperature in:
• whole of top surface of slab
• bottom of solid areas around columns of coffered slab construction
• bottom of solid areas of troughed slabs adjacent to beams
If welded fabric is used for coffered and troughed slabs it is essential to check that sufficient depth has been given
to fit all the layers of reinforcement at the laps in the fabric. For coffered slabs this must include two layers of main
tension bars together with at least two layers of fabric. Normally the top main tension bars will be positioned to lie
within the width of the ribs, even in the solid area of the slab (MD S8). Although this allows the bars to be fitted with
sufficient cover, it reduces the effective lever arm.
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Supplementary reinforcement may be required in coffered and troughed slabs for fire protection. This should be
provided by links and lacer bars for coffered slabs, and by welded fabric (D49) for troughed slabs as indicated in
MD S8.
Additional reinforcement may be required in prestressed concrete to resist bursting tensile forces in end zones, and
to control cracking from restraint to shrinkage due to formwork, before the prestress is applied.
Refer to Clause 9.3.1 of BS EN 1992-1-1 for further information.
6.2.2.14 Fabric reinforcement
Introduction (also see Sections 4.2.5 and 5.1.11)
3-M
k.
Suspended solid floor construction
Where the lever arm is important, the orientation should indicate the level of the primary reinforcement. For clarity on
plan it is recommended that the top sheets of fabric be drawn separately from the bottom sheets, preferably on the
same drawing. Fabric is identified by a chain double-dashed line.
.
Mk
T1
B1
Fabric detailing on plan
Each individual sheet is given a mark number and related on plan to the concrete outline. Indicate the direction of the
main reinforcement and its layer notation. Wherever multiple sheets of identical marks occur they can be combined.
Areas of reinforcement can be increased by double-layering.
Main
T1
T3
Also consider the possible advantages of ‘nesting’ the two sheets to maximise the lever arm.
Main
B2
Similarly, ‘nesting’ when main steel is required in two directions, crossing at 90°.
Main
T1
T2
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Areas of steel can be increased either by layering, or by using the ‘C’ fabrics as one-directional sheets,
laid perpendicularly in two layers. The main bars should always be in the same direction (e.g. facing down).
Structural fabric type ‘B’ is often specified for suspended slabs, possibly with the addition of loose bars. With
reasonable production runs, consideration should be given to specifying purpose-made fabric. For each fabric mark,
indicate its reinforcement in a table alongside the plan.
Laps in fabric
The need for laps should be kept to a minimum and, where required, should be located away from regions of high
tensile force. Allow sufficient clearance to accommodate any multi-layering of sheets at laps, reducing these
occurrences where possible by staggering sheets.
Lap
Lap
Show lap dimensions on plan and/or indicate minimum lap requirements in a note on the drawing. Minimum laps are
required to prevent cracks caused by secondary stresses.
3 sheets lap
Lap
2 sheets lap
Voided-slab construction
A nominal designated fabric is normally placed within the topping of trough and waffle-type floors. The extent of the
fabric is shown by a diagonal on the plan of the reinforcement drawing and the fabric type scheduled as gross area
(m2) by adding a suitable percentage to the net area of the floor to allow for laps. For ordering purposes, the
contractor should translate this gross area into the quantity of sheets required to suit the method of working.
Where more comprehensive detailing of fabric sheets is required, manufacturers will often be able to assist.
Ground-slab construction
The presence of fabric reinforcement can be indicated by a sketch and a prominent note on the drawing
(the GA drawing in straightforward cases). The note should include type of fabric, location within the depth of slab,
and minimum lap requirements. A typical section to clarify this construction should be included. The fabric type is
scheduled as a gross area by adding a suitable percentage to the net area of slab to allow for laps.
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6.2.2.15 Carpet reinforcement
Reinforcing bars in a roll-out ‘carpet’ are connected by steel tapes welded to the reinforcement to ensure correct
spacing. Each carpet roll contains a single layer of parallel bars.
The fixing of the spacers to support the carpets is more complicated than for fixing loose bars, but the advantages
of this system include:
• time saving. Rolling out a carpet takes minutes compared to hours fixing loose bars
• less labour. Rolling out a carpet requires only two or three people
Where this type of reinforcement is used, the rolling out of carpets must not clash with projecting column or wall
starter bars. Couplers on vertical reinforcement can overcome this.
Where the carpet uses bars cut from rod reinforcement (>20mm diameter), and if variable lengths are specified,
this could lead to considerable steel wastage from off-cuts. This is not the case where the bars are cut from coils.
It is important to recognise the handling requirements, as well as the possible need to strengthen falsework and
spacers to accommodate the initial loading from the carpet roll.
6.2.2.16 Shear reinforcement in flat slabs
Where punching shear reinforcement is required, it should be placed between the loaded area/column and 1.5d
inside the control perimeter at which shear reinforcement is no longer required, subject to a minimum of 1.5d from
the column. It should be provided in at least two perimeters of link legs. The spacing of the link leg perimeters
should not exceed 0.75d.
The spacing of link legs around a perimeter should not exceed 1.5d within the first control perimeter (2d from loaded
area) and should not exceed 2d for perimeters outside the first control perimeter where that part of the perimeter is
assumed to contribute to the shear capacity (Figure 6.8).
Figure 6.8: Recommendations for placing orthogonal links adjacent to edge column with hole
Column 400mm square
D
1123
375
6H20 @ 175 T2
6H16 @ 175 B2
8H20 T1 U-bars in pairs
uout
1
H10 @ 200 T1 U-bars
H10 @ 200 T1 U-bars
175
1
500
175
u1
175
Orthogonal links should be positioned
such that:
• between perimeters at 0.3d and 0.5d
from face, at least Asw is provided
• in the next perimeter band outwards,
0.75d wide, at least Asw is provided,
until uout – 1.5d is reached
175
175
1.5d
uout
175
175
175
175
175
Σ = 152H10 legs of links
@175mm centres
Ineffective area
CL
175 175 175 175175 175 200
d
= 250mm
0.75d ø 175mm
100
200 175 175 175 175 175 175
100
Asw per perimeter should be based on the perimeter reduced by
the hole. Asw should be provided along that reduced perimeter.
The same radial and tangential spacings should be used
through the ‘shadow’ or ineffective area as the effective area
In outer perimeters, spacing rules
will often dictate so that Asw per
perimeter is often exceeded
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Where punching shear reinforcement is required at ends or corners of walls, the design may be based on
perimeters extending 1.5d down the straight side of the perimeter. However, where shear reinforcement is not
required to extend beyond 1.5d, it is nonetheless recommended that it is provided for at least 3d along the
straight perimeter.
In the UK, it is traditional to use ‘bob-and-hooks’ (Shape Code 22) although U-bars (Shape Code 21) with dimension
(a) and (c) 10∅ straight, may be easier to fix. As the traditional method of fixing conventional shear reinforcement is
laborious, prefabricated shear reinforcement systems should be considered when construction time is limited. It is
recommended that the use of these systems is confined to punching shear, and not extended to general slab
reinforcement. The following are examples of proprietary systems currently available.
Stud rail system
This system consists of a series of studs with nail heads welded onto a flat strip (Figure 6.9). These rails are often
placed radially so as to fan out from each column, and can be lifted easily into position. Although simple to
incorporate into a conventional design, care should be taken in construction to ensure adequate cover to rails.
Orthogonal layouts use more studs but are less likely to clash with the main reinforcing bars and more likely to satisfy
the spacing requirements. The rails may be placed on spacers on the formwork or may be placed from the top once
flexural reinforcement is in place.
Note that some systems with European Technical Approvals (ETAs) or European Assessment Documents (EDAs)
do not necessarily comply with BS EN 1992-1-1, particularly with respect to spacing.
Figure 6.9: Stud rail system
Orthogonal grid to fit main bar spacing
Parallel to bottom mat,
covers unaffected
Perpendicular to bottom layer
∴ mat pushed up
(should not be critical)
Spacer to stud rail
Bottom rail with cover spacers to rail preferred
a) Placed radially
b) Placed orthogonally
Shear ladders
This is a system of prefabricated links welded to longitudinal bars to form ‘ladders’ which can be fixed easily with the
normal flexural reinforcement (Figure 6.10).
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Figure 6.10: Typical arrangement of shear ladders
of links
Centres
Centres of
ladders
Col.
Plan
Detail
Shear ladder also serves as
support to top layer reinforcement
Structural steel shear head
This system forms a column head of steel cross-members, sometimes welded to a perimeter of channels facing
outwards. These can easily be placed on reinforced concrete columns or pre-welded to steel columns. This method
has the advantage of allowing holes to be placed close to the column. Shear heads are relatively heavy, and
compaction and bearing onto concrete should be carefully considered.
Composite slabs using permanent metal formwork
Composite slabs usually have a number of constraints that require accurate placing of the reinforcement. This is
particularly important at the slab edge, where a U-bar is required. MD CS1 shows appropriate reinforcement to
provide sufficient cover and meet the requirement for the head of the shear stud to be above the reinforcement for
edge conditions for various slab thicknesses.
Others
Other types of proprietary systems include ‘flying saucers’, shear bands etc.
Refer to Clauses 6.4.5 and 9.4.3 of BS EN 1992-1-1 for further information.
6.2.2.17 Connection to walls
For simply supported conditions (e.g. a roof supported by brickwork) the details given in MD S3 are relevant.
For conditions where the wall continues above and below the slab, the details given in MD S2 (Detail A) are relevant.
However, for situations where the transfer of bending moment from slab to wall is large, it may be necessary to pass
the top reinforcement from the slab down into the wall (MD S2 – Details B and C). It may be necessary to give such
bars large diameter bends (Section 5.1.9).
In situations where the construction process requires that edge bars are cast flush with the face of the wall and then
have to be rebent to project into the slab, proprietary systems are available. These can either be pull-out bar systems
(MD PB1) or coupler/threaded bar systems (MD CBox1).
6.2.2.18 Movement/construction joints
Mechanical shear sliding dowels may be considered instead of half-joints to avoid the use of nibs. Two systems are
currently available (Figure 6.11). A double dowel connection provides a robust mechanical shear transfer with a
sliding joint. This allows contraction and expansion between the two connected pieces of structure.
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Figure 6.11: Dowel systems
a) Double dowel system
b) Single dowel system
6.2.3 Detailing information
Design information for detailing should include:
• layout and section drawings including details of holes and upstands, etc.
• concrete grade and maximum aggregate size (standard 20mm)
• nominal cover to reinforcement and the criteria governing this e.g. fire or durability (standard 20mm for internal
conditions, 40mm for external conditions)
• main reinforcement bar runs and positions. This should include:
○ diameter, pitch of bars and location (e.g. T1, T2, B1, B2, etc.)
○ type of reinforcement and bond characteristics (standard H)
○ fixing dimensions to position bar runs and ends of bars
• details of any special moment bars connecting slab to wall or column
• details of cut-off rules, if other than standard shown in MDs
• details of fabric required. For coffered slabs this should include the fabric required in the topping and in the
bottom of solid sections around columns. Sufficient details should be given to show that the reinforcement will fit
into the depth available, allowing for laps in the fabric. Guidance should be given for the additional area required
for laps, otherwise 22% will be assumed for 300mm lap
• details of insertions, e.g. conduit, cable ducting, cladding fixings, etc. should be given where placing of
reinforcement is affected
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6.2.4 Presentation of working drawings
Figures 6.12–6.15 are example drawings for different slab scenarios. Cover should be shown.
Figure 6.12: Single-way slab
5
9 H10 05–300 U-BARS
9 H10 06–300 B1
2×8 H10 05–300 U-BARS ES
2×8 H10 15–300 T2&B2
8 H12 08–150 T1
8 H12 09 ALT
4
5
19 H12 16–150 U-BARS TLL
18 H12 17 ALT
26 H12 04–150 B1
26 H12 03 ALT
52 H12 03–150 T1 STG
16 H12 07–150 L-BARS
17
04
16
08
03
09
4
5
12
14
4
12
03
52 H12 03–150 B1 STG
500
03
14
03
52 H12 03–150 T1 STG
600
12
14
600
3
03
2–2
200
52 H12 03–150 B1 STG
12
1
12
600
600
52 H12 03–150 T1 STG
12
13
13
03
03
2
52 H12 03–150 B1 STG
3
3
2
26 H16 10–150 T1
26 H16 11 ALT
10
2
03
12 13
11
3–3
1
10 01
11 02
1
SEE WALL
DRG RC10
03 10
2
10/11
12
69 H12 14–250 U-BARS
1
12
12
03
12
12
16 03
17 04
03/04
12 SEE WALL
DRG RC10
4–4
12
08/09
12
09
08
05
5
15
15
05
12
12
03
03
03 02
03 01
03 03
1–1
03 03
12
15
15
06
05
SEE BEAM
DRG RC10 06
12
07 03
04
03/04
07
01
02
03 11
16/17
01 02
71 H12 13–250 U-BARS
71 H10 12–250 B2
60 H10 12–300 T2
01 02
71 H10 12–250 B2
60 H10 12–300 T2
26 H12 01–150 U-BARS BLL
26 H12 02 ALT
12
03 SEE WALL
DRG RC10
5–5
| 75
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Standard method of detailing structural concrete (4th edition)
Figure 6.13: Flat slab
3
500
150
2
(6+5)
(14)
2
(14)
1
(7+7)
@200
B
800
2
28 H20 10–200 T2 STG
1
(7+6)
@250
(7+7)
@200
(6+5)
7 H12 06–250 T2
6 H12 07 ALT
12 H16 02–250 T2
10 H16 03 ALT
(6+5)
(7+7)
@200
(14)
35 H10 08–250 T2 STG
(6+5)
A
13 H12 09–250 T2 STG
21 H16 01–200 B2
20 H16 05 ALT
(7+6)
@250
(7+7)
@200
(14)
35 H12 13–250 U-BARS
12 H16 02–250 T1
10 H16 03 ALT
7 H12 06–250 T1
6 H12 07 ALT
35 H10 08–250 T1 STG
21 H16 11–200 B1
20 H16 12 ALT
13 H12 09–250 T2 STG
28 H20 10–200 T1 STG
35 H12 04–250 U-BARS
BAY A
02
3
02
08
08
08
09
10
13
02
03
02 03
10
09 10
10
08
09
B
08
10
08
09 10
10
10
10
13
05 01
05 01
11/12
11
12
1–1
11 12
05 01
11 12
05
SEE SLAB
DRG RC02
01
2–2
1
2
3
SHEAR LINKS NOT SHOWN
TO AID CLARITY
B
A
BA
A Y
C
KEY PLAN
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
10 H20 08 T2 AS
2 PER RIB
10 H20 06 B2 AS
2 PER RIB
14 H10 15 B2
2 PER RIB
2
10 H20 08 T2 AS
2 PER RIB
Figure 6.14: Coffered slab
3 H20 09
3 H20 10 T1 AP
2 PER RIB
(4)
3 H20 09
3 H20 10 T1 AP
2 PER RIB
(4)
5 H16 11
5 H16 12 T1 AP
2 PER RIB
3 H25 01
3 H25 02 B1 AP
2 PER RIB
5 H20 03
(4)
(4)
2
3 H25 01
3 H25 02 B1 AP
2 PER RIB
(4)
500
(4)
(4)
1900
1 LAYER MESH
FABRIC BS REF A252
TOP. 20 COVER
(4)
1900
(4)
(4)
(4)
(4)
1
32 H10 13 200 LINKS
PER RIB (7 no RIBS)
(4)
(4)
500
500
1900
1
(4)
5 H20 04 B1 AP
2 PER RIB
10 H20 08 T1 AS
2 PER RIB
6 H25 07 T1 AS
2 PER RIB
14
14
07
07
07
14
07
25 CVR TO 14
01 02
01 02
06
1–1
09
MESH
13
13
14
08
08
14
14
03 04
03 04
06
09,10
MESH
13
08 08
08 08
13
06 06
15 15
14
08 08
10
13
08
14
14
14
01 02
14
FOR DETAILS OF SHEAR REINF’T
REFER TO DRG NO. R006
6 H25 07 T2 AS
2 PER RIB
08
14
14
14
07 07
15 CVR TO 13
PLAN
08
MESH
14
28 H10 14 200 LINKS
PER RIB (9 no RIBS)
6 H25 07 T2 AS
2 PER RIB
6 H25 05 B2 AS
2 PER RIB
6 H25 07 T1 AS
2 PER RIB
13
01,02
06 06
15 15
2–2
02
01
SEE BEAM DETAILS
| 77
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Standard method of detailing structural concrete (4th edition)
Figure 6.15: Flat slab (shear reinforcement)
1
(See MD S6 for more detailed information)
150 225 225
1
20 H10 01 –150 P1 LINKS
20 H10 01 –210 P2 LINKS
A
20 H10 01 –270 P3 LINKS
400
400
1
6 H12 012 LACERS
LINKS TO BE EQUALLY SPACED AROUND
EACH PERIMETER, MAX. PITCH 375mm,
PROVIDE H12 HANGER BARS WHERE MAIN
REINFORCEMENT IS NOT AVAILABLE.
PS–1
(15 NOS)
A
150
01
02
02
02
02
225
225
02
02
02
02
SEE MAIN SLAB
REINF. DRG RC01
1–1
A
150
01
02
02
02
02
225
02
02
225
02
02
SEE MAIN SLAB
REINF. DRG RC01
1–1
(Prefered Contractor Alternative)
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
Slabs MD S1
ONE- AND TWO-WAY SLABS:
SPAN AND INTERNAL SUPPORT
Loose bar detailing or option to
use mesh with flying ends or
carpet reinforcement
Reinforcement for max.
hogging moment
Top bars alternately
staggered over support
GL
*
*
0.15l
(100% of
reinforcement)
Face of support
*
0.3l
(50% of reinforcement)
0.3l
(50% of reinforcement)
Reinforcement for max.
hogging moment
*
GL
0.15l
(100% of
reinforcement)
lbd
Face of support
Face of support
Face of support
l bd
10
dia.
0.2l
(40%)
(100%)
0.2l
(40%)
Reinforcement for
max. sagging moment
* or lbd
whichever is greater
Reinforcement to resist possible positive moments
(settlement of support, explosion etc.).
This reinforcement should be continuous,
which may be achieved by means of lapping
Simplified rules for slab —
continuous slab curtailment
0.3l *
GL
Face of support
*
GL
(50% of reinforcement)
*
0.15l
(100% of
reinforcement)
Face of support
10
dia.
Face of support
0.3l
(50% of reinforcement)
*
0.15l
(100% of
reinforcement)
Face of support
lbd
0.2l
(40%)
0.2l
(40% of reinforcement)
Reinforcement to resist possible positive moments
(settlement of support, explosion etc.).
This reinforcement should be continuous,
which may be achieved by means of lapping
Reinforcement to resist possible positive moments
(settlement of support, explosion etc.).
This reinforcement should be continuous,
which may be achieved by means of lapping
Alternative option —
lap bars at support
Preferred option on site —
lap bars at support,
option of splice bar through
support lapping either side
Pitch of distribution bars (mm)
Slab depth (mm)
Bar size
(mm)
100
125
150
175
200
225
250
275
300
325
350
375
400
10
350
425
425
350
300
275
225
200
200
175
150
150
125
450
450
450
400
350
325
275
250
250
250
200
450
450
450
450
450
425
400
375
12
16
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Slabs MD S2
80
ONE- AND TWO-WAY SLABS:
EXTERNAL AND RESTRAINED SUPPORTS
GL
This detail is used when X is
more than an anchorage length.
Otherwise Detail B or C is used
The area of U-bars equals half
the bottom steel at mid span
unless otherwise specified
#
Face of support
X
l0
50mm
A bar is placed inside each corner.
Bearing stress to be checked
by designer
# Greater of:
– 0.3 × clear span
– lbd
Detail A
GL
This detail is used when X is less than
an anchorage length, provided that
bearing stress inside standard bend
does not exceed limit. Otherwise Detail C
is used, to be checked by designer
#
Face of support
l0
50mm
Tension anchorage length
Bars extending down into wall from slab
should be detailed with wall drawings
wherever possible. Otherwise they must
be clearly cross-referenced
Detail B
GL
This detail is used when bearing stress
inside bend requires a nonstandard
radius of bend, to be checked by designer
#
Face of support
l0
Tension anchorage length
50mm
Detail C
Bars extending down into wall from slab
should be detailed with wall drawings
wherever possible. Otherwise they must
be clearly cross-referenced
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
GL
This detail is used for slab depth
>150. Details B or C are used
for slab depth <150mm
lbd
End U-bars are same dia.
as bottom bars
lbd
50% of span steel should
continue to support
(Clause 9.3.1.2 of BS EN 1992-1-1)
Face of support
Detail A
(Slab depth >150)
This detail is used for
support width <200mm
(otherwise Detail C is used)
GL
Minimum hook (Table C1)
lbd
Bobbed bars may be laid over
to ensure sufficient top cover
50% of span steel should
continue to support
(Clause 9.3.1.2 of BS EN 1992-1-1)
Support width
Detail B
(Slab depth <150)
This detail is used for
support width >200mm
(otherwise Detail B is used)
This detail is also suitable
for fabric reinforcement
GL
lbd
Support width
Detail C
(Slab depth <150)
50% of span steel should
continue to support
(Clause 9.3.1.2 of BS EN 1992-1-1)
Slabs MD S3
ONE- AND TWO-WAY SLABS:
EXTERNAL UNRESTRAINED SUPPORTS
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Slabs MD S4
82
CANTILEVER SLABS
GL
GL
Cantilever length k
0.5k Min.
l0
Max. 1.5k or 0.3l + d
(60% of reinforcement)
Max. 0.75k or 0.15l + d
(100% of reinforcement)
l0
l0
l0
l0
l0
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
When equivalent column dia. is less than
0.15 × width of panel 2/3 of bars for this
strip should be placed in centre half
GL
GL
Column strip
Middle strip
p11 p11
p1 p1 p1
Two bottom bars should
pass through column
p21 p21
p2
p2
Section of column strip
Optional mesh or
carpet reinforcement
p1 p1
p2
p2
Section of middle strip
1
p1 : pitch of column strip top bars
p21 : pitch of middle strip top bars
p1 : pitch of column strip bottom bars
p2 : pitch of middle strip bottom bars
Bars of longer span are placed in outer layer unless otherwise specified
Column strip
Slabs MD S5
FLAT SLABS: SPAN AND INTERNAL SUPPORT
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Slabs MD S6
84
FLAT SLABS: SHEAR REINFORCEMENT
Links may be fixed around T2 and B2
reinforcement wherever they occur on
the perimeter, provided that nominal
hanger bars are included where necessary
<0.75d
<0.75d
>0.3d
<0.5d
>0.3d
<0.5d
<0.75d
<0.75d
<0.75d
*
<0.75d
5Ø
but not <50mm
(d)
b
*
*
c
a
Shape Code 22
(a)
must be 13Ø o/a
10Ø but not <70mm
12 dia. fixing bars are required to
locate links in those positions
where main reinforcement is not
present. These bars should extend
an anchorage beyond last link
<0.75d
<0.75d
Links should be placed on rectangular plan
perimeters spaced as shown from column face.
Links are spaced evenly around each perimeter
with a max. pitch of 1.5d within 2d from
column face and max. pitch of 2d outside this
Shear reinforcement
(using Shape Code 22)
>0.3d
<0.5d
>0.3d
<0.5d
<0.75d
<0.75d
<0.75d
*
<0.75d
a
b
*
*
(c)
Shape Code 21
(a) and (c)
must be 13Ø o/a
Links should be placed on retangular
plan perimeters spaced as shown from
column face. Links are spaced evenly
around each perimeter with a max. pitch
of 1.5d within 2d from column face and
maximum pitch of 2d outside this
10Ø but not <70mm
>0.3d
<0.5d
<0.75d
<0.75d
Links may be fixed to same levels of
reinforcement wherever they occur on
perimeter, provided that nominal hanger bars
are included where neccessary
Shear reinforcement
(using Shape Code 21)
<0.75d
>0.3d
<0.5d
<0.75d
<0.75d
**
<0.75d
**
Shear rail
T1
**
T2
Shear reinforcement
(using shear studs/rails)
Shear studs with head dia. = 3× bar dia.
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
GL
75mm (min.)
Main bars
Nominal bars
Main bottom bars are carried through column drop.
Nominal reinforcement is provided in bottom of drop.
12 dia. bars at 300 pitch
Detail A
GL
Main bars
lbd
lbd
This detail is suitable when bottom steel
in column drop is used in design
Detail B
Slabs MD S7
FLAT SLABS: COLUMN DROPS
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Slabs MD S8
86
RIBBED AND COFFERED SLABS
300 unless otherwise
specified
Nominal fabric A252
is provided, unless
otherwise specified
12d minimum
Closed links should
be provided if required
for shear
12 dia. lacing bars are provided
if overall depth exceeds 750
If cover exceeds 40
supplementary reinforcement may be required
for fire resistance. This is provided by 6mm links
as shown (Max. pitch 200) plus nominal lacer bar
for coffered slabs
Detail A
Detail B
(Coffered slab)
(Coffered slab with supplementary reinforcement)
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
*Anchorage
B3/T3
B3/B4 or T3/T4
if bars overlap
4No. bars displaced
2No. each side
Provide diagonal bars
for anti-crack
top and bottom
*An
ch
ora
ge
Consideration to be given to the
congestion of multiple layers
Large isolated holes
with sides 500–1000mm
Hole 150–500mm similar but diagonal bars unnecessary UNO.
Hole <150mm bars to be displaced on site without changes being
made to RC drawings or schedule.
Hole >1000mm should have specific design, corners of walls etc.
(see core below)
Core wall
(re-entrant corner)
*An
ch
ora
ge
B3/T3
Core wall
(re-entrant corner)
*Designer/consultant to advise on anchorage, lap or other requirements
Openings MD OP1
Min. 50% of displaced bars to
be placed each side of opening
e.g. 4No. bars displaced
2No. each side
| 87
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Standard method of detailing structural concrete (4th edition)
Conc. slab edge
Specify min. edge
dim. to stud
SSL
Horizontal U-bars
Top cover
GL
Inverted flying end mesh
Slab
Assume A393 mesh inverted
Assume B10 U-bars
Spacer
35mm edge cover
Composite decking
Shear
stud
130mm COMPOSITE METAL DECKING SLAB
Conc. slab edge
Specify min. edge
dim. to stud
SSL
Horizontal U-bars
Top cover
GL
Inverted flying end mesh
Slab
Assume A393 mesh inverted
Assume B12 U-bars
Spacer
35mm edge cover
Composite decking
Shear
stud
140mm COMPOSITE METAL DECKING SLAB
Conc. slab edge
Specify min. edge
dim. to stud
SSL
Horizontal U-bars
Top cover
GL
Flying end mesh
Assume A393 mesh
Assume B12 U-bars
Slab
Composite slabs (composite metal decking) MD CS1
88
Spacer
35mm edge cover
Composite decking
Shear
stud
150mm COMPOSITE METAL DECKING SLAB
Always consider actual bar size
U-bars should be placed under stud head
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
Pull-out bar MD PB1
Legs bent and kept along the
wall face within the box
when casting wall
l0
l0
Legs to rebend to
lap with slab bars
when pouring slab
H
W
H
l0
H
W
l0
This detail is applicable if bar dia. is <16mm
35mm box (max.) to
maintain cover requirements
Pull-out bars or similar approved
| 89
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Coupler Box MD CBox1
90
COUPLER/THREADED BAR
(Coupler box or similar approved)
U-bar with coupler
Threaded bar (to coupler box
manufacturer’s specification)
l0
Poor bond lap
l0
Good bond lap
35mm box (max.)
to maintain cover
requirements
This detail is applicable if bar dia. is >16mm
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
| 91
6.3 Beams
6.3.1 Introduction
This guidance relates specifically to straight suspended beams with defined supports. Ground beams are considered
in Section 6.7. The detailing of holes in beams should not normally be carried out without specific design
instructions, as they can dramatically affect the structural adequacy of a beam.
6.3.2 Design and detailing notes
6.3.2.1 Minimum area of reinforcement
Tension reinforcement
As,min = 0.26btd fctm/fyk and not less than 0.0013btd
Where:
bt
d
fctm
fyk
= mean width of tension zone
= effective depth
= mean tensile strength of concrete (Table 6.1)
= characteristic yield strength (500MPa in UK)
See third column of Table 6.1 for minimum percentage of reinforcement.
Compression reinforcement
Asc,min ⩾ 0.002Ac
Transverse reinforcement in top flange
As,min ⩾ 0.0015hfl
Where:
hf = depth of flange
l = span of beam
Minimum diameter
12mm
Refer to Clause 9.2.1.1 of BS EN 1992-1-1 for further information.
6.3.2.2 Bar spacing
Minimum horizontal pitch
Sufficient space must be allowed for insertion of poker vibrator. Note that where bars are lapped, the pitch of the
reinforcement should allow for the laps (and this can be significant for larger bars, unless the lapped bars are
placed in a different layer). Table 6.4 provides the recommended pitch, allowing for actual bar size and for
vibrating poker.
Minimum vertical pitch
25mm or bar diameter, whichever is greater.
Maximum pitch
The following simplified values may normally be used:
• Tension bars: values given in Table 7.3 of BS EN 1992-1-1. The designer should advise the steel stress and crack
width wk
• Compression bars: 300mm, provided all main bars in compression zone are within 150mm of a restrained bar
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Standard method of detailing structural concrete (4th edition)
Table 6.4: Recommended minimum pitch of bars in beams (mm)
Bottom reinforcement
Top reinforcementa
Bar size
∅ (mm)
Actual bar
diameter (mm)
No laps occurring,
or lapped bars in
different layers
Where laps
occur
No laps occurring,
or lapped bars in
different layers
Where laps
occur
12
14
40
55
55
70
16
19
40
55
60
80
20
23
45
65
65
90
25
29
50
75
70
100
32
37
55
85
80
115
40
46
70
110
90
135
Notes
a
Allows 40mm space for vibrating poker
Pitch is distance between centre of bars. To calculate actual bar pitch use:
P = (b − 2cnom − 2fAlink − fAct)/(N − 1)
Where:
b
cnom
fAlink
fAct
N
= beam width
= nominal side cover
= actual link diameter (not bar size)
= actual bar diameter (not bar size)
= no. of bars
6.3.2.3 Bars along the side faces of beams
For beams with a total depth ⩾1000mm, additional reinforcement is required to control cracking in the side faces of the
beam. As a simplification, bars (16mm) should be placed along the sides inside the links, at a maximum pitch of 250mm.
Links
Asw/sbw ⩾ 0.085%
Where:
Asw = cross-sectional area of 2 legs of link
bw = average breadth of concrete below upper flange
s
= spacing of link (⩽15∅ of main compression bars)
Preferred minimum diameter 10mm.
Refer to Clause 7.3.3 of BS EN 1992-1-1 for further information.
6.3.2.4 Link spacing
Minimum pitch
100mm or [50 + 12.5× (No. of legs)]mm, whichever is greater. This ensures that the space taken up by links along
the beam is not overlooked (MDs B1 and B2).
6.3.2.5 Maximum pitch
300mm or 0.75d or 12∅ of compression bar, whichever is least.
6.3.2.6 Maximum lateral pitch of legs
600mm or 0.75d. Previous UK standards advised that the distance of a tension or compression bar from a vertical
leg should not be >150mm, but this is not a requirement in BS EN 1992.
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
| 93
6.3.2.7 Anchorage and lapping of bars
Minimum anchorage length
10∅ or 100mm, whichever is greater.
For high yield steel, Grade B500 and deformed bars, typical anchorage and lap lengths for ‘good’ and ‘poor’ bond
conditions (Fig. 5.6) are given in Appendix E.
Refer to Clauses 8.4 and 8.7 of BS EN 1992-1-1 for further information.
6.3.2.8 Simplified curtailment rules (longitudinal reinforcement in beams)
Figure 6.16 provides guidance on the curtailment of reinforcement for beams to meet the requirements of
Clause 9.2.1.3 of BS EN 1992-1-1.
Figure 6.16: Curtailment of reinforcement for beams
Face of support
100%
0.15l + al > lbd
Reinforcement for
maximum hogging moment
30%
60%
0.30l + al
0.30l + al
35%*
Position of
effective
support
*Reduce to 25%
for equal spans
100%
Reinforcement for maximum sagging moment
a) Continuous member, top reinforcement
b) Continuous member, bottom reinforcement
25%
Notes:
l = effective length
al = distance to allow for tensile force due to shear force
lbd = design anchorage length
Qk < Gk
Minimum of two spans required
Applies to uniformly distributed loads only
Shortest span must be >0.85× longest span
Applies where 15% redistribution has been used
lbd
0.08l
100%
Position of
effective support
c) Simple support, bottom reinforcement
Simplified rules for curtailment of bars may be used without bending moment diagrams, provided adjacent spans are:
approximately equal (within 15%) over at least three spans; the characteristic variable action Qk does not exceed the
characteristic permanent load Gk ; and the loading is uniformly distributed (Figure 6.17). The effective span L need not
be taken greater than: (clear span + d).
Figure 6.17: Layout of reinforcement for flexible detailing of beams
U-bars at
end support
Top bars at
internal supports
Hanger bars
Bars in
bottom span
Lacer bars
Bottom splice bars
at internal supports
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6.3.2.9 Hanger bars
At least 20% of maximum support area or sufficient for compression area required, whichever is greater, should be
carried to 25mm from each support. Diameter: 16mm (recommended size).
6.3.2.10 Top bars at internal support (simplified rules)
At least 60% of maximum support area should continue to a point where the hanger bars are sufficient, plus a
tension lap, or to a point of zero moment if the nominal hanger bars do not satisfy the minimum spacing rules for
tension reinforcement. Where no information is given concerning curtailment, this reinforcement should extend 0.25L
from the support face.
No reinforcement should extend less than 0.15L from the support face, or 45× bar diameter from the support face,
whichever is greater, where L is the effective span of beam.
6.3.2.11 Bottom splice bars at internal support
The area should not be less than the minimum percentage required. At least 30% of the maximum span area should
be supplied, if the simplified rules are used. Otherwise it should conform to the bending moment diagram as
modified by Figure 6.16.
These bars should extend for a tension lap with the main bottom bars or, if in compression, to a point at which
compression bars are no longer required, plus a compression lap.
6.3.2.12 Bottom bars in span (simplified rules)
The area should not be less than the minimum percentage required. At least 30% of maximum span area for
continuous beams and 50% of maximum span area for simply supported beams, is continued to 25mm from the
support. The remainder extends to within 0.15L of internal supports, 0.1L of exterior supports and 0.08L of simply
supported beam supports. The point of support may be considered up to d/2 inside the face.
6.3.2.13 U-bars at end of beam
These should provide the tension area required for support moment or 30% of maximum span area (50% for simple
supports), if the simplified rules are used, whichever is greater.
The length of the top leg of the bar should be calculated in the same way as for internal support bars.
The bottom leg of the bar extends to the same distance into the span as for internal support splice bars. Where the
design has assumed a simply supported end, sufficient top steel should be provided for crack control. Where this is
much less than the bottom reinforcement required, the U-bars should be replaced by L-bars, top and bottom.
The bars should extend for a tension lap from the support, both at the top and bottom.
6.3.2.14 Lacer bars at sides of beam
As specified in Section 6.3.2.3.
6.3.2.15 Anchorage of bottom reinforcement at end supports
The area of bottom reinforcement provided at supports with little or no end fixity assumed in design should be at
least 0.25 that provided in the span.
Refer to Clauses 8.4.4 and 9.2.1.4 of BS EN 1992-1-1 for further information.
6.3.2.16 Partial fixity with monolithic construction
Even when simple supports have been assumed in design, the section at supports should be designed for a bending
moment arising from partial fixity of at least 0.25 of the maximum moment in the span. This is the UK National Annex
value. The recommended value is 0.15.
Refer to Clause 9.2.1.2 of BS EN 1992-1-1 for further information.
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6.3.2.17 Flanged beams at intermediate supports of continuous beams
The total area of tension reinforcement As of a flanged cross-section should be spread over the effective width of
flange. Part of it may be concentrated over the web width (Figure 6.18). The designer should advise the effective
width of the flange beff .
Figure 6.18: Placing of tension reinforcement in flange cross-section
beff
As
hf
beff1
bw
beff2
Refer to Clause 9.2.1.2 of BS EN 1992-1-1 for further information.
6.3.2.18 Curtailment of longitudinal reinforcement in cantilevers
The curtailment of the main longitudinal reinforcement in cantilevers should always be related to the bending moment
diagram and should be advised by the designer. At least 50% of the max. area of reinforcement at the support
should be continued to the end of the cantilever.
6.3.2.19 Arrangement of links
Links are arranged such that if more than an enclosing link is required, other links are provided at the same section,
with the preferred arrangements as shown in Figure 6.19.
Figure 6.19: Preferred arrangement of links
A pattern which overlaps links makes it difficult to fix the reinforcement and should not be used (Figure 6.20).
Open links may be used for beam and slab construction using L-hooks where the width of rib is ⩾450mm. A top
locking link is also used (Figure 6.21). Where links are used for torsion they should be shaped as shown in
Figure 6.22.
Figure 6.20: Overlapping of links (not recommended)
Figure 6.21: Open links with top-locking links
10ø
75mm min.
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Figure 6.22: Required shape of torsion links
Refer to Clause 9.2.2 of BS EN 1992-1-1 for further information.
6.3.2.20 Connection to edge supports
Wherever possible, U-bars which can be placed within the depth of beam should be used.
Where a moment connection requires bars to be bent down into the column, refer to Section 6.4.2. Bending top
bars up into the column is not recommended.
For narrow edge supports each tension bar should be anchored by one of the following:
• an effective anchorage length equivalent to 12× bar size beyond the centreline of the support. No bend or hook
should begin before the centre of the support
• an effective anchorage length equivalent to 12× bar size plus d/2 from the face of the support, where d is the
effective depth of member. No bend or hook should begin before d/2 from the face of the support
These rules should be adhered to where there is no vertical reinforcement through the support (e.g. brickwork,
MD S3). Where vertical reinforcement exists, sufficient anchorage can be achieved by ensuring that some mechanical
link occurs between the beam and the vertical element. A typical example is where a beam is supported by a wall.
Horizontal bars can be threaded through U-bars (Figure 6.23).
Figure 6.23: Beam-to-wall connection
Beam
Wall
Where wide, shallow beams are required with narrow columns, it may be necessary to consider the provision of
design transverse top steel at the column position, to cater for corbel action, in addition to any links required for
shear. This is most likely to occur where precast slabs are used with no transverse beams (note: tying action also to
be considered). Generally, this will apply where the beam is wider than the column width plus twice the effective
depth.
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6.3.2.21 Deep beams
Where the span of the beam is less than 3× overall section depth it should be considered to be a ‘deep’ beam.
Note that it is the aspect ratio that determines the classification, not the actual depth of the beam.
Minimum area of reinforcement
Deep beams should normally be provided with an orthogonal mesh near each face with a minimum area of 0.002Ac
or 150mm2/m, whichever is greater, in each face and in each direction.
Maximum spacing of bars
The spacing of the bars in the orthogonal mesh should not exceed 2× beam width or 300mm, whichever is less.
Main tension reinforcement
The reinforcement corresponding to the ties in the design model should be fully anchored at the support node,
either by bending the bars, by using U-bars or by using end anchorage devices, unless there is sufficient length of
beam beyond the support for a full anchorage length of bar.
Refer to Clause 9.7 of BS EN 1992-1-1 for further information.
6.3.3 Detailing information
Design information for detailing should include:
• layout and section drawings including details of nibs and upstands etc.
• concrete grade and max. aggregate size (standard 20mm)
• nominal cover to reinforcement (standard 35 or 40mm), and the criteria governing this (fire resistance or durability).
Where nominal cover is >40mm, further information is required for fire resistance
• details of the main reinforcement and links including:
○ bar size and number, or pitch
○ type of reinforcement and bond characteristics (standard H)
○ curtailment of bars (if other than standard lap length or normal tension lap)
• details of any special moment bar connecting beam to edge columns with sketches at large scale
• details of insertion and openings e.g. conduit, cable ducting etc. should be given where the placing of
reinforcement is affected
6.3.4 Presentation of working drawings
Figures 6.24–6.26 are example drawings for different beam scenarios.
Traditional method
Individual beams are drawn related to specific gridlines (Fig. 6.24). This method is normally used where the project
has little repetition and it is simpler to show the details of all beams individually.
Representational method
The details relate to a general beam elevation and specific cross-sections (Fig. 6.25).
Bar location letters are used to cross-reference the reinforcement on the elevations and the table.
Fixing dimension of bars are labelled and cross-referenced from the elevations to the table.
The position of each beam is shown on a key plan which also shows the relevant gridlines.
Wide beams
Fig. 6.26 illustrates a situation where a wide beam is used.
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Figure 6.24: Working drawing (beams): Traditional method
B
2
1
A
1000
2000
4 H25 04 T1
2 H16 05 T1
2 H25 03 T2
4 H25 10–1000
SPACER BARS
2×1 H12 09 EF
160
250
225
REFER BEAM
DRG NO RC010
13 H12 06–150 LINKS
2
4 H20 01 B1
1
2 H20 02 UB
(19@300)
(5@200)
(13@150)
37 H12 07 LINKS
37 H12 08 CAP BARS
BEAM ON GRID 1/A–B
1
REFER SLAB
DRAWING
1
05 04
08
05
05
04 05
03 03
08
10
02
09
09
07
09
09
06
07
01
01
01
01
COLUMN BARS
1–1
2–2
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Figure 6.25: Working drawing (beams): Representational method
E
C
D
L1
DIM 2
Y
X
DIM 1
L2
E
L3
40 COVER
225
B
A
B
50
TO L3
Y
X
1525
BEAMS A.B.C.
1
1
04 04
03 03
04 04
05 05
06
08 08
03 03
06
08 08
05 05
06
06
02 02
01 01
02 02
01 01
02 02
07 07
02 02
07 07
1–1
4–4
2–2
5–5
BEAM A
12
11
REFER SLAB
DRG. R021
BEAM B
12 12
05 05
12
11
REFER SLAB
DRG. R021
E
1
06
06
10 10
09 09
10 10
09 09
3–3
6–6
BEAM–B
BEAM–C
KEY PLAN
BEAM DIM 1 DIM 2
REINFORCEMENT
A
1500
250
B
1400
200
C
1100
275
F
BEAM–A
BEAM C
A
OUTSIDE FACE
OF BEAM
B
C
D
E
L1
SECTION
L2
L3
2 H32 01 4 H25 02 2 H20 03 2 H12 04 2 H20 05 7 H10 06–175 10 H10 16–250 7 H10 06–175
(2+2)
4
H25 02 2 H20 03 2 H12 08 2 H20 05 7 H10 06–175 8 H10 06–250 7 H10 06–175
2 H3 07
(2+2)
2 H25 09 4 H20 10 2 H20 11 2 H12 12 2 H20 05 6 H10 06–200 5 H10 06–300 6 H10 06–200
(2+2)
X–X
Y–Y
1–1
4–4
2–2
5–5
3–3
6–6
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Figure 6.26: Working drawing (beams): Wide beams
E
F
1500
500
06
06
2 H12 07 T1
07
3
1
2
05
5 H20 05 T1
08
4 H12 08 T1
4 H20 06 T1
40 COVER
01
01
6 H20 01 B1
04
5 H20 04 UB
50
3
1
2
02
1000
5 H20 03 B2
02
3 H20 02 B1
(14@300)
(8@150)
1175
22 H10 09 –300 LINKS
2×22 H10 10 –300 LINKS
22 H10 11 –300 CAP BARS
BEAM ON GRIDLINE 6/E–F
6
07 04
04
UB
11
04 07
04 04 04
07 08
11
08
08
10
10
08 07
10
10
01
09
01
01 01
09
1–1
01
01
02
02
2–2
06
05
06
05
06
05
10
06
05
REFER SLAB DRG
05
10
09
03
01 01
03 03 03
01
01
3–3
03
01 01
01 01
02
05
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GL
GL
At lap
location links
spacing
should not
exceed
150mm
Reinforcement for maximum hogging moment
1
For moment
connection
between beam
and edge
columns
see Section 6.4.2
2
l0
l0
Nominal spacing of links to be
300mm, 0.75d or 15 x dia.
of compression bar
(whichever is less)
CL Support
or d/2
3
1
A
35% hogging steel
(reducing to 25%
for equal spans)
B
0.30l + d#
60%
Reinforcement for maximum (100%)
sagging moment
0.15l + 1.1d > lbd
for fixed support
l0 for simply supported (100% of reinforcement)
2
0.15l + 1.1d > lbd
(100% of reinforcement)
3
0.3l – d
for fixed support
(30% of reinforcement)
0.08l
for simply supported
(25% of reinforcement)
A
B
CL Support
or d/2
0.30l – d #
(30%)
l
Beam
depth
750
900
1200
1500
Beam
width
Side bar details
300
450
600
750
>900
3 H16
4 H16
5 H16
6 H16
3 H20
4 H16
5 H16
6 H16
3 H20
4 H20
5 H16
6 H16
3 H25
4 H20
5 H20
6 H16
3 H25
4 H25
5 H20
6 H20
Add additional bar for
each 300mm
>1500
NOTE: For deep beam refer to relevant section
‘Closer’ bars used
with open links to be
used for wide beams
(to be agreed with
contractor)
Hanger bars to
be 35% of max.
support steel
Bars specified
by designer
(or refer to table)
A–A
Min. of one clear space
to be left (75mm)
sufficient to insert
a poker vibrator
Bottom support
splice bars to
be placed inside
main bars.
At least 30% of
max. span steel
Special care should be taken to avoid congestion of
reinforcement. The following must be considered:
– Laps
– Splices
– Actual bar size
– Clear spacing between bars
For more than one
layer of main bars,
spacers are provided.
25 dia. or main bar diameter
(whichever is greater)
B–B
Beams MD B1
SPAN AND SUPPORT DETAILS
Nominal cover to all reinforcement specified by engineer
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Beams MD B2
102
BROAD SHALLOW SECTIONS
’Closer’ bar for overall link
(may not be required
where slab reinforcement
is coincident with links)
Min. end projection, P
(Table C1)
*
Detail B or C may be used
to maintain min. spacing
between legs
75mm
min.
*
Internal links should
not overlap
Max. lateral spacing of link legs
should be lesser of 0.75d or 600mm
(each bar in compression should be restrained,
or within 150mm of a bar that is restrained by link,
or designer to advise)
Detail A
3dia.
This should be checked
to ensure congestion
does not occur
Internal links may be detailed as
single leg to avoid overlap.
These links placed either side of
outer leg alternatively as shown
Plan view of links
arrangement
Detail B
Internal links may be detailed as
closed link to avoid overlap
Detail C
Beam
depth
Beam
width
750
900
1200
1500
>1500
Side bar details
300
450
600
750
>900
3 H16
4 H16
5 H16
6 H16
3 H20
4 H16
5 H16
6 H16
3 H20
4 H20
5 H16
6 H16
3 H25
4 H20
5 H20
6 H16
3 H25
4 H25
5 H20
6 H20
Add additional bar for
each 300mm
NOTE: For deep beam refer to relevant section
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Beams MD B3
CANTILEVER BEAMS
Maximum of
1.5k or 0.3l + 1.1d
GL
(60% of reinforcement)
Cantilever length, k
Maximum of
0.75k or 0.15l + 1.1d
(100% of reinforcement)
(100% of reinforcement)
l0
l0
l0
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6.4 Columns
6.4.1 Introduction
This guidance relates specifically to in situ rectangular and circular columns but can also apply to all irregular-shaped
columns. The Manual generally (but in this section in particular) is not applicable to seismic conditions10. Walls,
as defined in BS EN 1992 with a breadth/thickness ratio greater than 1:4, are considered in Section 6.5 of this Manual.
6.4.2 Design and detailing notes
Concrete grade
Concrete grades <28/35MPa (cylinder strength/cube strength) are not normally used. Care should be taken to
ensure that the design strength of concrete required in a column does not exceed 1.4× that in the slab or beam
intersecting with it, unless special measures are taken to resist the bursting forces.
Minimum area of reinforcement
0.002Ac or 0.10NEd/fyd, whichever is greater.
Where:
Ac = area of concrete
NEd = design axial compression force
fyd = design yield strength of reinforcement
The designer should advise if 0.10NEd/fyd is greater than 0.002Ac
Recommended minimum bar diameter is 12mm (UK National Annex31). For small section columns, <200mm,
the minimum of 8mm given in Clause 9.5.2 of BS EN 1992-1-1 may be applied, provided other requirements are met
(note the limited availability of 8mm bars).
For columns having a polygonal cross-section, at least one bar should be placed in each corner, i.e. for a square or
rectangular column the minimum number of bars is four.
Unless advised otherwise by the designer, the minimum number of bars for circular columns should be taken as six.
For small diameter columns <200mm, the minimum of four given in BS EN 1992 may be applied, provided the
designer has considered the most unfavourable arrangement of the bars in the design.
Refer to Clause 9.5.2 of BS EN 1992-1-1 for further information.
Maximum area of main reinforcement
Maximum area of reinforcement should not exceed 0.04Ac unless it can be shown that any resulting congestion of
reinforcement does not hinder the ease of construction.
At laps the maximum area of reinforcement should not exceed 0.08Ac .
Mechanical splices should be considered where congestion becomes a problem (Appendix D).
Refer to Clause 9.5.2 of BS EN 1992-1-1 for further information.
Bar spacing
Recommended minimum pitch of reinforcing bars is given in Table 6.5. These comply with the minimum spacing
rules for compaction of concrete and for bond.
Preferred maximum spacing:
• compression bars
300mm, provided that all main bars in compression zone are within 150mm of a restrained bar (Figure 6.27)
• tension bars
175mm
Refer to Clause 9.5.2 of BS EN 1992-1-1 for further information.
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Table 6.5: Recommended minimum pitch of bars in columns (mm)
Bar size
∅ (mm)
Actual bar
diameter (mm)
Sides where cranked bars
are into section
Sides where corner bars are cranked
along section (average pitch)
3 bars
4 bars
5 bars
6 bars
8 bars
10
13
40
55
50
45
45
45
12
14
40
55
50
50
45
45
16
19
45
65
60
55
55
50
20
23
50
75
65
60
60
55
25
29
55
85
75
70
70
65
32
37
70
110
95
90
85
80
40
46
90
135
120
110
105
100
Notes:
Pitch is distance between centre of bars. To calculate actual bar pitch (including average pitch) use:
P = (x − 2cnom − 2fAlink − fAct)/(N − 1)
Where:
x
cnom
fAlink
fAct
N
= relevant column dimension
= nominal side cover
= actual link diameter (not bar size)
= actual bar diameter (not bar size)
= no. of bars
Figure 6.27: Requirement of links in columns
<150mm
>150mm
Anchorage and lapping of bars
Minimum anchorage length
10∅ or 100mm whichever is greater.
Typical anchorage and lap lengths for ‘good’ and ‘poor’ bond conditions (Fig. 5.6) are given in Appendix E.
Lapping of bundled bars
When lapping bundled bars, care should be taken to avoid congestion. This may be achieved by staggering the laps
of the bars in each bundle (Section 5.4.4).
Refer to Clauses 8.4 and 8.7 of BS EN 1992-1-1 for further information.
Links
The size of link should be the greater of a quarter the maximum size of longitudinal bar and 8mm
(for very small diameter columns <200mm, the minimum of 6mm given in BS EN 1992 may apply).
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Bundled main bars may be represented by a single bar for the purpose of calculating link size and spacing.
This single bar has an equivalent size to give it the same cross-section area as the bundle.
An overall enclosing link is required, together with additional restraining links for alternate main bars or a bundle of
bars. Provided that all other main bars in the compression zone are within 150mm of a restrained bar no other links
are required (Fig. 6.27). Otherwise, additional links should be added to satisfy this requirement. Additional links are
not required for circular columns.
Maximum spacing of links
The least of:
• 20× size of longitudinal bars
• lesser dimension of the column
• 400mm
The maximum spacing should be reduced by a factor of 0.6 in sections within a distance equal to the larger
dimension of the column cross-section above and below a beam or slab.
Where the direction of the longitudinal bars changes (e.g. at laps), the spacing of links should be calculated.
Spacing should ensure there is a link close to the cranking positions of the main bars. These effects may be ignored
if the change in direction is ⩽1 in 12.
Links to resist bursting at laps
Where the diameter of the longitudinal bar is ⩾20mm, the links required to resist the bursting forces in the lapping
zone should have a total area ΣAst of not less than the area As of one lapped bar (ΣAst ⩾ 1.0As ). These links should
be positioned at the outer sections of the lap (Figure 6.28).
Figure 6.28: Links required for bursting at column laps
• Ast /2
• Ast /2
<150mm
Fs
Fs
l0
4ø
4ø
Moment connections between beam and edge column
Wherever possible, U-bars which can be placed within the depth of beam should be used.
L-bars which penetrate down into the column should be used when the distance ‘A’ (Figure 6.29) is less than the
anchorage length for that bar diameter. These bars must be fixed accurately at the top of the column lift which is a
difficult and unattractive site task; in this regard, U-bars can be more convenient because they do not need to
project from the column below the beam soffit.
If non-standard, the bend radius should be checked by the designer and specified in the detailing instructions. A bar
of the same size or greater should be placed inside the bend unless there is reason to justify the detail without it.
Where using a non-standard bend, a thorough check should be carried out to ensure the reinforcement fits and will
perform as intended. The critical effective depth may not be obvious, and various locations may need to be
assessed.
Special care should be taken by the designer and detailer to make sure this reinforcement does not conflict with any
beam reinforcement passing through the column in the other direction.
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Figure 6.29: Moment connection between beam and edge column
A
Critical effective depth
U-bar
Standard bend
Non-standard bend
Restraint to column bars
Where there is no edge beam intersecting at approximately the same level as the joint, transverse column
reinforcement should be provided within the depth of the beam (Figure 6.30) to restrain the main column steel.
This may be in the form of horizontal links or U-bars extending into the beam; links are required in corner columns.
Unless specified by the designer, the spacing should be as for the links in the column.
Figure 6.30: Shear enhancement of column
Horizontal U-bars
Refer to Clause 6.2 of BS EN 1992-1-1 for further information.
Bursting action
Where a change of column section occurs, particularly at edge and corner locations, links may be required to
provide adequate restraint to bursting action (i.e. end block action). These links may occur within the depth of beam
or slab, but may also extend further down.
Starter bars
The designer must take account of the construction sequence and foundation level, as this has implications on the
length of the starter bars (e.g. if the foundation reinforcement is placed at a depth lower than specified, the
consequent lap of the first lift of column bars is likely to be too short). For this reason, starter bars from pad footings
and pile caps are specified longer than required (MDs F1 and F2).
6.4.3 Detailing information
Design information for detailing should include:
•
•
•
•
•
section dimensions and its position and orientation relative to particular grid lines.
outline drawings which clarify what happens to the column above the lift being considered.
kicker height if other than 75mm.
concrete grade and aggregate size (standard 30/37MPa and 20mm).
nominal cover to all reinforcement (standard 35mm internal, 40mm external). Supplementary mesh reinforcement
if required.
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• simple sketch of cross-section of column showing the longitudinal reinforcement in each face of the column, i.e.
○ number and position of bars
○ type of reinforcement and bond characteristics (standard H)
○ diameter of bars
○ lap length (if other than normal compression, lap the linking reinforcement)
○ type of reinforcement (standard H)
○ diameter of links
○ spacing
○ pattern of links (if special).
• instructions for lapping of bunched bars if required.
• special instructions for links within depth of slab or beam.
• if a mechanical or special method of splicing bars is required this must be shown in a sketch, otherwise the
method given in the Model Details will be assumed.
• Special instructions and sketches should be given where services are provided within the column.
• Details of insertions, e.g. conduit, cable ducting, cladding fixings, etc., should be given where the placing of
reinforcement is affected.
6.4.4 Presentation of working drawings
Figures 6.31 and 6.32 are example drawings for different column scenarios.
Traditional method
Individual columns are drawn related to specific gridlines (Fig. 6.31). Reinforcement is shown in schematic form on
the elevations. Sections are shown with the column outline drawn to scale.
This method is normally used where the project has little repetition and it is simpler to show the details of all columns
individually.
700
Figure 6.31: Working drawing (columns): Traditional method
330
30.000
4 H20 19
7
6
6
26.750
COLUMN G7
19
19
19
G
15 H8 20 200
FOR DETAILS OF COLUMNS
BELOW SEE DRG R22
19
6–6
20
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Representational method
The detail (Fig. 6.32) relates general column elevations and sections, to X and Y directions, together with a table
giving details of reinforcement for each type of column. Bar location letters are used to cross-reference the
reinforcement on the drawing and in the table.
Column outlines to the elevations are not drawn. The section shapes of each column type are only representative,
and may not be drawn to scale.
Note:
• The X and Y directions must be related to the GA drawing
• Each column is related to a reinforcement type, either using a location plan or by tabulating the column grid
references (Fig. 6.32)
• The levels and any relevant fixing dimensions must be specified, either on the drawing or in the table
DIM D
Figure 6.32: Working drawing (columns): Representational method
DIM C
LEVEL B
Y
Y
G
E+F
X
LINKS G + H
E
E
E
E
E
E
X
E
E
F
F
F
F
E
E
H
LEVEL A
G
H
7–7
8–8
FOR DETAILS OF
COLUMNS BELOW
SEE DRG R12
MAIN BARS
E
F
COLUMN
REF
No
OFF
LEVEL A
LEVEL B
DIM C
DIM D
CAGE
SECTION
G6, H6
2
30.50
33.75
395
850
7–7
6 H25 03
K8, L8
2
30.50
34.00
395
1050
7–7
M9
1
31.50
34.75
425
850
8–8
LINKS
G
H
——
14 H8 07 200
14 H8 08 200
6 H32 10
——
14 H8 07 200
14 H8 08 200
4 H25 03
4 H20 10
14 H8 11 200
28 H8 12 200
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Columns MD C1
110
BOTTOM DETAIL
This detail allows bars to be
easily extended to give
foundation-level tolerance
A
Spacing of links at lap
not greater than:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– at least 3No. links
– 240 (round down to nearest 25mm)
– 150mm @ lap locations
(Refer to Figure 8.9 in BS EN 1992-1-1)
A
l0 + 50
(foundation-level tolerance)
Kicker: 100
(150 below ground if required)
Top of foundation
Unless specified
by design, use
H10-300 (3No. min.)
450 min.
(or 2 bars)
Cover to starter bars is given
from column faces
A–A
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1
1
150 150 150 150
max. max. max. max.
150 150
max. max.
SC51
100 Kicker
Lap length, l0
SC21
SECTION
1
SCALE 1:25
–
GL
1
150
max.
SC21
1
–
GL
150
max.
Main bars
BBS
Level by level
Spacing of links should be the least of:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– 240 (round down to nearest 25mm)
– Minimum size of links 8mm
(10mm for 40 dia. bar)
Beyond a distance equal to cross-section
of larger column dimension or 3 links from
slab/column interface, (whichever is greater)
spacing may be increased by a factor of 1.67.
Links should not exceed a spacing
of 150mm at lap location
SC51
150 150
max. max.
150 150
max. max.
1
–
SECTION
1
SCALE 1:25
–
Link at knuckle of crank
Lap length, l0
No special link required at crank
k length
Min. cran e offset
ntrelin
= 12 × ce
100 Kicker
Length of crank is 12 × centreline
joggle offset or 300mm but
shall not be less than:
– 10Ø for bars not exceeding
a nominal size 16mm
– 13Ø for nominal sizes
greater than 16mm
Centreline joggle offset
50mm
Min. overall joggle offset
= 2 dia. + 10%
Columns MD C2a
INTERMEDIATE DETAIL: NOMINAL LINKS FOR
NORMAL STRENGTH CONCRETE
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INTERMEDIATE DETAIL: NOMINAL LINKS FOR
HIGH STRENGTH CONCRETE
For HSC columns all links to be Shape Code 99
with link ears 135° hooks/180°
with hooks of 10 dia. straight
(or 70mm whichever the greater).
Shape Code 51 or 63 not acceptable
1
1
150 150
max. max.
150 150 150 150
SC99
100 Kicker
Lap length, l0
SC99
SECTION
1
SCALE 1:25
–
GL
1
SC99
150
SC99
150 150
150 150
max. max.
Main bars
1
–
1
–
In the UK, the designer
should specify link
spacing to comply with
requirements of Clause 9.5.3(3)
of the UK NA to BS EN 1992-1-1.
Links should not exceed a
spacing of 150mm at lap location
SECTION
1
SCALE 1:25
–
Lap length, l0
Link at knuckle of crank
No special link required at crank
Length of crank is 12 × centreline
joggle offset or 300mm but
shall not be less than:
– 10Ø for bars not exceeding
a nominal size 16mm
– 13Ø for nominal sizes
greater than 16mm
length
Min. crank e offset
ntrelin
= 12 × ce
100 Kicker
GL
150
BBS
Level by level
Columns MD C2b
112
Centreline joggle offset
50mm
Min. overall joggle offset
= 2 dia. + 10%
The Institution of Structural Engineers
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l0
Spacing of links above slab/beam
should be the least of:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– at least 3No. links
– 240 (round down to nearest 25mm)
– 150mm @ lap locations
(Refer to Fig. 8.9 in BS EN 1992-1-1)
Where columns are offset or
large moments exist these bars
should be anchored into
floor slab as shown
>75mm
Detail B may be applied if
column offset is less than 75mm
l0
Bursting steel specified by
designer in accordance with
Clause 6.7 of BS EN 1992-1-1
A
A
Detail A
Splice bars located by dimensions
from face of lower column
Minimum 3 sets of locating links required
(if no internal link present)
No bar within a compression zone should
be further than 150mm from a link
(Clause 9.53(6) of BS EN 1992-1-1)
Note:
This is applicable only when column is
located entirely within the perimeter
of the column below — otherwise
refer to designer
A–A
≤75mm
This detail is applicable only if this
is first lift of column — designer to advise
Bars may be cranked and lapped with
bars in the level above as necessary
Bursting steel specified by
designer in accordance with
Clause 6.7 of BS EN 1992-1-1
Detail B
Columns MD C3
INTERMEDIATE DETAIL: OFFSET COLUMNS
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TOP DETAIL
Detail A applies when slab depth is not less than:
– 200 using 20 size of column bars
– 250 using 25 size of column bars
– 300 using 32 size of column bars
otherwise Detail B applies
l0
l0
Spacing of links at lap not greater than:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– 240
Links should not exceed a spacing of
150mm at lap location
– At least 3No. links
PLAN
Detail A
Spacing of links at lap not greater than:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– 240
Links should not exceed a spacing of
150mm at lap location
– At least 3No. links
l0
Columns MD C4
114
Bars must be positioned
to avoid clashes
PLAN
Detail B
The Institution of Structural Engineers
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Min. hook (Table C1)
For height of larger dimension of column,
spacing of links not greater than:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– 240
Links should not exceed a spacing of
150mm at lap location
– At least 3No. links
2No. of location links
l0
Spacing of links at lap not greater than:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– 240
Links should not exceed a spacing of
150mm at lap location
– At least 3No. links
lbd
450 min.
Columns MD C5
TOP DETAIL (INCL. SPLICE BARS)
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l0
CIRCULAR COLUMNS: HELICAL LINKS
Main bars scheduled straight.
Cage is rotated to lap with cage below
Helical binders scheduled in 12m lengths.
Tension lap length is required between
helical binders
p = pitch of helix
l0
Columns MD C6a
116
0.5p
Pitch of helix not greater than:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– 240
Links should not exceed a spacing of
150mm at lap location
– At least 3No. links
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
l0
For height of larger dimension of column,
spacing of links not greater than:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– 240
Links should not exceed a spacing of
150mm at lap location
– At least 3No. links
l0
Main bars scheduled straight.
Cage is rotated to lap with cage below
Spacing of links at lap not greater than:
– 12 dia. of longitudinal bars
– 0.6 × lesser dimension of column
– 240
Links should not exceed a spacing of
150mm at lap location
– At least 3No. links
Columns MD C6b
CIRCULAR COLUMNS: CIRCULAR LINKS
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6.5 Walls
6.5.1 Introduction
This guidance relates specifically to walls that are vertical loadbearing members. It includes plain concrete walls as
defined in BS EN 1992. Columns, with a breadth/thickness ratio of not more than 1: 4 are considered separately in
Section 6.4 of this Manual. Walls thinner than 150mm are not recommended. Basement retaining walls are
considered in Section 6.6.
6.5.2 Design and detailing notes
Minimum area of reinforcement
• Vertical reinforcement
0.002Ac (half in each face).
Minimum bar diameter to ensure robust cage: 12mm
Refer to Table 6.6 for recommended minimum areas and suggested bar arrangements.
• Horizontal reinforcement
25% of vertical reinforcement or 0.002Ac (half in each face) whichever is greater.
Preferred minimum bar diameter not less than a quarter of the diameter of vertical bars.
Table 6.6: Suggested minimum reinforcement for walls
Wall thickness (mm)
Bar size and spacing for vertical/horizontal reinforcement
≤200
A252 fabric or 8 @ 200
225
A252 fabric or 8 @ 200
250
A252 fabric or 8 @ 200
275
10 @ 250
300
10 @ 250
350
A393 fabric or 10 @ 200
400
12 @ 250
450
12 @ 250
500
10 @ 150
600
10 @ 125
700
12 @ 150
800
16 @ 250
Note: Size and spacing proposed avoids specifying excessive reinforcement.
Links
Diameter to be not less than a quarter of the size of the largest compression bar.
Plain concrete walls
Where reinforcement is required for the purpose of controlling shrinkage or temperature (also applies to reinforced
concrete walls), it should comply with the minimum requirements for a wall with reinforcement.
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Minimum steel area for both vertical and horizontal reinforcement 0.0025Ac .
This reinforcement should consist of small diameter bars closely spaced, and placed (with adequate cover) near the
exposed surface. This reinforcement should be distributed with half near each face.
Refer to Clause 9.6.2 of BS EN 1992-1-1 for further information.
Maximum area of vertical reinforcement
0.04Ac
Refer to Clause 9.6.2 of BS EN 1992-1-1 for further information.
Bar spacing
Minimum spacing
Recommended minimum pitch of reinforcing bars is the same as for slabs and given in Table 6.3. These comply with
the minimum spacing rules for compaction of concrete and for bond.
Maximum spacing
Vertical and horizontal bars. The lesser of:
• 2× wall thickness
• 400mm
Links
Where the total area of the vertical reinforcement in the two faces exceeds 0.02Ac , links should be provided
(Section 6.4). The larger dimension referred to, need not be made larger than 4× wall thickness).
Maximum vertical spacing
The lesser of:
• 16× diameter of vertical bars
• 2× wall thickness
• 400mm (BS EN 1992-1-1 recommendation)
Maximum horizontal spacing
Any vertical compression bar not enclosed by a link should be within 200mm of a restrained bar. The spacing should
not exceed 2× wall thickness.
Refer to Clause 9.6.3 of BS EN 1992-1-1 for further information.
Anchorage and lapping of bars
Typical anchorage and lap lengths for ‘good’ and ‘poor’ bond conditions (Fig. 5.6) are given in Appendix E.
Lap lengths provided (for nominal bars etc.) should not be less than 15× bar size or 200mm, whichever is greater.
Refer to Clauses 8.4 and 8.7 of BS EN 1992-1-1 for further information.
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Notation for layers of reinforcement
Reinforcement is fixed in two layers at right-angles to form a mat (normally one at each wall face):
•
•
abbreviation for near face N
abbreviation for far face
F
F – far face
N – near face
Typical bar and indicator line
The convention for illustrating and ‘calling up’ bars on walls follows closely that for slabs (Section 6.2.2)
A zone of similar bars in one face:
20H10-63-150N1
A zone of similar bars in two faces:
40H10-63-150
(20N1-20F2)
A zone of dissimilar bars in two faces:
20H10-63-150N1
63
64
20H10-64-150F2
Identical bars appearing on different faces are itemised separately. To avoid congestion in thin walls <150mm thick,
a single mat of reinforcement may be provided, if design requirements permit.
Corner details
For most conditions of applied moment, MD W2 is suitable. For situations where the opening applied moment
requires more than 1.5% tensile reinforcement, consideration should be given to introducing a splay and diagonal
reinforcement (Annex J of UK National Annex to BS EN 199231).
Openings in walls
Isolated openings smaller than the pitch of the reinforcement need not be trimmed under normal circumstances.
Where an opening does affect the structural integrity, consideration should be given to the use of diagonal bars at
the corners of the hole, to provide better crack control.
Where an opening does not affect the structural integrity, it should be trimmed with bars of diameter one size larger
than that used in the surrounding wall. For such situations, the minimum wall thickness should be increased to
175mm. U-bars of the same size as the horizontal bars should be placed around the opening, enclosing the trimmer
bars (MD W4). Further guidance on trimming openings can be found in Section 6.2 and MD OP1.
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Edge wall connections to slabs
This method for detailing slab-to-edge walls is described in Section 6.2.2. It is similar to the beam-to-edge columns
described in Section 6.3.2. MD S2 shows the reinforcement detail for such a joint. Where slab starter bars are
required and cannot be inserted through holes left in the wall, MD W3 is used.
Half landings
Where starter bars are required for half landings these may be inserted in the walls, preferably using a proprietary
reinforcement continuity system which holds a Technical Approval issued by a suitably accredited product
certification body (e.g. CARES). Mechanical shear dowels and couplers may be considered as alternatives to
half-joints, avoiding the use of nibs.
6.5.3 Detailing information
Design information for detailing should include:
• layout and section drawings including details of slab intersections and holes, and details of the construction
system if known
• concrete grade and max. aggregate size (standard 20mm)
• nominal cover to reinforcement (standard 20mm for internal conditions, 40mm for external conditions), and the
criteria governing this (fire resistance or durability)
• details of any design reinforcement required including:
○ type of reinforcement
○ bar diameter
○ pitch or number
○ location
○ lap length (if other than normal compression lap)
• details of proprietary reinforcement, insertions and openings e.g. conduit, cable ducting, etc. should be specified
where the placing of reinforcement is affected. Provide this information at an early stage
• confirmation of whether the walls are to be slipformed (noting the affect this has on bond characteristic —
Chapter 5)
6.5.4 Presentation of working drawing
Figure 6.33 is an example drawing for a wall scenario.
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Figure 6.33: Working drawing: walls
19 H10 09–200 LINKS
19 H10 07–200 UB
12 H10 07–200 UB
1
19 H10 04–200 UB
2×19 H10 08–200 H EF
3
2×7 H10 05–200 H EF
2
16.675
2×5 H12 03–200 UB
PROVIDE DIAGONAL BARS
IF REQUIRED
REFER TO MW4
2×1 H16 06 H EF
600
3
2×2 H16 02 V EF
2
3
(8)
2×26 H12 01–200 V EF
2
(18)
75
1
12 H10 04–200 UB
12.675
WALL ON LINE ‘A’
A
16.675
07
01
01
A
01
03
01
05
08
03
03
05
09
01
01
07
01
08
03
03
2–2
01
01
A
01
01
03
05
05
04
04
04
06 06
1–1
3–3
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
U-bar may be replaced with L-bar for
thin wall, if width of U-bars does not
meet min. bending requirement
l0
100mm or below
slab bars
l0
100mm Kicker
(if required)
For edge walls, starter bars for slabs shown
on MD S2 (B and C) should be detailed with
wall drawings wherever possible. Otherwise
they must be clearly cross-referenced
l0
100mm Kicker
(150mm below ground if required)
lbd
Greater of 450mm or
2× Mat bar spacing
Where there is no specific design requirement, the bar size and pitch in Table 6.6 may be used.
Walls MD W1
GENERAL DETAILS
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l0
CORNER DETAILS
Two bars should be placed within loop
for wall thickness <300.
For wall thickness >300, four bars
should be included as shown
l0
Detail A
lbd
l0
Walls MD W2
124
Two bars should be placed within loop
for wall thickness <300.
For wall thickness >300, four bars
should be included as shown
(Designer to clearly advise design requirement)
lbd
l0
Detail B
(for large opening moments)
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
Legs bent and kept along
wall face within box
when casting wall
l0
H
l0
W
Legs to rebend to lap with
slab bars when pouring slab
H
Note: For slabs >250mm
thick this is poor bond lap
H
l0
W
l0
This detail is applicable
if bar dia. is <16mm
35mm box (max.)
to maintain cover
requirements
Detail A
(Pullout bars or similar approved)
U-bar with coupler
Threaded bar
Note: For slabs >250mm thick
this is poor bond lap
l0
l0
35mm box (max.)
to maintain cover
requirements
Detail B
(Coupler box or similar approved)
This detail is applicable
if bar dia. is >16mm
Walls MD W3
HALF-LANDING DETAIL
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Walls MD W4
l0
lbd
HOLE DETAILS
for trimmer bars
126
Trimmer bars at top/bottom of opening
(designer to advise design requirement)
Opening
Trimmer bars at
side of opening
Detail A
Section through top of opening
Section through bottom similar
Opening
lbd
l0
Trimmer bars at
top/bottom of opening
Trimmer bars at side of opening
(designer to advise design requirement)
Detail B
Section through left of opening
Section through right similar
l bd
Detail C
Typical opening corner
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| 127
6.6 Retaining walls
6.6.1 Introduction
This guidance relates specifically to retaining walls with two layers of reinforcement. The specification of joints and
waterbars for water-resistant structures is not covered — reference should be made to BS EN 1992-34 and
Water-resisting basements — a guide 12. Reinforced and plain concrete walls are considered in Section 6.5 of this
Manual. Foundations are considered in Section 6.7. Diaphragm walls are not considered.
6.6.2 Design and detailing notes
Minimum area of reinforcement
Simple earth-retaining walls
Retaining walls which provide means for water to drain, e.g. weep holes, and for which minor seepage does not
create problems.
• vertical reinforcement
0.002Ac (half in each face). Minimum bar size 12mm
• horizontal reinforcement
Greater of 25% of vertical reinforcement or 0.002Ac (half in each face)
See Table 6.6 for recommended minimum areas and suggested bar arrangements.
Refer to Clause 9.6.2 of BS EN 1992-1-1 (and BS EN 1992-3) for further information.
Water-resisting retaining walls or retaining walls which are required to prevent water seepage, e.g. basements
The designer should advise minimum reinforcement.
Maximum area of vertical reinforcement
0.04Ac
Refer to Clause 9.6.2 of BS EN 1992-1-1 for further information.
Bar spacing
Recommended minimum pitch of reinforcing bars is the same as for slabs and given in Table 6.3. These comply with
the minimum spacing rules for compaction of concrete and for bond.
Maximum spacing: 200mm
Refer to Clause 9.6.3 of BS EN 1992-1-1 and Clause 7.3.3 of BS EN 1992-3 for further information.
Anchorage and lapping of bars
Typical anchorage and lap lengths for ‘good’ and ‘poor’ bond conditions (Fig. 5.6) are given in Appendix E.
Lap lengths provided (for nominal bars, etc.) should not be less than 15× bar size or 200mm, whichever is greater.
Refer to Clauses 5.2.2–5.2.4 of BS EN 1992-1-1 for further information.
Edge wall connection to slabs
The method for detailing slab-to-edge walls is described in Section 6.2.2. It is similar to that for beam-to-edge
columns described in Section 6.3.2. MD S2 shows the reinforcement details for such a joint. Mechanical shear
dowels and couplers may be considered as alternatives.
Corner details
For most conditions of applied moment, MD W2 is suitable. However, for thin sections with a high applied opening
moment, a special detail may be required (Annex J of UK National Annex to BS EN 199231).
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Construction joints
Kicker height for walls below ground level should be a minimum of 150mm and cast integral with the foundations.
The requirements for movement joints need to be specified by the designer, taking any restraints and the
serviceability requirements (e.g. liquid retention) into account.
Wall starters
Wall starter bars should always be specified with the base slab reinforcement, and care should be taken to define
them relative to the wall section, or at least refer to their location on the drawing and schedule.
Links in walls
Where the total area of the vertical reinforcement in the two faces exceeds 0.02Ac links should be provided.
6.6.3 Detailing information
Design information for detailing should include:
• layout and section drawings including plan dimensions, depths and levels
• dimensions and positions of kickers (standard kicker height below ground 150mm, above ground 75mm)
• detail of design reinforcement required including:
○ type of reinforcement (standard H)
○ bar diameter
○ pitch or number
○ position
• details of construction joints
• details of any services fittings where placing of reinforcement may be affected, e.g. large openings, puddle flanges
6.6.4 Presentation of working drawings
Figures 6.34 and 6.35 are example drawings for retaining wall scenarios.
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
8 H16 04–250 T2
8 H12 05–250 B2
1
PANEL B
2×8 H12 03–250
T2 & B2
47 H16 01–150 T1
47 H12 02–150 B1
Figure 6.34: Working drawing (walls): Free-standing retaining wall
1
A
1
REFER PANEL D
50
14
08
2 (52)
2×11 H12 10
250 H EF
09
08 06
10
07
06
01
03 1.800
(2)
03
07
54 H12 06–150 V NF
54 H16 07–150 V FF
06
10
2
(2)
03
02
1–1
2×11 H12 10
250 H EF
3
11 H10 13 (A–K)
250 (UB)
3
(52)
500
09
07
2×11 H12 11–250 H NF
11 H12 12–250 H FF
08
03
75
1.800
1
54 H10 14–150 UB
54 H12 08–150 V NF
54 H16 09–150 V FF
4.300
4.300
10
14
09
10
PANEL – C PLAN
PANEL B
14
PANEL – C ELEVATION
12
09
09
1
09
09
08
13
10
10
13
3–3
08
08
10
11
10
11
2–2
08
PANEL A B B
B
C
11
12
D
REFER PANEL B
1
10
11
13
A
10
WALL A
KEY PLAN
A
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03
03
2×4 H16 02 T2 & B2
2×4 H16 01 T2 & B2
2×4 H12 03 SF
21 H12 04–300 T1
21 H12 05–300 B1
21 H12 06–300 B1
A
2×4 H12 03 SF
2×4 H16 02 T2 & B2
1
Figure 6.35: Working drawing (walls): Basement retaining wall
B
1
REFER SLAB
12
1
05
12 11
12
10
04
REFER
WALL B
10
40
COVER
1
06
13
13
11
50
COVER
CJ
(2)
550
2
16 H12 14–150 H EF
2×16 H12 15–150 H NF
2×16 H12 13–150 H EF
2×16 H12 16–150 H EF
2×16 H12 13–150 H EF
1
2×16 H12 15–150 H NF
16 H12 14–150 H FF
10.300
10
2
11
12
13
01
13
01
04
03
03
B
06
01
01
04
05
1–1
(45)
(2)
3
3
(45)
(2)
49 H12 10–150 V NF
49 H16 11–150 V FF
49 H12 12–150 U-BARS
6.800
(2)
07
1
09
49 H12 07–150 V NF
49 H16 09–150 V FF
WALL – A ELEVATION
14 13
13
16
11
CJ
10
10
13
16
2–2
13
16
15
13
B
A
15
11
11
14
10
REFER
WALL B
10
15
1
WALL A
13
3–3
KEY PLAN
WALL B
13
11
16
13
WALL B
16
13
11
11
07
09
WALL – A PLAN
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
Bar size and pitch for earth face
as specified by designer
l0
Cnom
Cnom
Bar size and pitch for exposed face
(based on min. wall thickness)
given in MD W1 (table),
unless otherwise stated
Granular fill
l0
Kicker:150
(if required)
l0
Bar size and pitch as specified by designer
Cnom
Cnom
Cnom
l0
l0
Nominal reinforcement given in MD S1,
unless stated otherwise
Key added (if required)
Large radius of bend specified
by designer if necessary
Cnom,minimum = 75mm against soil
= 50mm against prepared ground and blinding
= 40mm to formed surfaces
All are subject to design requirement
Retaining walls MD RW1
EXTERNAL CANTILEVER WALL
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Retaining walls MD RW2
132
BASEMENT RETAINING WALL
CJ
Legs bent and kept along
the wall face within the
box when casting wall
Pull-out bars
Legs to rebend to lap with
slab bars when pouring slab
CJ
l0
Vertical reinforcement fixed first
for ease of construction
Cnom
Cnom
Reinforcement not specified in
designer is given in MD W1 (table)
l0
Kicker: 150
(cast integrally for basements)
CJ
Cnom
300 min. overlap
Cnom
l0
Cnom
Cnom
Cnom
Large radius of bend specified
by designer if necessary
l0
Cavity drain slot
Kicker: 150
(cast integrally for basements)
Slab laid to falls
Cnom
Cnom
Cnom
300 min. overlap
Cnom
Cnom,minimum = 75mm against soil
= 50mm against prepared ground and blinding
= 40mm to formed surfaces
All are subject to design requirement
Note:
Details for water-resisting concrete are not included —
designer to advise on specific requirements if required
Large radius of bend specified
by designer if necessary
Cnom
l0
l0
l0
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
Waterbar (if required)
Splice bars of same size
and pitch as main bars
l0
l0
50mm
Detail A
Simple construction joint
Waterbar (if required)
U-bars of same size
and pitch as main bars
Dowel bars (if required)
specified by designer
l0
l0
If internal water bar is required,
U-bars are displaced to avoid clash
75mm
Detail B
Full contraction joint
U-bars of same size
and pitch as main bars
Waterbar (if required)
l0
l0
75mm
Detail C
Movement joint
Waterbars shown when required for basement walls.
Designer to advise on specific requirements for water-resisting concrete.
Retaining walls MD RW3
VERTICAL CONSTRUCTION JOINTS
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6.7 Foundations
6.7.1 Introduction
This guidance relates to:
•
•
•
•
rectangular pad footings and multi-column bases
piled foundations
rafts
ground beams and slabs
The specification of joints and waterbars for water-resistant structures is not covered — reference should be made
to BS EN 1992-34 and Water-resisting basements — a guide 12. Retaining walls are considered in Section 6.6.
Details for holding-down bolts are not included.
6.7.2 Design and detailing notes
Minimum area of reinforcement
• Tension reinforcement in flexural elements (Table 6.1, column 3).
• Reinforcement in sections classed as deep beams (Clause 9.7 of BS EN 1992-1-1):
As,dbmin = 0.001Ac ⩾ 150mm2/m
• Longitudinal reinforcement in piles (Clause 9.8.5 of BS EN 1992-1-1):
Pile cross-section Ac
Minimum area of longitudinal reinforcement As,dbmin
Ac ⩽ 0.5m2
AS ⩾ 0.005Ac
0.5m2 < Ac ⩽ 1.0m2
AS ⩾ 25cm2
Ac > 1.0m2
AS ⩾ 0.0025Ac
Bar diameters <16mm should not be used (except for lacers).
Bar spacing
Refer to Table 6.4.
Max. spacing:
Main bars: 200mm
Transverse bars: 300mm
Refer to Clause 9.8 of BS EN 1992-1-1 for further information.
Anchorage and lapping of bars
Typical anchorage and lap lengths for ‘good’ and ‘poor’ bond conditions (Fig. 5.6) are given in Appendix E.
Starter bars for columns should have a horizontal leg of sufficient length to be tied to two transverse bars in the
footing, typically 450mm minimum (MDs C1 and F1).
Column starter bars should be anchored, with a full compression lap length. However, bends and hooks cannot be
considered to contribute to the compression anchorage (Clause 8.4.1(3) of BS EN 1992-1-1). The compression lap
length may exceed the depth of the pad foundation or pile cap. In BS EN 1992, the effect of cover cannot be
considered. However, a report32 has demonstrated that it may be considered, and that it reduces the compression
anchorage length by a factor of 0.7. It is considered satisfactory to apply this factor to the compression lap length
given in Appendix E.
Refer to Clauses 5.2.2–5.2.4 of BS EN 1992-1-1 for further information.
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Pile caps
The full bar tension must be assumed to continue without curtailment. The full anchorage length should be provided
from the inner face of each outer pile to the end of each bar. The bars must, as a minimum, continue across the
full width of the piles.
Standard pile caps
The configuration of reinforcement normally adopted for standard pile caps is shown in Table 6.7.
Table 6.7: Layout of reinforcement for standard pile caps
No. of piles Bar ref. Shape Code Size and type
2
3
4+
1
2
3
21∗
12
21
Design H20, H25, H32 or H40 (large diameter bends)
Nominal H16, H20 or H25
Nominal H16
1
2
3
4
5
6
21∗
21∗
21
21
27
25
Nominal H16
Design H20, H25, H32 or H40 (large diameter bends)
Nominal H16 @ 200
Design H20, H25, H32 or H40
Nominal H16
Nominal H16
1
2
3
∗
21
21
12
Design H20, H25, H32 or H40
3
1
2
3
6
2
5
5
4
4
1
3
2
Nominal H16
3
Note: ∗ Where design requires a large mandrel size, Shape Code will be 99.
Ground slabs
TR34: Concrete industrial ground floors 11 provides guidance on lightly loaded ground slabs, typically in buildings.
Where such slabs are cast directly onto the ground, they should be reinforced to control cracking (Figure 6.36 in this
Manual). Square mesh fabric (A193) is suitable for this purpose. Laps of 300mm (min.) should be used. Details for
fully reinforced slabs are given in Section 6.2.
Figure 6.36: Detailing of ground slab cast directly onto ground
25 cover (slabs exposed
to weather 40)
Blinding
Sub base
Ground beams
Detailing of ground beams is discussed in Section 6.3 — except that cover to reinforcement should be increased to
75mm where formwork is not used.
Where ground beams span on to pad footings or pile caps which otherwise would not require top steel, the main
beam reinforcement should be continued across the entire foundation.
Where the ground beam is used as a tie between foundations, the main beam reinforcement should pass around the
column or wall starter bars and be fully anchored (Figure 6.37).
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Figure 6.37: Beam between two foundations
Horizontal U-bars
Rafts
Detailing reinforcement in rafts is dependent on the construction method and sequence. The designer should give
clear instructions which relate to a possible solution. These instructions should be confirmed with the contractor
before detail drawings are produced, and should include:
• position of construction joints for lapping of reinforcement
• position, width and depth of movement joints
• position of waterbar joints
In order to avoid congestion of reinforcement, consideration should be given to adding splice bars at lapping points
and placing them in a separate layer.
Ducts and trenches
Where ducts and trenches occur in ground slabs, if there is no requirement for design reinforcement, nominal
reinforcement should be placed around them (Figure 6.38).
Where they occur in rafts or multi-column foundations, special attention should be given to detailing continuity top
reinforcement, where moment transfer is required (Figure 6.39).
Walls for small trenches and manhole chambers should be detailed with a single layer of reinforcement in each
direction.
Figure 6.38: Nominal reinforcement for ducts and trenches
Tension lap
Tension lap
25 cover
(slabs exposed to weather 40)
Figure 6.39: Continuity reinforcement across trenches
Tension lap
Tension
anchorage
Tension anchorage
Tension lap
Tension
anchorage
Tension anchorage
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Column and wall starters
Wherever possible, column and wall starter bars should be specified with the footing reinforcement, and care taken
to define their position relative to the column section or wall.
Chairs
Where top reinforcement is required in multi-column foundations and rafts, consideration should be given to the
method of supporting this with chairs and edge U-bars (BS 797317,18). This should take into account the construction
sequence, the weight of top reinforcement and the depth of foundation; which affect the size and number of chairs
required. The concrete may be poured in more than one layer, and as such it may be possible to sit the chairs on an
intermediate level.
6.7.3 Detailing information
Design information for detailing should include:
•
•
•
•
•
•
layout drawings including column and wall outlines
plan dimensions including depth and level
dimensions and positions of kickers (standard kicker height below ground 150mm, above ground 75mm)
nominal cover to reinforcement (standard 75mm; bottom cover for piled foundations 100mm)
position in plan of starter bars
reinforcement parallel to x axis and parallel to y axis, clearly relating to layout drawings. This should include:
○ no. and pitch of bars
○ type of reinforcement and bond characteristics (standard H)
○ diameter of bars and direction of bottom bars
If standard pile cap see Table 6.7.
• reinforcement for starter bars and links. This should include:
○ number and position of bars
○ type of reinforcement and bond characteristics (noting Clause 2.4.2.5 of BS EN 1992-1-1)
• band width details of reinforcement when required
• details of L-bends. These are only required if anchorage length necessarily exceeds the length between the face
of the column or wall and the edge of foundation
○ details of construction joints
○ details of gullies etc. which affect slab detail
6.7.4 Presentation of working drawings
Figures 6.40 and 6.41 are example drawings for pad footing/pile cap scenarios.
Traditional method
Individual pad footings or pile caps are drawn related to specific gridlines (Fig. 6.40).
This method is normally used where the project has little repetition and it is simpler to show the details of all footings
individually.
Details of column starter bars are shown with the footing drawings wherever possible. The position of these must
take into account the position of the main column bars which are spliced to them.
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Figure 6.40: Working drawing (pad footings/pile caps): Traditional method
13 H25 02–250 B1
12
13 H25 01–250 B2
1
1
K
BASE K/12
12
100 KICKER
4 H20 03
2
4 H10 04–300 LINKS
01
2.75
01
02
1–1
12
03 03
K
2
04
03 03
65 COVER TO 03
2–2
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Representational method
The detail relates a general pad footing or pile cap to X and Y directions, together with a table giving details of
reinforcement for each type of footing, and where possible, column starters (Fig. 6.41).
The plan shape of each footing type is representative and not drawn to scale. Rectangular footings are divided into
those with and without banded reinforcement.
Note:
• The X and Y directions must be related to the GA drawing.
• Each footing is related to a reinforcement type, either by a location plan or by tabulating the column grid references.
• Column starters are shown, wherever possible, in the same table. Where column starters are not shown on the
same drawing, comprehensive cross-referencing of drawings is an essential requirement.
Figure 6.41: Working drawing (pad footings/pile caps): Representational method
A
Y
B
X
1
1
Y
Y
C
D
X
C
C
C
C
C
C
3–3
Y
100 KICKER
D
C
X
2–2
PLAN
C
C
= = =
Level
C
C
C
C
X
A
B
D
A
1–1
4–4
X – X Relates to lettered grids
Y – Y Relates to numbered grids
Base steel
D
Starters
MK C
MK D
Column
reference
No
off
Base
level
MK A
MK B
Cage
Sect.
A1, A3, A5, A7,
F1, F3, F7
7
2.75
15 H25 01–200
15 H25 01–200
2–2
6 H32 10
F5
1
2.75
15 H25 02–200
18 H25 02–200
3–3
8 H25 13
4 H10 14–300
C2, C4, C6
3
3.90
18 H25 06–225
18 H25 06–200
2–2
6 H40 16
4 H10 17–300
C5
1
4.20
12 H20 08–250
12 H20 08–250
4–4
8 H20 21
4 H10 22–300
4 H10 12–300
C
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Foundations MD F1
140
MULTI-COLUMN BASE
Cnom,minimum = 75mm against soil
= 50mm against prepared ground and blinding
= 40mm to formed surfaces
All are subject to design requirement
A
40 for exposed concrete
50 for buried concrete
Foundation level
Two (min.) layers of
lacers — H12s —
specified by designer
Cnom
A
300 min. overlap
Provide U-bars if depth is less than 400mm
Cnom
Two (min.) layers of lacers —
H12s — specified by designer
300 min. overlap
A–A
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Foundations MD F2
GROUND SLAB AND BEAM
Mesh fabric — A193 unless
specified otherwise
I0
Cnom
Extension to link not required
if width of link is 300 or more
Cnom,minimum = 75mm against soil
= 50mm against prepared ground and blinding
= 40mm to formed surfaces
All are subject to design requirement
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TRENCHES
TYPICAL DUCT DETAIL
I0
Cnom
Cnom
I0
I0
Detail A
Wall thickness <150
Ibd
Ibd
I0
Splay bars used when
design moment specified
Cnom
l0
Foundations MD F3
142
I0
Detail B
Wall thickness >150
Cnom,minimum = 75mm against soil
= 50mm against prepared ground and blinding
= 40mm to formed surfaces
All are subject to design requirement
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Kicker: 100
(150 below ground if required)
Footing level
Sufficient cover
to ensure no
problems of fit
Unless specified by designer,
use H10-300 (3No. min.)
Cnom
450 min.
(or 2 bars)
Cnom
Main bars normally straight.
Bars may be bobbed if required
by design
Cnom,minimum = 75mm against soil
= 50mm against prepared ground and blinding
= 40mm to formed surfaces
All are subject to design requirement
Cover to starter bars is
given from column faces
Pad footings MD PF1
l0 + 50 (foundation-level tolerance)
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Pile caps MD PC1
144
Cover to starter bars is
specified from column faces
l0 + 50 (foundation-level tolerance)
Kicker: 100
(150 below ground if required)
Pile cap level
Cnom
Sufficient cover to ensure
no problems of fit
Length of bob specified by design
450 min
(or) 2 bars
Two (min.) layers of lacers — H12s —
specified by designer
100 (allows for pile head)
75mm is adequate for small piles
e.g. up to 600mm dia.
Main bars are bent
at both ends
Bars normally rest on top of
piles — bottom cover allows for this
Cnom,minimum = 75mm against soil
= 50mm against prepared ground and blinding
= 40mm to formed surfaces
All are subject to design requirement
If large radius of bend, specified
corner bar shifted accordingly
Unless specified by design
use H10-300 (3No. min.)
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6.8 Staircases
6.8.1 Introduction
This guidance relates specifically to suspended in situ reinforced concrete stair flights and related half landings.
Precast concrete stair flights with half-joints are not covered.
6.8.2 Design and detailing notes
Minimum area of reinforcement
Tension reinforcement:
As,min = 0.26btd fctm/fyk and not less than 0.0013btd
Where:
bt
d
fctm
f
= mean width of tension zone
= effective depth
= mean tensile strength of concrete (Table 6.1)
= characteristic yield strength (500MPa in UK)
For common thicknesses see Table 6.1 for calculated minimum areas.
Refer to Clauses 9.2.1.1, 9.3.1.1 and 9.3.1.2 of BS EN 1992-1-1 for further information.
Bar spacing
Recommended minimum pitch of bars to allow for placing and compaction of concrete are given in Table 6.3.
Maximum pitch of bars:
Main bars: 3h ⩽ 400mm (in areas of concentrated loads 2h ⩽ 250mm)
Secondary bars: 3.5h ⩽ 450mm (in areas of concentrated loads 3h ⩽ 400mm)
Refer to Clauses 8.2 and 9.3.1.1 of BS EN 1992-1-1 for further information.
Anchorage and lapping of bars
Typical anchorage and lap lengths for ‘good’ and ‘poor’ bond conditions (Fig. 5.6) are given in Appendix E.
Refer to Clauses 8.4 and 8.7 of BS EN 1992-1-1 for further information.
End-supported stair flights
MD ST1 shows the arrangement of reinforcement and curtailment details for end-supported stair flights. An
alternative is for the landings to support the stair flight and to have a simple concrete recess at the end (Figure 6.42).
This method avoids congestion of starter bars at the corners of landings. Where there is an in situ wall at the edge
of stairs, the recess should be continued up the flight (Fig. 6.42) to avoid cracking.
Cantilever stair flights
Stair flights cantilevered from the side of a wall should be detailed as shown in MD ST2.
Connection to walls
This method for detailing connections of half landings to walls is described in Section 6.5.2.
Bottom connection of stair flights to ground floor or foundations
The following are recommended:
• Starter bars projecting from a prepared concrete surface. This is suitable when the position and height of the
starter bars is closely controlled.
• A pocket left in the ground floor (or foundations of sufficient size) to ensure fitting the end of the stair flight
reinforcement cage.
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Figure 6.42: Details for stair flight landing
a
Stair span
Landing at
mid floor level
Confine landing starters
to shaded area
Landing span
20 deep
formed recess
Distribution
reinforcement
a
Handrail supports
The designer should make sure that adequate consideration is given to the reinforcement detail for handrail supports.
If pockets are left in the concrete into which the handrail posts are later concreted, reinforcement must pass around
the pockets and be anchored into the main body of the concrete.
If inserts are set into the concrete, these should have reinforcement bars passing around them or have sufficient
anchorage ties built in.
6.8.3 Detailing information
Design information for detailing should include:
• layout and section drawings of staircase and landings. The setting-out of the soffit should be clearly shown
• concrete grade and aggregate size (standard 20mm)
• details of design reinforcement required including:
○ type of reinforcement
○ bar diameter
○ pitch or number
○ location
Otherwise, bar size and pitch given in MD ST1 is assumed
• Details of cast-in inserts or pocket details, and associated reinforcement details
6.8.4 Presentation of working drawings
Figures 6.43 and 6.44 are example drawings for stair flight scenarios.
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Figure 6.43: Working drawing: End-supported stair flights
2
1 H10 12 UB
12.102 (1st floor)
15.642 (2nd floor)
5 H10 10–200 UB
12 H10 01–200 UB
2×6 H10 09–200 T & B
(3)
(3)
6 H10 11–200 T
15 H10 11–200 B
1
25
50
1
5 H10 10–200 UB
6 sets of bars at 200 each set
(H10 02 B. H10 03 B.H10 04 B.
H10 05 B. H10 06 B. H10 07 T. H10 08 T)
08
08
06
05
15.642
12.102
05
11
2
11
06
03
07
03
01
07
09
01
09
09
11
05
11
01
02
04
04
07
09
03
WALL REINF’T
refer drg. R021
06
02
04
2
02
Flight B
1–1
2nd floor
Flight C
Flight B
1st floor
Flight A
Gnd floor
STAIR ST1
KEY ELEVATION
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Figure 6.44: Working drawing: Cantilever stair flights
6
7
6 H8 04 200 links per tread
10No. treads
Refer landing drg R012
1
1
20 H10 01 2 per tread
11 H10 02 B
11 H8 03 UB
1 per tread
6 sets of bars at 200 each set
(H10 05 B. H10 06 B.H10 07 B. H10 08 B.
H10 09 T. H10 10 T. H10 11 T)
FLIGHT B
2 No THUS
11
08
2
SPINE WALL
Refer drg R010
11
07
02
04
(typ.)
08
07
06
10
06
Position of
03s in tread
10
09
02
10
05
06
09
05
2
1–1
6
01
01
03
04
C
04
B
03
02
01
7
06
02
02
03
2–2
06
Flight C
Flight B
Flight A
STAIR ST2
KEY ELEVATION
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Distribution bars as for MD S1
U-bars for both landings to be 50% of area of main bottom reinforcement
A to be greatest of 0.1 × design span, tension anchorage length or 500
For detail where landing reinforcement spans in other direction see Section 6.5.2
See also MD W3
Nominal cover specified by designer (min. 20 or bar size whichever is greater)
See Section 6.8.2
lbd
l bd
Construction joint
A
l0
Similar bars to
main bottom reinforcement
l0
A
Construction
joint
l0
l0
Similar bars to
main bottom reinforcement
Staircases MD ST1
END-SUPPORTED WITH LANDINGS
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Staircases MD ST2
150
CANTILEVER FROM WALL OR EDGE BEAM
Linking to be H8s at 300
unless otherwise specified.
Bends to be adjusted
to suit on site
A
Position of H8 U-bar
Specified by designer
Distribution bars to be H10s at 300
unless otherwise specified
A
Corner bar detailed
with wall
lbd
Design reinforcement
Nominal H8 U-bar
Radiused bar to
design requirements
A–A
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6.9 Corbels, half-joints and nibs
6.9.1 Introduction
This section covers the detailing of in situ corbels, beam half-joints and continuous nibs. The detailing for these
elements is very closely related to the joint, and the designer must, in all circumstances, ensure that the detail design
is clearly specified. Details given in this section are not intended to cover all aspects of precast concrete corbels,
half-joints and nibs. Detailed information concerning the design of bearing pads is not included (for more information
refer to specific proprietary literature).
6.9.2 Design and detailing notes
Minimum area of reinforcement
As,min = 0.26btd fctm/fyk and not less than 0.0013btd
Where:
bt
d
fctm
fyk
= mean width of tension zone
= effective depth
= mean tensile strength of concrete (Table 6.1)
= characteristic yield strength (500MPa in UK)
See third column of Table 6.1 for minimum percentage of reinforcement.
Refer to Clauses 9.2.1.1, 9.3.1.1 and 9.3.1.2 of BS EN 1992-1-1 for further information.
Bar spacing
Minimum horizontal pitch
Sufficient space must be allowed for insertion of poker vibrator. Note that where bars are lapped, the pitch of the
reinforcement should allow for the laps. This can be significant for larger bars, unless the lapped bars are placed in a
different layer. Table 6.4 provides the recommended pitch, allowing for actual bar size and for vibrating poker.
Minimum vertical pitch
Minimum vertical space between individual bars: 25mm or bar size, whichever is greater
Continuous nibs
Maximum pitch of bars
Main bars:
3h ⩽ 400mm (in areas of concentrated loads 2h ⩽ 250mm)
Secondary bars:
3.5h ⩽ 450mm (in areas of concentrated loads 3h ⩽ 400mm)
Refer to Clauses 8.2 and 9.3.1.1 of BS EN 1992-1-1 for further information.
Anchorage and lapping of bars
Minimum anchorage length
Typical anchorage and lap lengths for ‘good’ and ‘poor’ bond conditions (Fig. 5.6) are given in Appendix E.
Refer to Clauses 8.4 and 8.7 of BS EN 1992-1-1 for further information.
Arrangement of reinforcement
The arrangement of reinforcement is very closely related to the design of corbels, half-joints and nibs, and the
designer must ensure that the detail design is clearly specified.
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Generally, small bar diameters ⩽16mm, should be used when detailing such elements. If larger diameter bars are
used, it is likely that welding will be required. This should normally be carried out off-site under factory conditions
(Section 5.5).
Corbels
The use of small bar diameters, horizontal U-bars or links with large diameter bends is preferred, as shown in
MD CB1. However, where the loading is high and the geometry restrictive, large bar diameters may be necessary —
in which case, welding them to a crossbar or plate may be the only solution. The size of this may be governed by
the strength of weld (Section 5.5). This is shown in MD CB2.
It is essential that the main tensile reinforcement is extended as close to the outer face of the corbel as possible,
and that it extends beyond the loadbearing area by a minimum of the distance shown on the MDs.
Where large horizontal forces are required to be transmitted into the corbel, a welded joint may be the only suitable
solution33.
Refer to Clauses 6.2 and 6.5 of BS EN 1992-1-1, Annex J of the UK National Annex to BS EN 1992-1-1, and
Annex A.3 of PD 668734 for further information.
Continuous nibs
The arrangement of reinforcement may control the depth of nib. Vertical U-bars or links should be used wherever
possible (MD N1). However, where a shallow nib is satisfactory, e.g. for supporting brickwork, horizontal U-bars may
be used.
In situations where horizontal movement may occur between the nib and the supported member, the outer edge of
the nib should be given a 20mm chamfer.
Refer to Clauses 6.2 and 6.5 of BS EN 1992-1-1 for further information.
6.9.3 Detailing information
Design information for detailing should include:
• detail and section drawings at half-scale, giving all relevant dimensions
• details of reinforcement required including:
○ type of reinforcement
○ bar diameter
○ number and position of bars (exact position of main bars should be given)
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Corbels MD CB1
WITHOUT WELDS
Vu
av < 0.5h
Top main bar Ast
>0
Start of bend
A
A
2/3d
lbd
d
h
Shear links >0.25Ast
lbd
Shear links >0.25Ast
Top main bar Ast
A–A
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Corbels MD CB2
154
WITH WELDS
Vu
av < 0.5h
Top main bar Ast
>C
Large radius of
bend required
C, Cover to transverse bar
A
A
2/3d
lbd
d
h
Transverse bar welded to the
main tension bar of equal
diameter and strength
Additional bar for
shear link anchorage
Shear links >0.25Ast
lbd
Shear links >0.25Ast
Top main bar Ast
A–A
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Nibs MD N1
Tension anchorage length
if U-bars are used
Links to be specified by
designer to take load on nib
Closed links or U-bars may be used
Cnom
Not less than bar dia.
or 0.75 × nominal cover,
whichever is greater
a2 + Da2
To be advised by designer
(Clause 10.9.5.2 of BS EN 1992-1-1)
or 75mm conservatively
Dia. of links to be
not more than 12mm
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6.10 Composite slabs
6.10.1 Introduction
This section focuses on concrete slabs formed by casting concrete on permanent metal formwork. The guidance
does not cover the propping of the slab, the design of the reinforcement or the requirements for fire resistance.
6.10.2 Design and detailing notes
MD CS1 shows the reinforcement arrangements required for edge beams.
•
•
•
•
The critical arrangement is usually where a 130mm thick slab is adopted.
The U-bar should be placed as low as possible in the slab so that it is under the head of the shear stud.
It is often necessary to invert the mesh so that main bars are at the same level as U-bars.
Flying ends should always be used for the reinforcement fabric.
6.10.3 Detailing information
Design information for detailing should include:
• layout and section drawings including details of holes and slab edges etc.
• shear stud spacing
• details of the reinforcement (including bar sizes and spacing, and U-bar sizes)
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7 Prestressed concrete
7.1 General
This section provides guidance on pre-tensioned and post-tensioned concrete (collectively: prestressed concrete)
reinforcement detailing. Further guidance on prestressed concrete design, detailing and systems are available35–36.
It should be read in conjunction with earlier chapters for concrete detailing rules and only additional requirements,
specific to prestressed members in buildings are considered here. For prestressed elements the designer should
specify both the prestressing system and also any additional reinforcement requirements. All standard detailing rules
apply as a basic requirement for detailing prestressed structural concrete elements; and in addition, the specific
requirements in this chapter also need to be detailed.
Post-tensioning is most commonly employed in in situ construction such as buildings and bridges, where a duct and
strand are cast into the structure and post-tensioned after the concrete has gained the required strength. It can also be
used with precast products such as beams. Post-tensioning is often used for economic reasons, as it has the advantages
of giving reduced reinforcement and concrete quantities compared with conventional reinforced concrete elements.
Pre-tensioning is typically used with precast concrete units where a tensile stress is applied to the wire/strand in a
mould or bed prior to pouring the concrete. Aside from the common forms of floor slabs (e.g. hollowcore and
double tee units), pre-tensioned beams may be used for longer spans.
7.2 Prestressing strand
The wire and strand used for prestressing in buildings in the UK should comply with the recommendations given in
BS 5896:201237. Note that BS EN 1992-1-1 refers to ‘BS EN 10138’ for the requirements for prestressing strand.
However, this document has not been published to date, and so the 2012 version of BS 5896 should be used.
The strand used in post-tensioning is normally 7-wire, low relaxation strand, defined as ‘Class 2’ in BS EN 1992-1-1.
For pre-tensioning, either 7-wire strand or individual wires to BS 5896 are used depending on the application.
For in situ applications, consideration should be given to using only one strand type on a project to avoid errors
during installation. This also simplifies the coordination of accessories and stressing equipment required. The most
common types used in post-tensioning for buildings in the UK are Y1860S7-12.9 and Y1860S7-15.7
(bold in Table 7.1).
Table 7.1: Prestressing strands commonly used in post-tensioning
Nominal
tensile
strength
(MPa)
Nominal
cross-sectional
area (mm2)
Nominal
mass
(kg/m)
Characteristic
value of max.
force (kN)
Characteristic
value of 0.1%
proof force
(kN)
∅
Rm
Ap
M
fpk
fp0.1k
1.1365
15.7
1770
150
1.172
266
234
Y1820S7G 1.1371
15.2
1820
165
1.289
300
264
Y1860S7
1.1366
12.9
1860
100
0.781
186
164
Y1860S7
1.1366
15.7
1860
150
1.172
279
246
Y1860S7G 1.1372
12.7
1860
112
0.875
208
183
Steel
name
Y1770S7
Steel
Nominal
number diameter,
d (mm)
Derived/adapted from Table 12 of BS 5896:2012.
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7.3 Post-tensioning
Anchorages are used to transmit the forces in the tendon strands to the concrete in the anchorage zone. In the UK,
anchorage components should be CARES-approved to CARES Appendix PT338 and BS EN 1339139, and comply
with the performance requirements of ETAG 01340 and EAD 160004-00-030141 for CE marking.
7.3.1 Anchorage and tendons
There are many different types of anchorage which vary by manufacturer. However, they can typically be identified by
the post-tensioning type, the method of application of force, and the location at which the force is applied.
Tendons are typically identified as ‘bonded’ (Figure 7.1) or ‘unbonded’ systems (Figure 7.2). Bonded systems are
grouted after tensioning operations are completed, while unbonded tendons are left in a greased duct for the lifetime
of the project. A void (or pocket) former is used during concreting at the live end anchor, which is removed when
the concrete has been cast, and the edge form removed (Section 7.3.3). The anchor head is then added and the
wedges placed prior to stressing.
The method of applying the post-tensioning force is contingent on whether one, or all, strands are tensioned
simultaneously. For typical flat slab applications, each strand is tensioned individually and is referred to as a
‘monostrand’ system, even when the anchorage contains more than one strand. For larger beams, transfer decks
and bridges a ‘multistrand’ system (Figure 7.3) is adopted with a circular anchorage, where all strands are tensioned
together in a larger stressing jack.
Figure 7.1: Bonded monostrand (live) anchor
Before concreting
Duct
Deviation cone
Grout entry
After concreting
Force transfer unit
Deviation cone
Pocket former
Duct
Grout entry
Shuttering
Wedges
Force transfer unit
Anchor head
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Figure 7.2: Unbonded monostrand (live) anchor
Before concreting
Force transfer unit
Concrete excluder
After concreting
Sealing washer
Concrete excluder
Bayonet fitting
Pocket former
Slotted nut
Shuttering
Sealing cap
Force transfer unit
Force transfer unit
Wedge
Figure 7.3: Multistrand (live) anchor
Locations where the stressing force is to be applied are referred to as ‘live’ anchorages. In some cases, a similar
anchor will be placed on both ends of the tendon (normally when the tendon length exceeds 35m due to friction
losses). However, if tensioning is not required at both ends, this is referred to as a ‘dead end’ or ‘buried’ anchor.
Alternatives include ‘passive’ or ‘basket/onion’ ends (Figure 7.4) — where an exposed length of strand is bonded
into the concrete. All systems should be covered by the relevant European Assessment Document (EAD).
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Figure 7.4: Buried, passive and basket/onion (dead end) anchors
7.3.2 Anchor cover and spacing
The minimum cover of the anchorage and any protruding strand should be provided in accordance with the
appropriate EAD. For durability, this should also refer to the requirements of BS EN 1992-1-1 (and for fire to
BS EN 1991-1-2). The anchor spacing and edge distances (Figure 7.5) should not be less than those supplied by the
manufacturer and as stated in the product EAD — with due regard for the concrete strength at time of load transfer
and considering cover to the anti-burst reinforcement.
Figure 7.5: Typical anchor cover and spacing requirements for beams (left) and slabs (right)
A
B
B
C
C
C
D
D
A
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7.3.3 Anchor pockets and stressing access
Anchors are normally fitted to the ends of the member with a void former or anchor pocket/recess. Recesses should
be dimensioned to provide adequate working clearance to the stressing equipment and sufficient depth to ensure
they can be subsequently filled with mortar or concrete to provide corrosion protection. The designer should clearly
specify the fill material, taking into consideration such requirements as strength, durability and fire resistance.
Reinforcement may be required to retain the concrete or mortar filling, particularly for larger multistrand anchorages.
A suitable approach is to use small diameter bars with couplers cast into the faces of the recess.
Space should be provided in front of the anchorages to enable the stressing jack to be lowered into position and fed
onto the protruding stressing length of strand, with its hydraulic pipes, allowing for it to be extended in line with the
tendon during application of force and to be removed after stressing (Figure 7.6). Typically for monostrand stressing,
a clear working space of approx. 1m is required. For larger multistrand systems, up to 3m can be required. There
must be enough space for the operators to stand alongside the jack.
Figure 7.6: Stressing pocket and jack access: a) monostrand b) multistrand c) dimensions to be obtained from
manufacturer
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Where stressing access will not be available at the vertical face of a member or pour, an alternative detail can be
used, such as stressing pans for flat slab anchorages (Figure 7.7). This allows the tendons to be stressed from the
top of the slab, although access is still required for the jack between the anchor head and the inaccessible face.
Congestion of pans should be avoided as they prevent placement of local top reinforcement and result in a local
reduction in slab thickness which can impact on the local slab design or punching shear design if near to columns.
The use of stressing pans should be limited where possible and their concentration and displacement must be
carefully considered and reviewed by the designer (Fig. 7.7).
For the use of pans and other surface stressing options for durability refer to TR72: Durable post-tensioned concrete
structures 42. Local reinforcement requirements should be advised by the designer. Stressing pans are infilled using
structural concrete of the same grade (or higher) as the surrounding slab unless specified otherwise by the designer
following grouting activities (for bonded tendons). Additional reinforcement is required around the pan for crack
control and to provide continuity of the reinforcement where the tendon stops short of the slab edge. The magnitude
and placing of the reinforcement should be coordinated with other reinforcement and be specified by the designer to
suit the specified post-tensioning system and pan dimensions.
Figure 7.7: Stressing pan anchor showing trimming reinforcement
Slab edge/face of core wall
1
er
lay
PT
1
O
6-T
4H
ing
ess
Str
r
cho
)
00
an
p
5
r (1
ye
2 la
T
OP
-T
12
2H
)
00
(20
1
PT
-TO
6
H1
er
lay
d
ace
0)
0
(10
da
har
Sp
r
aye
2L
PT
O
6-T
1
2H
a)
tb
ns
gai
pl
iral
2
ack
an
of
)
00
(15
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Figure 7.7: Continued
LAYERS TO SUIT
MAIN REINFORCEMENT
800
(TO FACE OF CORE WALL
OR EDGE OF SLAB U.N.O
ON PLAN)
50
642
50
550
50
285
4 B16 602 – 100 TOP [2300]
4 B16 602 – 100 BTM [2300]
D
100 100
2 B16 603 TOP [1200]
2 B16 603 BTM [1200]
SPIRAL PLACED HARD
AGAINST BACK OF ANCHOR
STRESSING PAN
b)
800
(TO FACE OF CORE WALL
OR EDGE OF SLAB U.N.O
ON PLAN)
STEEL FORMER PAN
(SLAB SURFACE WILL BE
FLUSH AFTER CASTING
AND INFILLING)
17
625
Typ
100mm
D
50
100 100
4 B12 601 TOP [1500]
4 B12 601 BTM [1500]
100
561
SECTION D–D
(N.T.S)
c)
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Slab systems are usually supplied with a recess block. However, beam systems often require the anchor recess to
be created with formwork (Figure 7.8). Note that actual sizes will depend on the specific product and number of
strands used. Refer to the manufacturer’s instructions.
Figure 7.8: Anchorage recess at end of member
220
550
475
215
475
220
210
2500
475
550
550
475
215
TYPE 5
STAGE 2
1500
215
550
475
550
475
550
220
220
600
475
550
END BLOCK
TYPE 6
STAGE 1
500
500
TYPE 4
STAGE 1
500
500
7.3.4 Tendon ducts
For bonded post-tensioning, metal or plastic ducts may be used. Most commonly used for internal building
applications with low exposure conditions, metal galvanised steel ducts should normally meet the requirements of
BS EN 52343 (but note that it does not specifically cover the flat galvanised ducts typically used in the UK). Spirally
wound, corrugated ducts should have a minimum wall thickness of 0.30mm, and flat smooth folded seam ducts
should have a minimum wall thickness of 0.35mm. Plastic ducts may also be used, typically where durability is a key
consideration (e.g. in car parks) and should be high density polyethylene or polypropylene with a minimum wall
thickness of 2.0mm. The designer should specify the type of duct required.
Most bonded monostrand post-tensioning systems in use in the UK adopt a rounded flat duct, approximately
19 × 70mm, although other sizes are available to suit particular systems. The minimum cover to rectangular ducts
should be taken as half the duct width (the larger dimension) plus deviation. The max. vertical and horizontal
curvature should comply with the manufacturer’s requirements and should be stated in the appropriate EAD for the
system. Where significant curvature on plan is close to openings, additional reinforcement may be required to prevent
bursting of the slab edge.
The cover to ducts for durability should be determined in accordance with BS EN 1992-1-1 and any supplementary
requirements of the product EAD. The axis distance to the centreline of the strand for fire resistance should be
determined in accordance with BS EN 1992-1-2, and typically requires an additional 15mm for the non-tensioned
reinforcement. The designer should specify the requirements to the detailer.
The duct spacing is given in Clause 8.10.1 of BS EN 1992-1-1 and Figure 7.9 of this Manual. The ducts should not
normally be bundled, unless a pair of ducts are placed vertically one above the another (Clause 8.10.1.3). The
exception to this is for unbonded tendons which are normally grouped away from the anchorage zone with up to
four strands grouped together horizontally (Figure 7.10).
Tolerances relating to the position of tendons are not stated in BS EN 1992-1-1, but guidance is given in
BS EN 1367028 and TR43: Post-tensioned concrete floors — design handbook 35. Typical values are presented in
Table 7.2 of this Manual, but should be confirmed by the designer. Note that anchor tolerance and duct tolerance
may not be the same, as often there are further constraints on anchor locations for items such as cast-in plates or
post-fixed anchors for cladding. Where this occurs, the tolerance for both the ducts and anchors should be stated
on the drawings.
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Figure 7.9: Minimum clear spacing between post-tensioning ducts
>dg + 5
>ø
>50mm
>dg + 5
>ø
>50mm
>ø
>40mm
>ø
>40mm
>dg
>ø
>40mm
>dg
>ø
>40mm
Note:
Where:
ø = diameter of post-tension duct
dg = max. size of aggregate
Figure 7.10: Grouping of unbonded strands
Table 7.2: Tolerances on tendon positioning
Slab thickness
Tolerances
Vertically
Horizontally
h ⩽ 200mm
±5mm
±150mm in slabs
h > 200mm
The smaller of ±h/40mm or Δcdev
±50mm in beams
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It is necessary for the duct to be straight where it connects to the anchorage (Figure 7.11). The recommended length
of straight tendon can usually be obtained from the anchorage manufacturer.
Figure 7.11: Minimum straight length of bonded tendon in a post-tensioned system a) typical for deep section,
b) typical for flat slab
Straight length from
anchorage manufacturer
Anchorage
CL
Tangent
Duct
a)
Tendon duct
Pocket
Refer to reinforcement plans
Refer to reinforcement plans
b)
Where tendon profiles are curved on plan, adequate concrete cover must be provided, and the designer should
advise the detailer of the requirements, including any additional confining reinforcement. Critical areas should be
identified on the detailing drawings. Changes in horizontal profile should be kept away from voids where possible.
7.3.5 Anti-bursting reinforcement
Anti-bursting reinforcement should be provided around the anchorage and/or group of anchors.
To prevent failure of the surrounding concrete, primary anti-bursting reinforcement should be placed around each
anchor and comply with the minimum requirements stated by the anchor manufacturer and the EAD. The location of
the anti-bursting reinforcement varies between manufacturers and should adhere to that given in the EAD, as this is
the position that it would have been used in any testing.
The spiral reinforcement is ordered loose and should be scheduled accordingly as it is not part of the anchor.
Example arrangements are shown in Figure 7.12.
Secondary anti-bursting or equilibrium reinforcement should be designed with reference to CIRIA Guide 144 to
account for stressing sequence and out-of-balance forces arising during the tensioning sequence, particularly for
beams. The designer should provide the additional requirements for this reinforcement, and any specific tensioning
sequence required should be clearly noted on the drawings.
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Figure 7.12a: Typical monostrand bonded post-tensioning primary anti-burst reinforcement
102
Anchor block to be fixed
to formwork prior to installation
of adjacent reinforcement
70mm
Flat duct
Vent pipe extends
vertically to protrude
through top of slab
Strands to be
110
degreased
D
C
171
A
B
Edge of slab
or face of beam
A
1000
Spiral H10 @ 40mm MK102
turns = 7
Plastic
former
Anchorage length
Refer to reinforcement plans
100
Refer to reinforcement plans
Figure 7.12b: Example multistrand bonded post-tensioning primary anti-burst reinforcement
500
10 turns @ 50 pitch
(B12 sprial)
350
350
ø110/
109
225
275
150
STRESSING ANCHORAGE
800–1200
DEAD END DETAIL
Figure 7.13 is an example of a secondary reinforcement cage for a large multistrand bonded post-tensioned
transfer beam.
7.3.6 Tendon profile detailing
Detailing of the post-tensioning will typically comprise of details of the strands (Figure 7.14) located on a plan drawing
(Figure 7.15). The duct profile for a slab will typically be shown along the length of a typical tendon on plan. Tendons
with a similar/identical tendon profile will be linked to this tendon on the plan.
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Figure 7.13: Secondary anti-burst (equilibrium steel) reinforcement for staged stressing
Figure 7.14: Legend for post-tensioned strand (alternative systems also used)
Height from slab soffit to
bottom of tendon duct
Number of strands
Live end
Dead end
45
1
2 strands
Tendon number
TENDON LEGEND
(N.T.S)
The duct profile for a beam should preferably be given in tabular form; the horizontal and vertical dimensions being
based on a datum, often the soffit of the beam, that is easy to identify on site. The profiles for each vertical row of
ducts should be tabulated separately (Figure 7.16) with X, Y and Z coordinates in particular showing setting-out
of the anchorages at the end of the beam on elevation.
Dimensions should be to the top or bottom of the duct/s and should be sufficiently frequent to define the profile,
taking account of its radius of curvature.
To avoid ambiguity, all tendon profiles supplied by the designer should indicate to the detailer whether they are
based on centreline of the strand within the duct, or to soffit of the ducting.
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Figure 7.15: Post-tensioned slab tendon layout drawing
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Figure 7.16: Duct profile drawing and coordinates table
300
195 305 305 195
2
1200
3
4
700
900
1
1000
END BLOCK
A
AA
B
C
Tendon 2, 3, 4
Tendon 1
Z
X
1055
700CL 900CL
1055
635 800
1055
540 640
1055
475 530
1055
435 460
1075
420 440
1075
465 485
1075
610 630
1075
845 865
1075
1180 1200
940
1370 1930
745 930
700CL 900CL
940
1170 1240
940
940
900 1045
Y
Tendon
2, 3, 4
Tendon
1
7.4 Pre-tensioning
7.4.1 Anchorage and debonding
Any requirements for debonding of the tendons should be marked on the section elevations, including the method
and length of debonding (Figure 7.17).
Figure 7.17: Debonding tendons for pre-tensioned elements
Debonded length
Strands fully bonded
Strands debonded
7.4.2 Transmission zones
In a pre-tensioned element, there are increased tension stresses around the anchorage lengths of the strand
(either at the end of the member or at the end of a debonded length). This length is calculated in accordance with
Clause 8.10.2 of BS EN 1992-1-1. Usually, additional shear links are provided in this zone to resist the tension,
and the size and spacing should be advised by the designer (Figure 7.18). Any debonded lengths should be clearly
identified.
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Figure 7.18: Transmission zones in pre-tensioned elements
Length of debonding
(see schedule)
Debonded tendon
Bonded tendon
Transmission zone
of bonded tendon
Transmission zone
of debonded tendon
7.4.3 Strand cover and spacing
The minimum cover with regard to bond cmin,b for pre-tensioned tendons is:
• 1.5× diameter of strand or plain wire
• 2.5× diameter of indented wire
Other requirements for cover such as fire or durability may be critical, and the designer should advise if an increased
cover is required.
The spacing requirements are given in Figure 7.19.
Figure 7.19: Minimum clear spacing between pre-tensioned tendons
ø
>dg
>2ø
>dg + 5
>2ø
>20
Note:
Where:
ø = diameter of pre-tensioned tendon
dg = maximum size of aggregate
Other layouts may be used if test results show satisfactory behaviour. BS EN 116836 outlines the requirements for
hollowcore slabs.
Strands should not be bundled in anchorage zones.
Tendons should be in vertical rows with spacing and edge dimensions compatible with the max. size of aggregate,
to allow placing and compaction of the concrete. For symmetrical concrete sections, the centroid of the tendons
should lie on the vertical centroidal axis (Figure 7.20).
7.4.4 Supports and bearings
For long-spans, bearings should be designed to allow for long-term creep and shrinkage of the element, and it may
be necessary to include these on the detailing drawings. Rotation may also need to be considered depending on the
span and expected movements. The designer should advise any requirements to the detailer.
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Figure 7.20: Symmetrical arrangement of tendons for pre-tensioned units
Tendon locations
Dimensions to suit aggregate size
and concrete compaction
CL
Pre-tensioned section
7.4.5 Tendon profiles
Any requirements for deflection of the tendons should be determined by the designer and marked on the section
elevations, including the horizontal and vertical dimensions (Figure 7.21).
Figure 7.21: Pre-tensioned element with deflected tendons
A
B
Elevation
Xm
Xm
B
A
60
50
Straight strands
Deflected strands
50
Strand positions not used
Section A–A
60
Section B–B
7.5 Exchange of information
Chapter 2 explains the importance of clearly conveying to the detailer all the information that is required to complete
the detailing drawings. Similar principles should be applied for prestressed concrete, and Boxes 4 and 5 provide
checkists of additional information required to complete the post-tensioning and pre-tensioning detailing drawings
respectively. Checklists for reinforced concrete detailing are given in Boxes 1 and 2 in Chapter 2.
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Box 4: Checklist of information to be provided by the designer: post-tensioning
1) GA drawings (refer to Box 1, Chapter 2)
2) Project specific information including:
• Strand size (size and grade)
• Prestressing system to be used — bonded/unbonded, mono/multistrand and relevant system parameters
such as duct friction, anchorage draw-in
• Cover requirements for all components (e.g. anchors, ducts)
• Anchor and duct placement tolerances
• Anchor pocket infill requirements (including any couplers for reinforcement)
• Any tying requirements for robustness using prestressing strand
• Jack access dimensions
3) Design requirements
•
•
•
•
•
Number, size and setting-out of tendons/strands
Forces to be applied to each tendon/strand (and tensioning sequence if appropriate)
Concrete class
Minimum strength required at transfer of prestress and any staged stressing requirements
Expected tendon extensions (not to be placed on site drawings)
4) Specific detailing requirements
(Notes and sketches to be provided by designer to detailer)
• Profiling of tendons to be clearly indicated and dimensioned both horizontally and vertically
• Deviation of ducts around openings — minimum concrete thickness and/or additional reinforcement
between ducts and edge of concrete
• Anti-bursting reinforcement requirements
• Reinforcement around pan anchors
• Edge reinforcement between anchorages
• Location of grouting points and vents where bonded tendons are used and requirements are for
intermediate vents
• Areas and extent of ordinary reinforcement (e.g. bottom reinforcement or mesh to control crack widths,
punching shear reinforcement, beam cage reinforcement, cantilever slabs etc.)
• Infill strips (size, location and requirements regarding minimum length of time before infilling strip with
concrete)
• Any requirements for camber
• Reinforcement around openings
• For beams curved in plan — any reinforcement to resist bending in web
• Reinforcement for interface with other elements
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Box 5: Checklist of information to be provided by the designer: pre-tensioning
1) GA drawings (refer to Box 1, Chapter 2)
2) Project specific information including:
• Strand size (size and grade)
• Cover requirements for all components
3) Design requirements
•
•
•
•
Number, size and setting-out of tendons/strands
Forces to be applied to each tendon/strand
Concrete class
Minimum strength required at striking of mould
4) Specific detailing requirements
• Any tendons to be debonded — marked on sections and elevations, and method and length of debonding
specified
• Deflection of tendons/strand to be clearly indicated and dimensioned both horizontally and vertically
• Any requirements for camber
• Bearing details for long-span pre-tensioned elements
• Anti-bursting reinforcement requirements
• Areas and extent of ordinary reinforcement
• Reinforcement for interface with other elements
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8 Precast concrete
8.1 Introduction
For a number of reasons, detailing precast concrete requires a different approach to that of in situ concrete detailing:
• Once manufactured, precast units need to be transported to site.
• Units are often incorporated into an existing or part-built structure, so consideration of tolerances is important.
• Units are often manufactured by third parties who may not have visited the site and may not have all the
design information. Early-stage communication with (and clarity of instruction to) the precaster is essential.
• Precast concrete structures usually require special consideration of joints.
Precast units are often cast in a different orientation to their final use, and decisions on how to cast are usually left to
the precaster. At the detailing stage the designer should make their intention clear on matters such as surface
finishes and tolerances etc. Areas where tolerances necessarily differ from the specification should be clearly noted.
Re-entrant or protruding corners are subject to breakages and unsightly finishes. Acute re-entrant corners are to be
avoided as it is difficult to remove the formwork without damage. Acute protruding corners are frequently broken
while handling, and are often discoloured because the large aggregate cannot find its way into corners.
The need to transport precast concrete units requires consideration of not only their physical measurements
(size and weight), but also permissible lifting positions/angles.
The following basic rules are not exhaustive (and relate to UK practice) but provide a guide for the detailer in
proportioning elements:
Length
<27.4m: no restriction (police notification required if over 18.3m)
>27.4m: special dispensation required from Department for Transport
Height
<4.88m: this gives a margin under motorway bridges where the minimum standard height is 5.03m
>4.88m: two days’ notice to traffic authorities required (re. route)
Width
<2.9m: no restriction
2.9–3.5m: possible (with notification to police)
3.5–5m: special dispensation required from Department for Transport
Weight
<26t no restriction on standard 32/36/42t trucks
Where weight of vehicle and load exceeds 44t, a ‘Special Types’ vehicle is required under the Road Vehicles
(Authorisation of Special Types) (General) Order 2003.
The most frequently used loads are with a 20t payload on a 32t gross truck. In these cases, with multiple numbers
of units on a load, significant savings can be made if the total weight approaches (but does not exceed) 30t,
i.e. 2No. 9.8t per load rather than 1No. 10.2t unit. Permissible support points and packing materials should also
be noted.
Lifting strengths for the concrete should be identified on the drawing, remembering that mould use for a repetitive job
can only be optimised if the minimum lifting strength is specified. The weight of the unit (for craneage and
transportation) should also be clearly stated.
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Reinforcement is considered generally unsuitable for use as lifting hooks. Some precast manufacturers do use
reinforcement for lifting purposes, but it is presumed they do so with proper care and attention to details and lifting
practices, and on the basis of practical tests and an assessment of the risks involved.
A range of proprietary inserts are available, both for fixing and lifting. It is important that these are used in
accordance with the manufacturer’s instructions, and with adequate factors of safety. It is also important that
secondary load effects or structural movements do not put forces on inserts for which they have not been tested or
designed. In these cases, fixings should be isolated so that only the correct forces are applied.
Where a drawing shows a part-unit cast onto another precast unit, the drawings of each should clearly state where
the weights are noted and that the weights are only for part-units.
Units of complex shapes should be discussed with a precaster before their details are finalised. Units with a
requirement for a high quality of finish may be required to be cast in one-piece moulds. In these cases, a drawing for
de-moulding is necessary, and the unit and its surrounding structure should be detailed accordingly.
The design of joints and the requirements for the detailing of reinforcement and concrete (half-joints, corbels and nibs
etc.) are covered in Design of hybrid concrete buildings 33.
Where in situ concrete is placed adjacent to precast units, e.g. an infill slab, the precast units should have a key joint
cast in the mutual face for mechanical anchorage or shear purposes. Where a precast concrete face is to receive
in situ concrete placed against it, that face should be properly prepared (e.g. scabbled when the concrete is ‘green’).
For precasting, the detailer needs to be fully aware of the method of moulding, and the assembly and handling of the
reinforcement cage. Advice should be sought from the specialist precaster.
8.2 Particular durability problems
In bridge and car park construction where there is a risk of chloride exposure, the joints between precast units
require special attention in order to protect the reinforcement from corrosion. Figure 8.1 illustrates an example where
severe exposure conditions (Exposure Class XD3) exist. Reference should be made to the literature45,46.
Figure 8.1: Example of severe exposure (XD3) positions for precast car parks and bridges
Zone with possibility of very severe
exposure if sealant fails
Floor slab
Transverse
beams
Areas of moderate exposure
Severe exposure
possible in splash zone
Soffit and ends of beams
can be subject to severe
exposure if sealant fails
1.0–1.5m
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Appendix A: Changes to
reinforcement since 1948
The following is a list of primary codes/standards and other guidance, used in the design and detailing of
concrete reinforcement in the UK between 1948 and 2020:
British Standards Institution. BS 785:1938. Hot rolled bars and hard drawn wire for the reinforcement of concrete.
London: BSI; 1938.
British Standards Institution. BS 1144:1943. Cold twisted steel bars for concrete reinforcement. London: BSI; 1943.
Reynolds CE. Reinforced concrete designer’s handbook. London: Concrete Publications Ltd; 1951.
British Standards Institution. CP 114:1957. The structural use of reinforced concrete in buildings. London: BSI; 1957.
London (County) Council. London building (constructional) by-laws, 1952. London: London (County) Council; 1952.
British Standards Institution. CP 114:1965. The structural use of reinforced concrete in buildings [Imperial].
London: BSI; 1965.
British Standards Institution. CP 114:1969. The structural use of reinforced concrete in buildings [Metric].
London: BSI; 1969.
British Standards Institution. BS 4466:1969. Specification for bending dimensions and scheduling of bars for the
reinforcement for concrete. London: BSI; 1969.
British Standards Institution. CP 110-1:1972. Code of practice for the structural use of concrete. Design, materials
and workmanship. London: BSI; 1972.
British Standards Institution. BS 4466:1981. Specification for bending dimensions and scheduling of reinforcement
for concrete. London: BSI; 1981.
British Standards Institution. BS 8110-1:1985. Structural use of concrete. Code of practice for design and
construction. London: BSI; 1985.
British Standards Institution. BS 4482:1985. Specification for cold reduced steel wire for the reinforcement of
concrete. London: BSI; 1985.
British Standards Institution. BS 4466:1989. Specification for scheduling, dimensioning, bending and cutting of
steel reinforcement for concrete. London: BSI; 1989.
British Standards Institution. BS 8110-1:1997. Structural use of concrete. Code of practice for design and
construction. London: BSI; 1997.
British Standards Institution. BS 4449:1997. Specification for carbon steel bars for the reinforcement of concrete.
London: BSI; 1997.
British Standards Institution. BS 4483:1998. Steel fabric for the reinforcement of concrete. London: BSI; 1998.
British Standards Institution. BS 8666:2000. Specification for scheduling, dimensioning, bending and cutting of
steel reinforcement for concrete. London: BSI; 2000.
British Standards Institution. BS 6744:2001. Stainless steel bars for the reinforcement of and use in concrete.
Requirements and test methods. London: BSI; 2001.
British Standards Institution. BS EN 1992-1-1:2004 + A1:2014. Eurocode 2. Design of concrete structures.
General rules and rules for buildings. London: BSI; 2004.
British Standards Institution. BS 4449:2005 + A3:2016. Steel for the reinforcement of concrete.
Weldable reinforcing steel. Bar, coil and decoiled product. Specification. London: BSI; 2005.
British Standards Institution. BS 8666:2005 + A3:2016. Scheduling, dimensioning, bending and cutting of steel
reinforcement for concrete. Specification. London: BSI; 2005.
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Table A1: Circa 1948–1956
Material properties
BS 785:1938
Mild steel:
Min. tensile strength
Symbol used on drawings
R
62,720 (432)
Medium tensile steel:
Min. tensile strength
Min. yield stress
Size: up to 2in
up to 112in
1in or less
M
High tensile steel:
Min. tensile strength
Min. yield stress
Size: up to 2in
up to 112in
1in or less
H
BS 1144:1943
Twin twisted bars:
Min. tensile strength
Min. yield stress
Square twisted bars:
Min. tensile strength
Size: 3/8in and over
under 3/8in
Min. yield stress
Size: 3/8in and over
under 3/8in
lb/in2 (MPa)
73,920 (510)
39,200 (270)
41,440 (286)
43,680 (301)
82,880 (571)
47,040 (324)
49,280 (340)
51,520 (355)
I
63,000 (434)
54,000 (372)
S
70,000 (483)
80,000 (552)
60,000 (414)
70,000 (483)
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Table A2: Circa 1957–1964
Material properties
Symbol used on drawings
lb/in2 (MPa)
CP 114:1957
Mild steel (permissible stress):
Tension:
Size: 12in and under
over
20,000 (138)
1
2in
18,000 (124)
Compression:
Size: 12in and under
over 12in
18,000 (124)
16,000 (110)
Other steels (permissible stress):
Tension: 12 × min. yield stress but not greater than
Compression: 12 × min. yield stress but not greater than
Shear:
30,000 (207)
23,000 (159)
20,000 (138)
London by-laws: 1952
Mild steel (permissible stress):
Tension/compression:
Other steels (permissible stress):
Tension: 12 × min. yield stress but not greater than
Compression: 12 × min. yield stress but not greater than
Tentor bars (round ‘high yield’ deformed bars):
Stress as for square twisted bars
Symbols used on drawings otherwise as for 1948–1956
18,000 (124)
27,000 (186)
20,000 (138)
T
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Table A3: Circa 1965–1971
Material properties
Symbol used on drawings
lb/in2 (MPa)
CP 114:1965
High yield bars (permissible stress):
Tension: 0.55 × min. yield stress
Size: 7/8in and under
over 7/8in
Compression and shear:
33,000 (227)
30,000 (207)
25,000 (172)
CP 114:1969 (metric)
High yield bars (permissible stress):
Tension:
Size: 20mm and under
over 20mm
Compression and shear:
230
210
175
BS 4466:1969
Round mild steel
R
High yield bars
No specification concerning deformed properties
Not covered by R or Y
Y
X
Before 1969 symbols as for 1948–1964
Table A4: Circa 1972–1980
Material properties
Symbol used on drawings
MPa
CP 110:1972
Hot rolled bars:
Cold worked bars:
Size: 16mm and under
over 16mm
Design tensile strength = (0.87 × characteristic strength)
Design compression strength =
design tensile strength
design tensile strength
1+
2000
410
460
425
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Standard method of detailing structural concrete (4th edition)
Table A5: Circa 1981–1982
Material properties
Symbol used on drawings
BS 4466:1981
Plain or deformed bars grade 250
Type 2 deformed bars grade 460/425
Not covered by R or T
20
R
T
X
32
33
A
34
A
L=A
L=A+h
35
37
A
A
L = A + 2h
L=A+n
38
41
D > 2d
A
A
L = A + 2n
43
L = A + B – 1/2r – d
C D
A
R
B
B
L = A + B – 1/2R – d
L = A + B + C – r – 2d
62
81
83
(C)
L = A + B for angles <45
else
L = A + C – 1/2r – d
39
A
A
(D)
C
D
L = A + B + C – 1/2r – d
54
A
B
(E)
C
A
L = A + B + C – r – 2d
65
72
73
A
R
L=A
These bars will be supplied straight when the
radius exceeds that given in Table 5 of BS 4466
74
Internal
dimensions
A
85
C
(D)
R
B r
B
L = 2A + B + 25d
86
A
L = A + B + 0.57C + D – 1/2r – 0.257d
Internal
dimensions
L = 2A + B + C + 10d
C
Helix
B
L = 2A + 3B + 20d
A
Internal
dimensions
55
(C)
D
L = A + B + C + D + E – 2r – 4d
B
B
A = Internal diameter (mm)
A
B = Helix pitch (mm)
C = Helix overall height (mm)
L = C/BΠ (A + d) when B < A/5
B
L = A + B + C for angles <45
else
L = A + B + C – r – 2D
B
C
C
L = A + B + C + D – 1 1/2r– 3d
D (C) E
(C)
D
53
B
Grade 460, 425, 485
A or B > 10d or 125mm
for sizes <20mm
Grade 460, 425
A or B > 12d for sizes >25mm
49
B
A
L = A + B + C + n for angles <45
(D) B
B
B
A
(C)
L = A + 0.57B + C – 1.57d
52
45
B
(D)
L = A + 2B + C + D – 2r – 4d
if
A and/or B and/or C are not
external, see Shape Code 99
42
A
A
L = 2(A + B) + 20d
B
L = 2A + 3B + 22d
R
A
B
B
Internal dimensions
L = A + B + C for angles <45
else
L = A + B + C – 2d
Internal
dimensions
C
B
D
60
(C)
B
L = A + 2B + C + E for angles <45
else
L = A + 2B + C + E – 2r – 4d
A
(C)
A
A
B
A
B
A
(B)
51
A
MPa
B
(E)
C
A
D
B
B
B
(E)
D
C
(E)
A
C
A
C
D
A
L = A + B + C + D + E – 2r – 4d
99 ALL OTHER SHAPES
A dimensioned sketch shall be drawn out over the schedule columns A to E.
Every dimension shall be specified and the dimension that is free to take up
tolerances shall be indicated in parentheses, otherwise the fabricator is free to
choose which dimension shall take up the tolerances. If the standard shape is
required but a different dimension is to take up the tolerance, the shape code
shall be drawn out as a 99 and the free dimension indicated in parentheses.
Derived/adapted from BS 4466:1981.
CP 110: amendment (1980) (characteristic strength)
Hot rolled and cold worked bars
Size: up to 16mm
over 16mm
460
425
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Table A6: Circa 1983–1984
Material properties
Symbol used on drawings
CP 110: amendment (1983) (characteristic strength)
All sizes
MPa
460
Table A7: Circa 1985–2004
Material properties
Symbol used on drawings
MPa
BS 8110:1985
Design compressive strength made equal to design tensile strength
which is (0.87 × characteristic strength)
BS 4466:1989
Plain or deformed
Type 2 deformed bars or fabric
Stainless reinforcement
Plain reinforcement to BS 4482
Type 1 deformed reinforcement to BS 4482
Not covered by others
20
32
33
L=A+h
35
37
A
L = A + B – 1/2r – d
B
C
D
B
(E)
51
L=A+n
38
41
(B)
A
B
R
B
L = A + B – 1/2R – d
L = A + B + C – r – 2d
61
B
L = A + B for angles <45
else
L = A + C – 1/2r – d
L = 2A + 3B + 18d
External dimensions
If B > 350mm see Clause 10.2 of BS 4466
Derived/adapted from BS 4466:1989.
BS 8110:1997
Design strength increased to:
Characteristic strength/1.05
D
(C)
82
A
B
A
A
62
(C)
(C)
A
B
B
A
L = A + 2h
L = A + 2B + C + E for angles <45
else
L = A + 2B + C + E – 2r – 4d
A
460
460
A
A
A
L = A + 2n
250
460
34
A
A
L=A
43
R
T
S
W
D
X
L = A + B + C for angles <45
else
L = A + B + C – 2d
L = 2(A + B) + 12d
External dimensions
Grade 460
A or B > 12d or 150mm for sizes <20
A or B > 14d for sizes >25
Grade 250, with 100mm min.
A or B > 10d for sizes <20
A or B > 12d for sizes >25
B
A
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Standard method of detailing structural concrete (4th edition)
Table A7: Continued
Material properties
Symbol used on drawings
MPa
BS 8666:2000
(replaced BS 4466)
Conformed with ISO and European standards
Conforming to BS 4449
R
250
Deformed Type 1 conforming to BS 4482
(and for fabric conforming to BS 4483)
F
460
Deformed Type 2 conforming to BS 4482 or Ductility A of BS 4449
(and for fabric conforming to BS 4483)
D
460
Plain round conforming to BS 4482
(and for fabric conforming to BS 4483)
W
460
Ductility A or B deformed Type 2 conforming to BS 4449
T
460
Ductility B deformed Type 2 conforming to BS 4449
(for bar or fabric conforming to BS 4483)
B
460
A specified grade and type of stainless steel conforming to BS 6744
S
Reinforcement of a type not included here, having material
properties that are defined in the design or contract specification
X
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Table A8: circa 2005–2019
Material properties
Symbol used on drawings
MPa
Either:
BS 8110-1:1997
Design strength = characteristic strength/1.15
(amendment 3, published 2005)
Or
BS EN 1992-1-1:2004 + A1:2014
Design strength = characteristic strength/1.15
For diameters ⩽12mm:
Grade B500A, Grade B500B or Grade B500C conforming to
BS 4449
H
500
Grade B500A conforming to BS 4449
A
500
Grade B500B or Grade B500C conforming to BS 4449
B
500
Grade B500C conforming to BS 4449
C
500
A specified grade and type of ribbed stainless steel conforming
to BS 6744:2001
S
For diameters >12mm:
Grade B500B or Grade B500C conforming to BS 4449
00
01
A
L=A
11
A
L=A
Stock lengths
See Note 4
13
Semi circular
A
B
L = A + (B) – 0.43R – 1.2d
Neither A nor B shall be less than P in
Table C1 nor less than (R + 6d). See Note 3
15
21
B
A
A
B
L = A + (C) – 4d
Neither A nor (C) shall be less than P
in Table C1. See Note 1
L = A + (C)
Neither A nor (C) shall be less than P
in Table C1. See Note 1
22
23
24
A
Semi circular
(D)
C > 2r + 2d
L = A + B + C + (D) – 1.5r – 3d
C shall not be less than 2(r + d).
Neither A nor (D) shall be less than P in
Table C1. (D) shall not be less than C/2 + 5d.
See Note 3
(C)
B
L = A + B + (C) – r – 2d
Neither A nor (C) shall be less than P
in Table C1
B
L = A + B + (C) – r – 2d
Neither A nor (C) shall be less than P
in Table C1
(C)
D
C
(C)
(C)
A
A
L = A + (B) – 0.5r – d
Neither A nor B shall be less than P
in Table C1
L = A + 0.57B + (C) – 1.6d
B shall not be less than 2(r + d).
Neither A nor C shall be less than P in
Table C1 nor less than (½B + 5d). See Note 3
B
R
(B)
(C)
A
12
(B)
14
(C)
A
25
A
B
C
B
A
L = A + B + (C)
A and (C) are at 90º to one another
D
(E)
L = A + B + (E)
Neither A nor B shall be less than P in
Table C1. If E is the critical dimension,
schedule a 99 and specify A or B as the
free dimension. See Note 1
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Table A8: Continued
26
27
(C)
B
28
(C)
A
B
(C)
(C)
A
D
D
29
B
B
D
D
A
A
L = A + B + (C)
Neither A nor (C) shall be less than P in
Table C1. See Note 1
L = A + B + (C) – 0.5r – d
Neither A nor (C) shall be less than P in
Table C1. See Note 1
31
32
A
A
34
(D)
C
A
L = A + B + C + (D) – 1.5r – 3d
Neither A nor (D) shall be less than P in
Table C1
C
35
44
46
47
(E)
A
B
B
D
A
B
L = A + 2B + C + (E)
Neither A nor (E) shall be less than P in
Table C1. See Note 1
(C)
(D)
B
(D)
C
L = A + B + C + D + (E) – 2r – 4d
Neither A nor (E) shall be less than P in
Table C1
51
A
(C)
D
C
D
C
B
L = A + B + C + (D) – r – 2d
Neither A nor (D) shall be less than P in
Table C1. See Note 1
D
(E)
B
L = A + B + C + (E) – 0.5r – d
Neither A nor (E) shall be less than P in
Table C1. See Note 1
B
May also be used for flag link:
E
L = A + B + C + (E) – 0.5r – d
Neither A nor (E) shall be less than P in
Table C1. See Note 1
(E)
L = A + B + C + D + (E) – 2r – 4d
Neither A nor (E) shall be less than P in
Table C1
A
A
A
D
C
A
C
D
A
(E)
B
(D)
(E)
B
D
A
A
36
C
B
B
L = 2A + 1.7B + 2(C) – 4d
A shall not be less than 12d + 30mm.
B shall not be less than 2(r + d).
(C) shall not be less than P in Table C1,
nor less than B/2 + 5d. See Note 3
L = A + B + C + (D) – 1.5r – 3d
Neither A nor (D) shall be less than P in
Table C1
(E)
41
Semi circular
C
L = A + B + (C) – r – 2d
Neither A nor (C) shall be less than P in
Table C1. See Note 1
(C)
33
B
(D)
B
L = A + B + (C) – 0.5r – d
Neither A nor (C) shall be less than P in
Table C1. See Note 1
L = 2A + B + 2(C) +1.5r – 3d
(C) and (D) shall be equal and not more than
A nor less than P in Table C1. Where (C) and
(D) are to be minimized the following formula
may be used:
L = 2A + B + max (21d, 240). See Note 3
L = 2 (A + B + (C)) – 2.5r – 5d
(C) and (D) shall be equal and not more than
A or B nor less than P for links in Table C1.
Where (C) and (D) are to be minimised the
following formula may be used:
L = 2 A + 2B + max (16d, 160)
67
A
C
B
R
56
63
C
(D)
B
A
(C)
(F)
(D)
B
(E)
A
L = A + B + C + (D)+ 2(E) – 2.5r – 5d
(E) and (F) shall be equal and not more than
B or C nor less than P in Table C1.
See Notes 1 and 2
L = 2A + 3B + 2(C) – 3r – 6d
(C) and (D) shall be equal and not more than
A or B nor less than P for links in Table C1.
Where (C) and (D) are to be minimised the
following formula may be used:
L = 2A + 3B + max.(14d, 150)
64
L=A
See Clause 10 of BS 8666
A
D
B
C
75
A
(F)
E
L = A + B + C + 2D + E + (F) – 3r – 6d
Neither A and (F) shall be less than P in
Table C1. See Note 2
(B)
L = π (A – d) + B
Where B is the lap
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Table A8: Continued
77
98
B
A
99
A
B
B
(D)
C = number of turns
L = Cπ (A – d)
Where B is greater than A/5 this equation no
longer applies, in which case the following
formula may be used:
C
All other shapes where standard shapes cannot be used. L to be calculated.
No other shape code number, form of designation or abbreviation shall be used in
scheduling. See Note 2.
A dimensioned sketch shall be drawn over the dimension columns A to E.
Every dimension shall be specified and the dimension that is to allow for permissible
deviations shall be indicated in parentheses, otherwise the fabricator is free to choose
which dimension shall allow for tolerance.
L = A + 2B + C + (D) – 2r – 4d
Isometric sketch. Neither C nor (D) shall be
less than P in Table C1
L = C ((π(A – d))2 + B2)1/2
Notes:
Unless specified otherwise all references to tables, are to tables in this Manual.
The values for minimum radius and end dimensions, r and A respectively, as specified in Table C1, shall apply to all shape codes.
The dimensions in parentheses are the free dimensions. If a shape given in this table is required but a different dimension is to allow for the possible deviations, the shape shall be drawn and given
the Shape Code 99 and the free dimension shall be indicated in parentheses.
The length of straight between two bends shall be at least 4d (Figure 6 of BS 8666).
Figures 4, 5 and 6 of BS 8666 should be used in the interpretation of bending dimensions.
1 The length equations for shapes 14, 15, 25, 26, 27, 28, 29, 34, 35, 36 and 46 are approximate and where the bend angle is greater than 45º, the length should be calculated more accurately
allowing for the difference between the specified overall dimensions and the true length measured along the central axis of the bar. When the bending angles approach 90º, it is preferable to
specify Shape Code 99 with a fully dimensioned sketch.
2 5 bends or more may be impractical within permitted tolerances.
3 For shapes with straight and curved lengths (e.g. Shape Codes 12, 13, 22, 33 and 47) the largest practical mandrel size for the production of a continuous curve is 400 mm. See also Clause 10 of
BS 8666.
4 Stock lengths are available in a limited number of lengths (e.g. 6m, 12m). Dimension A for Shape Code 01 should be regarded as indicative and used for the purpose of calculating total length.
Actual delivery lengths should be by agreement with the supplier. Tolerances for Shape Code 01, stock lengths, shall be subject to the relevant product standard, e.g. BS 4449:2005.
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Appendix B:
Bar shapes (BS 8666:2020)
Table B1: Bar shapes (BS 8666:2020)
Shape Code
Shape
00
A
01
A
Total length of bar L measured along centreline
A
A
Stock lengths
See Note 4
A + (B) − 0.5r − d
A
11
(B)
Neither A nor B shall be less than P in Table C1.
A + (B) − 0.43R − 1.2d
R
A
12
Neither A nor B shall be less than (R + d) + greater
of 5d or 90mm
(B)
A + 0.57B + (C) − 1.6d
(C)
Semi-circular
13
B
A
Neither A nor C shall be less than B/2 + greater of
5d or 90mm
B shall not be less than q in Table C1.
B shall not exceed 400 + 2d
D
A + (C)
A
14
B
Neither A nor (C) shall be less than P in Table C1.
See Note 1.
(C)
A + (C)
D
A
15
B
(C)
Neither A nor (C) shall be less than P in Table C1.
See Note 1.
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Table B1: Continued
Shape Code
Total length of bar L measured along centreline
Shape
A + B + (C) − r − 2d
A
(C)
21
B
Neither A nor (C) shall be less than P in Table C1.
A + B + 0.57C + (D) − 0.5r − 2.6d
B
22
Semi-circular, radius r
A
C
(D)
Neither A nor (D) shall be less than P in Table C1.
C shall not be less than q in Table C1.
C shall not exceed 400mm + 2d
D must not be less than C/2 + greater of 5d or 90mm
A + B + (C) − r − 2d
May also be used for as a Z bar:
A
A
(C)
23
B
B
(C)
Neither A nor (C) shall be less than P in Table C1.
A + B + (C)
(C)
B
24
D
A
E
A
25
Neither A nor (C) shall be less than P in Table C1.
A and C are at 90° to one another.
See Note 1.
B
C
D
(E)
A + B + (E)
Neither A nor B shall be less than P in Table C1.
If (E) is the critical dimension, schedule a 99 and
specify A or B as the free dimension.
If bend angles approach 90° schedule as a
Shape Code 99.
See Note 1.
A + B + (C)
(C)
B
26
D
A
E
Neither A nor (C) shall be less than P in Table C1.
See Note 1.
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Table B1: Continued
Shape Code
Total length of bar L measured along centreline
Shape
A + B + (C) − 0.5r − d
B
A
27
(C)
D
Neither A nor (C) shall be less than P in Table C1.
See Note 1.
E
E
A + B + (C) − 0.5r − d
B
(C)
28
D
A
Neither A nor (C) shall be less than P in Table C1.
See Note 1.
(C)
A + B + (C)
E
B
29
D
Neither A nor (C) shall be less than P in Table C1.
See Note 1.
A
A + B + C + (D) − 1.5r − 3d
A
(D)
31
B
C
Neither A nor (C) shall be less than P in Table C1.
A + B + C + (D) − 1.5r − 3d
A
B
32
(D)
Neither A nor (C) shall be less than P in Table C1.
C
2A + 1.7B + 2(C) − 4d
(C)
33
1
Semi-circular, radius r
A
B
A shall not be less than 12d + 30mm.
B shall not be less than q in Table C1.
B should not exceed 400mm + 2d
C must not be less than B/2 + greater of 5d or 90mm
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Table B1: Continued
Shape Code
Total length of bar L measured along centreline
Shape
F
34
A + B + C + (E) − 0.5r − d
C
(E)
D
B
Neither A nor (E) shall be less than P in Table C1.
See Note 1.
A
F
A + B + C + (E) − 0.5r − d
C
(E)
35
Neither A nor (E) shall be less than P in Table C1.
See Note 1.
D
B
A
A + B + C + (D) − r − 2d
(D)
36
A
C
E
B
Neither A nor (D) shall be less than P in Table C1.
See Note 1.
F
A + B + C + D + (E) − 2r − 4d
A
(E)
Neither A nor (E) shall be less than P in Table C1.
May also be used for flag link:
B
D
A
(E)
41
C
B
D
C
A + B + C + D + (E) − 2r − 4d
A
(E)
44
B
Neither A nor (E) shall be less than P in Table C1.
D
C
A
B
46
A + 2B + C + (E)
(E)
B
D
D
F
C
F
Neither A nor (E) shall be less than P in Table C1.
See Note 1.
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Table B1: Continued
Shape Code
Total length of bar L measured along centreline
Shape
q
2A + B + 2(C) + 2q − r − 3r − 6d
q
(C)
47
(D)
A
(C) and (D) shall be equal and not more than A,
nor less than P in Table C1.
B
(C)
2A + B + 2(C) − r − 2d
(D)
A
48
B
(C) and (D) shall be equal and not more than A,
nor less than P in Table C1.
(C)
2(A + B + (C)) − 2.5r − 5d
(D)
(C) and (D) shall be equal and not more than A or B,
nor less than P in Table C1.
B
51
Where (C) and (D) are to be minimised the following
formula may be used:
A
For bar sizes ≤16mm:
L = 2A + 2B + max. (16d, 160)
For bar sizes ≥20mm:
L = 2A + 2B + 15d
2(A + B) + 2(C) − 1.5r − 3d
(C)
(C) and (D) shall be equal and not more than B nor
less than P in Table C1.
A
(D)
52
Where (C) and (D) are to be minimised the following
formula may be used:
B
For bar sizes ≤16mm:
L = 2A + 2B + max. (20d, 180)
For bar sizes ≥20mm:
L = 2A + 2B + 21d
A + B + C + D + 2(E) − 1.5r − 3d
C
(D)
56
B
(F)
(E)
A
(E) and (F) shall be equal and not more than A or B,
nor less than P in Table C1.
See Note 1.
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Table B1: Continued
Shape Code
Total length of bar L measured along centreline
Shape
2A + 3B + 2(C) − 3r − 6d
(D)
(C)
(C) and (D) shall be equal and not more than A,
nor less than P in Table C1.
A
B
Where (C) and (D) are to be minimised the following
formula may be used:
63
For bar sizes ≤16mm:
L = 2A + 3B + max. (14d, 140)
For bar sizes ≥20mm:
L = 2A + 3B + 13d
A + B + C + 2D + E + (F) − 3r − 6d
A
Neither A nor (F) shall be less than P in Table C1.
D
B
64
(F)
E
C
A
A
See Table C3.
C
67
B
R
π(A − d) + B
A
Where B is the lap.
75
(B)
Cπ(A − d)
A
B
77
Key: C = number of turns
Where B is greater than A/5 this equation no longer
applies, in which case the following formula may be
used:
L = C((π(A − d))2 + B2)1/2
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Table B1: Continued
Shape Code
Total length of bar L measured along centreline
Shape
A + 2B + C + (D) − 2r − 4d
A
Isometric sketch.
B
98
Neither C nor (D) shall be less than P in Table C1.
B
(D)
C
All other shapes where standard shapes
cannot be used.
99–xx
No other shape code, number, form of
designation or abbreviation shall be used
in scheduling. A dimensioned sketch
shall be drawn over the dimension
columns A to R. Every dimension shall
be specified, and the dimension that is
to allow permissible deviations shall be
indicated in parentheses, otherwise the
fabricator is free to choose which
dimension shall allow for tolerance.
To be calculated.
See Note 2.
Coupler 99s to be scheduled to the end
of the rebar, excluding any coupler type.
Coupler 99s may be scheduled to the
end of the coupler when coupler type
and style are known.
Notes:
Unless specified otherwise all references to tables, are to tables in this Manual.
The values for minimum radius and end projection r and P respectively, as specified in Table C1, shall apply to all shape
codes (Clause 7.6 of BS 8666).
The dimensions in parentheses are the free dimensions. If a shape in this table is required but a different dimension is to
allow for the possible deviations, the shape shall be drawn out and given the Shape Code 99 and the free dimension shall
be indicated in parentheses.
The minimum length of any straight between two bends shall be 4d (Figure 8 of BS 8666).
Figures 4–7 from BS 8666 should be used in the interpretation of bending dimensions.
1. The length equation for Shape Codes 14, 15, 24, 25, 26, 27, 28, 29, 34, 35, 36, 46 and 56 are approximate and where
the bend angle is greater than 45°, or for Shape Codes 14, 29 and 56 with an acute angle, the bend angle is close to 90°
or exceeds 135°, the length should be calculated more accurately allowing for the difference between the specified overall
dimensions and the true length measured along the central axis of the bar.
2. Five beds or more might be impractical within permitted tolerances, unless agreed with the fabricator.
3. For shapes with straight and curved lengths (e.g. Shape Code 12) the largest practical mandrel size for the production
of a continuous curve is 400mm. See also Clause 10 of BS 8666.
4. Stock lengths are available in a limited number of lengths (e.g. 6m, 12m, 14m). Dimension A for Shape Code 01 should
be regarded as indicative and used for the purpose of calculating total length. Actual delivery should be by agreement with
the supplier. See also the footnote to Table 5 of BS 8666.
Derived/adapted from BS 8666:2020.
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Appendix C: Scheduling radii
Table C1: Minimum scheduling radii, madrel diameters and end projections
Bend (bob)
P
Bend (hook)
>5d
>5d
r
P
r
(B)
q
(B)
Nominal
size of
bar d
Minimum radius
for scheduling
r
Minimum
diameter of
the bending
mandrel
M
(mm)
(mm)
(mm)
Minimum end projection P
General bend
(bob) (refer to
Note 3)
(mm)
Links where
bend is <150°
(min 10d,
90mm straight
(mm)
Anticipated actual
hook diameter
q
(refer to Note 2)
(mm)
6
12
24
110a
110a
42
8
16
32
115a
115a
56
10
20
40
120a
130
70
12
24
48
125a
155
84
16
32
64
140
210
112
20
70
140
190
290
200
25
87
175
235
365
250
32
112
224
305
465
320
40
140
280
380
580
400
50
175
350
475
725
500
Notes:
a
Minimum end projection for smaller bars is governed by practicalities of bending bars.
1. The fabricator shall use the minimum mandrel size wherever possible or their closest mandrel size greater than the
minimum (M) and subject to positive tolerances given for bending in Table 5 of BS 8666.
2. An allowable deviation of 1d has been used for ‘Springback’ in value for q.
3. General bend (bob), including links where bend is ⩾150° and straight length is min. of 5d or 90mm whichever is least.
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Table C2: Minimum allowances between two bends
Example Shape Codes 21 and 23
r
r
>4d
>4d
X
r
Nominal size of bar d
X
r
Minimum value between two bends X
6
70a
8
80
10
100
12
120
16
160
20
260
25
325
32
416
40
520
50
650
Notes:
a
Minimum end projection for smaller bars is governed by practicalities of bending bars.
1. Due to ‘springback’ the actual radius of bends will be slightly greater than the radius of the bending former.
2. BS 4449:2005 Grade B500A in sizes below 8mm does not conform to BS EN 1992.
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Table C3: Limit for which a preformed radius is required
Bar size (mm)
Radius (m)
6
2.5
8
2.75
10
3.5
12
4.25
16
7.5
20
14.0
25
30.0
32
43.0
40
58.0
Notes:
1. Required curvature may be obtained during placing.
2. For shape codes with straight and curved lengths (e.g. Shape Code 12) the largest practical radius for the production of
a continuous curve is 200mm (400mm diameter mandrel), and for larger radii the curve may be produced by a series
of short straight sections.
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Appendix D:
Mechanical couplers for bars
Where the reinforcement in a section is congested, mechanical couplers47 may be used to good effect. There are
two distinct types:
• tension couplers
• compression couplers
Unless specified otherwise, tension couplers should be used.
Note that the cover provided for couplers should be that specified for the reinforcement.
The notation used on the drawings and schedules for any special end preparation requirements is given as ‘E’
immediately before the mark.
Couplers are mainly tested in tension, but as required, may be tested under compression, cyclic and fatigue regimes.
In the UK, couplers should be manufactured by a company holding a valid third party technical approval certificate
issued by CARES or equivalent. The couplers should be processed by fabricators in possession of a valid CARES
certificate of approval, or equivalent.
Several types of coupler are available for tensile and compressive bars:
Type 1: Couplers with parallel threads
Threads can be cut, rolled or forged. There are two variations. Type 1a uses reinforcing bars, with the threaded
portion having a smaller diameter than the rest. Type 1b uses bars with the threaded portion having a
cross-sectional area equal to or greater than the nominal size. The former is rarely used since the load capacity is
reduced, while the latter (which maintains the parent bar load capacity) is widely used. An alternative to Type 1 also
includes a variant where one end of a parallel threaded coupler is swaged (deformed) on to a bar.
Parallel (Type 1) couplers also have transitional and positional variants. The transitional coupler allows two bars
of different size to be joined. The positional coupler usually comprises two halves joined by a parallel thread and
locknut arrangement.
Internally-threaded
coupler
Threaded bar area
less than unthreaded
bar area
Enlarged bar end
Threaded bar area
the same as
unthreaded bar area
Internally-threaded
coupler
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Type 2: Couplers with taper-cut threads
This system consists of an internally-threaded metal coupler with a tapered thread, and matching tapered bars. It is
widely used due to its suitability for various structural applications.
Internally-threaded
tapered coupler
Matching tapered bars
The standard tapered coupler can only be used in situations where the continuing bars can be rotated. This is not
always practical, and more sophisticated tapered couplers have been developed which allow the joining of bars that
cannot be rotated, and the joining of bars where the continuing bar can neither be rotated nor moved (e.g. L-bars).
a) Positional coupler
b) Transitional coupler
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Type 3: Couplers with integral threads over full length bar
High yield reinforcing bars are specially manufactured with helical deformations along the full length of the bar.
The deformations form a continuous coarse thread onto which an internally-threaded coupler can be screwed.
Locknuts are used at either end of the coupler to prevent slippage on the coarse threads. A turnbuckle system for
when the continuing bar cannot be rotated is not available, but the coupler can be completely threaded onto one bar
and then run back onto the continuing bar to form the joint.
Locknut
Bar with helical
deformations
Internally-threaded
coupler
Locknut
Type 4: Metal sleeves swaged onto bars
A seamless malleable steel sleeve is slipped over the abutting ends of two reinforcing bars. The sleeve is then
swaged onto the ends of the bars using a hydraulic press. This action effectively splices the bars together.
The process can be carried out wholly in situ. The hydraulic press compresses the sleeve laterally onto the bars and
several ‘bites’ are usually necessary to cover the whole joint.
Sufficient working space must be available around the bars to enable the hydraulic press to swage onto them.
In addition, swaging equipment for large diameter bars (H40 and larger) may require mechanical support for safe
operation. It is important to consider this, both during construction sequencing and when detailing reinforcement in
confined areas.
Type 5: Threaded couplers swaged onto ends of reinforcing bars
In this system two malleable sleeves which are threaded internally for half their length are joined together by a
high tensile threaded stud.
Steel sleeve half-swaged
onto bars half-threaded
onto stud
Threaded stud
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The unthreaded parts of the sleeves are hydraulically swaged on the two ends of the bar to be joined. These ends
can be screwed together using the threaded stud. The swaging process can be performed by the fabricator prior to
arrival on site, in a stockyard at the site, or in situ. For in situ swaging there must be sufficient working space around
the bars. Connection of the bars with the threaded stud is performed in situ.
Type 6: Wedge locking sleeves
This system is used for connecting compression bars only. The bars are held in concentric bearing by the lateral
clamping action of a sleeve and wedge. The sleeve is cylindrical, with a wedge-shaped opening. This opening has
collared flanges, onto which a wedge-shaped piece of metal is driven. This action compresses the sleeve laterally
and clamps the bars together. It is very important that the bar faces are cut accurately and aligned to within a
3° max. angle tolerance.
Wedge
Sleeve
Type 7: Couplers with shear bolts and serrated saddles
This system does not require rebar threading and consists of a steel coupler with a line of lockshear bolts running
along its length. The two bars to be joined are placed inside the coupler on two hardened serrated steel locking
strips (‘saddles’), using a ratchet wrench or electric or air-powered nut runner, which forces the bars against the
longitudinal saddles. As this happens, the serrated saddles bite into the bar and wall of the coupler. When the
predetermined tightening torque for the bolts is reached, the bolt heads shear off leaving the installed bolt proud of
the coupler. This provides a visual check of correct installation.
This coupler has proved useful in refurbishment work, joining pile cage steel to pile caps and where couplers are
required with minimum lead time. They are however, relatively bulky requiring space for sockets to tighten bolts.
This should be taken into account when considering concrete placement. Reduced aggregated concrete is often
required in congested areas.
Coupler containing two
serrated locking strips
Lockshear bolts tightened
until bolts shear off
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Appendix E:
Lap and anchorage lengths
Table E1: Lap and anchorage lengths
Bond
condition
Reinforcement in tension, bar diameter, ∅ (mm)
8
10
12
16
20
25
32
40
Straight bars
only
Good
270
370
480
690
910
1180
1500
2040
47∅
Poor
380
520
680
990
1290
1680
2150
2920
67∅
Other bars
Good
370
470
570
750
940
1180
1500
2040
47∅
Poor
530
670
810
1080
1340
1680
2150
2920
67∅
Good
370
510
660
970
1270
1640
2100
2860
66∅
Poor
530
730
950
1380
1810
2350
3000
4080
94∅
Good
400
550
710
1030
1360
1760
2250
3060
70∅
Poor
510
790
1010
1480
1940
2320
3220
4370
100∅
Straight bars
only
Good
230
320
410
600
780
1010
1300
1760
40∅
Poor
330
450
580
850
1120
1450
1850
2510
58∅
Other bars
Good
320
410
490
650
810
1010
1300
1760
40∅
Poor
460
580
700
930
1160
1450
1850
2510
58∅
Good
320
440
570
830
1090
1420
1810
2460
57∅
Poor
460
630
820
1190
1560
2020
2590
3520
81∅
Good
340
470
610
890
1170
1520
1940
2640
61∅
Poor
490
680
870
1270
1670
2170
2770
3770
87∅
Reinforcement
in compression
Concrete class C20/25
Anchorage
length, lbd
Lap length,
l0
50% lapped in
one location
(α6 = 1.4)
100% lapped in
one location
(α6 = 1.5)
Concrete class C25/30
Anchorage
length, lbd
Lap length,
l0
50% lapped in
one location
(α6 = 1.4)
100% lapped in
one location
(α6 = 1.5)
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Table E1: Continued
Bond
condition
Reinforcement in tension, bar diameter, ∅ (mm)
8
10
12
16
20
25
32
40
Straight bars
only
Good
210
300
380
550
730
940
1200
1630
37∅
Poor
300
420
540
790
1030
1340
1720
2330
53∅
Other bars
Good
300
380
450
600
750
940
1200
1630
37∅
Poor
420
540
650
860
1070
1340
1720
2330
53∅
Good
300
410
530
770
1010
1320
1680
2280
52∅
Poor
420
590
760
1100
1450
1880
2400
3260
75∅
Good
320
440
570
830
1090
1410
1800
2450
56∅
Poor
450
630
810
1180
1550
2010
2570
3470
80∅
Straight bars
only
Good
210
280
360
530
690
900
1150
1560
36∅
Poor
290
400
520
750
990
1280
1640
2230
51∅
Other bars
Good
290
360
430
580
720
900
1150
1560
36∅
Poor
410
520
620
820
1030
1280
1640
2230
51∅
Good
290
390
510
740
970
1260
1610
2180
50∅
Poor
410
560
720
1050
1380
1790
2290
3110
72∅
Good
310
420
540
790
1040
1350
1720
2340
54∅
Poor
430
600
780
1130
1480
1920
2460
3340
77∅
Straight bars
only
Good
200
270
350
510
660
860
1100
1490
34∅
Poor
280
380
500
720
950
1230
1570
2130
49∅
Other bars
Good
270
350
420
550
690
860
1100
1490
34∅
Poor
390
490
590
790
980
1230
1570
2130
49∅
Good
270
380
490
710
930
1200
1540
2090
48∅
Poor
390
540
690
1010
1320
1720
2200
2980
69∅
Good
290
400
520
760
990
1290
1650
2240
51∅
Poor
420
570
740
1080
1420
1840
2350
3200
73∅
Reinforcement
in compression
Concrete class C28/35
Anchorage
length, lbd
Lap length,
l0
50% lapped in
one location
(α6 = 1.4)
100% lapped in
one location
(α6 = 1.5)
Concrete class C30/37
Anchorage
length, lbd
Lap length,
l0
50% lapped in
one location
(α6 = 1.4)
100% lapped in
one location
(α6 = 1.5)
Concrete class C32/40
Anchorage
length, lbd
Lap length,
l0
50% lapped in
one location
(α6 = 1.4)
100% lapped in
one location
(α6 = 1.5)
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Table E1: Continued
Bond
condition
Reinforcement in tension, bar diameter, ∅ (mm)
8
10
12
16
20
25
32
40
Straight bars
only
Good
190
260
330
480
630
810
1040
1410
32∅
Poor
260
360
470
680
890
1160
1480
2010
46∅
Other bars
Good
260
330
390
520
650
810
1040
1410
32∅
Poor
370
470
560
740
930
1160
1480
2010
46∅
Good
260
360
460
670
870
1130
1450
1970
45∅
Poor
370
510
650
950
1250
1620
2070
2810
65∅
Good
280
380
490
710
940
1210
1550
2110
48∅
Poor
390
540
700
1020
1340
1730
2220
3010
69∅
Straight bars
only
Good
170
230
300
440
570
740
950
1290
30∅
Poor
240
330
430
620
820
1060
1350
1840
42∅
Other bars
Good
240
300
360
480
600
740
950
1290
30∅
Poor
340
430
510
680
850
1060
1350
1840
42∅
Good
240
330
420
610
800
1040
1330
1800
41∅
Poor
340
460
600
870
1140
1480
1890
2570
59∅
Good
250
350
450
650
860
1110
1420
1930
44∅
Poor
360
500
640
930
1220
1590
2030
2760
63∅
Straight bars
only
Good
160
220
280
400
530
690
880
1190
27∅
Poor
220
310
400
580
760
980
1250
1700
39∅
Other bars
Good
220
280
330
440
550
690
880
1190
27∅
Poor
310
390
470
630
780
980
1250
1700
39∅
Good
220
300
390
560
740
960
1230
1670
38∅
Poor
310
430
550
800
1060
1370
1750
2380
55∅
Good
230
320
420
600
790
1030
1310
1780
41∅
Poor
330
460
590
860
1130
1470
1880
2550
58∅
Reinforcement
in compression
Concrete class C35/45
Anchorage
length, lbd
Lap length,
l0
50% lapped in
one location
(α6 = 1.4)
100% lapped in
one location
(α6 = 1.5)
Concrete class C40/50
Anchorage
length, lbd
Lap length,
l0
50% lapped in
one location
(α6 = 1.4)
100% lapped in
one location
(α6 = 1.5)
Concrete class C45/55
Anchorage
length, lbd
Lap length,
l0
50% lapped in
one location
(α6 = 1.4)
100% lapped in
one location
(α6 = 1.5)
204
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
Table E1: Continued
Bond
condition
Reinforcement in tension, bar diameter, ∅ (mm)
8
10
12
16
20
25
32
40
Straight bars
only
Good
150
200
260
380
490
640
820
1110
25∅
Poor
210
290
370
540
700
910
1170
1580
36∅
Other bars
Good
220
280
330
440
550
690
880
1190
27∅
Poor
310
390
470
630
780
980
1250
1700
39∅
Good
220
300
390
560
740
960
1230
1670
38∅
Poor
310
430
550
800
1060
1370
1750
2380
55∅
Good
230
320
420
600
790
1030
1310
1780
41∅
Poor
330
460
590
860
1130
1470
1880
2550
58∅
Reinforcement
in compression
Concrete class C50/60
Anchorage
length, lbd
Lap length,
l0
50% lapped in
one location
(α6 = 1.4)
100% lapped in
one location
(α6 = 1.5)
Notes:
1. Cover to all sides ⩾ 25mm distance between bars ⩾ 50mm (i.e. α2 < 1).
2. α1 = α3 = α4 = α5 = 1.0. For the beneficial effects of shape of bar, cover and confinement see Table B.2 of BS EN 1992.
3. Design stress has been taken at 435 MPa. Where the design stress in the bar at the position from where the anchorage
is measured, σsd , is less than 435 MPa the figures in this table can be factored by σsd/435. The minimum lap length is
given in Clause 8.7.3 of BS EN 1992.
4. The anchorage and lap lengths have been rounded up to the nearest 10mm.
5. Where 33% of bars are lapped in one location, decrease the lap lengths for ‘50% lapped in one location’ by a factor
of 0.82.
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
| 205
Appendix F:
Effective anchorage length
Table F1: L-bars
5ø
Mandrel dia.
Effective anchorage length = (π (mandrel dia. + ø)/4 + 5ø)/0.7
Mandrel size/Bar dia.
Effective anchorage length from start of bend (mm)
Bar sizes
4
5
6
7
8
9
10
11
12
13
14
8
10
12
16
20
25
32
40
102
78
84
90
97
103
109
115
122
128
134
128
139
150
161
172
184
195
206
217
229
240
153
166
180
193
207
220
234
247
261
274
288
204
222
240
258
276
294
312
330
348
366
384
255
277
300
322
345
367
390
412
435
457
479
319
347
375
403
431
459
487
515
543
571
599
408
444
480
516
552
588
624
659
695
731
767
510
555
600
645
690
735
779
824
869
914
959
206
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
Table F2: U-bars
5ø
Mandrel dia.
Effective anchorage length = (π (mandrel dia. + ø)/2 + 5ø)/0.7
Mandrel size/Bar dia.
Effective anchorage length from start of bend (mm)
Bar sizes
4
5
6
7
8
9
10
11
12
13
14
8
10
12
16
20
25
32
40
147
165
183
201
219
237
255
273
291
308
326
184
206
229
251
273
296
318
341
363
386
408
220
247
274
301
328
355
382
409
436
463
490
294
330
366
402
437
473
509
545
581
617
653
367
412
457
502
547
592
637
681
726
771
816
459
515
571
627
683
740
796
852
908
964
1020
588
659
731
803
875
947
1018
1090
1162
1234
1306
735
824
914
1004
1094
1183
1273
1363
1453
1542
1632
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
| 207
Appendix G: Minimum overall
depth of various U-bars
Table G1: Hook
5ø
Mandrel dia.
B
fy = 500 MPa
Minimum mandrel diameter:
for ø < 16mm
mandrel dia. = 4ø
for ø > 16mm
mandrel dia. = 7ø
Bar size
6
8
10
12
16
20
25
32
40
B
40
50
60
75
100
180
225
290
360
Table G2: Trombone
5ø
B
4ø
Mandrel dia.
fy = 500 MPa
Minimum mandrel diameter:
for ø < 16mm
mandrel dia. = 4ø
for ø > 16mm
mandrel dia. = 7ø
Bar size
6
8
10
12
16
20
25
32
40
B
60
80
100
120
160
260
325
420
520
208
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
Appendix H: Large diameter bends
Table H1: Internal diameter of large bends (mm) — Compressive strength class C20/25
ab (mm)
Actual ult. stress
in bar (MPa)
Bar diameter ∅ (mm)
10
12
16
20
25
32
40
25
100
150
200
250
300
350
400
450
60
90
120
155
185
215
245
280
80
120
160
200
240
285
325
365
125
185
250
315
375
440
505
565
180
270
360
450
540
630
720
810
255
385
515
645
775
905
1035
1165
50
100
150
200
250
300
350
400
450
45
70
95
120
145
165
190
215
60
90
120
150
180
215
245
275
90
135
180
225
270
315
360
405
120
185
245
310
370
435
495
560
170
255
345
430
515
605
690
775
250
375
505
630
755
880
1010
1135
360
540
720
900
1080
1260
1440
1620
75
100
150
200
250
300
350
400
450
40
65
85
105
130
150
175
195
50
80
105
135
160
190
215
245
75
115
155
195
235
275
315
355
105
155
210
265
315
370
425
475
140
215
285
360
430
505
575
645
205
305
410
510
615
715
820
920
285
425
570
715
855
1000
1145
1285
100
100
150
200
250
300
350
400
450
40
60
80
100
120
145
165
185
50
75
100
125
150
180
205
230
70
105
145
180
215
255
290
325
95
145
190
240
290
335
385
435
125
190
255
320
385
450
515
580
180
270
360
450
545
635
725
815
245
370
495
620
745
870
995
1120
150 and over
100
150
200
250
300
350
400
450
35
55
75
95
115
135
155
175
45
70
95
120
140
165
190
215
65
100
130
165
200
235
265
300
85
130
175
215
260
305
350
395
115
170
230
285
345
400
460
515
155
235
315
395
470
550
630
710
210
315
425
530
635
740
850
955
Notes:
Maximum design stress = characteristic yield stress/1.15 = 435MPa.
Minimum mandrel size may govern: for bar size: <20 4∅ mandrel size
⩾20 7∅ mandrel size
Minimum mandrel size, ∅m,min (mm)
∅m,min = Fbt((1/ab) + 1/(2∅))/fcd where: Fbt
= tensile force from ultimate loads (N)
∅
= size of bar (mm)
= half the pitch of bars or nominal cover + ∅/2 (mm)
ab
= design concrete strength = αccfck/γc (MPa)
fcd
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
| 209
Table H2: Internal diameter of large bends (mm) — Compressive strength class C25/30
ab (mm)
Actual ult. stress
in bar (MPa)
Bar diameter ∅ (mm)
10
12
16
20
25
32
40
25
100
150
200
250
300
350
400
450
45
70
95
120
145
170
195
220
65
95
130
160
195
225
260
290
100
150
200
250
300
350
400
455
140
215
285
360
430
500
575
645
205
310
415
515
620
725
830
935
50
100
150
200
250
300
350
400
450
35
55
75
95
115
135
155
170
45
70
95
120
145
170
195
220
70
105
145
180
215
250
290
325
95
145
195
245
295
345
395
445
135
205
275
345
415
485
550
620
200
300
400
505
605
705
805
910
285
430
575
720
860
1005
1150
1295
75
100
150
200
250
300
350
400
450
35
50
70
85
105
120
140
155
40
65
85
105
130
150
175
195
60
90
125
155
185
220
250
280
85
125
170
210
255
295
340
380
115
170
230
285
345
400
460
515
160
245
325
410
490
575
655
735
225
340
455
570
685
800
915
1030
100
100
150
200
250
300
350
400
450
30
45
65
80
95
115
130
145
40
60
80
100
120
140
160
185
55
85
115
145
175
200
230
260
75
115
155
190
230
270
310
345
100
155
205
255
310
360
415
465
145
215
290
360
435
505
580
650
195
295
395
495
595
695
795
895
150 and over
100
150
200
250
300
350
400
450
30
45
60
75
90
105
125
140
35
55
75
95
115
135
150
170
50
80
105
130
160
185
215
240
70
105
140
175
210
245
280
315
90
135
180
230
275
320
365
415
125
185
250
315
375
440
505
565
170
255
340
425
510
595
680
765
Notes:
Maximum design stress = characteristic yield stress/1.15 = 435MPa.
Minimum mandrel size may govern: for bar size: <20 4∅ mandrel size
⩾20 7∅ mandrel size
Minimum mandrel size, ∅m,min (mm)
∅m,min = Fbt((1/ab) + 1/(2∅))/fcd where: Fbt
= tensile force from ultimate loads (N)
∅
= size of bar (mm)
= half the pitch of bars or nominal cover + ∅/2 (mm)
ab
= design concrete strength = αccfck/γc (MPa)
fcd
210
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
Table H3: Internal diameter of large bends (mm) — Compressive strength class C28/35
ab (mm)
Actual ult. stress
in bar (MPa)
Bar diameter ∅ (mm)
10
12
16
20
25
32
40
25
100
150
200
250
300
350
400
450
40
65
85
110
130
155
175
200
55
85
115
145
170
200
230
260
90
135
180
225
270
315
360
405
125
190
255
320
385
450
510
575
185
275
370
460
555
645
740
835
50
100
150
200
250
300
350
400
450
30
50
65
85
100
120
135
155
40
65
85
105
130
150
175
195
60
95
125
160
190
225
255
290
85
130
175
220
265
310
355
400
120
185
245
305
370
430
490
555
180
270
360
450
540
630
720
810
255
385
510
640
770
900
1025
1155
75
100
150
200
250
300
350
400
450
30
45
60
75
90
105
125
140
35
55
75
95
115
135
155
175
55
80
110
140
165
195
225
250
75
110
150
185
225
265
300
340
100
150
205
255
305
360
410
460
145
220
290
365
440
510
585
660
200
305
405
510
610
715
815
920
100
100
150
200
250
300
350
400
450
25
40
55
70
85
100
115
130
35
55
70
90
110
125
145
165
50
75
100
130
155
180
205
235
65
100
135
170
205
240
275
310
90
135
185
230
275
320
370
415
125
190
255
320
385
450
515
580
175
265
355
445
530
620
710
800
150 and over
100
150
200
250
300
350
400
450
25
40
55
70
80
95
110
125
30
50
65
85
100
120
135
155
45
70
95
120
140
165
190
215
60
90
125
155
185
215
250
280
80
120
160
205
245
285
325
370
110
165
225
280
335
395
450
505
150
225
300
375
455
530
605
680
Notes:
Maximum design stress = characteristic yield stress/1.15 = 435MPa.
Minimum mandrel size may govern: for bar size: <20 4∅ mandrel size
⩾20 7∅ mandrel size
Minimum mandrel size, ∅m,min (mm)
∅m,min = Fbt((1/ab) + 1/(2∅))/fcd where: Fbt
= tensile force from ultimate loads (N)
∅
= size of bar (mm)
= half the pitch of bars or nominal cover + ∅/2 (mm)
ab
= design concrete strength = αccfck/γc (MPa)
fcd
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
| 211
Table H4: Internal diameter of large bends (mm) — Compressive strength class C30/37
ab (mm)
Actual ult. stress
in bar (MPa)
Bar diameter ∅ (mm)
10
12
16
20
25
32
40
25
100
150
200
250
300
350
400
450
40
60
80
100
120
145
165
185
50
80
105
135
160
190
215
240
80
125
165
210
250
290
335
375
120
180
240
300
360
420
480
540
170
255
345
430
515
605
690
775
50
100
150
200
250
300
350
400
450
30
45
60
80
95
110
125
145
40
60
80
100
120
140
160
180
60
90
120
150
180
210
240
270
80
120
165
205
245
290
330
370
115
170
230
285
345
400
460
515
165
250
335
420
505
585
670
755
240
360
480
600
720
840
960
1080
75
100
150
200
250
300
350
400
450
25
40
55
70
85
100
115
130
35
50
70
90
105
125
145
160
50
75
105
130
155
180
210
235
70
105
140
175
210
245
280
315
95
140
190
240
285
335
380
430
135
205
270
340
410
475
545
614
190
285
380
475
570
665
760
855
100
100
150
200
250
300
350
400
450
25
40
55
65
80
95
110
120
30
50
65
85
100
120
135
150
45
70
95
120
145
170
195
215
60
95
125
160
190
225
255
290
85
125
170
215
255
300
345
385
120
180
240
300
360
420
480
545
165
245
330
415
495
580
665
745
150 and over
100
150
200
250
300
350
400
450
25
35
50
65
75
90
100
115
30
45
60
80
95
110
125
140
40
65
85
110
130
155
175
200
55
85
115
145
175
200
230
260
75
115
150
190
230
265
305
345
105
155
210
260
315
365
420
470
140
210
280
350
425
495
565
635
Notes:
Maximum design stress = characteristic yield stress/1.15 = 435MPa.
Minimum mandrel size may govern: for bar size: <20 4∅ mandrel size
⩾20 7∅ mandrel size
Minimum mandrel size, ∅m,min (mm)
∅m,min = Fbt((1/ab) + 1/(2∅))/fcd where: Fbt
= tensile force from ultimate loads (N)
∅
= size of bar (mm)
= half the pitch of bars or nominal cover + ∅/2 (mm)
ab
= design concrete strength = αccfck/γc (MPa)
fcd
212
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
Table H5: Internal diameter of large bends (mm) — Compressive strength class C32/40
ab (mm)
Actual ult. stress
in bar (MPa)
Bar diameter ∅ (mm)
10
12
16
20
25
32
40
25
100
150
200
250
300
350
400
450
35
55
75
95
115
135
155
175
50
75
100
125
150
175
200
225
75
115
155
195
235
275
315
355
110
165
225
280
335
390
450
505
160
240
320
405
485
565
645
730
50
100
150
200
250
300
350
400
450
30
45
60
75
90
105
120
135
35
55
75
95
115
130
150
170
55
85
110
140
170
195
225
255
75
115
155
190
230
270
310
350
105
160
215
270
320
375
430
485
155
235
315
395
470
550
630
710
225
335
450
560
675
785
900
1010
75
100
150
200
250
300
350
400
450
25
40
50
65
80
95
105
120
30
50
65
85
100
120
135
150
45
70
95
120
145
170
195
220
65
95
130
165
195
230
265
295
90
135
180
225
270
315
360
405
125
190
255
320
385
445
510
575
175
265
355
445
535
625
715
805
100
100
150
200
250
300
350
400
450
25
35
50
60
75
90
100
115
30
45
60
80
95
110
125
145
45
65
90
110
135
160
180
205
60
90
120
150
180
210
240
270
80
120
160
200
240
280
320
365
110
170
225
280
340
395
450
510
155
230
310
385
465
545
620
700
150 and over
100
150
200
250
300
350
400
450
20
35
45
60
70
85
95
110
30
45
60
75
90
105
120
135
40
60
80
105
125
145
165
185
50
80
105
135
160
190
215
245
70
105
140
180
215
250
285
320
95
145
195
245
295
345
395
440
130
195
265
330
395
460
530
595
Notes:
Maximum design stress = characteristic yield stress/1.15 = 435MPa.
Minimum mandrel size may govern: for bar size: <20 4∅ mandrel size
⩾20 7∅ mandrel size
Minimum mandrel size, ∅m,min (mm)
∅m,min = Fbt((1/ab) + 1/(2∅))/fcd where: Fbt
= tensile force from ultimate loads (N)
∅
= size of bar (mm)
= half the pitch of bars or nominal cover + ∅/2 (mm)
ab
= design concrete strength = αccfck/γc (MPa)
fcd
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| 213
Table H6: Internal diameter of large bends (mm) — Compressive strength class C35/45
ab (mm)
Actual ult. stress
in bar (MPa)
Bar diameter ∅ (mm)
10
12
16
20
25
32
40
25
100
150
200
250
300
350
400
450
35
50
70
85
105
120
140
160
45
65
90
115
135
160
185
205
70
105
140
180
215
250
285
325
100
150
205
255
305
360
410
460
145
220
295
370
445
515
590
665
50
100
150
200
250
300
350
400
450
25
40
55
65
80
95
110
120
35
50
70
85
105
120
140
155
50
75
100
125
155
180
205
230
70
105
140
175
210
245
285
320
95
145
195
245
295
345
395
445
140
215
285
360
430
505
575
650
205
305
410
510
615
720
820
925
75
100
150
200
250
300
350
400
450
25
35
50
60
75
85
100
110
30
45
60
75
90
105
125
140
45
65
90
110
135
155
180
200
60
90
120
150
180
210
240
270
80
120
160
205
245
285
325
370
115
175
230
290
350
410
465
525
160
245
325
405
490
570
650
735
100
100
150
200
250
300
350
400
450
20
35
45
55
70
80
95
105
25
40
55
70
85
100
115
130
40
60
80
100
125
145
165
185
55
80
110
135
165
190
220
245
70
110
145
185
220
255
295
330
100
155
205
255
310
360
415
465
140
210
285
355
425
495
570
640
150 and over
100
150
200
250
300
350
400
450
20
30
40
55
65
75
85
100
25
40
55
65
80
95
110
120
35
55
75
95
115
130
150
170
50
75
100
125
150
175
200
225
65
95
130
160
195
230
260
295
90
135
180
225
270
315
360
405
120
180
240
300
360
425
485
545
Notes:
Maximum design stress = characteristic yield stress/1.15 = 435MPa.
Minimum mandrel size may govern: for bar size: <20 4∅ mandrel size
⩾20 7∅ mandrel size
Minimum mandrel size, ∅m,min (mm)
∅m,min = Fbt((1/ab) + 1/(2∅))/fcd where: Fbt
= tensile force from ultimate loads (N)
∅
= size of bar (mm)
= half the pitch of bars or nominal cover + ∅/2 (mm)
ab
= design concrete strength = αccfck/γc (MPa)
fcd
214
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
Appendix I: Abbreviations
The following abbreviations are in common use:
ABR
ABS
Add’l
ALT
AP
B1
alternate bar reversed
alternate bar staggered
additional
alternate bar
alternately placed
bottom layer 1
(layer nearest to face of concrete)
B2
bottom layer 2
B3
bottom layer 3
blk
blockwork
BW
both ways
bwk
brickwork
cc
centre to centre
CL
centreline
crs
centres
dia or ∅ diameter
drg
drawing
EF
each face
EL
existing level
ES
each side
EW
each way
FF
far face
FF1
far face first layer
(layer nearest to face of concrete)
FF2
FFL
FS
horiz
LB
NF
NF1
NF2
NTS
pkt
PS
RC
SB
SOL
SOP
SSL
Stagg
STG
T1
T2
T3
UB
vert
far face second layer
finished floor level
full-size
horizontal
L-shape bars (also known as‘ bob bars’)
near face
near face first layer
(layer nearest to face of concrete)
near face second layer
not to scale
pocket
punching shear
reinforced concrete
side bars
setting-out line
setting-out point
structural slab level
staggered bars
staggered bars
top layer 1 (layer nearest to face of concrete)
top layer 2
top layer 3
U-shape bars
vertical
P1
P2
PO
SF
TH
TLL
V
punching shear perimeter 1
punching shear perimeter 2
pull-out bars
side face bars
threaded bars
top long leg
verticals
These abbreviations are also used:
BLL
CP
EC
H
HB
IF
OF
bottom long leg
coupler bars
each corner
horizontals
holding bars
inner face
outer face
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Standard method of detailing structural concrete (4th edition)
| 215
Appendix J: Fabric types
Table J1: Fabric types
Fabric reference
Longitudinal bars
Nominal bar
size mm
Transverse bars
Pitch
mm
Area
mm2/m
Nominal bar
size mm
Pitch
mm
Area
mm2/m
Mass
kg/m2
Square
mesh
A393
A252
A193
A142
10
8
7
6
200
200
200
200
393
252
193
142
10
8
7
6
200
200
200
200
393
252
193
142
6.16
3.95
3.02
2.22
Structural
mesh
B1131
B785
B503
B385
B283
12
10
8
7
6
100
100
100
100
100
1131
785
503
385
283
8
8
8
7
7
200
200
200
200
200
252
252
252
193
193
10.9
8.14
5.93
4.53
3.73
Long mesh
C785
C636
C503
C385
C283
10
9
8
7
6
100
100
100
100
100
785
636
503
385
283
6
6
6
6
6
400
400
400
400
400
70.8
70.8
49
49
49
6.72
5.55
4.51
3.58
2.78
Wrapping
mesh
D98
D49
200
100
98
49
5
2.5
200
100
98
49
1.54
0.77
5
2.5
Notes:
Stock sheet size: length 4.8m, width 2.4m, sheet area 11.52m2.
Derived/adapted from BS 4483:2005.
216
Institution of Structural Engineers
| The
Standard method of detailing structural concrete (4th edition)
References
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
British Standards Institution. BS EN 1992-1-1:2004+A1:2014. Eurocode 2. Design of concrete structures.
General rules and rules for buildings. London: BSI; 2004.
British Standards Institution. BS EN 1992-1-2:2004+A1:2019. Eurocode 2. Design of concrete structures.
General rules. Structural fire design. London: BSI; 2005.
British Standards Institution. BS EN 1992-2:2005. Eurocode 2. Design of concrete structures. Concrete bridges.
Design and detailing rules. London: BSI; 2005.
British Standards Institution. BS EN 1992-3:2006. Eurocode 2. Design of concrete structures.
Liquid retaining and containing structures. London: BSI; 2006.
CARES – UK Certification for Reinforcing Steels. Available from: https://www.ukcares.com/
[Accessed: 8th December 2020].
British Standards Institution. BS 6744:2016. Stainless steel bars. Reinforcement of concrete.
Requirements and test methods. London: BSI; 2016.
British Standards Institution. BS 8666:2020. Scheduling, dimensioning, bending and cutting of steel
reinforcement for concrete. Specification. London: BSI; 2020.
Bamforth PB, Price WF. Concreting deep lifts and large volume pours (R135). London: CIRIA; 1995.
Bamforth PB. Control of cracking caused by restrained deformation in concrete (C766). London: CIRIA; 2018.
British Standards Institution. BS EN 1998-1:2004+A1:2013. Eurocode 8. Design of structures for earthquake
resistance. General rules, seismic actions and rules for buildings. London: BSI; 2005.
The Concrete Society. TR34: Concrete industrial ground floors. A guide to design and construction. 4th ed.
Camberley: The Concrete Society; 2018.
Johnson RA. Water-resisting basements — a guide. Safeguarding new and existing basements against water
and dampness (R139). London: CIRIA; 1995.
British Standards Institution. BS 6349-1-1:2013. Maritime works – General. Code of practice for planning and
designs for operations. London: BSI; 2013.
British Standards Institution. BS EN 1992-4:2018. Eurocode 2. Design of concrete structures.
Design of fastenings for use in concrete. London: BSI; 2018.
Health and Safety Executive. Managing health and safety in construction: Construction
(Design and Management) Regulations 2015. London: HSE; 2015.
British Standards Institution. BS 6100-9:2007. Building and civil engineering. Vocabulary.
Work with concrete and plaster. London: BSI; 2007.
British Standards Institution. BS 7973-1:2001. Spacers and chairs for steel reinforcement and their specification.
Product performance requirements. London: BSI; 2001.
British Standards Institution. BS 7973-2:2001. Spacers and chairs for steel reinforcement and their specification.
Fixing and application of spacers and chairs and tying of reinforcement. London: BSI; 2001.
British Standards Institution. BS 4449:2005+A3:2016. Steel for the reinforcement of concrete.
Weldable reinforcing steel. Bar, coil and decoiled product. Specification. London: BSI; 2005.
British Standards Institution. BS EN 10080:2005. Steel for the reinforcement of concrete.
Weldable reinforcing steel. General. London: BSI; 2005.
British Standards Institution. BS 4483:2005. Steel fabric for the reinforcement of concrete. Specification.
London: BSI; 2005.
British Standards Institution. BS 4482:2005. Steel wire for the reinforcement of concrete products. Specification.
London: BSI; 2005.
British Standards Institution. BS EN 13877-3:2004. Concrete pavements. Specifications for dowels to be used in
concrete pavements. London: BSI; 2005.
British Standards Institution. BS EN 10088-1:2014. Stainless steels. List of stainless steels. London: BSI; 2014.
British Standards Institution. BS EN 1990:2002+A1:2005. Eurocode. Basis of structural design.
London: BSI; 2005.
The Institution of Structural Engineers. Manual for the design of concrete building structures to Eurocode 2.
London: IStructE Ltd; 2006.
Brooker O et al. How to design concrete structures to Eurocode 2. 2nd ed. Camberley: The Concrete Centre;
2018.
The Institution of Structural Engineers
Standard method of detailing structural concrete (4th edition)
| 217
28 British Standards Institution. BS EN 13670:2009. Execution of concrete structures. London: BSI; 2010.
29 British Standards Institution. BS 8500-1:2015+A2:2019. Concrete. Complementary British Standard to
BS EN 206. Method of specifying and guidance for the specifier. London: BSI; 2015.
30 British Standards Institution. BS 8548:2017. Guidance for arc welding of reinforcing steel. London: BSI; 2017.
31 British Standards Institution. NA+A2:14 to BS EN 1992-1-1:2004+A1:2014. UK National Annex to Eurocode 2.
Design of concrete structures. General rules and rules for buildings. London: BSI; 2005.
32 Whittle R. Are modern pad footings and pile caps too shallow? Concrete. 2011;45(4): 53–55.
33 Whittle R and Taylor H. Design of hybrid concrete buildings. Camberley: The Concrete Centre; 2009.
34 British Standards Institution. PD 6687-1:2020. Background paper to the National Annexes to BS EN 1992-1,
BS EN 1992-3 and BS EN 1992-4. London: BSI; 2020.
35 The Concrete Society. TR43 Post-tensioned concrete floors — design handbook. 2nd ed.
Camberley: The Concrete Society; 2005.
36 British Standards Institution. BS EN 1168:2005+A3:2011. Precast concrete products. Hollow core slabs.
London: BSI; 2005.
37 British Standards Institution. BS 5896:2012. High tensile steel wire and strand for the prestressing of concrete.
Specification. London: BSI; 2012.
38 CARES – UK Certification for Reinforcing Steels. CARES Product Certification. Appendix PT3: Quality and
operations schedule for the production and supply of prestressing anchorages for post-tensioning systems.
Sevenoaks, Kent: CARES; 2017.
39 British Standards Institution. BS EN 13391:2004. Mechanical tests for post-tensioning systems.
London: BSI; 2004.
40 European Organisation for Technical Approvals. ETAG 013. Guideline for European Technical Approval of
post-tensioning kits for prestressing of structures. Brussels: EOTA; 2002.
41 European Organisation for Technical Approvals. EAD 160004-00-0301. Post-tensioning kits for prestressing of
structures. Brussels: EOTA; 2016.
42 The Concrete Society. TR72: Durable post-tensioned concrete structures. 2nd ed.
Camberley: The Concrete Society; 2010.
43 British Standards Institution. BS EN 523:2003. Steel strip sheaths for prestressing tendons.
Terminology, requirements, quality control. London: BSI; 2003.
44 Clark JL. Guide to the design of anchor blocks for post-tensioned prestressed concrete members.
London: CIRIA; 1976.
45 The Institution of Structural Engineers. Design recommendations for multi-storey and underground car parks.
4th ed. London: IStructE Ltd; 2011.
46 Whapples C, McKibbins L. Recommendations for the inspection, maintenance and management of car park
structures. 2nd ed. London: ICE Publishing; 2018.
47 Paterson WS, Ravenhill KR. Reinforcement connector and anchorage methods (R92D). London: CIRIA; 1981.
Appendix K: Bar areas/weights
Table K1: Bar areas number
Sectional area (mm2)
Number
Size (mm)
6
8
10
12
16
20
25
32
40
50
1
28
50
79
113
201
314
491
804
1257
1963
2
57
101
157
226
402
628
982
1608
2513
3927
3
85
151
236
339
603
942
1473
2413
3770
5890
4
113
201
314
452
804
1257
1963
3217
5027
7854
5
141
251
393
565
1005
1571
2454
4021
6283
9817
6
170
302
471
679
1206
1885
2945
4825
7540
11781
7
198
352
550
792
1407
2199
3436
5630
8796
13744
8
226
402
628
905
1608
2513
3927
6434
10053
15708
9
254
452
707
1018
1810
2827
4418
7238
11310
17671
10
283
503
785
1131
2011
3142
4909
8042
12566
19635
11
311
553
864
1244
2212
3456
5400
8847
13823
21598
12
339
603
942
1357
2413
3770
5890
9651
15080
23562
Perimeter (mm)
18.85
25.13
31.42
37.70
50.27
62.83
78.54
100.53
125.66
157.08
Weight (kg/m)
0.222
0.395
0.616
0.888
1.579
2.466
3.854
6.313
9.864
15.413
Table K2: Bar areas pitch
Sectional area (mm2)
Pitch (mm)
50
Size (mm)
6
8
10
12
16
20
25
32
40
50
565
1005
1571
2262
4021
–
–
–
–
–
75
377
670
1047
1508
2681
4189
6545
–
–
–
100
283
503
785
1131
2011
3142
4909
8042
–
–
125
226
402
628
905
1608
2513
3927
6434
10053
–
150
188
335
524
754
1340
2094
3272
5362
8378
13090
175
162
287
449
646
1149
1795
2805
4596
7181
11220
200
141
251
393
565
1005
1571
2454
4021
6283
9817
250
113
201
314
452
804
1257
1963
3217
5027
7854
300
94
168
262
377
670
1047
1636
2681
4189
6545
Table K3: Bar weights pitch
Weight (kg/m2)
Pitch (mm)
Size (mm)
6
8
10
12
16
20
25
32
40
50
50
4.44
7.89
12.33
17.76
31.57
49.32
–
–
–
–
75
2.96
5.26
8.22
11.84
21.04
32.88
51.38
84.18
–
–
100
2.22
3.95
6.17
8.88
15.78
24.66
38.53
63.13
–
–
125
1.78
3.16
4.93
7.10
12.63
19.73
30.83
50.51
78.92
–
150
1.48
2.63
4.11
5.92
10.52
16.44
25.69
42.09
65.76
102.76
175
1.27
2.25
3.52
5.07
9.02
14.09
22.02
36.08
56.37
88.08
200
1.11
1.97
3.08
4.44
7.89
12.33
19.27
31.57
49.32
77.07
250
0.89
1.58
2.47
3.55
6.31
9.86
15.41
25.25
39.46
61.65
300
0.74
1.32
2.06
2.96
5.26
8.22
12.84
21.04
32.88
51.38
Standard method of detailing
structural concrete
This fourth edition of the industry standard Manual develops
on previous editions to address detailing uncertainties in
Eurocode 2 — providing practical guidance on the application
of the code to typical building structures.
It has been comprehensively updated to include:
•
•
•
•
new Model Details consistent with current industry practice
new detailing aids
a revised chapter on pre-stressing
reworked text that provides more emphasis on the
requirements for detailing, rather than design
• a fully refreshed reference list
Shape Codes have been also updated to meet the
requirements of BS 8666:2020.
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