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Reinforcement Detailing Manual - Foreword
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Arup 13 Fitzroy Street London W1T 4BQ
Tel +44 (0) 20 7636 1531 Fax +44 (0) 20 7755 4020
www.arup.com
FOREWORD
This manual was originally prepared by Robin Whittle, Arup Research and Development, in 1978 under the guidance of a client committee including Vic Kemp (Chairman), Cecil Balmond, Les Dobinson, Mike Glover, John Hopkins and Tony Stevens. The graphic artwork was carried out by Ray Ingles.
A major revision was made in 1990 to include updates from CP110 to BS8110 under the guidance of a revision panel including Les Dobinson, Paul Duizand, Tim George, David Osborne and Tony Stevens.
The 1997 revision was carried out by Zoe Rushby and Matt Jackson under the direction of Robin Whittle, and included: o The addition of detailing information for post-tension prestressing o Pre-Eurocode information explaining differences of approach to that in the UK o The BS8110-1: 1997 revisions
The 2000 revision includes changes due to the transition from BS4499 to BS8666, the work being carried out by Richard Lawson under the direction of Robin Whittle.
This 2006 revision incorporates: o The revision of BS8666: 2000 to BS8666: 2005 o The replacement of BS5328-1 by BS8500-1: 2002, the complimentary standard to BS EN206-1. o The amendments to BS8110-1: 1997 to align the standard to the above changes o Pre-Eurocode information removed in anticipation of separate guidance to the finalised EC2.
The latest revision of this manual was prepared by Richard Robertshaw under the direction of Tony Jones.
Reinforcement Detailing Manual - Foreword
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Technical comments are always welcome; please send them direct to Tony Jones, Arup R+D.
Reinforcement Detailing Manual - Introduction
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IN THE ABSENCE OF AN INSTRUCTION FROM THE ENGINEER FOR A
PARTICULAR DETAIL OR FOR NOMINAL REINFORCEMENT, THE STANDARDS
DESCRIBED BY THIS MANUAL WILL BE APPLIED.
Reinforcement Detailing Manual - Exclusions
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EXCLUSION NOTE
This Manual does not give appropriate reinforcement details for:
Heavy civil engineering structures: For example bridges, dockyards, jetties.
Earthquake conditions: See OAP Structural Guidance Note 4.9, Seismic design of buildings in areas of low and moderate seismicity,
Water retaining structures: See CIRIA Report 139, Water-resisting basements.
Precast concrete: See Concrete Society, Guide to precast concrete cladding, Technical Report No. 14, 1977.
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GENERAL
CONTENTS
1.1 Assumptions and Limitations
1.1.1 Assumptions 1.1.2 Limitations
1.2 Detailing Instructions
1.3 Preferred Detailing Methods
1.3.1 Preformed Cages 1.3.2 Flexible Detailing 1.3.3 Straight Bars 1.3.4 Chairs
1.4 Reinforcement
1.4.1 Supply 1.4.2 Sizes 1.4.3 Length 1.4.4 Type 1.4.5 Bond Classification for Deformed Bars 1.4.6 Ductility 1.4.7 Prestressed Concrete
1.5 Bar Referencing
1.6 Anchorage
1.7 Bar Bending
1.7.1 Schedules 1.7.2 Bar Tags 1.7.3 Bar Shapes 1.7.4 Mesh 1.7.5 Tolerances 1.7.6 Effective Anchorage Length of a Hook or Bend
1.8 Large Radius Bends
1.9 Bundled Bars
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1.10 Rebending of Bars
1.11 Mechanical Splicing
1.11.1 Couplers with Parallel Threads 1.11.2 Couplers with Taper-cut Threads 1.11.3 Couplers with Integral Threads over Full Length Bar 1.11.4 Metal Sleeves Swaged onto Bars 1.11.5 Threaded Couplers Swaged onto the ends of Reinforcing Bars 1.11.6 Wedge Locking Sleeves 1.11.7 Couplers with Shear Bolts
1.12 Welding of Reinforcement
1.13 Lightweight Aggregate Structural Concrete
1.13.1 Cover 1.13.2 Anchorage and Lap Length 1.13.3 Bearing Stress Inside Bends
1.14 High Strength Concrete
1.14.1 Beams and Slabs 1.14.2 Columns 1.14.3 Walls 1.14.4 Bond and Anchorage Length
1.15 Changes to Reinforcement since 1948
TABLES
1a Bar Shapes (BS 8666: 2005)
1b Bar Shapes (BS 8666: 2000)
1c Bar Shapes (BS 4466: 1989) 2 Bar Areas : Number
3 Bar Areas : Pitch
4 Bar Weights 5 Fabric Types
6 Anchorage and Lap Lengths: High Yield Deformed Bars
7 Effective Anchorage Length 8 Large Radius Bends : fcu = 25N/mm^2
9 Large Radius Bends : fcu = 30N/mm^2
10 Large Radius Bends : fcu = 35N/mm^2
11 Large Radius Bends : fcu = 40N/mm^2
12 Large Radius Bends : fcu = 45N/mm^2
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1.2 DETAILING INSTRUCTIONS
The established means of producing detailing instructions is by submitting to the Detailing Group extracts from the relevant design sections of the production calculations. However, for any particular type or size of project, the calculations, and consequently the detailing instructions, produced by different engineers vary considerably both in format and content.
These variations affect the efficiency of the firm, particularly in that: a) The variations make the checking of calculations and instructions by engineers within the firm time-consuming and laborious. In addition the communication of design information to external checking authorities can be unnecessarily confused and protracted. b) It takes longer for the Detailing Group to absorb the reinforcement information given and increases the possible need for clarification. It can also lead to a degree of abortive work and misunderstanding between engineers and detailers.
It is important to improve the efficiency of this part of our work. However, it is not suggested that a rigorous format for calculations be adopted throughout the firm. It is preferred that the engineer should recognise and tailor the guidelines given in this Manual to suit the different situations that arise. As far as the general presentation of calculations forming an instruction to the Detailing Group is concerned the following points should be considered when planning production calculations: a) Instructions should be indexed. An edited calculation index is normally sufficient. b) Basic design information relating to concrete and reinforcement grades, fire resistance, durability and associated concrete covers should be given by a calculation sheet preceding the detailing instructions. c) Detailing instructions should comprise only the calculation sheets describing the geometric and reinforcement requirements of a particular structural element. There is no need to give sheets relating to general analysis of the structure, e.g. stability analysis, computer listings. d) Detailing information should be given in the right hand margin of the calculation sheet. Notwithstanding this, 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. e) The use of marked-up outline drawings as a summary is acceptable where justification calculations sufficient to constitute a permanent design record have been prepared and are submitted to the Detailing Group as instructions. f) Sketch details, reinforcement runs and curtailments should only be given if the required detail is not covered by the standards given in this Manual. Where reinforcement is congested or there are particularly complex connections e.g. deep beams to thin cross-section walls or columns, details should be sketched at full-size to confirm buildability. g) Each particular structural element requires specific design and geometric information. This information is given in outline in the 'Detailing Information' sub- section of each section of the Manual. h) Ensure that the Detailing Group is always provided with the latest revision of relevant G.As and sections to avoid abortive work and the possible issue of incorrect details.
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IN THE ABSENCE OF AN INSTRUCTION FROM THE ENGINEER FOR A
PARTICULAR DETAIL, OR FOR NOMINAL REINFORCEMENT, THE
DETAILER WILL ASSUME THAT THE STANDARDS DESCRIBED BY THIS
MANUAL ARE TO BE APPLIED.
Where the Model Details given in this Manual are not applicable to the geometric configuration, the detailer will provide suitable alternatives based on similar principles.
It should be recognised that on occasion the Detailing Group will use external detailers to produce detailing instructions. In such cases, while the Detailing Group may act as an interface, the need for clarity and completeness in the information submitted is even more important.
There is a further option, although not one which is expected to be widely used in the short- term, which is the Contractor detailing route, as envisaged in the National Concrete Frame Specification. In the past the contractor has undertaken this duty more often in the production of precast concrete works than for in-situ works.
Where contractor-detailing is adopted for a project (and there is a separate Guidance Note which deals with the particular procedures which should be adopted) the following additional issues, which may be of general relevance, should be addressed in particular:
i) the standard of detailing instructions will depend upon the structure involved. These may range from hand-drawn sketches with BM/SF diagrams to CAD drawings. In all cases the information must be clear, accurate and unambiguous, allowing interpretation by both the detailer and other members of the discipline team. It should be checked in accordance with the group QA instructions.
ii) standard details should be issued whereby certain design requirements may be imposed on the detailer. It is important that special details are identified at an early stage e.g. beam/column junctions in unbraced frames. The use of large scale (e.g. full-size) detail sketches will remain essential.
iii) the default option for detailing will be as provided in this Manual unless agreed otherwise.
iv) agree any methods preferred by the contractor before detailing information is issued
v) agree in advance whether non-typical bends etc are to be shown on the drawings or only included on the schedules - this will depend on whether the latter are to be reviewed
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This arrangement of steel has two major advantages. First, the links, bottom span bars and link hanger bars can be completely prefabricated. Second, 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.
1.3.2 Flexible Detailing
The term 'Flexible Detailing' is used to mean the method of detailing end bars 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 of this is the detail of separate bottom splice bars at the supports of continuous beams which lap on to the main span bars.
1.3.3 Straight Bars
Straight bars are easier to detail, supply and fix than bars with bends. They should be used wherever possible. Bars 12mm dia. and over should be scheduled to a maximum of 12 metres. Bars less than 10mm dia. should be scheduled to a maximum of 6 metres.
1.3.4 Chairs
In general this Manual does not include the detailing of top steel support chairs since this is assumed to be the contractor's responsibility. An exception to this concerns multi-column foundations and rafts (see 2.2.12 below).
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1.4 REINFORCEMENT
1.4.1 Supply
British reinforcement is supplied in accordance with BS 4449: 2005, Steel for the reinforcement of concrete – Weldable reinforcing steel – Bar, coil and decoiled product - Specification, which replaced BS 4449: 1997 in January 2006. Two main types of deformed bar exist:
Hot - rolled ribbed bar. This is generally a high tensile bar. When conforming to the British standard for high tensile reinforcement it should have a distinctive mark rolled into the surface.
Cold - worked ribbed bar. This bar is superficially similar to the previous bar. It is also a high tensile steel but has been cold - worked (by twisting) to achieve these properties.
The CARES mill identity is as shown below and should appear on all deformed bars supplied by mills holding a CARES Certificate of Approval.
1.4.2 Sizes
The standard metric sizes of bar are 6, 8, 10, 12, 16, 20, 25, 32, 40 and 50mm. 6 & 50mm bars usually take longer to obtain, since they are not preferred sizes.
1.4.3 Length
The length of bars normally supplied from stock is 12 metres for bars 12mm dia. and over. Longer bars may be specially ordered. However, this will generally extend the delivery time, increase the cost and lead to transport / handling problems. Bars less than 12mm dia. are normally supplied from coils.
Dot-dash-dot: the CARES approval mark.
Five ribs between dots means bar was produced in U.K.
One rib between dots
Three ribs between dots Means mill number 13
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Table 1.
Grade Yield strength, Re (N/mm^2 )
Tensile/yield strength ratio, R (^) m/Re
Total elongation at maximum force, Agt %
B500A B500B B500C
Total elongation at maximum force shall be measured and recorded and available for inspection, but shall not be a cause for non-conformance.
1.4.7 Prestressed Concrete
Prestressing tendons should comply with BS 5896. Anchorages should comply with ETAG 013: 2002, Post-tensioning kits for prestressing of structures.
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1.5 BAR REFERENCING
Example : 20H3201.
Number of bars 20 Type of steel H Diameter of bars 32 Mark No. 01 Pitch of bars (where applicable) 300mm
Other abbreviations that may be added to the end of this string include:
B bars in bottom of slab B1 bottom layer of bottom reinforcement where more than one (previously BB) B2 next to bottom layer of bottom reinforcement where more than one (previously B) B3, B4 etc. layer of bottom reinforcement inside previous one T bars in top slab T1 top layer of top reinforcement where more than one (previously TT) T2 next to top layer of top reinforcement where more than one (previously T) T3, T4 etc. layer of top reinforcement inside previous one EF bars in each face NF bars in near face of wall FF bars in far face of wall AP bars alternately placed AR bars alternately reversed AS bars alternately staggered UB 'U' bars LB 'L' bars LLT long leg top LLB long leg bottom
Example : 20H3201.300 B
Where special end preparation is required for bars (e.g. for couplers) the bar mark should commence with 'E' (see BS8666: 2005, Cl. 5.1).
Example : 20H32E02.300 B
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1.7 BAR BENDING
1.7.1 Schedules
The specification for bending dimensions and scheduling of bars is given in BS 8666. The layout of the Arup standard Bending Schedule sheet is as follows (not to scale):
Ove Arup & Partners Bending Schedule
Job No. Drawing No. (^) Sheet No. Rev.
Revision A^ B^ C Originator /Date: C hd. by/Date: Location REV
Bar mark
Type and
Number of groups
Numberin each Length Totalnumber of each bar Shapecode AAll bending dimensions are in accordance with BS 4466 B C D E/R
mm mm mm mm mm
49800 R/FH/13/-1/05 3 OF 4
THE ROYAL OPERA HOUSE DEVMT. FLORAL HALL STAGE LEVEL -1 BEAMS
JF 08/ R KB 08/
8-8 60a T 20 2 2 4 2400 38 1100 300 (1100) 60b T 20 2 2 4 2300 38 1045 300 (1045) 60c T20 2 2 4 2175 38 985 300 (985)
1.7.2 Bar Tags
A typical bar tag is shown below. These are tied to each bundle, and give to the number of the schedule to which they correspond:
BAR TAG
JOB : 51968 SCHED : FH / 13 / -1 / 05 BARMARK : 60C DIAM : T20 TOT BAR : 4
LENGTH : 2175 SHAPE : 38 BENT
DIAMS : A B C 985 300 0 DIMS : D E R 0 0 0
1.7.3 Bar Shapes
Standard shapes as defined in BS 8666: 2005, are given in Table 1a. The shapes from the superseded BS 8666: 2000 and the older BS 4466: 1989 are given in Tables 1b and 1c respectively.
1.7.4 Mesh
Preferred types of steel fabric are defined in BS 4483: 2005 and are available in sheets of the standard size 4.8 x 2.4m, giving a sheet area of 11.52m^2.
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1.7.5 Tolerances (BS 8110, Cl. 7.3)
Normally bending dimensions of reinforcement are given without adding or subtracting tolerances. However, 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 job. Large scale sketches may help to show up any problems.
Tolerances which should be taken into account include placing framework, placing reinforcement and bending reinforcement, particularly where reinforcement is congested.
A number of definitions and terms should be understood:
Bar size This is the diameter of a circle of equivalent area as the bar. For deformed bars the actual diameter is about 10% larger than the given size.
Nominal cover (BS 8110, Cl. 3.3.1; BS 8500, Cl. 3.1.8) This is the value used in design and normally specified on drawings. Nominal cover is defined in BS 8500 as a minimum cover plus a tolerance, Δc, to accommodate fixing precision; these nominal covers are specified in BS 8500, Tables A.10 to A.14, for different exposure classes. Table A.6 defines the characteristics of the Exposure classes. Nominal cover should be specified to all steel reinforcement including links (BS 8110 Cl.7.3). The effect of variations for this on the effective depth assumed in the calculation should be carefully considered. Throughout this Manual a fixing tolerance, Δc, of 10mm has been assumed; this may be reduced to 5mm if the fabrication is subjected to a rigorous quality assurance system. See BS 8110 Cl. 3.3.1.1. Other values may apply for bridge structures.
Actual cover (BS 8110, Cl. 7.3) This is what it says and, for a given value of nominal cover, could be within a range depending on the tolerance values.
The actual cover to reinforcement compared with the nominal cover specified depends on the size of the bar is as given in Table 1.
Table 1. Bar diameter / mm Actual cover / mm φ ≤ 12 nominal cover ± 5 12 < φ ≤ 25 nominal cover +10 to - φ > 25 nominal cover +15 to -
1.7.5.1 Cutting and Bending Tolerances (BS 8666)
Where an overall or an internal dimension of a bent bar is specified the tolerance, unless otherwise stated, is as given in Table 1.3.
