concrete detailing handbook

The Inst i tut ion of Structural Engineers

The Concrete Society

AUGUST 1989

Standard method of

detailing structural concrete

Published by the Institution of Structural Engineers

11 UPPER BELGRAVE STREET, LONDON SW1X 8BH

Constitution of Joint Committee

Rex Lancaster, BSc(Eng), CEng, FIStructE, FICE, FCIArb, FACI ChairmanPeter Campbel l , JP, DIC, CEng, FIStructE, FICE, FIMarE, ACIArb*E. C. Chaplin, BSc(Eng), CEng, FICE, FIHTColin Davies, BSc(Eng), MSc(Eng), CEng, FIStructE, FICED. K. Doran, BSc(Eng), DIC, CEng, FIStructE, FICE J. B. HigginsM. R. Hollington, BSc(Eng), PhD, DIC, CEng, MIStructE, MICEB. R. Rogers, MA, CEng, MICE§R. A. TerryJ. R. Walmsley, CEng, FIStructE, MICERobin Whittle, MA, CEng, MICEJ. Willbourne, BSc(Eng), MSc(Eng), CEng, MIStructER. W. J. Milne, Secretary to the Joint Committee

*Chairman of a joint committee of the Concrete Society and the Institution of Structural Engineersresponsible for preparing the section on prestressed concrete. Other members of that committee were:

A. E. Andrew, CEng, FIStructEW. Thorpe, CEng, FIStructEJ. R. Walmsley, CEng, FIStructE, MICEK. R. Wilson, MA, CEng, MICE

Died December 1985§Died 1988

© 1989 The Institution of Structural Engineers

T h e I n s t i t u t i o n o f S t r u c t u r a l E n g i n e e r s , a s a b o d y i s n o t r e s p o n s i b l e f o r t h e

s ta tements made or the opin ions expressed in the fo l lowing pages .This publ ica t ion i s copyr igh t under the Berne Convent ion and the In te rna t iona lCopyr ight Convent ion . Al l r igh ts reserved . Apar t f rom any copying under the UK

Copyright Act 1956, part 1, section 7, whereby a single copy of an article may besupplied, under certain conditions, for the purposes of research or private study by al ib ra ry o r a c lass p resc r ibed by the UK Board of Trade Regula t ions (S ta tu tory

Instruments, 1957 no. 868), no part of this publication may be reproduced, stored in aretrieval system or transmitted in any form or by any means without prior permissionof the Ins t i tu t ion of S t ruc tura l Engineers . Permiss ion i s no t , however , requi red to

copy ext rac ts on condi t ion tha t a fu l l re ference to the source i s shown. Mul t ip lec o p y i n g o f t h e c o n t e n t s o f t h e p u b l i c a t i o n w i t h o u t p e r m i s s i o n c o n t r a v e n e s t h ea f o r e m e n t i o n e d A c t .

2 IStructE Detailing Manual

Contents

Foreword

1 Introduction and scope

2 Drawings2.1 General2.22.3

Types of drawingPhotocopying and reduction

2.4 Abbreviations2.5 Drawing standards2.6 Dimensions of drawing sheets2.7 Borders2.8 Title and information panels2.9 Key2.10 Orientation2.11 Thickness of lines2.12 Lettering2.13 Spelling2.14 Dimensions2.15 Levels2.16 Scales2.17 Plans2.18 Elevations2.19 Sections2.20 Grid lines and recommended

reference system2.21 Procedure for checking drawing and

bending schedules

3 Data for detailers3.1 Bar reinforcement3.23.3

Sizes and reinforcing barsOverall dimensions of reinforcing bars

3.4 Shop practice3.5 Properties of reinforcingbars3.6 Rebending bars3.7 Fabric reinforcement3.8 Large radius bends3.9 Cover3.10 Anchorage lap lengths and shear

reinforcement3.11 Full-strength joints in reinforcing barsAppendix 3A Large-radius bendsAppendix 3B Anchorage and lap lengthsAppendix 3C Shear resistance of beams

4 Detailing and scheduling4.1 Detailing techniques4.2 Tabular method of detailing4.3 Preprinted drawings4.4 Overlay drawings4.5 Computer-aided detailing and scheduling4.6 Detailing reinforcement4.7 Spacing of reinforcement4.8 Bundled bars4.9 Points to consider before detailing4.10 Detailing for offsite fabrication4.11 Schedules and scheduling

5

7

888899999

1010101010101011111111

11

11

13131313131313131314

1818232633

353535353535353939394345

5 Structural elements5.1 Layouts5.2 Slabs5.3 Columns5.4 Beams5.5 Foundations5.6 Walls5.7 Stairs

6 Specific details6.1 Concrete inserts6.1 Corbels, half-joints and nibs

7 Prestressed concrete7.1 Introduction7.2 Drawings7.3 Components

7.57.4 Reinforcement detailing

Other effects of prestressing7.6 Typical details

8 Precast concrete

9 Water-retaining structures9.1 General9.2 Cover9.3 Spacing of reinforcement9.4 Bar anchorage lengths

10 References

Notes: 1. Words underlined are suitable for a tab index.2. Yellow pages denote data sheets and model details.

51525671778995

103

107107110

113113113113118121122

129

133133133133133

137

IStructE Detailing Manual 3

Foreword

The metric version of the previous Standard method of detailing reinforced concrete was

published in 1970 and this was followed in 1973 by the Concrete Society’s publication on

Standard reinforced concrete details. This version incorporates the two earlier

publications, and as it now incorporates a section on prestressed concrete, the title has

been amended to the Standard method of detailing structural concrete. As with the

original Standard method, the Committee is a joint one between the Institution of

Structural Engineers and the Concrete Society.

I t is hoped that this document wil l become the s tandard reference work instructural

design offices in conjunction with the Manual for the design of reinforced concrete

building structures (1985) prepared jointly by the IStructE and the ICE.

The Joint Committee has relied entirely on BS 8110 for detailing principles and has

not taken any decis ions on matters of design. However , the dis t inct ion between the

detailer’s field and that of the designers’ is not always clear, and some criticisms have

been made that we have strayed too much into the design field. In practice, many

decisions that are taken by the detailer are strictly in the province of the designer, and

the detailer often makes up his own reference tables because they are not available

elsewhere. We have at tempted to provide such guidance in our document , and in so

doing, we do not believe we have encroached on the design area.

We have also had criticisms from some designers on the length of the document. We

have taken the views of detailers on this, in particular the comments from detailers

at tending t ra ining courses a t the Cement & Concrete Associat ion. As they have found

the whole document useful and are quite happy to abstract key pages (principally the

yel low pages) for everyday reference, we have been persuaded to retain almost the

whole of the draft that was made available for comment. We are grateful for the many

helpful comments we have received, all of which have been considered, and most of

t h e m a c c e p t e d .

The original Standard method has been widely distributed and accepted both in the

UK and abroad. When I have checked in design offices they invariably confirm that

they are using the principles set out in the documents. Unfortunately, also invariably,

they then qualify their statement by saying ‘Well 90% of it anyway’. On investigation it

always transpires that the 10% not being used is a different 10% in every office! This is

not standardization. We hope this time to achieve 100% in every office!

The Joint Committee were saddened by the sudden deaths of Jim Higgins in

December 1985 and Dick Terry in 1988 and would wish me to pay tribute to their great

contribution to our work. Jim Higgins was particularly associated with Section 5 while

Dick Terry was responsible for much of the artwork in other Sections.

R. I . Lancaster , Chairman


Previous Pageis blank

1 Introduction and scope

The object ive of this manual is to provide a workingdocument on structural concrete that can be used by thedetai ler in the design off ice to interpret the designer’sinstruct ions in the form of drawings and schedules forcommunication to the site. For prestressed concrete, thesection is addressed more to the designer–detailer, since ageneral knowledge of prestressing terms and practice isnecessary in this field. Large design offices may choose toincorporate the principles and the detai ls in their ownmanuals. It is intended that the manual will be the standardreference work used on t raining courses and by designengineers. During the early stages of the development ofthis document Ove Arup & Partners made their detailingmanual available to the Joint Committee, and this was avery useful base document.

A basic assumption in the preparation of this manual hasbeen that it is the responsibility of the engineer to specifyclear design requirements to the detai ler and i t is theresponsibility of the detailer to impl e m e n t t h e s e r e q u i r e -ments in a consistent way that will be clear, complete andunambiguous to all users. In detailing structural concrete,t he i n t e r e s t s o f a l l pa r t i e s shou ld be bo rne i n m ind ;practices in the drawing office that lead to problems orextra costs on site cannot be termed good detailing.

It has not been the intention of the Joint Committee todecrease in any way the responsibi l i ty of the engineer ,although it is recognized that certain details have designimplications; therefore engineers should design with fullknowledge of this manual. The words ‘standard method’need clarification. It is not intended that any one detailshould be copied slavishly for al l s i tuations, but i t isintended that all the principles should be followed, both ingeneral and in detail. Details can be prepared with differentobjectives in mind, e.g. to reduce labour on site by detailingto allow off-site prefabrication of the reinforcement intocages, or to utilize the materials most readily available on a

particular site. It is believed that such different objectivescan be achieved (but not necessarily all at the same time)within the principles covered in this manual.

W h e r e a n o t h e r a u t h o r i t a t i v e d o c u m e n t e x i s t s , t h i smanual refers to it rather than repeating it in full; it alsoexcludes the sort of expertise associated with proprietarymethods or materials. In general, the conventional use ofmaterials covered by British Standards is assumed; whereno standard or consensus of opinion exists no recommenda-tion has been made.

The principles covered by BS 4466 and BS 1192 havebeen adopted. BS 4466 def ines a s tandard method ofs c h e d u l i n g a n d a s e t o f b a r s h a p e s t h a t , i n s u i t a b l ecombination, are sufficient for any detailing situation; it isconsidered to be an essential companion document to themanual. The principles set out in this manual cover allforms of reinforced concrete construction; where relevantBS 8110, BS 8007 and BS 5400 have been used as a basis.

It is generally accepted that any division between civiland structural engineering is somewhat arbitrary, and ittherefore follows that what is good practice in structuralengineering will also be so in civil engineering. There are,however, a number of factors that occur in civil engineeringand large-scale work of which account should be takenwhen detailing reinforcement. These include:

• the provision of access for men to place concrete inmassive concrete sections such as raft foundations

• adjustments of reinforcement to take account of largepours of concrete. Attention is drawn to CIRA report 49,Large concrete pours — a survey of current practice (J. C.Birt)

• suitable reinforcement arrangements to suit long-stripmethods of laying ground slabs

• recognition of the likely positioning of construction jointsand their effect on reinforcement arrangements.

7IStructE Detailing Manual


2 Drawings

2.1 GeneralDrawings are prepared so that the structural designer cancommunicate his requirements through the detailer to thecontractor in a clear, concise and unambiguous manner. Itis important to ensure that drawings are not unnecessarilycongested or complicated.

Drawings used on construction sites will get dirty, wetand dog-eared. The clarity of the original drawing that willbe reproduced is, therefore, most important, and this willusually be enhanced by the use of ink in the preparation ofthe original drawings.

It is recommended that A1 size drawings are generallyused, larger sized drawings being used only when unavoid-able. For each project, the chosen drawing size should beused consistently. The written descriptions on drawingsshould be as brief as possible, consistent with complete-ness, and the lettering should be clear. Any instructions ondrawings should be positive; they should be written in theimperative.

Each drawing should give all the information (togetherwith reference to associated drawings) necessary for theconstruction of the portion of the work shown, omittingother irrelevant detail. Details of materials to be used willnormally be given in a separate specification, and referenceto the concrete or other types of material on drawings willbe in an abbreviated form.

Reference to any special items concerned with construc-tion details should be made on the general arrangementdrawings and not in a separate letter or document. Specialrequirements of the designer , e .g . detai ls of cambers ,chamfers, sequence of construction, position and type ofjoints, etc., should all be described on the general arrange-ment drawings.

2.2 Types of drawingThere are two principal types of drawing necessary for thepreparation of reinforced concrete drawings and details.These are general-arrangement drawings and reinforce-ment drawings.

2.2.1 General-arrangement drawingsGeneral-arrangement drawings for concrete s t ructuresconsist of dimensional data necessary for the setting outand construction of the concrete formwork, e.g.:

• setting out of the concrete structure on site

• plans, sections and elevations where appropriate showinglayout, dimensions and levels of all concrete memberswithin the structure

2.2.2 Reinforcement drawingsReinforcement drawings describe and locate the reinforce-ment in relation to the outline of the concrete work and torelevant holes and fixings.

Generally, circular holes up to 150mm diameter andrectangular holes up to 150 × 150mm in slabs or walls needneed not be indicated on the reinforement drawings. Holesof larger size should be indicated on the reinforcementdrawing and should be t r immed by sui table reinforcingbars.

Separate drawings or plans for top and bottom layers ofr e in fo rcemen t shou ld be u sed on ly fo r f ab r i c and i nexceptional cases, e.g. hollow bridge decks with four layersof reinforcement.

Reinforcement drawings are primarily for the use of thesteel fixers. It is preferable that general arrangement andreinforcement drawings be kept separate, but for simplestructures a combined drawing will suffice.

2.2.3 Standard detailsStanda rd de t a i l s a r e t hose de t a i l s t ha t a r e u sed on arepetitive basis. Details used in this way must be carefullyworked out, fully detailed and totally applicable to eachlocation where they are to be specified.

S t anda rd de t a i l s may app ly to conc re t e p ro f i l e s o rreinforcement arrangements, and they should be drawn toa large scale.

2.2.4 DiagramsDiagrams may be used as a means of communicating designideas during both pre-contract work and the post-contractperiod. Diagrams may be formally presented or sketchedf r eehand p rov id ing they convey in fo rma t ion c l ea r ly ,neatly and in detail.

The information contained in diagrams should prefer-ably be drawn to scale.

2.2.5 Record drawingsWhen the re inforced concrete s t ructure has been con-structed, the original drawings used for the constructionprocess should be amended to indicate any changes indetail that were made during the construction process. Asuffix reference should be added to the drawing number toindicate the drawing is a ‘record drawing’. The amend-ments should be described in writing against the appropri-ate suffix reference. A register of drawings should be keptlisting reference numbers, titles and recipients of drawings.

2.3 Photocopying and reductionThere are a number of considerations that must be made ifphotographically reduced drawings are to be fully intelligi-ble in their reduced form. These include:

• location of all holes, chases, pockets, fixings and itemsaffecting the concrete work • the chosen range of line thickness

• north point • the size and nature of the script used

• notes on specifications, finishes and cross-references of • whether the drawing is produced in ink or pencil

the construction. • the arrangement of the information on the drawings,avoiding congestion

All these matters should be considered at the outset of • the need to ensure that graphic and script information is,every drawing programme. as far as possible, kept separate

Detai led examples of s t ructural layout drawings and • the possibil i ty that solid black areas wil l not , printguidance notes are illustrated at the beginning of Section 5. properly.


Since many drawings will be reduced for archive storageon completion of the construction, all these matters shouldbe considered at the outset of every drawing programme.

2.4 AbbreviationsThe fol lowing s tandard abbreviat ions are recommendedbut, if there is any risk of confusion or ambiguity with theuse of these abbreviations in any particular circumstances,t h e n t h e w o r d s s h o u l d b e w r i t t e n i n f u l l . N o o t h e rabbreviations should be used unless clearly defined on allthe drawings on which they appear.

Particular attention is drawn to the use of lower-case andcapital letters. All abbreviations are the same in the pluralas in the singular.

2.4.1 Generalreinforced concrete R Cblockwork blkbrickwork b rkdrawingfull size

drgF S

not to scale N T Sdiameter dia*centres crssetting-out pointsetting-out line

S O PS O L

centre-linefinished floor level F F Lstructural floor level S F Lexisting level E Lhorizontal h o rvertical ve r* F o r b a r d i a m e t e r u s e ‘ b a r s i z e ’ o n d r a w i n g s w h e r enecessary and φ in formulas.

2.4.2 Relating to reinforcementf a r (face) F1 (outer layer) F2 (second layer)n e a r (face) N1 (outer layer) N 2 (second layer)bo t tom (face) B1 (outer layer) B2 (second layer)t o p (face) T1 (outer layer) T 2 (second layer)

Note: Since the contractor may not be familiar with thisnotation it should be illustrated by a sketch on the relevantdrawings.

Add i t i ona l abb rev i a t i ons may be u sed bu t a r e no trecommended for use without a clear description as theyhave been found to be ambiguous.

2.5 Drawing standardsI t i s the in tent ion that BS 1192 Recommendat ions fordrawing practice should be read in conjunction with thisd o c u m e n t , t h e t w o d o c u m e n t s b e i n g m u t u a l l y c o m -plementary. Par ts 1 and 3 of BS 1192 are par t icular lyrelevant to the reinforced concrete detai ler s ince theydefine the general pr inciples of drawing pract ice andsymbols. In Part 2 of BS 1192 are examples of reinforcedconcrete drawings, which also comply with the Standardmethod.

2.6 Dimensions of drawing sheetsT h e r e c o m m e n d e d d i m e n s i o n s o f d r a w i n g s h e e t s a r egiven below; Fig. 1 shows the relative sizes.

Size of drawing sheets

B S r e f e r e n c e dimensionsmm × mm

A0 841 × 1189A l 594 × 841A2 420 × 594A3 297 × 420A4 210 × 297

Note: Margins and information panels are within these dimen-sions

IStructE Detailing Manual

A 0

A 2

A 1

A 4

A3

Fig. 1

2 .7 BordersAll drawings should have a 20mm fi l ing border on thelef t -hand s ide. Elsewhere the border should be 20mm(minimum) for A0 and Al and 10mm (minimum) for A2,A3 and A4. The border margin l ine should be at least0.5mm thick.

2.8 Title and information panels

0.5mm minimum

20 minimumA0 – A1

20 minimum10 minimum

B A2 – A3 – A4

A 180

Fig. 2

Key information relating to the job and drawings shouldbe placed in the bottom right-hand corner of the drawingsheet (Fig. 2, panel A). Panel A should include at least thefollowing information:

• office project number

• project title

• drawing number with provision for revision suffix

• drawing title

• office of origin

• scales (a drawn scale is necessary when the drawing is tobe microfilmed – see also BS 5536)

• drawn by (name)

• checked by (name)

• date of drawing.

Immediately above panel A a box should be provided tocontain the necessary reference to relevant bar and fabric-schedule page numbers.

Panel B may be developed vertically from panel A toinclude such information as revis ions working up frompanel A and notes (working down from the top of panel B).

Notes on reinforcement drawings should include cross-references to general-arrangement drawings, a l is t ofabbreviations, specified covers and the relevant ‘schedulerefs’.

9

2.9 KeyOn jobs where a portion of the work has to be divided intoseveral drawings, it is useful to have a small diagrammatickey on each drawing, with the portion covered by thatdrawing clearly defined, and adjacent panels identif iedwith a given drawing number.

2.10 Orientation2.10.1 Site plansThe direction of the north point should be clearly shown.

2.10.2 All other drawingsAll other drawings relating to particular buildings or majorsubdivision of a job should have consistent orientation,which should preferably be as close as possible to thesite-plan orientation.

2.11 Thickness of linesThe ob j ec t i ve o f u s ing va ry ing l i ne t h i cknes se s i s t oimprove clarity by differentiation. The scale of drawing andthe need for c lear pr ints to be taken from the or iginalshould be borne in mind The fol lowing suggested l inethicknesses are considered suitable for reinforced concretedrawings:

concrete outlines generally and generalarrangement drawings 0.35mmc o n c r e t e o u t l i n e s o n r e i n f o r c e m e n tdrawings 0.35mmmain reinforcing bar 0 .7mmlinks 0.35mm–0.7mmdimension lines and centre-lines 0.25mm

Cross-sections of reinforcement should be drawn approx-imately to scale.

2.12 LetteringDistinct and uniform letters and figures ensure the produc-tion of good, legible prints; the style should be simple.Capital letters should be used for all titles and sub-titles andshould preferably be mechanically produced. Lower-caseletters may be used in notes.

2.13 SpellingThe spelling of all words should be in accordance with BS2 7 8 7 o r o t h e r w i s e t h e L i t t l e O x f o r d D i c t i o n a r y , e . g .asphalt, kerb, lintel, etc.

2.14 DimensionsThe general-arrangement drawing should show all setting-out dimensions and sizes of members. The reinforcementdrawings should contain only those dimensions that arenecessary for the correct location of the reinforcement. Thepoints to which the dimension lines relate should be asshown in Fig. 3.

1104 1800

Fig. 3

Dimensions should be written in such a way that theym a y b e r e a d w h e n v i e w e d f r o m t h e b o t t o m o r t h er i g h t - h a n d s i d e o f t h e d r a w i n g . T h e y s h o u l d , w h e r epossible, be kept clear of structural detail and placed nearto and above the line, not through the line.

For site layouts and levels, the recommended unit is themetre. For detailing reinforcement and the specificationof small sections, the recommended unit is the millimetre.I t i s n o t n e c e s s a r y t o w r i t e m m . D i m e n s i o n s s h o u l dnormally be to the nearest whole millimetre. Thus:

4.250114.200

6 210m

515

1 725

2.15 Levels

2.15.1 DatumOn civil-engineering and major building works it is usuallynecessary to relate the job datum (a TBM or transferred OSbenchmark) to the Ordnance Survey datum. On otherworks, a suitable fixed point should be taken as job datumsuch that all other levels are positive. This datum should beclearly indicated or described on the drawings, and al llevels and vert ical dimensions should be related to i t .Levels should be expressed in metres.

2.15.2 Levels on planI t is important to differentiate on si te layout drawingsbetween existing levels and intended levels.

Finished floor levels or structural floor levels should beindicated thus:

F F L S F L

12.335 12.000

Existing levels should be indicated thus:

E L

11.445

2.15.3 Levels onThe same method

section and elevationshould be used as for levels on plan,

excep t t ha t t he l eve l shou ld be p ro j ec t ed beyond t hedrawing with a closed arrowhead indicating the appropriateline.

When construct ing a s t ructure i t i s the level of thestructure that is important. If it is necessary to refer to thefinished floor level, this should be a reference in addition tothe structural floor level, as shown in Fig. 4.

4 0 F.F.L. S.F.L.12.000

Fig. 4


2.16 ScalesScales should be expressed as, for example, 1:10 (one toten). The following scales are recommended as a suitablefor concrete work:

general arrangements 1:100wall and slab detail 1:50beam and column elevations 1:50beam and column sections 1:20

Where larger scales are required, the preferred scalesspecified in BS 1192 are: 1:20, 1:10, 1:5, 1:2 or full size.

2.17 PlansPlans should be drawn in such a way as to illustrate them e t h o d o f s u p p o r t b e l o w , w h i c h s h o u l d b e s h o w n a sbroken lines. This is achieved if one assumes a horizontals e c t i o n d r a w n i m m e d i a t e l y a b o v e t h e s u r f a c e o f t h estructural arrangement or component . Dimension l inesshould be kept clear of the structural details and informa-tion.

2.18 ElevationsAn elevation on a portion of a structure will normally betaken as a vertical cut immediately adjacent to the elementunder consideration. Structural members cut by the sectionshould be shown in full lines. Other connecting membersbehind the member being detai led should be shown bybroken lines.

2.19 SectionsWhere sections are taken through structural elements, onlythe material in the cutting plane is shown on a section; ingeneral a cut showing features beyond should not be used.For clarity, the cut member may be shaded. The directionsof sections should be taken looking consistently in the samedirection, looking towards the left for beams and down-wards for columns. A section should be drawn as near aspossible to the detail to which it relates.

2.20 Grid lines and a recommendedreference systemA grid system provides a convenient datum for locating and

referencing members, since columns are usually placed ator near the intersection of grid lines.

1.2.3.

4.5.

6.

3 A 2 3 B 2

2.5 Ba2

2 B 4

2 A 2 2 B 2

1A6

1A4

1A2 1B2

Fig. 5 Framing plan sketch

Grid notation should be agreed with the architect andwould normally be numbered 1, 2, 3, etc. in one direction,and lettered A, B, C , . . . . . . X, Y, Z, AA, AB, etc. (omittingI and O) in the other direction. These seqstar t a t the lower lef t corner of the grid

uences should

plementary grids, if required, can be incorpsystem. Sup-

orated withinthe system and identified as follows: Aa, Ab, AC, Ba, 2.5,4.2, etc.*

Referring to the framing plan sketch Fig. 5:

al l beams within a f loor panel are referenced from thecolumn situated in the lower left corner of that panel, e.g.column reference 2B occurs at the intersection of grids 2and B.each beam reference includes the column reference plus asuffix number, e.g. 2B1, 2B3, etc. for beams spanning upthe panel, and 2B2, 2B4, etc. for beams across the panel.

Similarly for supplementary column 2.5 Ba.This format is similar to the system used successfully for

s tructural s teelwork. Beams should be label led on thegeneral arrangement drawing, particularly off-grid mem-bers. Beams on grid lines may have their labels omitted, inwhich case strings of beams are described as follows:

e.g. beams along grid line 2/A to C

2.21 Procedure for checking drawings andschedulesAll drawings and bar and fabric schedules must be checkedb y a c o m p e t e n t p e r s o n o t h e r t h a n t h e d e t a i l e r . T h echecking of drawings falls into 3 stages:

Stage 1: Des ign checkThat the drawing correct ly interprets the design asdescribed as described in and supported by the checkedcalculations.

Stage 2: Deta i l ing checkThat the drawing has been prepared in accordance withcurrent standards and meets the requirements of thatpar t icular job. That the information agrees with thegeneral arrangement and other associated drawings andbar and fabric schedules, with particular reference todimensions, termination of reinforcement, constructiondetails, notes, etc., and that the details shown can, inpractice, be constructed.

Where drawings are traced they must be checked toensure they have been traced correctly, and where thelayout of the drawing has been rearranged on the tracing,that the traced drawing continues to convey the inten-tions of the originator to the user.

Stage 3: Overal l checkThat the checks under stages 1 and 2 have been carriedout. That the drawing is in all respects suitable for itsp u r p o s e a n d t r u l y r e f l e c t s t h e r e q u i r e m e n t s o f t h eproject .

Each drawing should have a ‘box’ containing the name ofthe draughtsman and checker.

Standard checking lists may be a useful aid but must notbe considered a complete check, since no checklist can betotally comprehensive. Set out below are some items thatcould be used to form the basis for a checklist.

Is general presentation and orientation correct?Are title, scales, drawing numbers correct?Are revision letters correct and location of revisionsshown?Are sufficient sections and details given?Are general notes complete and can they be under-stood?Is spelling correct?

* After completion of the sketch above and then all the other sketches BS 1192 waspublished and it required the use of letters vertically and numbers horizontally.


7.

8.9.

10.11.12.

13.

14.15.

16.17.18.19.20.21.

Have all standards and codes of practice been compliedwith?Are setting out dimensions correct?Check dimensions?Do running dimensions agree with overall dimensions?Can materials specified be obtained?Do number, sizes and reinforcement agree with therelevant calculations and other drawings?Has cross-referencing to other drawings and bar andfabric schedules been provided?Where applicable is ‘no. off’ correct?Are chamfers, fillets and drips and similar featuresshown?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?

22.23.

24.

25.26.27.

Are cranks required where bars cross?Is layering of reinforcement correct both on plan andsection?Is reinforcement required for anti-crack or fire resist-ance?Do hooks foul other reinforcement?Are schedules correct?H a v e d r a w i n g s b e e n s i g n e d b y t h e d e t a i l e r a n dchecker?

Method of checkingI t is useful to adopt a s tandard checking system usingdifferent coloured pencils . A suggested colour systemwould be:

b l u e – c o r r e c tred – addit ions and correct ions.

W h e n t h e a m e n d m e n t s h a v e b e e n c o m p l e t e d t h efinished drawing must be checked against the check print.


3 Data for detailers

3.1 Bar reinforcementT w o m a i n t y p e s o f b a r a r e a v a i l a b l e :

Appearance yield strength BS(grade)N/mm 2

abbreviatedreference

letter

T460 4449(deformed

type 2)(Transverse r ibs with or withoutt w o l o n g i t u d i n a l r i b s )

Plain round

250 4449 R

(P la in round )

0 4 6 0 3 A

Other types are as defined in job specification; the abbreviatedreference letter is X

7Note 1: Square twisted bars and chamfered square twisted bars toBS 4461 (deformed type 1) are obsolete.

Note 2: BS 8110 states:‘Different types of reinforcement, each complying withthe British Standard, may be used in the same structuralmember . ’

3.2 Sizes of reinforcing barsPreferred sizes of high-yield (grade 460) reinforcing barsare 8, 10, 16, 20, 25, 32 and 40mm. Size 6 is not freelyavailable owing to low demand and infrequent rollings.Size 50 is not generally stocked by fabricators but can beavailable to order and is dependent on rolling programmes.Since off-cuts of 50mm are useless, the size tends to beordered cut to length from the mill and requires carefulplanning. Consideration should be given to using the freelyavailable size 40 in bundles where size 50 would otherwisebe used. Grade 250 (mild steel) bars are available in sizes 8,10, 12 and 16mm.

(For weights and cross-sectional areas see Tables 6 to 10at the end of this Section.)

3.3 Overall dimensions of reinforcing barsStandard length of bars available from stock is 12m (12mmand above) or for smaller sizes (8, 10mm) 8, 9 or 10m. Themaximum length of bar available and transportable is 18m,but extra costs and delays may be involved if 12m lengthsare exceeded.

For a bent bar to be transportable the shape should becontained by an imaginary rectangle where the shortestside does not exceed 2.75m.

The word ‘size’ rather than ‘diameter’ is used to describethe nominal s ize of a bar . For example, on a s ize 20deformed bar no cross-dimension measures 20mm becauseof the surface deformations. Most deformed bars can becontained in a circumscribing circle 10% more than the

nominal size of the bar, however, because of variations inrib size individual sections can measure 13% or 14% morethan the nominal size at the largest cross-dimension (seep. 19).

3 . 4 S h o p p r a c t i c eFor s chedu l e s and s chedu l ing , s ee Sec t i on 4 . Labe l sattached to bundles of bars by the fabricator and BS 4466requires that the following information is contained onthem:

B a r S c h e d u l eR e f .

B a r M a r k

3 .5 Proper t i e s o f re in forc ing barsThe cross-sect ional areas , weights and perimeter tabu-lated are basically for plain round bars. For bars to BS4449 having projected transverse rib areas of less than 3%by mass, the same areas, weights and perimeters apply.

The effective perimeter of a bar may be taken as 3.14times its nominal size.

3.6 Rebending barsRebending grade 460 bars on site should not be permitted.Grade 250 bars not exceeding 12mm in size may be used forthis purpose (e.g. for connecting stairs of half-landing towalls) provided that care is taken not to reduce the radius ofbend below twice the bar size. It is impractical to bendlarger s izes of higher grades without the possibi l i ty ofreducing the strength of the bars at some point (usuallywhere cast-in bars emerge from the concrete).

3.7 Fabric reinforcementFor detailing and scheduling, see Section 4. For BritishStandard fabrics, see Table 10 at the end of this Section.

3.8 Large radius bends ( B S 8 1 1 0 , c l a u s e3 . 1 2 . 8 . 2 6 )The designer will normally be responsible for the calcula-tion of large radius bends, but the detailer should be awareof their exis tence and should be able to recognize thedifference between the occasion when a large radius bend isrequired and when a standard bend is required. For furtherguidance on large radius bends see Appendix 3A.


3.9 Cover3.9.1 Nominal cover reinforcementCover should be specified on the drawings as ‘nominalcover to all steel’. Nominal cover to all steel reinforcement(including links) should be determined by considerations offire resistance and durability in envisaged conditions ofexposure. The actual minimum cover to all reinforcementmay be up to 5mm less than the nominal cover.

The nominal cover to a l ink should be such that theresulting cover to the main bar is at least equal to the size ofthe main bar (or to a bar of equivalent size in the case ofpairs or bundles of three or more bars). Where no links arepresent, the nominal cover should be at least equal to thesize of the bar.

hammering)Where special surface treatments are used (e.g. bush

, the expected depth of t reatment should beadded to the nominal cover.

Sufaces subject to moisture, washing down, etc. shouldbe considered as subject to moderate exposure.

Nominal cover as specified in BS 8110 is given in Tables 1to 5; for equivalent data on bridges see BS 5400.

Nominal covers should not be less than the maximum(nominal) aggregate size.

The categories of exposure in the durability tables in BS8110 are defined as:

mild:

moderate:

severe:

very severe:

extreme:

concrete surfaces protected against weatheror aggressive conditionsconcrete surfaces sheltered from severe rainor freezing while wet; concrete subject tocondensation; concrete surfaces continuous-ly under water ; concrete in contact withnon-aggressive soilconcrete surfaces exposed to severe rain,alternate wetting and drying and occasionalfreezing, or severe condensationconcrete surfaces exposed to sea-water sprayor de-icing salts directly or indirectly orcorrosive fumes or severe freezing conditionswhile wetconcrete surfaces exposed to abrasive action,e.g. sea water carrying sol ids, or f lowingw a t e r w i t h p H ≤ 4 . 5 , o r m a c h i n e r y o rvehicles.

Tables 1 to 5 give the nominal covers required fordurability and fire protection. For further guidance on fireprotection see BS 8110. Although it is not the responsibilityof the detai ler , Table 3 sets out , for information, theminimum dimensions of members for fire resistance.

3.9.2 Example of determining nominal coverFor a s imply supported beam with mild exposure usinggrade 30 concrete and requiring 1½ hour fire resistance.

requirement for BS 8110 ref. nominal cover

main bar size 32mm clause 3.3.1.2 (32-8) mm = 24mmlink size 8mm

mild exposure Table 3.4 25mm

1½ hour fire resistance Table 3.5 20mm

20mm aggregate clause 3.3.1.3 20mm

All reinforcement should be fixed to the nominal coverspec i f i ed on t he d r awings . The pe rmi s s ib l e t o l e r anceshould be as follows:

• the actual concrete cover should be not less than thes p e c i f i e d c o v e r m i n u s 5 m m ( N o t e : t h e e x p r e s s i o n s‘nominal cover’, ‘cover’ and ‘specified cover’ are usedinterchangeably, but they all mean ‘absolute minimumcover +5mm).

• where reinforcement is located in relation to only oneface of a member (e.g. a straight bar in a slab) the actualconcrete cover should not be more than the requirednominal cover plus:

5mm on bars up to and including 12mm size10mm on bars over 12mm up to and including 25mm size15mm on bars over 25mm size.

3.9.4 Achieving the required coverNon-structural connections for the positioning of reinforce-ment should be made with steel wire, tying devices or bywe ld ing . I t i s no t neces sa ry t o t i e o r we ld eve ry ba rintersection provided that rigidity of the cage or mat can beobtained while the concrete is being placed and vibrated.

Layers of bars in beams can be separated by means ofshort lengths of bar. The spspecified on the drawings

acing along the beam should be(usually 1m), and the bar spacers

should be detailed on the schedules.There are two main views among designers on how

spacers and chairs should be dealt with. Some believe thatthe method of achieving cover and position should be leftentirely to the contractor, while others specify spacers anddetail chairs. In practice, insufficient attention is paid to theimportance of achieving cover. If bent reinforcing bars(e.g. shape code 83) are specified as chairs, they should beshown on the relevant bar schedules. It should be noted,however, that BS 4466: 1981 allows hard drawn wire chairsto be substituted with the designer’s agreement.

Where the designer specifies the method of achieving thecover and positioning of the spacers, the following types ofspacers and chairs are examples and the detailer shouldestablish what the designer’s requirements are and use theguidance below if appropriate.

The main way of maintaining cover is by the use of spacerblocks. A wide range of plastic and concrete spacers isavai lable. Some are designed to provide two differentnominal covers, and it is desirable for the nominal covers tobe provided to be marked on the spacer . Examples ofspacers to achieve bottom cover are shown below:

Adopt 25mm nominal coverSpecify 25mm as nominal size of spacers

3.9.3 Tolerance on cover

In the case of concrete spacers, the concrete should becomparable in strength, durability, porosity and appear-ance with the surrounding concrete , they should reta intheir strength when wet and should not contain anythingharmful to concrete , s teel or hands. Si te-manufacturedconcrete or mortar spacers should not be used.

Cover to reinforcement is liable to variation on account o fthe cumulat ive effect of inevitable small errors in the

The type of formwork to be used and the finished facerequired may also influence the choice of spacer. Trials

dimensions of formwork and the cut t ing, bending and may be necessary if a particularly high grade of finish isfixing of the reinforcement. required. The spacing is usually a matter of trial and will


Table 1 Nominal cover (in mm) to all reinforcement (including links) to meet durability requirements (see note)

conditions of exposure nominal covermm mm mm mm mm

mild 25 20 20* 20* 20*moderate — 35 30 25 20severe — — 40 30 25very severe — — 50 40† 30extreme — — — 60† 50

maximum free water/cement ratio 0.65 0.60 0.55minimum cement content, kg/m3

0.50 0.45275 300 325 350 400

lowest grade of concrete C30 C35 C40 C45 C50

*These covers may be reduced to 15mm provided that the nominal maximum size of aggregate does not exceed 15mm.†Where concrete is subject to freezing while wet, air-entrainment should be used.

Note: This Table relates to normal-weight aggregate of 20mm nominal maximum size.

Table 2 Nominal cover (in mm) to all reinforcement (including links) to meet specified periods of fire resistance forreinforced concrete (see notes 1 and 2)

fireresistance beams floors ribs columns

periodh

simply supported continuous simply supported continuous simply supported continuous

½ 20** 20** 20** 20** 20** 20** 20**

1 20** 20** 20 20 20 20 20**

1½ 20 20** 25 20 35 20 20

2 40 30 35 25 45 35 25

3 60 40 45 35 55 45 25

4 70 50 55 45 65 55 25

** These covers may be reduced to 15mm provided that the nominal maximum size of aggregate does not exceed 15mm.

Note: 1: The nominal covers given relate specifically to the minimum member dimensions given in Table 3. Guidance on increased covers necessary if smaller members are used is given in BS 8100: Part 2.Note 2: Cases that that are stippled require additional measures necessary to reduce the risks of spalling (see BS 8110: Part 2: Section 4).

Table 3 Minimum dimensions (in mm) of reinforced concrete members for fire resistance

fire beams ribs floors columns wallsresistance min. width b min h (dimension b)

h b (for open fully 50% one sidesoffit)

(minimum thickness)p< 0.4% p < l % p > l %

exposed exposed exposedb

½ 80 125 75 150 125 100 150 100 75

1 120 125 95 200 160 120 150 120 75

1½ 150 125 110 250 200 140 175 140 100

2 200 125 125 300 200 160 200 160 100

3 240 150 150 400 300 200 200 150

4 280 175 170 450 350 240 240 180

Note: p is the cross-sectional area of the steel relative to that of concrete

b b

b b b

Beam

h

Plain soffit Opens o f f i t

Floors

Fully exposed

Columns

b

50% exposed

b

One face exposed

b


—

—

Table 4 Nominal cover (in mm) to all steel (including links) to meet durability requirements for prestressed concrete

conditions of exposure nominal covermm mm mm mm

mild 20 20* 20* 20*moderate — 30 25 20severe — 40 30

40†25

very severe — 50† 30extreme — — 60† 50

maximum free water/cement ratio 0.60 0.55 0.50 0.45minimum cement content, kg/m3 300 325 350 400lowest grade of concrete C35 C40 C45 C50

* These covers may be reduced to 15mm provided that the nominal maximum size of aggregate does not exceed 15mm.† Where concrete is subject to freezing while wet, air-entrainment should be used.

Note: This table relates to normal-weight aggregate of 20mm nominal maximum size.

Table 5 Nominal cover (in mm) to all steel to meet specified periods of fire resistance for prestressed concrete(see Notes 1 and 2)

fire beams floors ribsresistance simply supported continuous simply supported continuous simply supported continuous

h

½ 20** 20** 20 20 20 20

1 20 20** 25 20 35 20

1½ 35 20 30

** These covers may be reduced to 15mm provided that the nominal maximum size of aggregate not exceed l5mm.

Note: The nominal covers given relate specifically to the minimum member dimensions given in table 3. Guidance on increased covers necessary if smaller members are used is given in BS 8110: Part 2.Note 2: Cases that are stippled require attention to the additional measures necessary to reduce the risks of spalling (see BS 8110: Part 2).

** For the purposes of assessing a nominal cover for beams and columns, the cover to main bars, which would have been obtained from the tables in BS 8110: Part 2, have been reduced by it notionalallowance.

Tendon in ducts. The cover to any duct should be not less than 50mm. Precautions should be taken to ensure a dense concrete cover, particularly with large or wide ducts.

External tendons. Where these are to be protected by dense concrete of at least grade C40, added subsequently, the thickness of this cover should not be less than that required for tendons inside thestructural concrete in similar conditions. The concrete cover should be anchored by reinforcement to the prestressed member and should be checked for crack control in accordance with Section 3 of BS8110.


2

3

4

60

70

80

35

6070

40

55

65

25

35

4555

45

55

65

75

35

45

5565

depend on the strength of the spacer, the size and centres oft h e r e i n f o r c e m e n t a n d t h e l o a d i n g s a p p l i e d t o i t , t h ebearing area and the type of formwork. Spacers will notusually be further apart than 1m each way or closer than,say, 0.5m each way.

An example of a spacer for vertical application is shownbelow:

The Concrete Society will be publishing a document onspacers, which will represent the latest views.

3.9.5 Achieving the correct positionProvided that the correct cover is achieved, the laterallocation of the steel in horizontal and vertical members isnot usually critical. A different situation arises, however, ina ribbed f loor, and here it is desirable to indicate the use ofa spacer that will both locate the steel and provide cover.An example is shown below:

Where 2 bars are used in a rib, links should be provided tolocate the reinforcement.

The correct positioning of top steel (particularly impor-tant in cantilevers) can be achieved by one of the followingfive basic methods:

1. with specially shaped reinforcement, which may be tiedor welded to other reinforcement

T i e d


2.

3.

4.

by the use of ‘goalposts’ at specified centres (if specifiedthey should be fully detailed on the bar schedule)

by the use of high wire chairs

by the use of continuous high wire chairs

5. by the use of ‘trombone’ shapes.(shape code 38).

For methods 1, 2 and 5 the bars are usually supplied bythe reinforcement fabricator, and if they are shown on thedrawings they must also be included in the bar schedules

Chairs should be designed to support the main steel andthe weight of workmen walking on it during construction. Itneed not, normally, be designed to take other constructionloads, since other loading ought not to occur. The size ofbar used and the centres of the chairs will vary with theheight of chair required and the weight to be supported. Aminimum size of R10 is recommended for slabs, but thismay have to be increased substantially for heavy reinforce-ments. The centres of chairs should be specified on thereinforcement detai l drawings and should not normallyexceed about lm in two direct ions at r ight-angles. Asufficient number of chairs should be included on the barschedules to allow some flexibility in sequence of construc-tion.

For method 3 (high wire chairs) similar considerationsapply, but 4 or 5mm hard drawn wire is usually used tomanufacture such high chairs and a typical design looks likethis:

17

Nominal coverMethod 4 (continuous high chairs) is growing in the UKbecause of the saving in steel fixing time. Such continuouschairs are used to space two layers of steel. Typical designslook like this. The chairs are designed using 4 or 5mm harddrawn wire and are available in 1m lengths; they are usuallyfixed at about 1m centres.

Vertical steel can be spaced using horizontal U-bars (notless than R6), but i f they are specif ied they should beincluded on the bar schedules. Two layers of vertical steelin walls should be kept apart by horizontal U-type spacersof suitable size (not less than R6). Sufficient spacers shouldbe used to ensure the rigidity of the reinforcement. The sizeof reinforcement will not only determine the length of thevertical bars but will, in conjunction with the height of thelift, determine the number and size of spacers. At least onehorizontal line of spacers should be employed in each lift ofconcrete, and the spacers should be included on the barschedules.

3.10 Anchorage lap lengths and shear rein-forcementThese should be determined by the designer, Appendix 3Bgives equivalent s t ra ight anchorage lengths , hooks andbends, and minimum overall depths of various U-bars.

3.11 Full-strength joints in reinforcing bars( B S 8 1 1 0 , c l a u s e 3 . 1 2 . 8 . 8 . )3.11.1 CompressionFor joints entirely in compression the two types of sleevesillustrated below are available.

Not to project intonominal cover

It is necessary to square saw-cut the bar ends so that anygap after butting the bars does not exceed 3°. Sleeves for20mm size bars and larger are available. To cater for thepossibility of some tensile forces it is desirable to staggercompression joints or provide a small size bar (say, T10) asa splice lapping across the joint.

The normal cover requirements for durability and for fireshould apply from the outside face of the coupler and notfrom the reinforcement bar. Normally the cover specifiedto the links or stirrups will ensure adequate cover to thecoupler.

3.11.2 Tension

1. tapered threaded couplers (10mm and above)2. swaged couplers (16mm rubbed and above)3. s leeves f i l led with molten metal (12mm rubbed and

above)4. welding (butt, lap or splice joints)

Method 1 is essentially a factory-based operation withthe threads being tightened on site; however the threadingcan be carried out on site for larger projects. Methods 2, 3and 4 are site operations in their basic form. However, byintroducing an intermediate stud, method 2 can be swagedin the factory and tightened on site.

Methods 3 and 4 are applicable to both straight and bentbars, but with the basic threaded (1) and basic swaged (2)methods, the second bar to be f ixed must be s t ra ight .Modified versions of both methods are available where the


Table 6 Cross-sectional areas of bars at specific spacings in mm2 per m width:

bar sizemm 50 75

6* 566 3778 1 066 670

10 1 570 1 04712 2 262 1 50816 4 022 2 68120 4 18925 6 54532 40 50*

* non-prefered sizes, but given for sake of completeness

100

283503786

1 1312 0113 1424 9098 042

125

226402628905

1 6082 5133 9276 434

10 053

bar spacing, mm150

188335524754

1 3402 0943 2726 3628 378

13 090

175

162 141 113 94287 251 201 168449 393 314 262646 565 452 377

1 149 1 005 801 6701 795 1 571 1 257 1 0472 805 2 454 1 963 1 6364 596 4 021 3 217 2 6817 181 6 283 5 027 4 189

11 220 9 617 7 854 6 545

200 250

Table 7 Cross-sectional areas in square millimetres of specific numbers of bars (and perimeters)

sizemm 1 2 3

6* 28.3 56.5 84.88 50.3 100 151

10 78.5 157 23612 113.1 226 33916 201.1 402 60320 314.2 628 94225 490.9 982 1 47332 804.2 1 608 2 41340 1 257 2 513 3 77050* 1 963.5 3 927 5 890

* non-preferred sizes, but given for sake of completeness

4

113201314452804

1 2571 9633 2175 0267 854

number5

141251393566

1 0051 5712 4544 0216 2839 812

of bars6

170302471679

1 2061 8852 9454 8257 540

11 781

7 8

198 226352 402550 628792 905

1 407 1 6082 199 2 5133 436 3 9275 630 6 4348 790 10 053

13 744 15 708

Table 8 Actual size of deformed bars

9 10perimeter

mm

255 283 18.85452 503 25.13707 785 34.12

1 018 1 131 37.701 810 2 011 50.272 827 3 142 62.834 418 4 909 78.547 238 8 042 100.5

11 310 12 566 125.717 671 18 635 157.1

300

a

nominal bar size 6 8 10 12 16 20 25 32 40

maximum barsize ‘a’ 8 11 13 14 19 23 29 37 46


—————

———

——

Table 9 Weights of bars in kilogrammes per square metre (reinforcement in one direction only)

spacing of bars in millimetres125 150 175

lengthper tonne

m

4 6052 5321 8231 126

63340625915810165

1.7763.1604.9287.104

12.6319.7330.8350.5078.91

1.480 1.2692.633 2.2574.107 3.5205.920 5.074

10.53 9.02316.44 14.0925.69 22.0242.09 36.0765.76 56.37

102.75 88.07

bar weightsize per metremm kg

6* 0.2228 0.395

10 0.61612 0.88816 1.57920 2.46625 2.85432 6.31340 9.86450* 15.413

* non-preferred sizes

50 75 200 250 300100

2.960 2.2205.267 3.9508.213 6.160

11.84 8.88021.05 15.7932.88 24.6651.39 38.54

63.13

4.4407.900

12.32017.76031.580

1.110 0.888 0.7401.975 1.580 1.3173.080 2.464 2.0534.440 3.552 2.9607.895 6.316 5.263

12.33 9.864 8.22019.27 15.42 12.8531.57 25.25 21.0449.32 39.46 32.8877.06 61.65 51.38

Table 10 Equivalent bar sizes

2 bars

total equivalentarea sizemm2 mm

402 23628 28982 35

1610 452510 573927 71

3 bars 4 bars

total equivalent total equivalentarea size area sizemm2 mm mm2 mm

603 28 804 32943 35 1260 40

1470 43 1960 502410 55 3220 643770 69 5030 805890 87 7854 100

sizemm

162025324050

Table 11 Designated fabric (BS 4483)

type of size of meshfabric mm × mm

BSref. no.

A98A142A193A252A393

weight size cross-sectional size cross-sectionalkg/m3 mm area mm2/m mm area mm2/m

1.54 5 98 5 982.22 6 142 6 1423.02 7 193 7 1933.95 8 252 8 2526.16 10 393 10 393

B196 3.05 5 196B283 3.73 6 283B385 4.53 7 385

B503 5.93 8 503B785 8.14 10 785B1131 10.90 12 1131

C283 2.61 6C385 3.41 7C503 4.34 8

283385503

C636*C785

D31D49D98

5.55 96.72 10

636785

0.49 20.77 2.51.54 5.0

31 2 3149 2.5 4998 5.0 98

notes

7 193

8 252

5 49

6 71

fabric made ineither hard-drawnwire (BS 4482) orbars (BS 4449)

exceptions: A98and all long-meshfabrics and mainwires of B196,plain hard drawnwire only.stock sheets2.4m wide4.8m long

square mesh 200 × 200

100 × 200

100 × 400

structural mesh

long mesh

wrapping 100 × 100

200 × 200

stock sheets2.4m × 1.2m

The BS reference number is the area of the main wires in mm2 per metre width rounded to the nearest mm2

The prefix letter indicates:A square meshBC

structural mesh (cross wires to comply with BS 8110)long mesh (light cross wires)

DX

wrapping fabricother fabrics


————— —

—— —

— —

second bar is bent and cannot therefore be rotated, but bycareful detailing it is usually possible to use the second bar

3.11.3 Detailing joints

in a straight form, e.g. where the second bar would haveCompression joints should be detailed like this:

been bent to provide a nominal end anchorage it is oftenpossible to lap a small size bar instead. A slim version of

(shape code 99)

method 1 is available with approximately the same overall 2000

diameter as a ribbed bar.

Tension joints should be detailed like this:

3000

Where a bent second bar is completely unavoidable itmay be possible to join it to the first bar before the first bar

Since couplers do not appear in BS 4466 an explanationof the signs should be given in the general notes on each

is concreted into position. drawing and bar schedule.

Note: In all cases the detailer should assume that the barterminates at the centre of coupler (i.e. allow for no gap).The necessary adjustments to length can then be madeaccording the system chosen. For long runs of coupled bars(e.g. multi-storey columns), small amounts of dimensional‘creep’ may occur because of the accumulative effect oftolerances, and the desired length of the final bar should bechecked in situ before end preparation.

1 2 3

Grade 250 and grade 460 bars are defined as readilyweldable in BS 4449.

Full-strength welds can be obtained with both grades ofbars. It is a common fallacy that cold-worked bars revertto mild steel, but this is not true for the time/temperatureinput associated with welding. Care needs to be taken toensu re t ha t p rope r ly qua l i f i ed we lde r s ca r ry ou t a l lwelding of full strength joints in reinforcement.

Metal-arc butt weld with double-V preparation

15 × bar size with two metallic-arc fillet welds 5 × × bar size in length

Butt weld with fillet weld 10 × × bar size in length

For more information on 1 to 4, refer to CIRIA report 92and to coupler and reinforcement suppliers.


and scheduled like this:

and scheduled like this:

(shape code 99)

Appendix 3A Large-radius bends

a b

The radius of bend is required to be greater than the standardwhere bars are stressed beyond a distance of four times the barsize past the end of the bend (BS 8110, clause 3.12.8.25).

Examples of where large radius bends may be required:

end column and wall connections to beam or slabcantilever retaining wallscorbelsbottom bars for simple pile caps.

f cu = 25 N/mm 2

In circumstances where triaxial compressive stresses exist orwhere a bar is placed inside and perpendicular to the bend, it ispossible to reduce the large radius of bend. In this instance theengineer should be consulted.

a b

Table A1 Large-radius bends: internal radius of bend, mm

design stress in bar atultimate load

N / m m 2bar size, mma b

m m

25

50

10 12 16 20 25 32 40

100 30 35150 45 55200 55 75250 70 90300 85 110350 100 130400 115 150

100 20 30 40 55 80150 35 40 60 85 120200 45 55 80 115 155250 55 70 105 140 195300 65 85 125 170 235350 75 100 145 200 275400 90 110 165 225 315

100 20 25 35 50 65 95150 30 35 55 70 100 140200 40 50 70 95 130 185250 50 60 90 120 165 235300 60 75 110 145 195 280350 70 85 125 170 230 325400 80 100 145 195 260 375

100 20 25 35 45 60 80 115150 30 35 50 65 90 125 170200 40 45 65 85 120 165 225250 45 60 85 110 145 205 285300 55 70 100 130 175 245 340350 65 80 115 155 205 290 395400 75 95 135 175 235 330 450

100 20 25 30 40 50 70 95150 25 35 45 60 80 110 145200 35 45 60 80 105 145 195250 45 55 75 100 130 180 240300 55 65 90 120 155 215 290350 60 75 105 140 185 250 335400 70 85 120 160 210 285 385

75

100

150andover

Notes:1. Maximum design stress = characteristic stress/1.15

grade 250 217.4 N/mm2

grade 460 400 N/mm2

2. Minimum radius may governgrade 250 2 × bar size

grade 460 4 × bar size (≥ 25 mm)grade 460 3 × bar size (≤ 20 mm)



a b

f c u = 3 0 N / m m 2

a b



N/mm 2 10 12 16bar size, mm

20 25 32 40

100 25 30150 35 45200 45 60250 60 75300 70 90350 80 110400 95 125

100 20 25 35 45 65150 25 35 50 70 100200 35 45 70 95 130250 45 60 85 120 165300 55 70 105 140 195350 65 80 120 165 230400 75 95 135 190 260

100 20 25 30 40 55 80150 25 30 45 60 80 115200 35 40 60 80 110 155250 40 50 75 100 135 195300 50 60 90 120 165 235350 60 75 105 140 190 270400 65 85 120 160 220 310

100 20150 25200 30250 40300 45350 55400 65

20

304050607080

30 40 50 70 9540 55 75 105 14055 75 100 135 19070 90 125 170 23585 110 145 205 28595 130 170 240 330

110 145 195 275 375

100 20 20 30 40 50 65 80150 20 25 40 50 65 90 120200 30 35 50 65 85 120 160250 35 45 65 85 110 150 200300 45 55 75 100 130 180 240350 50 65 90 115 155 210 280400 60 75 100 135 175 240 320

a bmm

25

50

75

100

150andover


grade 250 217.4 N/mm2

grade 460 400 N/mm2

2. Minimum radius may governgrade 250 2 × bar sizegrade 460 3 × bar size ( ≤ 20 mm)grade 460 4 × bar size ( ≥ 25 mm)


f c u = 3 5 N / m m 2



N/mm 2bar size, mma b

mm 10 12 16 20 25 32 40

100 20 25150 30 40200 40 55250 50 65300 60 80350 70 90400 80 105

100 20 25 30 40 55150 25 30 45 60 85200 30 40 60 80 110250 40 50 75 100 140300 45 60 90 120 170350 55 70 105 140 195400 65 80 120 160 225

100 20 25 30 40 50 65150 20 25 40 50 70 100200 30 35 50 70 95 135250 35 45 65 85 115 165300 45 55 75 105 140 200350 50 60 90 120 165 235400 55 70 100 140 185 265

25

50

75

100 20 25 30 40 50 65 80150 20 25 35 45 65 90 120200 25 35 45 65 85 120 160250 35 40 60 80 105 145 200300 40 50 70 95 125 175 240350 45 60 85 110 145 205 285400 55 65 95 125 170 235 325

65 8075 105

100 140130 170155 205180 240205 275

100

100 20 25 30 40150 20 25 35 45200 25 30 45 55250 30 40 55 70300 40 45 65 85350 45 55 75 100400 50 60 85 115

50557595

110130150

150andover


grade 250 217.4 N/mm2

grade 460 400 N/mm2

2. Minimum radius may governgrade 250 2 × bar sizegrade 460 3 × bar size (≤ 20 mm)grade 460 4 × bar size (≥ 25 mm)


Appendix 3B Anchorage and lap lengths(BS 8110, clause 3.12.8)

Table Bl Equivalent straight anchorage lengths of standard hooks & bends, mm

t y p e value N / m m 2 8 10 12 16 20 25 32 40anchorage f y bar size, mm

4 Ø180° Hook

Equiva len t

90° Bend

4 Ø

r

Equ iva len t

16Ø 250 128 160 192 256 320 400 512 640

24Ø 460 192 240 288 384 480 600 768 960

8 Ø 250 64 80 96 128 160 200 256 320

12Ø 460 96 120 144 192 240 300 384 480

Table B2 Minimum overall depth of various U-bars, mm

shape code

32 (Hook)39 (Hairpin)

B r

38 (Trombone)

r

B 4 Ø

r

B r fyN/mm 2

6 Ø 2 Ø 250

8 Ø 3 Ø 460

10Ø 4 Ø 460

10Ø 2 Ø 250

12Ø 3 Ø 460

14Ø 4 Ø 460

8

5 0

65

–

8 0

100

–

4010

60

80

–

100

120

–

bar size, mm12 16 20

75 100 120

100 130 160

– – –

120 160 200

145 195 240

– – –

2 5 32

150 195

– –

250 320

250 320

– –

350 450

–

4 0 0

400

–

(a) The lap length is increased to 1.4 × anchorage length (seeTables B4 to B7) if:

(i) the minimum cover to lapped bars in the top of a section

240

560

(ii) the minimum cover to lapped corner bars (not in top) of

Tension laps (BS 8110, clause 3.12.8.13) a section is less than 2 × bar size, or

Tension laps should be at least equal in length to the anchoragelength necessary to develop the design stress in the bars. If the > 2 Ølapped bars are of unequal size, then the lap length is based on thesize of the smaller bar. Furthermore:

as cast is less than 2 × bar size, or

< 2 Ø

> 7 5

< 2 Ø

< 2 ØLapped ba rs

< 7 5 o r < 6 Ø

(iii) the clear distance between adjacent laps is less than 75mm or 6 × bar size, whichever is greater.


Notes: These values are not hook allowances for forming 180° hooks, or bend allowances for forming 90° bends.Ø = bar size, mm

> 6 Ø

< 2 Ø

< 2 Ø

< 75 or < 6Ø

(b) The lap length is increased to 2.0 × anchorage length (seeTables B4 to B8) if conditions (a) (i) and (ii) above apply.

Compression laps (BS 8110, clause 3.12.8.15)The length of the compression lap should be 1.25 × thecompression anchorage length necessary to develop the designstress in the bars (see Tables B4 to B7).

Lapping of bundled bars(BS 8110, clause 3.12.4.1)At laps no more than four bars may be in contact.

I

Lap Lap Lap

For bundles of three bars, laps should be staggered.

Lap Lap

For bundles of two bars (pairs), laps are preferably staggered.

Lap

Where bundles of two barss are lapped but not staggered, then thelap length will be based on the equivalent diameter of the twobars. Otherwise the lap length is based on the value of the singlebar.


Anchorage and lap lengths (BS 8110, clause 3.12.8)(For lap lengths in accordance with BS 8007: 1987, see Section 9).

Grade 250 (mild-steel plain bar to BS 4449)

Design ultimate stress in tension or compression = 0.87 y = 217.5 N/mm2

Design ultimate anchorage bond stress b u

c u , N/mm 2 25 30 3.5 40

tension 1.4 1.53 1.66 1.77compression 1.75 1.92 2.07 2.21

Table B3

size of bar, mm 8 10 12 16 20 25 32 40

tension anchorage = 0.87fy × Ø/4 b u, mm

25 310 390 465 620

c u 30 285 355 425 57035 265 330 395 52540 245 310 370 490

compression anchorage = 0.87 y × Ø/4 b u, mm25 250 310 375 500

c u 30 225 285 340 45535 210 265 315 42040 195 245 295 395

tension lap = tension anchorage, 15Ø or 300 mm, whichever is greatest

tension lap × 1.4 (BS 8110, clause 3.12.8.13)

25 435 545

c u 30 395 49535 370 46040 345 430


25 620 780

c u 30 570 71035 530 66040 490 620

775 975710 885655 820615 770

620 775565 710525 655490 615

25 310 390 465 620 775 970

c u 30 300 355 425 570 710 88535 300 330 395 525 655 82040 300 305 370 490 615 770

650 870 1085 1360595 795 995 1240550 735 920 1150515 690 860 1075

930 1240 1550 1940850 1140 1420 1770790 1050 1310 1640740 980 1230 1540

compression lap = compression anchorage × 1.25, 15Ø or 300 mm, whichever is the greatest

2 5 310 390 465 620 775 970

cu

30 300 355 425 570 710 88535 300 330 395 525 655 82040 300 305 370 490 615 770

1245 15551135 14201050 1315985 1230

995 1245910 1135840 1050785 985

1245 15551135 14201050 1315985 1230

1740 21751590 19851470 18401375 1720

2490 31102270 28402100 26301970 2460

1245 15551135 14201050 1315985 1230


f

f

ff

f

f

f f

f

f

f

f


Grade 460 (high yield deformed bar type 2 to BS 4449 and BS 4461)



c u , N/mm 2 25 30 35 40


Table B4

size of bar, mm 8 10 12 16 20 25 32 40

tension anchorage = 0.87 y × Ø/4 b u, mm

25 320 400 480 640

c u 30 290 365 440 58535 270 340 405 54040 255 315 380 505

compression anchorage = 0.87 y × Ø/4 b u, mm

25 255 320 380 510

c u 30 230 290 350 46535 210 270 320 43040 200 250 300 400

tension lap = tension anchorage, 15Ø or 300 mm, whichever is greatest

25 320 400

c u 30 300 36535 300 34040 300 315


25 450 560

c u 30 410 51035 380 47540 355 445


25 640 800

c u 30 585 73035 540 67540 505 635

480 640 800 1000 1280 1600440 585 730 915 1170 1460405 540 675 845 1080 1355380 505 635 790 1010 1270

670 895 1120 1400 1795 2240615 820 1025 1280 1635 2045570 760 945 1185 1515 1895530 710 885 1105 1415 1770

960 1280 1600 2000 2560 3200875 1170 1460 1825 2340 2925810 1080 1355 1690 2165 2705760 1010 1265 1580 2025 2530

800 1000 1280 1600730 915 1170 1460675 845 1080 1355635 790 1010 1265

635 795 1015 1270580 725 930 1160535 670 860 1075500 630 805 1005


25 320 390 475 635 795 995

c u 30 300 360 435 580 725 9053 5 300 335 405 535 670 84040 300 315 375 500 630 785

1270 15901160 14501075 13401005 1255


f

ff

f

f

f

f

f

f

f

f

f f

Anchorage and lap lengths (BS 8110, clause 3.12.8)(For lap lengths in accordance with BS 8007:1987, see Section 9).

Grade 460 (plain wire to BS 4482)



c u , N/mm 2 25 30 35 40


Table B5

size of bar, mm 5 6 7 8 9 10 12


25 355 430 500 570c u 30 325 390 455 585

35 300 360 425 48540 280 340 395 450


25 285 345 400 455c u 30 260 315 365 420

35 240 290 340 38540 225 270 315 360

tension lap = tension anchorage, 15Ø or 300 mm whichever is greatest

25 355 430c u 30 325 390

35 300 36040 300 340


25 500 600c u 30 455 550

35 425 50540 395 475


25 715 860c u 30 650 785

35 605 72540 565 680

500 570 645 715 860455 520 585 650 785425 485 545 605 725395 450 510 565 680

700 800 900 1000 1200640 730 1820 1915 1095590 675 760 845 1015555 635 710 790 950

1000 1145 1285 1430 1715915 1045 1175 1305 1565845 965 1085 1210 1450790 905 1015 1130 1355

645 715650 785545 605510 565

860

725680

515 570 685470 520 625435 485 580405 450 540


25 355 430 500 570 645

c u

30 325 390 455 520 585

35 300 360 425 485 545

4 0 300 340 395 450 510

715 860650 785605 725565 680


ff

f

f f

f

f

f

f

f

f

f f


Grade 460 (deformed type 2 wire to BS 4482)



cu , N/mm 2 25 30 35 40


Table B6

size of bar, mm 5 6 7 8 9 10 12

25 300 300

c u 30 300 30035 300 30040 300 300


25 300 335

c u 30 300 30535 300 30040 300 300


25 400 480

c u 30 365 44035 340 40540 315 380


25 200 240 280 320

c u 30 185 220 255 29035 170 205 235 27040 160 190 220 255


25 160 190 220 255

c u 30 145 175 205 23035 135 160 190 21540 125 150 175 200

tension lap = tension anchorage, 15Ø or 300 mm whichever is greatest

300 320 360 400 480300 300 330 365 440300 300 305 340 405300 300 300 315 380

390 450 505 560 670360 410 460 510 615330 380 425 475 570310 355 400 445 530

560 640 720 800 960510 585 660 730 875475 540 610 675 810445 505 570 635 760

360 400 480330 365 440305 340 405285 315 380

285 320 380260 290 350240 270 320225 250 300


25 300 300 300 320 355

c u 30 300 300 300 300 32535 300 300 300 300 30040 300 300 300 300 300

395 475360 435335 405315 375


ff

f

f f

f

f

f f

f

f

f

f


Grade 460 (welded wire fabric to BS 4483)



f c u , N/mm 2 25 30 35 40


Table B7

size of bar, mm 5 6 7 8 9 10 12


25 155 185 215 245

c u 30 140 170 195 22535 130 155 180 21040 120 145 170 195

compression anchorage = 0.87 y × 0/4 b u, mm

25 125 150 175 200

c u 30 115 135 160 18035 105 125 145 16540 100 115 135 155

tension lap = tension anchorage, but not less than 250 mm

25 250 250 250 250

c u 30 250 250 250 25035 250 250 250 25040 250 250 250 250

tension lap × 1.4 (BS 8110, clause 3.12.8.13) but not less than 250 mm

25 250 260 300 345

c u 30 250 250 275 31535 250 250 255 29040 250 250 250 275

tension lap × 2.0 (BS 8110, clause 3.12.8.13) but not less than 250 mm

25 310 370 430 495

c u 30 280 335 395 45035 260 310 365 41540 250 290 340 390

compression lap = compression anchorage × 1.25, but not less than 250 mm

25 250 250 250 250

c u 30 250 250 250 25035 250 250 250 25040 250 250 250 250

275 310 370255 280 335235 260 310220 245 290

220 245 295205 225 270190 210 250175 195 235

275 310 370255 280 335250 260 310250 250 290

390 430 515355 395 470330 365 435305 340 410

555 615 740505 560 675470 520 625440 485 585

380 310 370255 280 340250 260 315250 250 295


ff

f

f

f

f

f

f

f f

f f

Appendix 3C Shear resistance of beams(BS 8110, clause 3.4.5)

Table C1 Ultimate shearing resistance provided by a single system of links

type of barreinforced size factor spacing of links (single system) (sv), mm

cement mm 50 75 100 125 150 175 200 225 250 275 300

Ksv 246 164 123 98 82 70 61 54 49 44 41bvmax 615 410 307 246 205 175 153 136 123 111 102

grade 250 KSv 437 291 218 175 145 125 109 97 87 79 73f y v = 2 5 0 bvmax 1093 729 546 437 364 312 273 243 281 198 182N/mm2

Ksv 683 455 341 273 227 195 170 151 136 124 114bvmax 1708 1139 854 683 569 488 427 379 341 310 284

Ksv 984 656 492 393 328 281 246 218 196 179 164bvmax 2460 1640 1230 984 820 703 615 546 492 447 410

Ksv 452 301 226 181 150 129 113 100 90 82 75bvmax 1131 754 565 452 377 323 283 251 226 205 188

grade 460 Ksv 804 536 402 322 268 230 201 178 161 146 134f y v = 4 6 0 bvmax 2011 1341 1006 804 670 574 503 447 402 365 335N/mm2

Ksv 1257 838 628 503 419 359 314 279 251 228 209bvmax 3143 2095 1571 1257 1047 898 785 698 628 571 524

Ksv 1810 1207 905 724 603 517 452 402 362 329 301bvmax 4526 3017 2263 1810 1509 1293 1131 1006 905 823 754

Ksv =0.87fyvAsv

Sv= ultimate shearing resistance provided by single system in N/mm of effective depth

bvmax= maximum permissible width of section with nominal links (single system), mm

Table C2 Ultimate shearing resistance in kN by barsinclined at 45°

ultimate resistance when Ø = 45°

barsize

1620253240

fy = 250singlesystem

30.948.375.5

123.7193.3

N/mm2

doublesystem

61.896.6

151.0247.4386.5

fy = 46singlesystem

56.988.9

138.9

d 1

d

45° 45°

227.6355.6

0 N/mm2

doublesystem

113.8177.8277.8455.2711.2

Face of support Bent-up barsa t 45 °

d - d 1 d - d 1

Double system

d1

d

45° 45°

1.5d 1.5d

Single system


6

8

10

12

6

8

10

12

4 Detailing and scheduling

4.1 Detailing techniquesThe majority of detailing examples contained in this reportare based on a manual detailing system, detailing fully allaspects of each element. This method, being the ‘tradition-al’ method of detailing in the UK, tends to be simpler toplan and operate than the other methods listed below, butin certain circumstances takes longer to produce.

•4.2 Tabular method of detai l ingThe tabular method may be adopted where a number ofconcrete elements have similar profile and reinforcementarrangement but have differing dimensions and quantity ofreinforcement. A typical element is drawn, usually not toscale, but visual ly representat ive of i ts shape, wi th thedimensions and reinforcement given as code let ters . Atable is given to show the actual values of these code lettersfor each individual element (see Table 12).

AdvantagesA large number of similar elements may be detailed on afew drawingsQuicker to produce therefore saving detailing time.

DisadvantagesElements are not drawn to scaleChecking of drawings and schedules tends to take longer

and is more prone to errorOnce alterations or additions are made, special details

may be required to which the initial tables have torefer: this complicates the system and leads to errors

Visual checks of drawings may be misleading.

4 . 3 P r e p r i n t e d d r a w i n g sThese are used where a library of drawings are kept fortypical elements or details that may be required on othercontracts. Examples of this may be:

s tandard notespile caps with schedulesconcrete box culvertsconstruction expansion joint details.

Copy negatives are taken of the original, and the title box iscompleted to suit a particular contract. The advantages ofthese drawings is obvious but care must be taken to ensurethat the details given do, in fact, apply to the conditionrequired. A check should also be made to ensure that thepreprinted drawing complies with current standards.

4.4 Overlay drawingsThese are par ts of drawings produced on clear acetatenegatives so that various parts may be brought together,laid on top of each other, and printed to form a singlenegative. These drawings are, by their nature, not to scaleand have s imilar advantages and disadvantages as thetabular method of detailing.


4.5 Computer-aided detai l ing and schedulingI t h a s b e e n e s t i m a t e d t h a t t h e m a n u a l d e t a i l i n g a n dscheduling of a reinforced concrete structure takes twice aslong as the design s tage. Therefore i t fol lows that anyautomatic method of detailing and scheduling should havesignificant effect on design office procedures.

At present detailing and scheduling programs fall intofour main categories:

Scheduling programs with no detailing capabilityThis type of program was the first to be developed andremoved the ar i thmetic drudgery and the inevitableerrors f rom the preparat ion of schedules and cut t inglists.

• Scheduling programs with detailing capability based online printer diagrams and preprinted sheetsThe output from some of the more sophisticated types ofscheduling programs contain line printer diagrams andare intended to be used as reinforcement details whenread in conjunct ion with pr inted schedules or detai lsheets.

• Detailing and scheduling programs with visual display andlimitations on plotter outputThe capability of these programs can include full interac-tive input of data and drawn-to-scale details produced bythe plot ter . These programs are normally l imited tostructures based on a rectangular grid.

• Detailing and scheduling system with virtually no restric-tion on plotter output with all drawing activities carried outon a graphics displayIn systems of this type the detailer uses a high-resolutiongraphics dispdrawings.

lay at every stage to produce and check hisThe results are passed to a plotter for drawing

production. The schedule is automatically produced on aprinter, as a direct result of the computerized draughtingprocess.

Most of the scheduling programs were developed 10–15years ago when computer graphics equipment was veryexpensive, but although this type of hardware is now moreread i ly ava i l ab l e , i t mus t be r emembered the cos t o fp roduc ing o r buy ing t he so f twa re fo r a soph i s t i c a t eddetailing program is a significant item. The ideal program isone that requires the minimum input for the maximumoutput, and experience has shown that a combination ofhandwork and computer graphics is probably the mosteconomic method of detailing and scheduling

The relat ive advantages of different computer-aidedmethods will vary from office to office depending on thehardware, software and staff that are available, but it isimportant to bear in mind that a computer-based detailingand scheduling system is only a useful tool that has to beused in a responsible way by a suitably experienced person.

4.6 Detai l ing reinforcementRein fo rcemen t de t a i l i ng shou ld be kep t a s s imp le a spossible consis tent with showing i ts shape and exactlocation. The standard sequence of description on drawingis as follows:

Number, type and grade, size, mark, bar centres, location orcomment. For example, in a slab 20T16-63-150B1 describes20 no. deformed type 2 bars of 16mm nominal size at a pitchof 150mm in the bottom outer layer. The bar mark is –63–.

35


Table 12 Examples of tabular method of detailing

Y

X

B 2

B1

ZB1

Level C

75

B

lin

din

g

co

nc

.

P l an

B 2

E l e v a t i o n

column bases

basereinforcement level-

no. off X Y ZB1 B2 C

7A, 7B, 7C 3 1800 1800 400 12 T20-1-150 12 T20-1-150 19.00

8A, 8B, 8C 3 1800 1350 400 9 T16-2-150 12 T20-1-150 19.000

L a pE

leng th

Level D

F

Level C

A

75 KickerE

F

E

A

F B

E E

A - A 1–1 2 – 2

column starters

level reinforcement column dimscol no. off sect elev

C D E F A B

7A, 7B7C, 7D 5 19.000 19.400 4 T32-3 3 T10-4-150 1-1 A-A 350 550

8C 4 19.500 19.950 6 T25-5 6 T10-6-1502-2 A-A 575 575

+ 6 T10-7-150


E

B

E E

E E E


Note that bar centres, location or comment, are not usuallyrequired for beams and columns (see Section 5). To avoidconfusion when totalling quantities for entry on the sche-dule, the number of bars in a group or the number of sheetsof fabric in a set should be stated only one on the drawing.

The position of reinforcement should be established bydimensions to the faces of the concrete or the formwork.

All reinforcement that needs to be fixed in a certain partbefore it can be concreted should be detailed with that part,e .g . s tar ters f rom a tank f loor into the walls must bedetailed with the floor.

Although the elements of a structure, such as beams,slabs and columns, are detailed separately, the designerand the detailer should always consider each element as apart of the entire structure. Frequently the arrangement ofreinforcement in an element will affect the arrangement inthe adjacent elements, and the following cases often arise:

at beam-to-column intersections where the beam rein-forcement must avoid the column reinforcement

at beam-to-beam intersections where the levels of theseveral layers of reinforcement in each beam mustbe such that they will pass over each other and givethe correct cover to the upper and lower layers

at s lab-to-beam intersect ions the cover over the topreinforcement in the beam must be suff ic ient forthe top steel in the slab to pass over the beam withthe correct cover.

Generally it is advisable early in the design to establish asystem for achieving the above, particularly in projects onwhich several detailers may be working simultaneously onadjacent elements of the structure.

I t can be useful to detai l to a large scale a typicalbeam-column junction to determine reinforcement loca-tions. Subsection 4.9 gives some guidelines and points toconsider when producing this drawing.

Detailing should be carried out so that fabrication ofreinforcement units off-si te is faci l i tated. Sketches ofd e t a i l s t o a c h i e v e t h i s a r e s h o w n i n s u b s e c t i o n 4 . 1 0onwards. The decision to preassemble the reinforcementwil l normally be taken by the contractor: however thedetailer should bear the possibility in mind.

4.7 Spacing of reinforcementMinimum distances between bars (BS 8110, c lause3 .12 .11 .1 )Horizontal distanceThe horizontal distance between bars should not be lessthan (h agg + 5mm), where hagg is the maximum size of thecoarse aggregate.

(a)

(b)(c)

(d)

(e)(f)

(g)

(h)

(i)

(j)

(k)

(l)

Vertical distanceThe vertical distance between bars should not be less than2/3 hagg (see Fig. 16).

h a g g + 5 But not less than the bar size orequivalent bar s ize whicheveris the greater

2/3 hagg But not less than the bar size orequivalent s ize when theseexceed hagg + 5mm

Fig. 16

1.

2.

3 .

When the bar size or equivalent bar size is greater thanh a g g + 5mm, both the ver t ical and horizontal dis tancesshould be not less than the bar size or equivalent bar size.

Using 20mm maximum size aggregate , the minimumhorizontal distance will be 25mm and the vertical distance


will be 16mm. These spacings will be satisfactory for singlebars up to 25mm diameter and for bundles using smallerb a r s , e . g . 2 T 1 2 . G e n e r a l l y t h e m i n i m u m s p a c i n g f o rb u n d l e d b a r s w i l l b e d e t e r m i n e d f r o m t h e e q u i v a l e n tdiameter .

4.8 Bundled bars (BS 8110 , c l ause 3 .12 .4 .1 )A bundle is defined as a group of parallel bars in contact toact as a single unit and, for the purpose of design, is treatedas a single bar of equivalent area. The equivalent size ofa bundle is the size of a single round bar having an areaequal to the area of the bundle.

I t i s some t imes advan t ageous t o bund l e t en s i l e o rcompressive reinforcement with two, three or four bars incontact to provide for better placing of concrete around andbetween the reinforcement in heavily reinforced members.Not more than four bars may be grouped into one bundleeven at laps.

No more than two bars should be bundled in one plane.Typical bundle shapes are triangular, square, or L-shapedpatterns.

4.9 Points to consider before detai l ing

Points to consider before detailing are shown in Figs. 17,18 and 19 used in conjunction with the general guidelinesgiven below.

General guidelinesstudy and be familiar with what is to be detailed, checkthat calculations, setting-out details, concrete profiles,services, concrete covers, type of reinforcement, con-crete grade required are knowndecide which scales to be usedplan drawings for content and therefore number ofdrawings requireddetermine which are secondary and which are mainbeams from calculat ions and general-arrangementdrawings; check direction of slab spans and layering ofs lab reinforcementdetermine setting out of column reinforcementconsider any difficult junctions and draw sketch detailsto a scale of 1:10 or larger to clarifycheck that beam reinforcement will pass column rein-forcementcheck beam-to-beam connections and ensure layers ofreinforcement do not clashcheck location of laps remembering maximum lengthsof bar availabledetail all beams in one direction, then beams in otherdirectiondraw sufficient sections or details to show reinforce-ment arrangement not only in simple areas but particu-larly in congested areas of reinforcementcheck wording required for t i t le boxes, notes , jobnumber and drawing number

(m) produce bar or fabric schedules, using a print of thedrawing and mark off bars as they are listed; updatedrawing with errors found during scheduling

(n) provide check prints of both drawing and schedulesfor checking by another competent person.

Notes relating to Figs. 17, 18 and 19every column bar must be retained by a l ink exceptwhere the distance between column bars is 150mm orlesscheck that where column reinforcement is bent out, e.g.top lift of column, the concrete cover will be maintainedand there is clearance for slab and beam reinforcementsecondary-beam reinforcement to have increased topcover (check with designer that this reduction in leverarm is satisfactory)

39


Column re inforcement f roma b o v e cranked ins ide.Crank 1:10

1

10Check that when column barsare cranked in they do notfoul any other re inforcement

Co

mp

res

sio

n

of

ten

sio

n

lap

50

K icker

See note 3

S e e e n l a r g e d e t a i l

2 (Fig. 18)

S p a c e b a r s

Hole for v ibrator , a l low 75mm spacefor every 300mm of beam width

Check sufficient space for slabre inforcement at correct covers

Cross t ies a t 1000 crs to l imi tf ree height of l ink to 400mm

Nominal longi tud inal lac ing bar

Check concrete cover ismainta ined to l ink

Check i f chamfers and f i l le ts arerequired. (They may af fect thecover to the re inforcement)

Fig. 17 Typical section through main beam


de

pe

nd

ing

o

n

de

sig

n

See note

If corner bar has to move to theright use smaller diameter to fit

into radius of link.

Check with designer

See 4 -7

L i n k

Spacer bars

at 1000

Check that standard radius forboth l inks and secondary beamreinforcement wi l l pass between

main reinforcement

B e a m b a r

Enlarged corner detai l

RADIUS = 2 × SIZE OF BAR FOR GRADE 250= 3 × SIZE OF BAR FOR GRADE 460 ( FOR SIZES UP TO 20 )= 4 × SIZE OF BAR FOR GRADE 460 ( FOR SIZES 25 TO 50 INCLUSIVE)

ACTUAL SIZE OF DEFORMEDBARS.

NOMINALBAR SIZE 6 8 10 12 16 20 25 32 40

MAXIMUMBAR SIZE ‘a ’ 8 11 13 14 19 23 29 37 46

Fig. 18


L i n k

41

Check that i f main bar is

displaced i t wi l l not foulany other bar

a

Check that there is suf f ic ient space between l inksto a l low concrete and a v ibrator to pass through.When calculat ing the actual space between l inksremember to add the th ickness of the returnedlegs of the link

Returned leg of l ink

With large columns i t is advisableto keep central area f ree of l inksto allow access for cleaning outformwork pr ior to concret ing

See note 2

See note 1

Check if chamfers are required. They may a f fec t the cover tothe re inforcement

• Denotes column bars from

be low

42

Fig. 19


4.10 Detailing for off-site fabrication

Internal intersectionsTop reinforcement

In na r row beam sec t i ons , i tmay be advantageous to posi-tion some bars within the slaboutside the limits of the beamin order to leave openings wideenough for the insertion of avibrator. An additional stirrupmay be required since BS 8110requires all tension reinforce-ment to be enclosed.

Bottom reinforcement

The top reinforcement in themain beam is in the form ofstraight bars that are curtailedb y d e s i g n c o n s i d e r a t i o n s .S m a l l b a r s ( 1 2 m m , s a y ) a r eused to locate the tops of thelinks in the beam cage. The topsteel in the secondary beamp a s s e s u n d e r t h e r e i n f o r c e -ment in the main beam.

Alternatively, bundled barsmay be used without any lossof lever arm.

l a p l e n g t h

The bot tom reinforcement inthe beam does not extend intothe column, and the structuralc o n t i n u i t y i s p r o v i d e d b ylacing bars of a suitable size.


External intersections

A useful method of connection if reversiblem o m e n t s , s u c h a s t h o s e c a u s e d b y w i n dl o a d i n g , h a v e t o b e t r a n s m i t t e d t o t h ecolumn, is to fit loose U-bars into the pre-fabricated beam cage.

In cases where a considerable degree of fixityis required at the end of the beam. L-barswi th t he ve r t i c a l l eg ca s t i n to t he l owercolumn are normally required. The bottomreinforcement should be taken across thec o l u m n a n danchorage.

p r o v i d e d w i t h a n a d e q u a t e

44


4.11 Schedules and schedulingScheduling is the operationtype and size, number

of listing the location, mark, off , length and bending detai ls of

each bar or sheet of fabric. When dealing with bars thecompleted lists are called ‘bar schedules’ (see pages 49 and5 0 ) . T h e b a r s s h o u l d b e g r o u p e d t o g e t h e r f o r e a c hstructural unit, e.g. beam, column, etc. In a building, thebars should be listed floor by floor.

Separate schedules should be prepared for fabric rein-forcement using the form of fabric schedule shown (seepage 00). Fabrics should be grouped together according totheir BS reference number and the size of sheet.

For cutting and bendingprovided as separate A4 s h

purposes schedules should beeets and not as par t of the

detailed reinforcement drawings. Each schedule should bea document complete in i tself , and reference to earl ierschedules by the use of such terms ‘as before’ or ‘repeat as1st floor’ should not be allowed.

Schedules are used by:

the detai lerthe person checking the drawingthe contractor who orders the reinforcementthe organizat ion responsible for fabricat ing the rein-

forcementthe steel fixerthe clerk of works or other inspectorthe quantity surveyor.

The schedules should have simple consecutive referencenumbers not exceeding s ix characters , and should becross-referenced to the relevant drawing number. Suchterms as page number, sheet number, etc., can be confus-ing a n d a r e n o t r e c o m m e n d e d . A c o n v e n i e n t w a y o fachieving this is to use the first three characters to refer tothe drawing number ( implying that the project wil l bedivided into units with a maximum number of 999 drawingsper unit), to use the next two characters to describe theschedule number (s tar t ing a t 01 and not exceeding 99schedules per drawing), and to reserve the last character forrevision letters. If an internal job number or other internalreference number is used, it is suggested that this should beincorporated in the site reference – rather than extendingthe reinforcement schedule reference.

The form of bar and fabric schedule and the shapes of barused should be in accordance with BS 4466. The preferredshapes in this Standard account for more than 95% of ther e i n f o r c e m e n t t h a t i s u s e d . I t i s p r e f e r a b l e t h a t b a r sshould be listed in the schedule in numerical order.

I t is qui te common for a reinforcement supplier toprepare separate lists using the schedule as a basis. Theselists are referred to as ‘cutting and bending lists’, and onthese, the bars are usually sorted into delivery batches bysequence of typ

It is essentiale, size and length.that the bar mark reference on the label

attached to a bundle of bars refers uniquely to a particulargroup or set of bars of defined length, size, shape and typeused on the job. This unique reference is achieved by acombinat ion of the bar schedule reference number andthe bar mark number (to comply with BS 4466, both theschedule reference number and the bar mark must appearon the label attached to the bundle of bars).

Thus the bar-schedule reference number (046 02A in theexample that follows, (note the importance of the zeros) andthe bar mark are associated, and the bar-marking systemthat fol lows is based on the assumption that the bar-schedule reference numbering system set out in BS 4466 isu sed p rec i s e ly a s de sc r ibed w i th no va r i a t i ons . Eachschedule must have a different reference number and mustrefer only to one drawing. Such terms as sheet number,page number, 1 of 8, 2 of 8, etc. and such practices asIncluding the date, the year, the draughtsman’s initials, thejob number or other internal reference as par t of thereference number must not be used with this combinedsystems of bar marking and schedule numbering. Each ofthese practices may have intrinsic merits, but they should


be abandoned in favour of a system that is universal lyapplicable and universally understood.

Correct scheduling is not possible without a thoroughknowledge of BS 4466.

The bar size is not part of the bar mark, and prefixes orsuff ixes of le t ters or other characters to describe thelocation of the bars should not be included in the bar mark.The exception to this rule is when bars of varying shape orlength are used and are described on the drawing thus:

8T20–1(a to h)–150

The bar mark given on the schedule is therefore 1a, 1b,1c....

On a small job with only a few drawings i t may beconvenient to start at bar mark 1 and carry on through thewhole job in a consecutive sequence. On larger jobs it maybe more convenient to start scheduling each drawing withbar mark 1, relying on the site to distinguish between mark1 on drawing 1 and mark 1 on drawing 2.

When top and bot tom reinforcement are detai led onseparate drawings it is advantageous to allocate a group ofbar marks for each drawing, e.g. bottom reinforcement barmarks 1–99, top reinforcement bar marks 100–199.

When it becomes necessary to revise a bar item on theschedule the schedule number should be given a revisionletter (not a number). The same letter should be written inthe right-hand margin of the schedule in line with the barmarks affected. The bar-schedule reference number wouldthen become 1201A but the bar mark would remain 63 asbefore. The revision letter to the schedule is unrelated to arevision letter on the drawing, the schedule may be revisedbut without a revision to the related drawing.

Allowances for tolerancesCover to reinforcement is liable to variation on account ofthe cumulat ive effect of inevi table small errors in thedimensions of formwork and the cut t ing, bending andfixing of the reinforcement.

All reinforcement should be fixed to the nominal covershown on the drawings, using spacers of the same nominalsize as the nominal cover. The term ‘nominal cover’ impliesa permissible negative tolerance of 5mm, i.e. the actualcover could be 5mm less than the nominal cover.

Where a reinforcing bar is to fit between two concretef a c e s ( e . g . a s i n g l e r e c t a n g u l a r l i n k i n a b e a m ) , t h edimensions on the schedule should be determined as thenominal dimension of the concrete less the nominal coveron each face and less an allowance for all other errors as inTable 12.

45

Deducation for tolerances in position of bent steel (BS 8110,clause 3.12.1.3)

overall concrete dimension deduction to determine(measured in direction of bending dimension

tolerance)mm mm

(i) 0–1000 10(ii) 1000–2000 15(iii) over 2000 20

Deduction for tolerances at endsof straight bars

(iv) any length 40

These deducat ions apply to most reinforced concreteconstruct ion, but where tolerances on member s ize isgreater than 5, 5, 10 and 10mm for the four categories,respect ively, larger deduct ions should be made or thenominal cover increased (see Fig. 26).

Bending dimension to beshown on scheduleie: Nominal member size less2 × nominal cover less anallowance for all other errors

N o m i n a l Nominalcove r cover

Concrete Concretef a c e face

Reinforcement betweentwo concrete faces

Nominal size minusallowable tolerance

Nominal size of membershown on drawing

Bending dimension to link to beshown on bar scheduleie: Nominal member size less2 × nominal cover less anallowance for all othertolerances as given above

Reinforcement Nominal cover to linkbetween twoconcrete faces

Concrete face Concrete face

Nominal member sizeminus allowable tolerance

Nominal size of membershown on drawing

Fig. 26


as given above


P a p e r w i d t h 2 1 0

1 5 25 15 12 10 12 12 15 10 15 15 15 15 15 9

5 5 5 5 5 5 5 5

30

2 0

10

5

5

23×10= 230

XY and pa r t ne rs B a r s c h e d u l e r e f :

S i t e r e f : Date prepared : Date revised :

P r e p a r e d b y : C h e c k e d b y

Totalno

Shapecode A * A * C * D * E/r*

m m m m m m m m m m

Lengthof each

Bar Type No No ofMember mark and of bars

size mbrs ineach

bar †mm

P a p e rl e n g t h2 9 7

T h i s s c h e d u l e c o m p l i e s w i t h t h e r e q u i r e m e n t s o f B S 4 4 6 6

* S p e c i f i e d i n m u l t i p l e s o f 5 m m † S p e c i f i e d i n m u l t i p l e s o f 2 5 m m



55

Paperlength297

30

20

10

Paper width = 210

15 12 9 9 9 15 9 9 12 12 12 10 18 10 10 10 10 10 8

405 5 5 5 5 5 5 5

XY and pa r tne rsSite ref : Job number 1235

Rev letter

Fabric schedule ref 0 4 6 0 4

Date prepared. 9 . 6 . 8 0 Date revised 6 . 1 0 . 8 0

Prepared by. A . B . C Checked by D . E . FChemistry block. Eastwood

BS re fe rence o r shee t de ta i l s Sheet

Fabric N o Size Pitch Length Overhangs length

mark of of† † O1 O2 " L " †

wires wires O3 O4

mm mm mm m m m m m

Schedu led fab r i c examp le

2 0 10 1 2 5 6 6 0 0 3 0 0 3 0 0 6 6

0 42 5 8 2 5 0 2 4 5 0 2 5 5 0

Designated fabric example

0 5 8 7 8 5 6 . 2

23 × 10= 230

This schedule complies with the requirements of BS 4466

Sheetwidth

"B" †

m

2.54

2 . 2

12

12

SpecialNo Shapeof code

sheets

detai ls

Bendinginstruction

38

3 7

A* B* C *

m m m m m m

1 5 0

5 0 0

dimensions

D * E/r*

mm mm

† Specified in multiples of 25 mm.


a n d / o r bending

* Specified in multiples of 25 mm.

5 Structural e lements

Gene ra l gu idance fo r t he p r epa ra t i on o f d r awings i sprovided in Section 2; more detailed guidance is providedin this Section.*

Each element described for detailing is divided into threeparts:

1. design information that the detailer needs to and hisunderstanding of the requirements (for clarity cross-references are given to the relevant clause in BS 8110although equivalent requirements may appear in otherdesign codes)

2. detailing methods3. examples of detailing (yellow pages).

*Note 1 Throughout this Section † denotes reference to clause number in BS 8110.Note 2 See BS 1192 for preferred method of showing sections and dimensions.


5.1 LAYOUTS

Layout drawings, commonly known as general arrangement drawings (or GAS) are developed over a period oftime and coordinated from dimensional information prov ided by t he a r ch i t ec t , engineer and special is ts . Thed i m e n s i o n s s h o u l d b e c h e c k e d a n d a p p r o v e d b e f o r ecommencing the detailing of reinforcement.

80

20

0

200

30

0

90 200

100

5.1.10 Methods of preparing general arrangement drawings for concrete structuresProjects vary in size and complexity. It is important toselect a scale that will enable the final drawing to be readwith clarity. Large floor areas can be spread over severaldrawings and linked and referenced by means of key plans.Local complexities, such as staircases, can be isolated andreferenced to a larger-scale drawing.

5.1.11 Information shown on general arrange-ment drawings for concrete structures5.1.11.1 On plan(a) Grid lines

T h e s e f o r m a n e t w o r kacross the job and pro-vide a convenient datumfor dimensioning and ref-erencing elements (seesubsection 2.20).

Grids usually coincidewith the centre- l ines ofcolumns; clarify if theydo not.

hb

(b)

50

30

50

co l .

BASE150

2003 B4

500 × 300

550

× 3

00

4B1

(c)

Centre-linesT h e s e o f t e n c o i n c i d ewith gr id l ines . Other-wise notate and locateb y o f f s e t d i m e n s i o n s

MILL

from nearest grid. I t isuseful to locate groups

I

of holes, pockets, isolated bases, plinths, machinery,plant, etc.

ColumnsState overal l concrete size(largest dimension first) andlocate relative to the nearestgrid lines. If the size of thec o l u m n i s g r e a t e r b e l o wfloor, show the lower profiledotted; its size will be indic-ated on the lower floor plan.

100 2 0 0

30

0

col.

h

b

h

b

3 C2

2.570

800 × 350

Where repetition occurs it 500 × 300may be convenient to add anexplanatory note , e .g . a l l columns 300 × 300 andcentred on grid lines unless noted.

(d) Nibs on columns

Dimension on plan.

Where the profilebecomes more com-plex it may be neces-sa ry t o r e f e r t o anen la rged de t a i l f o rd i m e n s i o n s . E l e -va t ions wi l l be r e -quired if the verticalextent of the nibs isn o t o b v i o u s f r o mthe plan.

(e) Downstand beamsS t a t e b e a m r e f e r e n c e( s e e s u b s e c t i o n 2 . 2 0 )a n d o v e r a l l c o n c r e t esize (h × b), both pre-ferably at the centre ofs p a n . T h e d o t t e d l i n eplots the profile of thel o w e s t b e a msoffit.

W h e r e r e p e t i -tion occurs it maybe convenient toa d d a n e x p l a n -a t o r y n o t e , e . g .all internal beams600 × 300 unlessnoted.

(f) Upstand beamsState beam reference andoverall concrete size (h ×b ) . A d d l e v e l t o t o p o fbeam and/or draw sectionto clarify.


50 80

S e eDETAIL 'A'

(g) Nibs and kerbson beams

47

5 4 5 0

225 BlockWALL

425 1575

Locate extent ofp r o j e c t i o n o np l a n a n d n o t a t e ,indicat ing depth.Clarify with sec-t i o n a n d / o r a d dlevels to top.

200 deep

150 175

6 0 0150

KERB150 high

(h) Bases and (150)425 225 Brick WALL

above slab onlyGROUNDSLAB

( j ) Suspended slabs

ground s labsNotate and indi-cate thickness.

NIB2.150

(500)

BASEType 'A'

Show direct ion of span andindicate thickness of slab, pre- 160

ferably near the centre of thepanel.

one-way spanning

two-way spanningcantilever

175

150CANTILEVER

tapered cantilever(add section)

(k) WallsState wall thicknessand its location rel-ative to the nearestd a t u m . I f t h e w a l lsize under is differ-e n t t h e n s h o w i t sp r o f i l e d o t t e d ; i t sthickness will be in-dicated on the lowerfloor plan.

105

95

15

0

15050 STEP

(l) Dwarf walls andparapets 350

PARAPET31.100

32.500

150.000

T h e s e w a l l s a r eviewed just abovetheir top and nota t e d . S e c t i o n sand /o r l eve l s a r eadded for clarity.

150 to 200CANTILEVER

(m) Loadbearingwalls(i) Indicate wall

material andt h i c k n e s sand its loca-t ion relat iveto the nearestdatum. Supporting walls under to be shown dottedand notated on the lower floor plan.

(ii) Locate andidentify wallsabove floorsthat are notcontinuouslysupported bywalls below.

General ly non-loadbearing part i t ions are not shown onstructural drawings.

(n)

(p)

LevelsT h e s e p r o v i d e a v e r t i c a l d a t u m a n d s h o u l d b edisplayed prominently at each level as appropriate,thus:

(i) top level of concrete,e.g. foundation base

(ii) top of structural floorlevel

(iii) top of finished floorlevel

(iv)

( v )

(vi)

top of existing level

a r r o w i n d i c a t e s d i r e c -t i o n o f d o w n s l o p e s a n dfalls and up slopes

125.000

SFL

150.050

F F L

150.075

E L

150.075

50 FALL

UP

LEDGE

245.750arrow indicates level totop surface as noted.

Steps in levelLines at a change in level canb e q u i c k l y i d e n t i f i e d b yadding sectional hatching tothe plan as follows:

s t e p o ntopsurface

splay on slab soffitshown dot ted

l o c a t e s t e p s t o t h eneares t datumappropriate.

45° splayunder1002000


95 1

50

150

150

(q)

Description of

JOINT

5 2 5 0

(r)SFL

1.500

600

STAIR 1See drg..........

(s)group

4 5 0 175 2 0 0

250

170

17

5 350175 × 100

2 no. HOLES100 × 100

160

OPENING7.500 Bottom.

150 high

(t)

JointsAny special joint required by the engineershould be located andnotated on plan with abold chain-dotted lineand supported by a section if required forclarification.

StairwellsOn floor plans, complicated areas suchas s tairwells are often referred to anenlarged layout drawing. The directionof s tair f l ights should be indicated asthough s tanding on the subject f loor .The area referred to is crossed.

HolesAll should be drawn

holes with across.

(iii) holes through beams or walls.Indicate level to bottomof hole, e.g.

1250 350

window sill. x 500

Show cross 9.750dotted ifbelow the 500 500section, e.g.downstandbeam.

An elevation will be requiredif holes are too complicated toshow on plan.

Pockets and recesses(i) similar to holes but

iden t i fy a r ea wi thd i agona l on ly andnotate

(ii) small pockets sucha s t h o s e u s e d f o ra n c h o r b o l t s a r eusually identified bya l a r g e d o t a n dnotated.

5.1.11.2 On sectionSections are drawn to clarify the plan and provide mainlyvertical information:

(a)

(b)

General cross-sectionsThese provide a general impression of the ent i revert ical s t ructure. Major dimensions and levels areshown. Complicated profiles etc. can remain undimen-sioned – these will be shown by local section preparedwith the floor layouts. The elevation of backgroundwalls and columns are often included to increase theimpression.

Local sectionsShow al l vert ical dimen-s i o n s a n d l e v e l s . S o m eh o r i z o n t a l d i m e n s i o n sadded will help to t ie inwith the plan. Local sec-t i o n s a r e p r e f e r a b l yplaced alongside the plan.

5.1.11.3 Fixing in concreteWhere ancil l iary f ixings are l ikely to affect the properlocation of the reinforcement they should be located on thedrawings. Where extensive, these fixings may be indicatedon ly and r e f e r r ed t o o the r d r awings fo r l oca t i on e t c .Consideration shoud also be given to any extra reinforce-ment required.

175 2 0 0

75

pkt.

350

25 deep

325

350

4 no. pkt.125 x 125

170 275100 deep


to scale, sized andlocated to the neareast datum:(i) hole through

holes with

(ii) groupsofholes.

80

5.1.20 Example of general-arrangement drawing for concrete structures

7th FLOOR LAYOUT

All columns 300 x 300 and centred on grids, unless noted.

IStructE Detailing Manual55

5.2 SLABS

5 2 . 1 0 D e s i g n i n f o r m a t i o nThese data are output from the approved calculations foreach span which should indicate:

(a) For slabs designed and detailed in accordance with BS8110 simplified rules (for bar curtailment rules etc, seeclause 5.2.11.1)

reinforcement related to the slab thickness and rein-forcement type (see Table 15)

Minimum reinforcement is generally provided as:

(i) distribution bars in B2 layer for 1-way slabs(ii) lacer bars to top main bars.

(i) concrete grade to determine laps, durability, etc.(ii) design method assumed, i.e. 1-way, 2-way, flat

slab, etc.(iii) type of support assumed, i.e. simple, restrained,

cantilever, etc.(iv) cover for top T1 and bottom B1 bars (see clause

5.2.22. 1a)(v) orientation for layering bars, e.g.

or

(vi) type of reinforcement and any size restrictions(v i i ) a r ea o f ma in s t ee l f o r bo t t om and t op ba r s

(required) As(mm 2 /m) or , preferred type/sizeand pitch (actual)

(viii) special requirements, i.e. data for tie, torsion,shear bars, trimming of holes, internal radius ofbends i f non-standard, e tc . Provide sketcheswhere appropriate .

(b) For other slabs, in addition to above:(ix) location of bar curtailments, if non-standard (for

BS 8110 bar curtailment general rules see clause5.2.11.2)

( x ) l o c a t i o n o f c o m p r e s s i o n b a r s i f r e q u i r e dA's(mm2 /m)

(xi) width of non-standard width column strips in flatslabs

(xii) lap lengths required if non-standard(xiii) any special requirements, i.e. data for column

drops

(c) Summary of slab calculationsFor convenience it is often possible to rationalize mainreinforcement areas/type, size and pitch. These can besummarized for the detailer by marking up a copy oft h e r e l e v a n t g e n e r a l , a r r a n g e m e n t d r a w i n g , u s i n gcoloured pencils to differentiate top from bottom bars,or using the abbreviat ions B1, T1, e tc . (see clause5.2.22. 1a), i.e.locate As bottom on panel thus:

B1 B1

1000 mm2/m T16 @ 200locate As top on panel thus: or

T1 T1

1300mm2/m T16@150

The additional data outlined in (a) or (b) above can benoted in the margins or sketched on plan to suit.

(d ) Minimum reinforcementThese data are not always provided in the calculations,but are based on minimum or nominal percentages of


52.11 Design code requirements5.2. 11.1 Simplified rules for bar curtailments in slabs(BS 8110 , c lause 3 .12 .10 , F ig . 3 .25)Assumptions:

a. Slabs are of approximately equal span (within 15%) d.b. Slabs support substantially uniformly distributed loadsc. Check that top slab reinforcement satisfies beam flange e.

requirements (3.4.1.5†)

(i) simple end support, no restraint

T i e f o r c e r e q u i r e m e n t s s h o u l d a l s o b e c o n s i d e r e d(3.12.3†)Consider torsional effects in 2-way slabs where cornersare prevented from lifting (3.5.3†).

(ii) discontinuous edge (flat slab)

(iii) restrained end support (iv) continuous internal support


(v) cantilever

5.2.11.2 General recommendations for bar curtailments in slabs (clause 3.12.9.1†)

5.2.11.3 End anchorage alternatives based on BS 8110: general recommendations (3.12.9.4†)

Simply supported ends(a) straight bars in bottom (b) bent bars in bottom

Restrained ends

(a) U-bars in top (b) U-bars extended (c) 'trombone' bars (d) L-bars in top

5.2.11.4 Tie provis ion ( internal and/or peripheral)(3.12.3†)Ensure that any reinforcement specified for stability ties iseffect ively continuous by lapping and/or anchoring asnecessary.


Table 15 Minimum tension reinforcement in slabs (3.12.5.2.)†Table3.27

Spacing of minimum tension reinforcementflange h

F y = 460N/mm 2 b = 1000 Fy = 250N/mm2

0.13% bh 0.24% bh 0.15% fl .h(both directions) h (both directions) (across flanged beams)

bar nominal size, mm bar nominal size, mm bar nominal size, mmslab s l ab

8 10 12 16 d e p t h 8 10 12 16 depth 8 10 12 16

pi tch, mm mm pi tch, mm mm pi tch, mm

200 200 100 200 200 100 200 200

300 300 125 150 250 300 125 275 300

250 375 375 150 125 200 300 375 150 225 350

200 300 450 175 100 175 250 450 175 175 300 400

175 300 400 200 150 225 400 200 150 250 350

150 250 350 225 125 200 350 225 150 225 300

150 200 300 250 125 175 300 250 125 200 300

125 200 250 500 300 100 150 250 300 100 175 250 400

100 150 250 400 350 125 225 350 150 200 350

150 200 375 400 100 200 400 125 175 300

100 175 300 500 150 500 100 150 250

Note: The above chart is not applicable to water-retaining structures.

Table 16 Maximum spacing of tension bars in slabs

(a) In all cases, maximum spacing not to exceed the lesser of 3d or 750mmNormal cracking controlled using following rules:(b) Fy = 250, maximum slab depth = 250mm(c) Fy = 460, maximum slab depth = 200mm(d ) A s < 0 .3% b d

(3 .12 .11 .2 .7† )

(e) When A s = 0.3 → 1.0% bd limit bar spacing to value from Table below% re inforcement

(f) When A s > 1% bh use appropriate spacing (mm) from Table below

Spacing of bars according to % redistribution

% moment to or from section considered

f y – 3 0 – 2 5 – 2 0 – 1 5 – 1 0 0 + 1 0 + 1 5 + 2 0 + 2 5 + 3 0

250 210 225 240 255 270 300 300 300 300 300 300 c o

460 115 120 130 135 145 160 180 185 195 200 210

Note : I f % momen t r ed i s t r i bu t i on unknown a s sume (–15 ) a t suppo r t , ( 0 ) f o r span (3 .12 .11 .2 .8 )

5 . 2 . 2 0 D e t a i l i n g5.2.21 Methods of detailing slabsThere are several techniques possible for detailing slabs —choice perhaps depending on the size of the project, itscomplexity and the degree of panel repetition. Normallythe concrete profile dimensions are abstracted from therelevant general-arrangement drawings. These togetherwith the calculations should be at their final stage beforecommencing the detailing stage.

5.2.21.1 Combined top and bottom reinforcement(a) Multipanels

P r e p a r e c o n c r e t e p r o f i l e s f r o m t h e g e n e r a l -arrangement drawing to a suitable scale, usually 1:50.Identify similar panel types, and detail bottom then topreinforcement for each different panel type. Largefloors may spread over several drawings linked by keyplans.

(b) Unit panelsSimilar to clause 5.2.21.1a, but different panel typesare identified and drawn as single panels linked by keyplan. Method particularly flexible when panel typesrepeat throughout a job. Adjacent panel reinforce-ment should be carefully coordinated.

5.2.21.2 Separate top and bottom reinforcementUseful when detailing fabric or when the reinforcement isvery complicated. Top and bottom reinforcement is sepa-rated for clarity and drawn onto two identical outlines,preferably on the same drawing. Sui table instruct ionsshould ensure that these separate layers are constructedtogether .


5.2.21.3 Tabular method bar type/

Combinat ions of informa- mark s ize e tc .

tion such as bar mark, bar 63 T10type and size, bar pitch, etc.can be scheduled alongside etc e tc

the detail. This will tend toreduce congestion on the drawing and improve checkingp r o c e d u r e s , c o m p u t e r m e t h o d s a n d t h e w o r k o f t h equantity surveyor Each typical bar should be identified onthe drawing by its bar mark and bar layer (see clauses5.2.22.1 and 5.2.34 example.)

20T10-63 150 T1

20T10-63 150 T1

Stg.63 64

Alt .

5.2.21.4 Computer methodsWhere drawings are produced fully or partly by computerg r a p h i c s t h e m e t h o d o f p r e p a r a t i o n a n d p r e s e n t a t i o nshould follow standard principles wherever possible.

5.2.22 Bar detailing on slabs5.2.22.1 On plan

SE DRG

s.o.p

(a) Locating layers of reinforcementReinforcement is f ixed in layers s tar t ing from thebot tom of the s lab upwards and bar marks shouldpreferably follow a similar sequence of numbering.Notation is as follows:

(i) abbreviation fortop outer layer T1

T2 T1 T2

(ii) abbreviation fortop second layer

(iii) abbreviation forbottom second layer B2

T 2 e .g .

B1 B2 B1

(iv) abbreviation for bottom outer layer B1

Note: Repeat this sketch on each relevant drawing for clarity and presentation.

(b) Typical bar and indicator lineGenerally each bar mark is represented on plan by atypical bar drawn to scale, using a thick line. The bar ispositioned approximately midway along its indicatorline, the junction highlighted by a large dot. The firstand last bars in a zone of several bars are representedby short thick lines, their extent indicated by arrow-heads.

Bends or hooks, when they occur at either end of thetypical bar are represented by a medium dot or similar

(i) one bar only 1T10-63-T1

(ii) two bars 2T10-63-150T1

(iii) a zone of three or more bars20T10-63-150T1

( i v ) m u l t i p l e z o n e s , s h o w i n gsimilar marks in each zone,with quantities indicated inbrackets

20T10-63-150T1

(12) (8)

6 3 6 4(v) multiple zones,

showing 12T10-63-150T1d i s s i m i l a r m a r k s i n e a c hz o n e 8T20-64-200T1

General ly the ‘cal l ing up’ of bars is located at theperiphery of the detail on an extension of the indicatorline, as shown above.

(vi) when space is restricted‘calling up’ can be writ-ten within the zone of theindicator line, or in ex-treme cases:

(vii) written along the bar it-self

(v i i i ) ins t ruc t ions to s taggerbars of same mark

(ix) instructions to alternatebars of different mark

(c) Bars detailed ‘elsewhere’ are shown asa thick dashed line

(d) Bars set out from a radius in a ‘fan’zoneThe indicator line can be located on adatum radius for measuring the pitchof the bars . Locate end of bars todatum.

(e) Bars of varying length in a zoneE a c h b a r i n t h e z o n e i sgiven the same bar markbut a different suffix, be-ginning with ‘a’. The bars c h e d u l e w i l l a l l o c a t ed i f f e r e n t b a r l e n g t h s t oeach suffix as appropriate.

(f) Bars in long panelsTo simplify the ‘callingup’ of strings of bars invery long panels , e .g.distribution bars in one-w a y s l a b s , i d e n t i c a lb a r s o f a c o n v e n i e n tl eng th can be l appedfrom end to end of thepanel . State minimumlap. The use of randoml e n g t h b a r s i s n o t r e -commended.

(g) Cranked and bent barsThese are sometimes, for 6 3c o n v e n i e n c e , d r a w n o nplan as though laid f lat .H o w e v e r , c o n f u s i o n o n

64 Alt.

site can result if some ofthese bars are required to be f ixed f la t and someupright . Sect ions and notes should be provided toclarify this method if used.

(h) Fixing dimensionsD i m e n s i o n s ( m m ) a r e r e s - t r ic ted to those required by 1750the steel-fixer to locate barsnot already controlled by endcovers . Dimension l ines arethin lines terminated by shortobliques.

3×8T10-63- 150 B2

min. lap 300


f

5.2.22.2 In section — drawn where required to clarifythe fixing(a)

(b)

(c)

B a r s i n e l e v a t i o n a r e r e p r e -sented by thick line with markindicator.First and last bars in a zone areindicated by a dot in section withappropriate mark.Curtailed bars are identified bys h o r t 3 0 ° o b l i q u e s w i t happropriate mark. If congestedclarify ends with pointers.

64

63

22

3

5.2.23 Other requirements for slabs5.2.23.1 Special notes for slabsIn addition to standard notes for reinforcement drawings(see subsection 2.8) the following note should appear on allslab drawings:

(a) Cover to outer reinforcement: B1...T1...end...(b) Bar layer notation: top outer layer T 1

top second layer T2bottom second layer B2bottom outer B1

5.2.23.2 Chairs and spacersChairs support the top reinforcement . Where specif ied,t r a d i t i o n a l b e n t c h a i r s o f s h a p e c o d e 8 3 s h o u l d b escheduled using the following guidelines:

(a)(b)

(c)(d)

(e)

bar size for slab less than 200mm thick — 10mmbar size for slab greater than 200mm thick — 12mmminimum.location within panel — along periphery of 0.1 spanadd i t i ona l l oca t ion fo r f l a t s l ab — a long in t e r io rsupportsspacing of chairs (and spacers) — 1000mm.

The bottomlayer is generally supported from the deck byplastic or concrete-block spacers selected to provide theapp rop r i a t e conc re t e cove r . Fo r more comprehens iveinformation concerning chairs and spacers, see Section 6.

5.2.(a)

(b)

23.3 Trimming of holes in slabsWhere holes, or groups of holes are considered to be ofstructural s ignif icance ( i .e . in f lat s labs, e tc . ) , thedesign data should indicate any special reinforcement.Where holes, or groups of holes are considered to bestructurally insignificant,apply:

t h e n t h e f o l l o w i n g r u l e s

(i) minimumunsupportededge distance =width of hole w 1

(ii) maximum widthof isolatedopeningmeasured atright-angles tospan = 1000

(iii) maximum lengthof isolatedopeningmeasuredparallel to span =0.25 span lx

(iv) maximum total width (w 1+w2+w3) of multipleholes measured at right-angles to the span lx =0.25 span ly

(v) small isolated holes with sides 150mm or less cangeneral ly be ignored structural ly. Signif icantholes should be drawn to scale and shown on thereinforcement drawing.

(vi) larger isolated holes with sides 500mm or lessei ther:

d i s p l a c e a f f e c t e d b a r sequally either side of hole,p r o v i d e d t h a t r e s u l t a n tspacing does not exceedt h e v a l u e s s h o w n i nTables 15 and 16.or:

cut or slide back affectedbars to face of hole. Com- p e n s a t i n g b a r s o f e q u a larea should be providedto trim all sides.Trimmers should extend am i n i m u m 4 5 Ø ( n o m i n a lanchorage length) beyondthe hole.

(vii) large isolated holesw i t h s i d e s ( 5 0 0 -1000)mmTreat as (vi) above,but in addition trimt o p o f h o l e s w i t hsimilar bars. If deptho f s l a b e x c e e d s250mm, provide di-a g o n a l r e i n f o r c e -ment of similar areai n t o p a n d b o t t o m ,b u tconsideration should be given to the congestionof multiple layers.

(viii) groups ofholes withinboundary of500mm orlessTrim assingle holeusingmethodsdescribed in( v i ) a b o v e .Bars shouldpassalongside holes where possible.

( i x ) g r o u p s o f h o l e s w i t h i n b o u n d a r y o f ( 5 0 0 -1000)mm or lessTrim as single hole using methods described in(vi) and (vii) above.


5.2.24 Shear reinforcement in slabs (where minimum 5.2.26 Fabric reinforcement in slabsdepth = 200mm) (3.5.5.3†) Table 3.17† (a) General

Generally provided by vertical links which also serve as Two-directional reinforcement can be factory welded

chairs. and fabricated into sheets to help speed f ixing andachieve economy in construction costs. BS 4466:1981defines three types of fabric:

5.2.24.1 Flat slabs (3.7.6†)

(a) Column shear heads(3.7.7.5†)

(i) A minimum of 2shear perimetersare spaced at 0.75dfrom face of column

(ii) Vertical shear legsare shape code 81(2 legs) or shapecode 85 (1 leg)spaced at amaximum of 1.5daround eachperimeter

(iii) Links can be threaded onto say T12 lacer bars toform convenient ‘ladders’ which are fixed alongside the B2 then T2 layers of slab reinforcement.This detail also ensures that adequate cover tolinks is achieved.

(b) Column drops(i) Main slab

reinforcementcarries through

(ii) Nominal mat:T12 at 300each wayDesign data to specifyo t h e r

Alternatively, consider the use of fabric in these regions(see subsection 2.6)

T1

B1

(ii)

52.25 Torsion reinforcement in restrained slabs(3.5.3.5†)

5.2.25.1 At corners (2 discont inuous edges, bothsimple supports)(a) Torsion

reinforcementrequired topand bot tom.

(b) Gross arearequired = 0.75 ×maximum A s spanbot tom each wayin both top andbot tom.

(c) Extent of torsion bars = 0.2 × shorter span.


(i) Designated (standard mesh) fabric — see Tables,Section 3.Stock sheet sizes are 4.8 × 2.4m; these can bereduced by cutting to suit. Wire sizes range up to1 2 m m w i t h s t a n d a r d 1 0 0 / 2 0 0 m m m e s h e s .Peripheral wires are welded at ½ pitch from theedge of the sheet.Scheduled (non-standard) fabricWire sizes (maximum 12mm) and sheet sizes canbe varied. Wire pitches must remain constant butmay be non-standard. Wire projections at edges

(iii)may vary.Detai led (purpose-made) fabricT h e s e s h e e t s c a n b e s p e c i f i e d u s i n g s t a n d a r dreinforcing bars. These bars can be set at varyingpitches and edge projections. Sheet sizes can varywith due considerat ion given to handl ing andtransporta t ion.

All fabrics can be bent to most BS shapes. However, ensurethat redundant cross-wires do not inhibi t f ixing. Thesewires can be eliminated by specifying purpose-made fabric.For further guidance consult the manufacturers of fabric.

(b) Suspended solid floor constructionFor clar i ty on plan i t is recommended that the topsheets of fabric be drawn separately from the bottomsheets , preferably on the same drawing. Fabric isidentified by a chain double-dashed line.(i) Fabric detailing on plan. Each individual sheet is given a mark

number and related on plan to theconcrete outline.Indicate thedirection of themain re inforcementand its layer notation.Wherever multiple sheetsof identical marks occurthey can be combined asshown.

Areas of reinforcementcan be increasedby double ‘layering’.

main

T1

T3

Also consider thepossible advantages of‘nesting’ the two sheetsto maximize the lever arm.

main

B2

Similarly ‘nesting’ whenmain

main steel is required T1in two directions,crossing at 90º. T2

Structural mesh type ‘B’ is often specified forsuspended slabs, possibly with the addit ion ofloose bars. With reasonable production runs, con-sideration should be given to specifying ‘purpose-made’ fabric . For each fabric mark indicate i tsreinforcement in a table alongside the plan. Mini-mum reinforcement requirements are shown inTable 15.

lap

(c) Voided-slab construction

(d)

A nominal designated fabric is normally placed withinthe topping of t rough and waff le- type f loors . Theextent of the fabric is shown by a diagonal on the plano f t h e r e i n f o r c e m e n t d r a w i n g a n d t h e f a b r i c t y p escheduled as gross area in m2 by adding a suitable per-centage to the net area of the floor to allow for laps. Forordering purposes, the contractor should translate thisgross area into the quantity of sheets required to suithis method of working. Where more comprehensivedetailing of fabric sheets is required refer to clause5.2.26a.

Ground-slab constructionThe presence of fabric reinforcement can be indicatedby a sketch and a prominent note on the drawing. Thiscan be the general-arrangement drawing (in straight-forward cases.) The note should include type of fabric,location within the depth of slab and mini-mum lap requirements. A typical section toclarify this construction should be included.The fabric type is scheduled as a gross area byadding a suitable percentage to the net areaof slab to allow for laps. For ordering pur-poses, the contractor should t ranslate thisgross area into the quantity of sheets required to suithis method of working. Where more comprehensivedetailing of fabric sheet is required, refer to subclause5.2.26(a).

(ii) Laps in fabricThe need for lapsshould be kept to aminimum and, whererequired, should belocated away fromregions of high tensileforce. Allow sufficientclearance toaccommodate any‘multi-layering’ ofsheets at laps,reducing these 3 sheets lapoccurrenceswhere possible by 2 sheets lap‘staggering’ sheets.Show lap dimensions on plan and/or indicatem i n i m u m l a p r e q u i r e m e n t s i n a n o t e o n t h edrawing. Minimum laps are required to preventcracks caused by secondary stresses. Explanatorynotes and Tables of lap lengths for welded fabricare given in Appendix 3B.


lap

lap

5.2.30 Examples of detai l ing

5.2.31 Typical one-way spanning slab



5.2.32 Typical ribbed-slab panel

17 R 10-12 300

17 R 8-13l inks 17 R 8-10-300 links


5.2.33 Typical flat-slab panel


F ix i ng i n fo rma t i on

5.2.34 Typical flat-slab panel (tabular method)

Layer - Pitch (mm) MK Type/size No.bars Layer - Pitch(mm) MK Type/size

T 2 5 7 T2 2 0 0 – 9 – T12

T25 9 2 5 0 – 10 – T12

T 2 5 6 2 0 0 – 11 – T 2 5

T25 3+3 2 5 0 – 12 – T16

T 2 5 3+3 T1 175 – 13 – T 2 5

T20 10 250 – 14 – T16

T 2 0 10 175 – 15 – T25

T20 6 + 6 2 5 0 – 16 – T12

No.bars

18

8 + 8

6+6

15

7

B1 175 – 1 –

2 5 0 – 2 –

175 – 3 –

B2 2 0 04 –

5 –

6 –175

7 –

T2 2 0 0 – 8 –

8

6

3 + 6


5.2.35 Typical flat-slab panel showing fabric reinforcement

PART PLAN –BOTTOM FABRIC+ BARS

PART PLAN –TOP FABRIC

Fabric

MK Type Main Secondary

101 B1131 T12 e 100 T8 e 200

102 A252 T8 e 200 T8 e 200

103 Detailed T12 e 150 T8 e 200

104 Detailed T16 e 150 T8 e 200


5.3 COLUMNS

5.3.10 Design informationThese data are output from the approved calculations foreach column type and should indicate:

(a) General(i) concrete grade to determine laps, durabil i ty,

etc.(ii)

(iii)cover requirements to vertical bars or linkstype of reinforcement and any size restrictions

(iv) required area and distribution of main verticalbars A sc (mm2) or preferred actual type/size, andlocation

(v) kicker height, otherwise assumed as 75mm(vi) state lap length requirements at column splices

and whether tension or compression(vii) state link type/size and pitch otherwise assumed

to be as code requirements, see below, also Table17

(viii) any special requirements.

Summary of column calculationsFor convenience and simplicity it is often pos-sible to rationalize similar reinforcement areas/type, size and location:

For example, these can be summarized at theend of the calculations as columns – reinforce-ment types A, B, etc . Mark their locat ion onc o p y o f t h e r e l e v a n t g e n e r a l - a r r a n g e m e n tdrawings.

5.3.11 Design code requirements(a) Main vertical reinforcement

(i) Minimum area — 0.4% of cross section(3.12.5.3† ) Table 3.27†

(ii) Minimum size of bars — 12mm(iii) Minimum number of bars — no. in rectangular

columns(iv) Minimum number of bars — 6 no. in circular

columns(v) Maximum area if vertically cast — 6% of cross-

section (3.12.6.2†)(vi) Maximum area if horizontally precast — 8% of

cross-section (3.12.6.2†)(vii) Maximum area at laps — 10% of cross-section

(3.12.6.2†)(vii i) Minimum overall jog-

gle offset = 2 Ø + 10%tolerance

(ix) Minimum joggle length= 1 0 × c e n t r e - l i n eofset or 300mm mini-m u m

(x) A l low 75 c l ea r ancea b o v e l o w e r b a r t ostart of joggle for toler-ance


(b) Horizontal links( i ) M i n i m u m s i z e — ¼ s i z e o f

largest vertical bar (3.12.7.1†)(ii) maximum pitch — 12 × size of

smallest compression bar (seeTable 17).

(iii) all vertical corner bars or groupsto be tied by links at minimum135°. (3.12.7.2†)

(iv) al ternate outer vert ical bars orgroups should be t ied by l inks3.12.7.2†)

(v) however, outer vert ical bars orgroups, should be tied if spacingbetween them exceeds 150mm.(3.12.7.2†)

(vi) circular links or spiral reinforce-ment provides adequate restraintin circular columns. (3.12.7.3†)

(c) In sect ion, the length of the longerside should not exceed 4 × length ofthe shorter side. (3.8.l†)

Table 17 Column link data

nominal sizeof vertical minimum size of links maximum pitch

bars of linksmm mm mm

12 6 (8 preferred) 125



25 8 300

32 8 * 375 often

40 10 475 reduced

50 16 600 to 300* Reduce pitch of links to 200 at laps when cover is less than 1½ × largest vertical barsize (3.12.8.12 )

5 . 3 . 2 0 D e t a i l i n g5.3.21 Methods of detailing columnsMost columns with straightforward profiles are prepared intabular form, especially for the larger jobs. Alternatively,columns can be shown in ful l e levat ion. Normally theconcrete profile dimensions are abstracted from the re-levant general-arrangement drawings. These, togetherwith the calculations, should be at their final stage beforecommencing the detailing stage.

5 . 3 . 2 1 . 1 C o l u m n s c h e d u l e sThe elevation is prepared in economical tabular form, theconcrete profile appearing only in the section.

71


Each column type is sche-d u l e d , i n d i c a t i n g s t o r e yheight, floor levels, kickerheights and depth of hori-zontal member. The vert i -cal reinforcement and linksare added to the scheduleand bar mark location iden-t i f i e d f r o m a m i d - s t o r e yheight sect ion. Addit ionalsect ions may be added fors p e c i a l f e a t u r e s . C o l u m nstarter bars cast with and projecting from other members,e.g. bases, should be detailed with those members.

5 . 3 . 2 1 . 2 C o l u m n e l e v a -t ionsConcrete profi les are ele-vated from at least one sided e p e n d i n g o n t h e i r c o m -p l e x i t y a n d p r e f e r a b l ydrawn looking from a con-sistent direction. Main ver-tical and link reinforcementis added, with sect ions toclarify the fixing.

5 . 3 . 2 1 . 3 C o l u m n / b e a m i n t e r s e c t i o n sOf ten t he mos t c r i t i c a l de t a i l s on a j ob w i l l be t hecolumn–beam junctions. Careful thought should be givenat an early stage to the arrangement of bars. Preferably onedetail solution should be consistently followed throughoutthe job.

(a)(ii) In the elevated form bars

a r e r e l a t e d t o t h e c o n -c re t e p ro f i l e s . Ba r s a r egeneral ly ‘cal led-up’ onindicator lines.

(b) Links

(b)

The simplest solution is toal low the column bars torun through the beam atconstant cover. The trans-verse beam reinforcementis detailed to avoid thesebars. The lower end of thevertical bar is joggled toaccommodate the splice with the lower member.

Alternatively, the top endof the vertical bar is jog-g l ed to avo id beam ba r sa n d / o r t o a c c o m m o d a t ethe splice above. Howev-e r , t h i s r e d u c e s t h e m o -ment capacity of the col-u m n a t t h e k i c k e r . T h i sdetail is also useful whent h e c o l u m n a b o v e d e -c rea se s i n s i ze by up to75mm, say.

Gene ra l ly the sp read o f l i nks i s i nd ica t ed by anindicator line terminated by arrowheads. The links areprovided to restrain the vertical bars from buckling.Generally the top link terminates at the soffit of theslab for peripheral columns, or a t the soff i t of theshallowest beam for internal columns. Mild steel linkswith their s tandard 2d internal bend radius al lowvertical corner bars to fit more closely into corners.

(i) single links

W h e n t h e r e a r e l a r g ereductions in size of thecolumn above, the stepbetween faces can be-come exces s ive fo r abar to joggle. Usuallythe vert ical bar is ter- m i n a t e d w i t h i n t h e b e a m a n d a s e p a r a t es t a r t e r b a r p r o v i d e d .These s tar ter bars areprovided with links tied into the lower column bars toalign them to lap with bars in the offset column above.For bars with top bend, allow top clearance for beamreinforcement (say, 100mm cover).

(ii) multiple links

5 . 3 . 2 2 . 2 O n s e c t i o nGenera l l y s ec t i ons a r e d r awn a t m id -storey height looking down. Sections arepreferably drawn to a sui table scale toclarify the fixing of the links and to locatethe vertical bars. Reinforcement in nibsand projections should also be indicated.Bars cut in section appear as black dotswith appropriate mark. Any star ter barsbeyond appear as open circles. Links aredrawn with a thick line.


( d ) W h e r e l a r g e b e n d i n gmoments occur at ends, it issometimes necessary to pro-vide separate bars fixed witht h e c o l u m n t o c a r r y t h e s em o m e n t s f r o m t h e f r a m i n gbeam. They of ten require al a r g e r a d i u s b e n d ( s e eAppendix A) and are difficultt o p l ace accu ra t e ly . Thesebars should be detailed witht h e c o l u m n , n o t w i t h t h eb e a m , a n d r e f e r e n c e d e x -t r emely ca re fu l ly to avo idclashes with other beam reinforcement. If structurallyfeasible a U-bar placed and detailed with the beam is apreferred detai l .

5.3.22 Bar detailing on columns5 . 3 . 2 2 . 1 O n e l e v a t i o n

(a) Vertical barsGenerally each bar mark is illustrated by a typical bard rawn a s a t h i ck l i ne i n e l eva t i on . Ba r s de t a i l ed‘elsewhere’ are shown as a thick dashed line.(i) In the tabular form jog-

gles and bends are drawnin their correct relat iveposition. ‘Calling-up’ ofbars can be written alongt h e b a r . L o o s e b a r sshould be located from af l o o r d a t u m . N o t e a n ys p e c i a l o r i e n t a t i o n o fbends required.

( c )

5.3.23 Other requirements for columns5 . 3 . 2 3 . 1 S p e c i a l n o t e s f o r c o l u m n sIn addition to standard notes for reinforcement drawings(see subsection 2.8) the following note should appear on allcolumn drawings:Nominal cover to links.....mm, unless noted.

5 . 3 . 2 3 . 2 C o l u m n h e a d sColumn head shear reinforcement is a special requirementspecified by the designer. This can be incorporated with thecolumn reinforcement or referenced and detai led as aseparate item or with the slab.



COLUMN ELEVATIONS

COLUMNS 3B, 4B (2 No)



5.4 BEAMS

5 . 4 . 1 0 D e s i g n i n f o r m a t i o nThese data are output from the calculations for each spanand the designer should indicate:

(a) For beams designed and detailed in accordance with BS8110 simplified rules (for bar curtailment rules etc. seesubclause 5.4.11.1)

(i) concrete grade to determine laps, durability,etc.

t i e

p=pi tch

b(ii) type of support assumed, i.e. simple restrained,

cantilever, etc.(iii) nominal cover requirements to links/longitudin-

al bars with proper regard for durability and fireresistance (see clause 3.3.9). Clearance shouldbe allowed for the layering of slab reinforcement(see clause 5.2.22.1) and for beam bars at thebeam/column intersection (see clause 5.4.21)

(iv) type of reinforcement and any size restrictions(v) area of main longitudinal tension bars (required)

As (mm 2 ) or , preferred type/size, with sketch(actual)

(vi) location of shear zones with dimensions fromcentre-line of supports

(vii) area of shear reinforcement in each shear zone(required) A s v (mm 2 ) or , preferred type/sizeand pitch of link legs both in elevation andsect ion, with sketch actual)

(viii) any special requirements, e.g. location of com-pression bars, torsion bars, bent-up shear bars,trim for slots and holes, tie bars, laps and criticalstresses, radius of bend, etc.

(b) For o ther beams, e.g.addition to above:

those w i th po in t l oads , i n

(ix) location of bar curtailments, if non-standard (forBS 8110 general bar curtailment rules see clause5.4.11.2). Provide bending moment diagrams ifavailable.

(c) Summary of beam calculationsWhen large areas of s imple f loor beams occur i t ispossible to rationalize main reinforcement areas/type,size including shear links. For example, these can besummarized and presented to the detailer by markingup two copies of the re levant general arrangementdrawing – one copy for east/west beams, the secondcopy for north/south beams. Top from bottom data canbe different iated by using coloured penci ls , or theabbreviations B and T.i.e. locate As bottom midspan thus:

Additional data required can be sketched or notedon the print etc.

(d) Minimum reinforcement(i) For minimum link reinforce-

ment see Table 19.( i i ) For min tension reinforce-

m e n t u n d e r v a r i o u s c o n d i -tions see Tables 21 and 22.

B e a m s w h o s e d e p t h e x c e e d s750mm should be provided withside lacers (3.12.11.2.6†)maximum pitch 250mm

minimum bar size =s b × b

f ymm. (3.12.5.4†)

where sb is the bar spacingb is the breadth of section at the point consi-dered (or 500mm if less).

locate As top support1 0 0 0 m m 2 B o r 2T25B

1600mm2 T o r 2 T 3 2 Tlocate Asv links and extent

500 mm 2/m or R8@175



5.4.11 Code requirements for beams5.4.11.1 Curtailment and areas of bars based on BS 8110 simplified rules (Fig 3.24, 3.12.10†)Assumptions:(a) Continuous spans are approximately equal (within 15% of longest)(b) Beams support dominantly uniformly distributed loads(c) Characteristic imposed loads do not exceed characteristic dead loads(d) Tie force requirements should also be considered.

(i) simply supported end (ii) cantilever end

(iii) restrained end (iv) continuous interior


5.4.11.2 Bar curtailments for beams based on BS 8110: general recommendations (3.12.9†)

Restrained end support Continuous interior support

5.4.11.3 Anchorage alternatives based on BS 8110: general recommendations

Simply supported ends (3.12.9.4†)

(a) Straight bars in bottom o r (b) Bent bars in bottom

Restrained ends

(c) L-bars in top(d) U-bars in top


Table 18 Areas of reinforcement for various link combinations

nominal

ba r

size

no. off

link

legs

areas, mm2

pitch of links (maximum 0.75d), mm (3.4.5.5.†)

6

75 100 125 150 175

2 754 566 452 378 324

4 1508 1132 904 756 648

6 2262 1698 1356 1134 972

8 3016 2264 1808 1512 1296

10 3770 2830 2260 1890 1620

2 1342 1006 804 670 574

4 2684 2012 1608 1340 1148

8 6 4026 3018 2412 2010 1722

8 5368 4024 3216 2680 2296

10 6710 5030 4020 3350 2870

2 2100 1570 1256 1046 898

4 4200 3140 2512 2092 1796

10 6 6300 4710 3768 3138 2694

8 8400 6280 5024 4184 3592

10 10500 7850 6280 5230 4490

2 3020 2260 1810 1508 1292

4 6040 4520 3620 3016 2584

12 6 9060 6780 5430 4524 3876

8 12080 9040 7240 6032 5168

10 15100 11300 9050 7540 6460

2 5360 4020 3220 2680 2300

4 – 8040 6440 5360 4600

16 6 – 12060 9660 8040 6900

8 – 16080 12880 10720 9200

10 – 20100 16100 13400 11500

2 8380 6280 5020 4180 3600

4 – 12560 10040 8360 7200

20 6 – 18840 15060 12540 10800

8 – 25120 20080 16720 14400

10 – 31400 25100 20900 18000

Check that clear distance between groups of multiple links is 60mm minimum.Maximum pitch of link legs at 90° to span = 1.0 effective depth. d (3.4.5.5.†)

200

284

568

852

1136

1420

504

1008

1512

2016

2520

786

1572

2358

3144

3930

1132

2264

3396

4528

5660

2020

4040

6060

8080

10100

3140

6280

9420

12560

15700

225 250

255 226

510 452

765 678

1020 904

1275 1130

453 402

906 804

1359 1206

1812 1608

2265 2010

707 628

1414 1256

2121 1884

2828 2512

3535 3140

1018 904

2036 1808

3054 2712

4072 3616

5090 4520

1804 1608

3608 3216

5412 4824

7216 6432

9020 8040

2830 2520

5660 5040

8490 7560

11320 10080

14150 12600

300 400

189 142

378 284

567 426

756 568

943 710

336 252

672 504

1008 756

1344 1008

1680 1260

524 393

1048 786

1572 1179

2906 1572

2620 1965

754 566

1508 1132

2262 1698

3016 2264

3770 2830

1340 1010

2680 2020

4020 3030

5360 4040

6700 5050

2100 1570

4200 3140

6300 4710

8400 6280

10500 7850


Table 19 Minimum areas of shear reinforcement

A = 0.4 b vsv

0.87fyv

m m 2

f y v , N/mm 2

150

200

225

250

bread th 275

o f 300

b e a m 325

b y 350

mm 375

400

450

500

600

750

1000

100

250 460 250 460 250 460 250

28 15 42 23 56 30 69

37 20 56 30 74 40 92

42 23 63 34 83 45 104

46 25 69 38 92 50 115

51 28 76 42 102 55 127

56 30 83 45 111 60 138

60 33 90 49 120 65 150

65 35 97 53 129 70 161

69 38 104 57 138 75 173

74 40 111 60 148 80 184

83 45 125 68 166 90 207

92 50 138 75 184 100 230

111 60 166 90 221 120 276

138 75 207 113 276 150 345

184 100 276 150 368 200 460

150

minimum area links (A s v ) at any section

pitch of links along beam(Sv) , maximum 0.75d

200

mm

250 300

460

38

50

57

63

69

75

82

88

94

100

113

125

150

188

250

250 460 250 460 250 460

83 45 97 53 111 60

111 60 129 70 148 80

125 68 145 79 166 90

138 75 161 88 184 100

152 83 178 97 203 110

166 90 194 105 221 120

180 98 210 114 240 130

194 105 226 123 258 140

207 113 242 132 276 150

221 120 258 140 295 160

249 135 290 158 332 180

276 150 322 175 368 200

332 180 387 210 442 240

414 225 483 263 552 300

552 300 644 350 736 400

350 400

Note: Maximum pitch of link legs in section = l.0d (3.4.5.5.†)examples: 1. f y v = 460, b v = 400, sv = 3 0 0 . As v = 120 – U s e 2

f y v

legs T10 (157) @ 3002. = 250, b v = 500, sv = 2 0 0 . A s v = 184 – U s e 4 legs R8 (201) @ 200

Table 20 Maximum distance between tension bars Table 3.30† (3.12.11.2.3†) (3.12.11.2.5†)% Redistribution of moments

f y = 4 6 0N/mm2 – 3 0 – 2 5 – 2 0 – 1 5 – 1 0 0 + 10 + 15 + 2 0

115 120 130 135 145 160 180 185 195

57 60 65 68 72 80 90 93 97

Note: For minimum distance between bars see subsection 4.7.

+ 2 5 + 3 0

200 210

100 105


s v

∴∴

f y = 460 N /mm 2 250 300 350 400 450 500 600

web/flange <0.4 ≥0.4 <0.4 ≥0.4 <0.4 ≥0.4 <0.4 ≥0.4 <0.4 ≥0.4 <0.4 ≥0.4 <0.4 ≥0.4

m i n i m u m % 0.18 0.13 0.18 0.13 0.18 0.13 0.18 0.13 0.18 0.13 0.18 0.13 0.18 0.13

250 113 82 135 98 158 114 180 130 203 147 225 163 270 195

275 124 90 149 108 174 126 198 143 223 161 248 179 297 215

300 135 98 162 117 189 137 216 156 243 176 270 195 324 234

325 147 106 176 127 205 148 234 169 264 191 293 212 351 254

350 158 114 189 137 221 160 252 182 284 205 315 228 378 273

375 169 122 203 147 237 171 270 195 304 220 338 244 405 293

400 180 130 216 156 252 182 288 208 324 234 360 260 432 312

425 192 139 230 166 268 194 306 221 345 249 383 277 459 332

450 203 147 243 176 284 205 324 234 365 264 405 293 486 351

475 214 155 257 186 300 217 342 247 385 278 428 309 513 371

500 225 163 270 195 315 228 360 260 405 293 450 325 540 390

525 237 171 284 205 331 239 378 273 426 308 473 342 567 410

550 248 179 297 215 347 251 396 286 446 322 495 358 594 429

575 259 187 311 255 363 262 414 299 466 337 518 374 621 449

600 270 195 324 234 378 273 432 312 486 351 540 390 648 468

750 338 244 405 293 473 342 540 390 608 439 675 488 810 585

depth

o f

b e a m

m m

Table 21 Minimum areas of reinforcement, mm2 Table 3.2.27† (3.12.5.3†)

Flanged beamsweb in tension due to flexure

breadth of web. mm

Note: Rectangular section subjected to flexure: minimum % reinforcement = 0.13(use ≥ 30.4 table above)

Maximum tension/compression reinforcement = 4% gross cross-section concrete (3.12.6.1†)


Table 22 Minimum areas of reinforcement, mm2 Table 3.27† (3.12.5.3.†)

Flanged beamsflange in tension due to flexure over a continuous support

breadth of web. mm

f y = 460 N /mm 2 250 300 350 400 450 500 600

flange type T L T L T L T L T L T L T L

minimum % 0.26 0.20 0.26 0.20 0 . 2 6 0.20 0.26 0 . 2 0 0.26 0 . 2 0 0.26 0.20 0.26 0.20

250 163 125 195 150 228 175 260 200 293 225 325 250 390 300

275 179 138 215 165 251 193 286 220 322 248 358 275 429 330

300 195 150 234 180 273 210 312 240 351 270 390 300 468 360

325 212 163 254 195 296 228 338 260 381 293 423 325 507 390

350 228 175 273 210 319 245 364 280 410 315 455 350 546 420

d e p t h 375 244 188 293 225 342 263 390 300 439 338 483 375 585 450

o f 400 260 200 312 240 364 280 416 320 468 360 520 400 624 480

b e a m 425 277 213 332 255 387 298 442 340 498 383 553 425 663 510

m m 450 293 225 351 270 410 315 468 360 527 405 585 450 702 540

475 309 238 371 285 433 333 494 380 556 428 613 475 741 570

500 325 250 390 300 455 350 520 400 585 450 650 500 780 600

525 342 263 410 315 478 368 546 420 615 473 683 525 819 630

550 358 275 429 330 501 385 572 440 644 495 717 550 858 660

575 374 288 449 345 524 403 598 460 673 518 748 575 897 690

600 390 300 468 360 546 420 624 480 702 540 780 600 936 720

750 488 375 585 450 683 525 780 600 878 675 975 750 1170 900

Note: For (i) Flanged beam with web in compressionor (ii) Rectangular beam in compression

Minimum % reinforcement for either if required for ULS = 0.20% (use L-column in table)


5 . 4 . 2 0 D e t a i l i n g5.4.21 Methods of detailing beamsCareful consideration should be given to the relationship ofthe beam with its column junction, including the construc-tion technique to be adopted. General-arrangement draw-ings and design calculations should be at their final stage.

5.4.21.1 Splice-bar methodThis simple method uses many straight bars and is ideal for (b)

prefabrication.links

end support top link top internal

splice bars hangers support

L or U bars splice

suitable bars

bottom bottom bottomspan bars

end span

Span and link hanger bars stop usually 50mm inside theface of the support. These bars together with the links formthe span cage, which during construction can be lifted thenlowered between supports . For cont inui ty the separatesplice bars are threaded through the vertical bars at thesupport and lap alongside the span bars in the cage. Thecover to the splice is independent of the span, allowinggreater freedom to deal with the various clearances re-quired to avoid other bars, including those from intersect-ing beams and columns. Normally it can be arranged thatcolumn bars simply run through (see clause 5.3.21.3a).

ELEVATION

ELEVATION

ELEVATION

Each beam can conveniently be detailed separately as auni t span and can be al located a ‘reinforcement- type’r e f e r e n c e n u m b e r — s i m i l a r b e a m s s h a r i n g t h e s a m ereference. For locat ion these reinforcement- type refer-ences can be added to the general-arrangement drawingalongside the unique beam reference number (see subsec-t ion 2.20) , or perhaps added to a separate key plan orseparate schedule.

5.4.21.2 Alternative methodWith this method bottom-span bars are normally lapped atthe centre- l ine of internal supports , a l though at widesupports butted bars may be more suitable. Link hangerslap with the ends of top support bars. Obstructions areavoided either by stopping or by joggling bars, resulting infewer s traight bars . Adjacent spans are often detai ledtogether in beam ‘runs’.

l i n ks top internaltop end support bars

supportbars

Critical detailing often occurs at intersections as follows:

1500

2T12-3 4 1100 2T25-45 2T25-5

2400

2 2T25-12T20-2

(a) Beams same breadth as(i) If column bars (see

Columns 5.3.21.3a)are run through thej u n c t i o n , t h e n o b -structed beam barsare s topped.

column

PLAN

(c)

(d)

( i i ) Column bars (seec l a u s e 5 . 3 . 2 1 . 3 b )can be jogg led toa l l o w t h e o u t e rbeam bars to pass,pa r t i cu l a r ly whenm e m b e r s a r enarrow.

col. PLAN

SECT.

Beams of different breadth to columnC o l u m n b a r s a r e n o r -ma l ly a l l owed to runt h r o u g h t h e j u n c t i o nand the beam bars areusual ly unaffected butthis should be checked.W i d e b e a m s w i l l r e -quire extra links along-

col. col.

side the column. SECT. or SECT.

S e c o n d a r y b e a m s s a m e d e p t h a smain beamGenerally the cover to the top beamsteel is increased to allow clearancefor the main beam and s lab rein-forcement. Bottom bars can be jog-gled over at the support.

Narrow membersC a r e s h o u l d b e t a k e n t o a v o i dcongestion, particularly at laps inbottom bars at column supports. Ifbut ted bars are unsui table , i .e . alap is required for compression orfo r t i e f o r ce pu rpose s , cons ide reither:

(i) extending joggle to lapo u t s i d e c o l u m n

or (ii) using splice bar method(see clause 5.4.21.1)

5.4.22 Bar detailing on beams5.4.22.1 On elevation(a) Longitudinal bars

Generally each bar mark is illustrated by a typical bardrawn as a thick line and related to its supports and theformwork. Bends and joggles are shown to scale wherepossible. The ‘calling up’ of bars is indicated approx-imately midway along the bar — maintaining design‘groups’ where possible, to assist checking. Ends ofcurtailed bars are identified by short obliques drawn at30° and tagged with the appropriate bar mark.

(b) Shear linksUsually the spread of l inks is indicated above theelevation with an indicator line terminated by arrow-heads.

col.

SECT.


l i n khangers

bot tom bars

end span internalspans

(i) Single zone, single links For wider beams use shape code 73End links should be a maximum of 0.5 pitch inside —which has no hooks, but anchor endsthe edge of support with minimum 8d straight beyond the

73

bend. These links can also be employed nominally rein-forced side beams, with one leg extended into slab

(ii)

300 20 R10-6-300

Single zone, multiple links

300 20 R10-6 2×20R8-7 -300

(iii) Multiple zones

If cage is to be lifted provide nominal link top closersshape code 35 — for stiffness

Combinat ions of these l inks can be employed on wider beams to suit.

35

5.4.23 Other requirements for beams5.4.23.1 Special notes for beamsIn addition to the standard notes for reinforcement draw-ings (see Section 2) the following note should appear on allbeam drawings:

nominal cover to links, mmT o p . . . . . . . . . . . . . . . . .B o t t o m . . . . . . . . . . . . . . . unless notedSides . . . . . . . . . . . . . . . . .E n d s . . . . . . . . . . . . . . . . .

Dimension all but one of the ‘gaps’ between linkzones — usually adjacent to the nominal zone —to allow some tolerance for fixing. Gaps should

5.4.23.2 Bent-up shear bars (3.4.5.6.†)

not exceed the adjacent pi tch.The f i rs t l ink isThese are occasionally used in conjunction with shear links

usually located 75mm inside the edge of support.to resist up to 50% shear force.

(a) Setting-out of a single 45° system

2 0 0225 BR12-6 12R10-8-300 8R12-6 225

BR10-7 -150 BR10-7 -150

Ensure that all corners of links contain a longitu-dinal bar, especially near the supports where barscurtail.

single shear d1

d45°

1.5 d 1.5 d 1.5 d

5.4.22.2 On section(b) Setting-out of a double 45° system

T y p i c a l s e c t i o n s a r eselected to clarify the fixingo f t h e l o n g i t u d i n a l b a r swithin the link cage, includ-ing any nibs, upstands, etc.Sections are drawn lookinglef t a t the elevat ion. Barsc u t i n s e c t i o n a p p e a r a sblack dots, with appropriatemark. Those bars beyond, ifr equ i r ed , appea r a s opencircles. If not evenly spaced,

9

5 5 5 5

76

3 4 4 31 2 2 1

5spacer

single

shear d1

45°

bars should be located from one side face. Links are drawnin a thick line with a mark indicator.

5.4.22.3 Links on sectionWhen selecting links consider the following:

Normally provide closed link shape code 6060

Open link shape code 72 allows easier accessbut check that hooks do not foul other bars

72

double shear

d

d-d1 d-d1 d-d1 d-d1

E a c h h o r i z o n t a l l e g s h o u l d e x t e n d a t l e a s t a t e n s i o nanchorage length Check radius of bend for bearing stresseson the concrete. This radius is likely to be at least 6 × barnecessitating a shape 99 bar (3.4.5.7†)

For torsion-link shape code 74 is used 74



5.4 .31 Splice-bar method



5.4.32 Alternative method


5.5 FOUNDATIONS

This subsection deals with the following types of founda-tions: l y l y

lx l x

A B

padspilecapstie beams for pilecapsstripground beamscontinuous footingsanchor or strap beamsrafts.

The methods of detailing these items, in particular tiebeams and rafts, are similar to those employed in detailingslabs and beams (see subsections 5.2 and 5.4.), but thereare certain additional considerations to take into account,and described in this subsection.

Ground f loor s labs are deal t with in clause 5.2.26d.Retaining walls are dealt with in subsection 5.6.

Caissons, cofferdams, basements, shafts, piles and dia-

Strip footings

t y p e Fabric ReinforcementBS reference

A n o n e

B C283 B

C C283 T & BA B C

phragm walls are not illustrated specifically, but can bedetailed using the principles and details in this section.

5 . 5 . 1 0 D e s i g n i n f o r m a t i o nT h e s e d a t a a r e o u t p u t f r o m t h e a p p r o v e d f o u n d a t i o ndesign calculations and should indicate:

(a) (i) concrete grade to determine laps, durabil i ty,etc.

(ii) dimensions of each foundation(iii) level to top of each foundation(iv) type of reinforcement and any size restrictions(v) required area and distribution of all reinforce-

m e n t

lacer

type reinforcement lx reinforcement ly bars starters links

A 10T20 10T20 4T16 4T32 T12-200

B 10T16 10T16 4T16 4T25 T12-200

C 10T20 15T16 4T16 6T25 T12-200

D 12T16 12T16 4T16 4T25 T12-200

E 15T16 20T16 4T16 5T25 T12-200

(vi) lap, anchorage and splice lengths(vii) curtailment of reinforcement

(viii) link type, size and pitch(ix) position of reinforcement to avoid cut-off tops of

piles

l yl y l y

A,D B C,E

l x l x l x

(x) cover requirements, bottom, sides, top(xi) position, number, size of starter bars

(xii) type and thickness of blinding(xiii) position, number and size of holding down bolts,

if any(xiv) any other special requirements(xv) type of backfill between the top of the bases and

the underside of the ground floor slab.

(b) Summary of calculationsFor convenience and simplicity it is often possible torationalize reinforcement:

(ii) For solid rafts, grillage rafts, combined or con-tinuous footings, tie beams and strap or anchorbeams, the re inforcement can be presented orsummarized for the detailer by the methods out-lined for slabs (see clauses 5.2.10c and 10d) orbeams (see clauses 5.4.10c and 10d).

5.5 .11 Design code requirements5 . 5 . 1 1 . 1 G e n e r a l(a) BS 8004

(i) For pad footings, simple strip footings, pilecaps – BS 8004: 1984: Code of practice for foundations dealsby tabulating the reinforcement for the foundation with the overall design of all types of foundations for allpad, lacer bars, column starters bars and starter types of buildings and various types of soils. It does notbar l inks, and cross referencing to prel iminary deal with the detailing of individual elements of RCgeneral arrangements for orientation of columns. foundations.

(b) BS 8110

Pad footings

type re inforcement l x re inforcement l y s t a r t e r s links

A 10T16 10T16 4T25 T12-200

B 10T20 20T16 4T25 T12-200

Pilecaps

BS 8110: 1985: The structural use of concrete containsguidelines for detai l ing individual elements of RCfoundations.

(c) CoverC o v e r s r e c o m m e n d e d b y B S 8 1 1 0 a r e s e t o u t i nsubsection 3.9. Where concrete is cast directly againstearth faces, the nominal cover should be a minimum of


75mm. Where concrete is cast against blinding con-crete , the nominal cover should be a minimum of40mm (excluding blinding).

(d) Minimum area of reinforcement (3.12.5.3†)Refer to subsections 5.2 and 5.4.

(e) Maximum area of reinforcement (3.12.6†)Refer to subsection 5.4.

(f) Spacing of reinforcement (3.12. 11†)Refer to subsections 5.2 and 5.4.

(g) Anchorage and lapping of bars (3.12.8†)Refer to Appendix 3B.

5.5.11.2 Pad footings(a) In certain conditions, i.e.

when l oads a r e sma l l o rw h e n t h e a l l o w a b l eground pressures are high,reinforcement may not berequired. In this event thedepth should be such thata line at 45° from the edgeof the supported columnor base intersects the ver-tical face of the base.

(b) In reinforced bases the arrangement of the reinforce-ment must be specified by the designer.

T h e t o t a l a r e a o f r e i n -forcement should generallybe evenly spread across thesection considered. Howev-e r , i f t h e b r e a d t h o f t h esection is greater than 1.5( c + 3 d ) w h e r e c i s t h ebreadth of the column mea-sured parallel to the sectionbreadth and d is the effec-t ive depth of the base, a tleast two-thirds of the areaof reinforcement should bec o n c e n t r a t e d i n a b a n dwidth of (c + 3d) centred onthe column (see also exam-ples below).

(c) Distribution of reinforcement in pad footingsE x a m p l e E G 1(a) If ly>1.5 (cy + 3d):

two-thirds of re inforcementspanning in lx direction to bebanded within a width of (cy

+ 3d), where d is the effectivedepth of the base.

(b) if lx>1.5 (cx + 3d):

two-thirds of re inforcementspanning in ly direction to beb a n d e d w i t h i n a w i d t h o f(cx + 3d).

Example EG2( a ) R e i n f o r c e m e n t s p a n -

ning in lx direction:

l y 1 a n d l y 2 s h o u l d b econsidered separately.

( b ) R e i n f o r c e m e n t s p a n -ning in ly direction:

Band width to be consi-dered as lesser of (cx1 +3d) and (cx2 + 3d).

Example EG3( a ) R e i n f o r c e m e n t s p a n n i n g

in lx direction:

as example EG2a above( b ) R e i n f o r c e m e n t s p a n n i n g

in ly direction:(i) bottom reinforcement

under columns:

a s e x a m p l e E G 2 babove

(ii) Top reinforcement (ifa n y ) b e t w e e n c o l -umns:

a l l r e i n f o r c e m e n tshould lie within lx2.

If lx2>1.5 (cx2 + 3d), two-th i rd s o f t h i s r e i n fo r ce -ment should lie within cen-tral (cx2 + 3d) .

5.5.11.3 PilecapsThe distribution of reinforcement for pilecaps should be asf o r p a d f o o t i n g s , e x c e p t t h a t t h e a r r a n g e m e n t o f t h ereinforcement should be specified by the designer wherethe pile centres are greater than 3 times the pile diameter.

5 . 5 . 2 0 L a y o u t o f f o u n d a t i o n s5.5.21 Foundation planR e f e r t o s u b s e c t i o n 5 . 1 f o r m o r e i n f o r m a t i o n o n t h epreparation of general arrangements drawings.

The position of each foundation will be given relative tothe grid lines. The width, length and depth will be given andthe level of the bottom of the foundation will be givenrelative to a given datum.

This information is often given in tabular form. Eachfoundation is given a distinguishing letter that will serve as across-reference for the foundation details, detailed else-where.

T h eshould

minimum allowable safe ground bearing pressurebe shown in note form on the drawing. The bearing

thickness and type of blinding should be noted.It is usual to have a separate general arrangement or

piling plan, when piling is employed. This takes the form ofa plan showing the position of piles relative to grid lines andwill contain a schedule and notes including the followingrelevant items depending upon the project:

pile reference numberdiametersafe working load of pileimposed momentimposed horizontal forcecut-off levelminimum toe levelmain reinforcementhoop re inforcementangle of rakepile positional tolerances.

It is normally stated in the piling specification what thehorizontal dimensional permissible deviation should be,but it should also be repeated on the piling plan.


5.5.30 Detailing5.5.31 Pad footings5.5.31.1 IntroductionThese can be detailed in two ways:

(i) traditional method(ii) tabular method

5.5.31.2 Tradition methodThis method in normally used when the project is small orwhen there is little repetition. Individual pad footings aredetailed usually in the form of a plan and a section. Gridl i ne s a r e shown on each de t a i l . The de t a i l w i l l g ivereinforcement information in the base, in the stub column ifthere is one, starter bars where the foundation is supportingan RC column or holding-down bolts in the case of steelcolumns.

Where kickers are specified care should be taken that thelength of the starter bar is an appropriate lap length (for thestress in the bar) from the top of the kicker and that thestarter bars do not clash with the column bars. It may bemore economical in some cases to use the bottom length ofthe column reinforcement as s tar ters . Minimum covershould be indicated. End anchorages should be avoidedw h e r e p o s s i b l e , b u t t h e i r u s e o r o t h e r w i s e s h o u l d b econfirmed by the designer.

5.5.31.3 Tabular methodWhere there are large numbers of bases and/or extensiverepetition the details can be drawn schematically and theinformation for the individual bases given in tabular form.This can save time and drawings, but care must be takenthat clarity is not sacrificed by producing tables that are toocomplicated. It is usual to draw a plan, section and enlargedstub column or column starter details, all not to scale,cross-referenced to a table.

5.5.32 Piled foundationsThese can a l so be de t a i l ed by t r ad i t i ona l o r t abu la rmethods.

5.5.32.1 Traditional methodThe notes on pad footings applyto p i l e caps w i th t he fo l l owingadditions:

The pile cut-off is usually car-r ied out with pneumatic tools ,leaving a very rough surface tothe p i l e s . Bo t tom s t ee l shou ldtherefore be detai led, such thatthe bottom of the bars is a mini-mum 75mm above the theoreticalcut-off level . The cut-off levelshould be 75mm above the bot-tom of the base.

If moment has to be transmit-ted from column to pile via thepilecap, then sufficient reinforcement from the pile shouldbe left projecting into the pilecap to transfer that moment.Care should be taken that the reinforcement does not clashwith reinforcement in the base or with starter bars in thecolumn. It should be remembered that piles are not alwaysaccurately placed and the pilecap details should allow forsuch inaccuracies.

I t is usual for pi lecaps to have horizontal loop steelaround the perimeter of the pilecap. These should be at200–300mm centres and a minimum of 12mm in size.

The designer should be consulted to check if large-radiusbends are required on the bent-up bars.

co lumn no. level base reinforcement section links startersreference off A B D C

A1, A2, A3 3 105.000 10T20-1-150 10T20-1-150 1-1 3T8-2 4T25-3

B3, B4 2 108.000 8T20-4-150 10T16-5-150 1-1 3T8-2 4T25-3

C1, C2 2 104.500 8T20-6-150 12T16-7-150 2-2 6T8-8 6T25-9

D1, D 2 2 104.500 10T20-10-150 12T16-11-150 2-2 6T8-8 6T25-9


5.5.32.2 Tabular methodThis can be successfully employed when large numbers ofpilecaps and/or repetitious details are required. The tableshould contain al l the relevant information as for padfootings plus pile-cut off levels and hoop-steel details.

‘X’ relates to lettered grids‘Y’ relates to lettered grids

column base n o . base cut-off base reinforcement sect ion links startersreference type o f f level level A B C D E

A1, A5 A 2 105.000 105.150 10T20-1-150 10T20-1-750 3T12-2-200 2-2 3T8-3 4T25-4

A2, A3, A4 B 3 105.000 105.150 8T20-5-150 8T20-6-150 3T12-7-200 3-3 6T8-8 6T25-4

B4, B5 A 2 105.000 105.150 12T20-9-175 12T20-9-175 3T12-10-200 2-2 3T8-11 4T25-4

B2, B3, B4 C 3 105.000 105.150 12T20-9-150 8T20-12-150 3T12-13-200 4-4 9T8-14 8T25-4

C1, C5 A 2 104.500 105.150 10T20-1-150 10T20-1-150 3T12-2-200 3-3 6T8-8 6T25-4

C2, C3, C4 B 3 104.500 105.150 10T25-15-200 10T25-16-150 3T12-17-200 3-3 6T8-18 6T25-4

5.5.33 Tie beams for pilecaps

When piles are used singly orin pairs it is necessary to tiethe pilecaps together using tiebeams. Piles cannot be drivenaccurately, and it is usual tospecify a horizontal permissi-ble deviat ion in posi t ion,usually 75mm, both in thespec i f i ca t ion and on thed r a w i n g s . T h e m o m e n tcaused thereby should beadded to any other imposedm o m e n t s a n d s h o u l d b e aminimum design case even ifneither moment nor horizon-tal forces exist at the bottomof columns.

The detailing of these beams will not differ significantlyfrom other beams except that the amount of cover shouldbe carefully checked for the particular ground conditions.I t i s , h o w e v e r , u s u a l t o h a v e e q u a l t o p a n d b o t t o mreinforcement, since inaccuracies can occur on any axis.

Tie beams are not normally required where pi les areplaced on groups of three or more.

5.5.34 Strip footingsThese are foundations that are con-t i n u o u s a n d w h e r e t h e l o a d s a r eapplied continuously, as in the caseof brick or blockwork or reinforced-concrete walls. The amount of rein-forcement required in s imple s tr ipfoo t i ngs va r i e s w i th t he t ype o fground on which they are placed. Indomestic building, footings are oftenunreinforced, providing the depth isadjusted such that a line at 45° fromthe edge of the brickwork intersectsthe vertical face of the footing.

9 2 IStructE Detailing Manual

Steps in strip footings, necessarywhen the ground is sloping, shouldbe in brick dimensional increments.The foundation should be lapped forat least twice the thickness of thefoundation or twice the depth of thestep, whichever is the greater.

In bad ground, top and bot tomreinforcement may be necessary, inwhich case it is better to use cages ofbar reinforcement since it is difficultto maintain fabric in position in thetop of the s lab during concret ing.Longitudinal bar reinforcement should be a minimum of12mm with 8mm links in order that cages are sufficientlyr ig id . Re in fo rcemen t shou ld be adequa t e ly l apped instepped foundations in sloping ground.

Care should be taken that the cover is adequate for thetype of ground in which the concrete is to be placed. Covershould be generous s ince the s ides and bot tom of theexcavations will be rough.

For larger strip footings, where loading is heavier or forfoundat ions for RC walls , the s t r ip foot ings should bedetailed as beams and the rules in subsection 5.4 should beapplied.

5.5.35 Ground beamsW h e n t h e u p p e r l a y e r o fground has such a low bear-ing pressure that it is incap-able of sustaining the loadsimposed on a ground floorslab, the floor slab is sus-p e n d e d a n d s u p p o r t e d o nbeams, cast in the ground.The beams are in turn supported at column positions onpad or piled foundations.

Care must be taken that adequate cover is allowed for,depending on the ground conditions, acidity, etc.

cove r i s a l l owed fo r , depend ing onground conditions, acidity, etc.

5.5.36 Continuous footingsT h e s e a r e f o o t i n g s t h a tsustain two or more col-umns, often in ground oflow bearing capaci ty andwhere the centres of thecolumns are so close that independent pad footings wouldb e s o l a r g e a n d s o c l o s e t o g e t h e r t h a t t h e y b e c o m euneconomic.

Care must be taken that adequate

In some cases depending on groundconditions, they may be more economi-cally designed, and therefore detailed,as inverted T-beams.

5 .5 .37 Anchor , s t rap orcantilever footings

These foundations are similarto combined footings, but theterm is appl ied when one ormore of the loads is positionedon the edge of the foundation,usually because of the proxim-ity of other buildings, founda-tions, etc. An internal column is used as a counterweight,and consequently, main reinforcement is required in thetop of the beam.

Aga in , t he no rma l ru l e s fo r de t a i l i ng beams ( s eesubsection 5.4) will apply, and attention should be paid tocover.

The detail at the junction ofthe column on the edge of the

U - Star ters

f o u n d a t i o n n e e d s p a r t i c u l a r U - Bars or hairpins

attention. Since the top steeli n t h e f o u n d a t i o n i s o f t e nhighly stressed at this point ,large-radius b e n d s ( s e esection 3) may be needed, andcare should be taken that the

COLUMN/BASE JUNCTlON

c o l u m n r e i n f o r c e m e n t d o e s n o t c l a s h w i t h b e a mreinforcement. It is advisable to provide horizontal U-barsaround the starter bar cage.

5.5.38 RaftsThere are several different

types of raft foundations:

piledstiffflexiblelight raftscellular

PILED RAFT

The design varies with each type, butthe common purpose of all rafts is tospread a whole system of loads over alarge area generally to give a low linear-ly-imposed load on to the ground be-low. The exception to this is the flexibleraft , which resul ts in a variable, yettolerable, imposed ground pressure.

SECTION - STIFF RAFT

SECTION - FLEXIBLE RAFT

SECTION - CELLULAR RAFTS

a) Wi th bot tom s lab b) Wi thout bot tom s lab

SECTION - LIGHT RAFT


5.5.40 Examples of general arrangement drawing for foundations

PILE SCEDULE

PILE Nos. CUT OFF L. MIN TOE L. REMARKS

1 - 8 97.825 87.000

9 - 1 5 9 5 . 5 7 5 85.000

16-19;20-27 98.075 87.000

32-38

4 2 - 5 2

29-31 97.925 87.000

28,40 & 41 97.925 87.000 RAKE 1:15


5.6 WALLS

5 . 6 . 1 0 D e s i g n i n f o r m a t i o nThese data are output from the approved calculations foreach wall type, which should indicate:

(a) concrete grade, to determine laps, durability, etc.(b ) design type assumed, i.e. plain or reinforced vertical

loadbearmg wall, propped or full cantilever retainingwall, etc.

(c) cover to outer bars each face(d) orientation of outer bars, i.e. whether horizontal or

vertical(e) type of reinforcement, and any size restrictions( f ) area of main/secondary reinforcement required As or

As c (mm 2 /m)or, preferred type/size and pitch (actual)wall faces with minimum reinforcement requirements(see tables)any special requirements, i.e. data for links, tie bars,trimming for holes, etc.

Provide sketches where appropriate, e.g.

Propped-cantilever retaining wall

5.6 .11 Design code requirements5 . 6 . 2 2 . 1 A v e r t i c a l l o a d b e a r i n gmember is defined as a wall when itslength exceeds four times its thick-ness

(1.2.4.1.†)

5.6.11.2 Walls may be either plain or reinforced:(1.2.4.7†)

(a) Plain wallsPlain walls contain either zero reinforcement or lessthan the minimum requirements for reinforced walls.Any reinforcement that is provided however is ignoredin design when considering the strength of the wall. Tocounteract possible f lexural , thermal and hydrat ionshrinkage cracks, particularly in external walls and atthe junction of internal members, minimum reinforce-ment is required. This should be provided as a mat ofsmall bars at relatively close spacings, with reinforce-ment areas expressed as a percentage of the grossconcrete cross-sect ional area. The horizontal barsshould be placed in the outer layer.

Minimum reinforcementin both horizontal andvertical directions

(b) Reinforced walls

g r a d e g r a d e250 460

1 f ace , o r 0 .3% 0 .25%½ eachface 0 . 1 5 % 0 . 1 2 5 %

Reinforced walls are considered to contain at least theminimum area of reinforcement expressed as a percen-tage of the gross concrete cross-sectional area(i) Vertical reinforcement

Minimum Asc not less than 0.4% (0.2% each face)(3.12.5.3†) Table 3.27†

Maximum Asc not to exceed 4% (3.12.6.3†)Maximum bar spacing, when As c exceeds 2%,should not exceed 16 × vertical bar size

(ii) Horizontal reinforcement(3.12.7.5†)

This reinforcement should be evenly spaced in theouter layers to minimize crack widths and containthe vertical compression bars.

Where vertical bars are in tension, particularly inretaining walls, these are sometimes placed in theouter layer to facilitate fixing and to maximize thelever arm.

g r a d e g r a d e250 460

Minimum horizontalreinforcement

1 f ace , o r 0 .3% 0 .25%½ eachface 0 . 1 5 % 0 . 1 2 5 %

The minimum size of bar should not be lessthan one quarter the size of the vertical bar andpreferably not less than 8mm diameter.

(3.12.7.4†)Cantilever retaining wall

Provide minimum reinforcement, unless shown.


(g )

(h)

Addi t iona l hor i -z o n t a l r e s t r a i n i n glinks should be pro-v i d e d t h r o u g h t h et h i c k n e s s o f t h ewall when the areao f v e r t i c a l c o m -pression reinforcement exceeds 2%. Link spacingshould not exceed twice the wall thickness in anydirection. Any unrestrained vertical bars shouldbe within 200mm of a linked bar. (3.12.7.5†)

5.6.11.3 Plain and reinforced walls in tension(3.9.3.6†)Bars should be arranged in two layers and the max-imum spacing of tension bars should general ly notexceed 150mm where Fy = 460 N/mm2 or 300mm whereFy = 250 N/mm2 (3.12.11†)


Table 23 Optimum bar spacing for varying % reinforcement and different wall thicknesses

minimumreinforcement

%

0.125

0.15

0.2

0.25

0.3

0.4

0.45

0.8

maximumreinforcement

%

2.0

4.0

bar nominal sizem m

8 10 12 16wall thickness, mm

100 150 200 250 300 100 150 200 250 300 100 150 200 250 300 150 200 250 300 350

— 250 200 150 125 — — 300 250 200 — — — — 300 — — — — —

300 200 150 125 100 — 300 250 200 150 — — — 300 250 — — — — 300

250 150 125 100 — — 250 175 150 125 — — 275 225 175 — — — 300 250

200 125 100 — — 300 200 150 125 100 — 300 225 175 150 — — 300 250 200

150 100 — — — 250 150 125 100 — 300 250 175 150 125 — — 250 200 175

125 — — — — 175 125 100 — — 275 175 125 100 — — 250 200 150 125

100 — — — — 150 100 — — — 250 150 125 100 — 275 200 175 150 125

— — — — — 100 — — — — 125 100 — — — 150 125 100 — —

Bar nominal sizemm

2 0 25 32 40Wall thickness, mm

100 150 200 250 300 100 150 200 250 300 100 150 200 250 300 100 150 200 250 300

150 100 — — — 240 160 120 90 80 400 260 200 160 130 610 420 310 250 210

— — — — — 120 80 — — — 200 130 100 80 — 310 210 150 120 100

Note: These tables can be used for plain and reinforced walls, etc. (see clause 5.6.11)


5 . 6 . 2 0 D e t a i l i n g5.6.21 Method of detailing wallsMost walls are detai led on elevat ion supplemented bysections drawn to clarify the fixing, especially at memberjunctions, openings, etc. The concrete profile dimensionsare abstracted from the relevant general-arrangementdrawings, which together with the design calculat ions,should be at their final stage.

5.6.21.1 Wall layout WALL A

When e l eva t i ng wa l l s f o rdetai l ing, the direct ion of WALL B

view should be consistent,i.e. normally viewing fromt h e b o t t o m / r i g h t e d g e s o f

WALL C

t h e d r a w i n g . W a l l s c a s tagainst an inaccessible face

Key plan

should be viewed from the Denotes direction of view

‘open’ side. A key plan isuseful particularly when the plan is complex, e.g. lift shafts,more especially if the above convention is unable to befollowed, e.g. walls ‘A’ & ‘D’.

Starter

75 Max

Slope 1:10min length

300

barsVertical

5.6.22 Bar detailing on walls5.6.22.1 On elevation(a)

(b)

Notation for layers of reinforcementReinforcement is fixed in two layers at right-angles toform a mat, normally one mat at each wall face

(i) Abbreviation for near face,outer layer Nl

(ii) Abbreviation for near face,second layer N2

(iii) Abbreviation for far face,outer layer Fl

( iv) Abbreviat ion for far face, N1

second layer F2 F2

Typical bar and indicator lineThe convention for illustrating and ‘calling up’ bars onwalls follows closely that of slab (see subsection 5.2)e.g. :

(i) A zone of similar bars in oneface 20Tl0-63-150Nl

(ii) A zone of similar bars in twofaces 40T10-63-150

(20N1-20F2)

(ii i) A zone of dissimilar bars intwo faces 20T10-63-150N1

20T10-64-150F2

Note that identical bars appearing on different faces areitemized separately.

To avoid congestion in thin walls less than 150mm thick,a single mat of reinforcement may be provided, if designrequirements permit.

5.6.22.2 On section(a) Intermediate storeys

Wal l s a re normal ly cas t instorey-height lifts, with stan-dard 75mm high kickers a teach floor level. Kickers helpto align the formwork above.T h e v e r t i c a l r e i n f o r c e m e n tshould not be less than 12mmand is lapped above the kick-er to provide structural con-tinuity.

Level3

Verticalbars

Level2 lap

75 Kicker

(b) Top storeys Roof

A variety of details level

are possible depend-i n g o n d e s i g n a n dc o n s t r u c t i o n r e -q u i r e m e n t s . A l l o wsufficient top coverfor clearance ofintersectingreinforcement.

(d)

(e)

(f)

(c) Offset walls aboveNormally offsets of up to75mm can be achieved byjoggling the relevant ver-tical bars. Otherwise, thelower bar is terminated be-low the floor and a sepa-rate splice-bar starter pro-vided.External wall/slab junctionIn the case where a significantbending movement is transmit-ted into the wall from the slab, it Check formay be necessary to use a L- non-standard

s h a p e d b a r t o p r o v i d e f u l l radius

anchorage. If the L-bar is to be

Anc

hora

ge

cast with the wall it should bescheduled with the wall reinforcement, but this is anon-preferred detail (see subsection 5.2).Half-landingsA 20mm deep rebate ispreformed in the sup-porting wall to provideb e a r i n g f o r t h e s l a bpoured later. The junc-tion is provided with upt o 1 2 m m , p r e f e r a b l ym i l d s t e e l , U - b a r swhich are temporari lyfolded back behind theformwork and later re-bent into their correctposition for the slab.Corner details(i) Closing corners

(ii)

For corners that areclosing, two simplea l t e r n a t i v e s a r eshown. Bars shouldb e p r o v i d e d w i t ha d e q u a t e a n c h o r -age and app rop r i -ate laps to suit.Opening cornersF o r c o r n e r s t h a t a ro p e n i n g , t h e m e t h o dof detailing is far moreimpor tan t , e spec ia l lyif the bending momenti s s i gn i f i can t . Tes t sh a v e s h o w n t h a t t h em a x i m u m o p e n i n gbending moment thatcan be transmitted byt h e d e t a i l s s h o w nabove for closing cor-ners can be less than 25% of the flexural strength ofthe corresponding wall section. A looped bar ismore efficient structurally, although difficult tobend and fix. The recommended detail shown ismore practical and has a high structural efficiency.

In all cases, the structural efficiency will be improvedconsiderably if it is practicable to provide a splay cornerreinforced with diagonal bars.


WA

LL

D

WA

LL

E

WA

LL

F

SFL


56.23 Other requirements5.6.23.1 Special notesIn addition to the standard notes for reinforcment draw-ings (see subsection 2.8), the following notes should appearon all wall drawings.

(a) cover to outer re inforcement N1. . . .Fl . . . .End. . . .(b) bar-layer notation: Near face outer bar Nl

Near face second bar N2Far face outer bar FlFar face second bar F2

5 . 6 . 2 3 . 2 W a l l r e i n f o r c e m e n tspacersW h e r e l i n k s a r e n o t r e q u i r e d t orestrain vert ical compression bars ,reinforcement spacers can be used tostabilize the two faces during con-s t ruct ion. Adopt say Rl0 @ 1000,shape code 38. Cover to the outerbars is normally achieved by usingplastic spacers

T i e s

Tie to

N F 2 +

F F 2

5 . 6 . 2 3 . 3 T r i m m i n g o fholes in wallsTo prevent cracks springingf r o m c o r n e r s , p r o v i d enominal bars placed diago-nally as shown. Additionalt r im requirements shouldbe indicated in the calcula-tions.

5.6.23.4 Miscellaneous itemsWhen detailing reinforcement, ensure that adequate clear-ance is allowed for items such as fixings, pipes, water bars,weep holes, etc.

5.6.23.5 Fabric reinforcement in wallsConventional wall layouts lend themselves to the advan-tages of fabrication as described in clause 5.2.26. Purpose-made wall sheets can be ordered to deal effectively withlapping and intersection details. For guidance, consult themanufacturers of fabric.


U Bars

DiagonalsAnchorage

5.6.30 Examples of detai l ing5.6.31 Typical internal wall panel

WALL '6'

A - A Cover: N1 = 20

F1 = 20

End = 20


5.7 STAIRS

5.7.10 Design informationRequirements for stairs are similar to those indicated forslabs (see subsection 5.2).

TYPICAL STAIR NOTATION

Notes on setting-outThe stair structural-layout or general-arrangement drawingshould indicate all the dimensions required to set out theconcrete profile.

The architect wil l normally locate the s tair betweenfloors using the top of the finishes as his vertical datum. Theheight of risers will be equal but the thickness of finish mayvary, particularly at floors and landings. It follows thatstructural risers may vary in height. Treads may requiresloping risers to provide a nosing, and fillets may be neededto maintain a constant waist thickness.

I t i s o f t e n a r r a n g e d t h a t t h e f i n i s h e s t o nosings o fadjacent flights will line through across the stair. Some-times the junctions of all soffits are made to line through.

5.7.11 Design code requirementsBar curtailment rules for stairs follow the simplified orgeneral rules recommended for slabs (see clause 5.2.11).

VERTICAL RISERS SLOPING RISERSWITH FILLETS

Finishes to treads of Finishes to soffite junctioneach flight line through line through

TYPICAL STAIR FLIGHTS SHOWING REINFORCEMENT(Ear curtailments based on BS8110 simplified rules (3.12.10.3)†fig 3.25


Struct. risers vary to suitthickness of finish

Finishes risers equal


5 . 7 . 2 0 D e t a i l i n g5.7.21 Methods of detailing stairsIn all cases concrete profiles are extracted from the relevantgeneral-arrangement drawings. Each different f l ight isdrawn in section to a suitable scale, and the appropriatereinforcement is carefully related to the profile.

5.7.21.1 Simple flightsThese can be detailed on section alone, probably with theaid of a key plan to identify various flights and sectionstaken. Separate sections may be necessary across landings.

5.7.21.2 Stair complexesReinforcement is shown on the plan of flights and landingswhere they differ for each storey height. Sections takenshould clarify the positioning of the bars.

5.7.21.3 Surrounding structuresStarter bars for landings etc. may be required to projectfrom support ing members for the s ta i r construct ion toproceed at a later date. These bars may be folded back frombehind the formwork (see clause 5.6.22.2) and should bedetailed with the support.

5.7.22 Bar detailing on stairsThis follows the conventions used for detailing slabs (seeclause 5.2.22).


5 . 7 . 3 0 E x a m p l e s o f d e t a i l i n g

7 T 12 - 4 -150 B17 T 12 - 3 -150 B1

4 T 10 - 2 - 300 T2

10 T 10 - 2 - 300 B2

4 T 10 - 6 - 300 B24 T 10 - 6 - 300 T2

SFL

3.475

15 T 10 - 5 - 150U-Bars

5 T 10 - 2 - 300 T2

10 T 10 - 2 - 300 B2

7 T 12 - 8 - 150 B1 7 T 12 - 11 - 150 - B1 7 T 12 - 13 - 150 T17 T 12 - 9 - 150 T17 T 10 - 10 - 300 T2

TYPICAL STAIRSShows flights "A","B" and landing detailed on plan

TYPICAL STAIR FLIGHTShows flight "A" and part-landing detailed on section


7 T 12 - 150 B1 (3)

7 T 12 - 12 - 150 B1

4 T 10 - 6 - 300

15 T 10 - 5 - 150

See drg no...

4 T 10 - 6 - 300

7 T 12 - 4 - 150

7 T 12 - 3 - 150

7 T 12 - 1 - 150SFL

-0.025

See drg no...

4 T 10 - 7 - 3007 5

4 5

SFL1.725

(2) (2)

(2)

"A"

"B"

HP

DN

SFL

- 0. 0

25

SFL

1 . 72

5 (3)

4 T 10 - 7 - 300 T1

4 T 10 - 2 - 300

10 T 10 - 2 - 300

1 3

(2)

(2)

6

6.1 Concrete inserts6.1.1 TypesConcrete inserts may be of the following types:

cast-inbonded with resinsbonded with cementitious groutexpandingshot-fired.

Fixings are usually characterized by their shape, or theway in which anchorage to the concrete is achieved andsometimes by the purpose for which they are used. A widevariety of studs, eyes, rods, hangers, loops, bolts, channels,sockets, blocks and nails may be installed, but in all casesthe manufacturer’s advice and instal la t ion instruct ionsmust be strictly adhered to.

6.1.2 Problems and solutionsProblems are usually brought about by a lack of technicalknowledge of the f ixing, a fai lure in communicat ionsbetween supplier and installer or a misunderstanding of theprinciples of the fixing. Problems may also be induced bythe location of the reinforcement, the formwork systememployed or the compactive effort used in placing theconcrete.

Always consult the supplier of a f ixing before i t isdetailed and ensure that the installation is specified on thedetail drawings and contract documents. Particular atten-tion should be paid to the following:

edge distances and spacings of fixings, particularly whenused in groups

( a )

concrete strength and aggregate sizehole diameter and depthproximity of reinforcement and any special reinforce-

ment to hold the fixing in placefixings to be used with lightweight aggregate concretespecification of components to be set in concrete using

jigs to prevent displacementsetting-out of fixings on drawings using reference lines

and running dimensionscover requirements for fixing and reinforcementrecommendations regarding compatibility of materials.

6.1.3 Durabil i tyThis covers three aspects:

corrosion (normally applies only to ferrous f ixings,although the normal rules of galvanic action must stillbe observed)

fire resistance (if the fixing is not protected with therequisi te amount of f i reproof material a f i re testshould be carried out)

long-term performance.In all these, guidance must be sought from the manufac-

turer before the installation is specified. (c)

6 .2 Corbe l s , ha l f - jo in t s and n ibsThe detailing of these elements must relate to the designassumptions, and the designer should in all circumstancesensure that the detailed design is clearly specified.


Specific details

6.2.1 Concrete corbelsIn details (a) and (c) (see Fig. 27) the edge of the bearingand the inside of the welded transverse bar or the inside ofthe main reinforcement in the form of horizontal loopsshould not be less than the bar diameter. For detail (b) thebend should not commence before a bar size beyond theedge of the bearing plate . In al l cases these distancesshould be increased to the cover to the bar where this isgreater than the bar diameter. It can be seen that the totalprojection of the corbel will be much greater in detail (b)than in the other two details because a larger radius bendthan the s tandard radius may be required to l imit thebearing stress of the concrete inside the bend. Because ofthis, details (a) and (c) may be preferable; it is suggestedthat detail (a) be used when using bars of size 20mm orgreater (see also Fig. 28) and detail (c) for bars of 16mmand smaller (see also Fig. 29).

Main steel welded to a

transverse bar of equal size

Horizontal shear steel (Asv)

as stirrups over uppertwo - thirds of d

kept clear of bend in mainreinforcement (minimum

A s t

( b )

of horizontal loops

Bars provided to anchor

horizontal stirrups

Detailing rules

1. hy 0.5h

2. 0.4 < 100 Ast/bd < 1.3

3. 0.6 < 100(Ast + Asv) bd < 2.0

4. Other details as per diagramsFig. 27

107

Ast

Vu

Ø

Outside edge of bearing to b

clearance = 1 bar size)

hy

dh

Ast

Vu

Ø

l

Main reinforcement in the formAst

Vu

Ø

Øav


Two column links should beplaced close to corbel top

Large radius ofbend required

Tension lap

This detail is suitable when using 20mm barsor greater for the main tensile reinforcement

A

Main tensile bars weldedto a cross bar of equaldiameter and to thever t ica l compression bars

Compression anchorage

Sectional plan on A – A

1 0 8 IStructE Detailing Manual

A

Distance between edge of bearingand inside of bar to be a minimumof the bar size or coverwhichever is greater

Horizontal links. Total areashould not be less than 0.5 ofarea of the main tensilere inforcement

Two column links should beplaced close to corbel top

4

This detail is suitable when using 16mm size barsor smaller for main tensile reinforcement

Tension lap

7 7

Distance between edge of bearingand inside of bar to be a minimumof the bar size or coverwhichever is greater

A

Main tensile reinforcement.Large radius of bendis required

7

Compression anchorage

3,4,5

1 7 2

Sectional plan on A–A

Fig. 29


Secondary horizontalreinforcement. Total area of thisshould not be less than 0.5times area of main tensilereinforcement

Outer compression bars angledto pass inside links

A2

6

3

4

5

1

2

4

1

2

77

6 4 5 6

1 7

7

3

Horizontal forcesWhen corbels are designed to resist horizontal forces thenadditional reinforcement should be provided to transmitthis force in its entirety. This re inforcement should bewelded to the bearing plate.

6.2.2 Concrete nibsNibs are not usually greater than about 300mm deep. Fordetailing requirements, the tension reinforcement that willbe near the top surface of the nib can be in the form ofU-bars in the vertical or horizontal plane or straight barswelded to a transverse bar.

a

E f fec t i ve dep th

( b ) H o r i z o n t a l l o o p s ( s e e F i g . 3 1 )(i)

(ii)adequate top cover to reinforcement in nib

(iii)main re inforcement in the beam. I f main re in-forcement is too low, then additional bars shouldbe provided (see below)

(iv)and wired to at least two main longitudinal bars

(v)horizontal U-bar

(vi)between the legs of the U-bars to be not greaterthan 3 times the effective depth.

( c ) W e l d e d b a r s ( s e e F i g . 3 2 )Requirements will be the same as for horizontal loops.

Ful l s t rengthweld

Fig. 30 Vertical loops

Fig. 32 Welded bars

(a) Ver t ical loops (see Fig. 30)

(i)12mm

(ii)high-yield bars or 6φ plus two covers for mild-steelbars

(iii)U-bars are used and the width of beam is sufficientto allow this. If the width is not sufficient then aclosed link can be used with an additional longitu-dinal bar introduced as indicated

(iv)member then there should be a minimum horizon-tal overlap of reinforcement in the nib and rein-forcement in the supported member of 60mm

(v)greater than 3 times the effective depth.

a

E f fec t i ve dep th

6.2.3 Halved-jointsThe preferred arrangement shown (see Fig. 34) does notinclude inclined links or bars as these are often difficult tofix properly. However, inclined links or bars can be usedespecially when large size bars are required and a weldedsolution is adopted.

Fig. 31 Horizontal loops

1 1 0 IStructE Detailing Manual

size of bar to be not greater than 16mmdep th o f t he n ib t o be su f f i c i en t t o p rov ide

nib reinforcement to be placed on and wired to the

dimension a should be a tension anchorage length

lacer bar in the nib to be the same diameter as the

Horizontal spacing of the legs of the U-bar or

size of links or U-bars to be not greater than

depth of nib not less than 8φ plus two covers for

dimension a to be a tension anchorage length if

if the nib is supporting a reinforced concrete

horizontal spacing of the links or U-bars to be not

A A

Tension anchorage

Tied to at least twomain longitudinal bars

Horizontal 'U' bars.Size to be not morethan 16

Lacer bars to be samed i a m e t e r a s ' U ' b a r s

Sectional plan on A-A Pitch of 'U' bars to be not morethan 3 x effective depth

Fig. 33


Effectivedepth

Check that any fixings required doNominal hanser links not interfere with reinforcement

'U' bar same sizeas main bottom

Full length l inks suff icient to resisttotal reaction, equally spaced

B – B

A – A

Fig. 34 Halved joint.


Tensionanchorage

Distance between edge ofbearing and inside of bar tobe a minimum of the bar sizeor cover whichever isthe greater

'U' bar 2

4A

hh

3

1

2

A B B

150 150 hh

1 1

2 2

3 3

3

4 4

1

2

7 Prestressed concrete

7 . 1 I n t r o d u c t i o nDesign and detailing of prestressed concrete are to a largeextent inseparable and this section is therefore addressed tothe designer/detailer. Only those structural members thatare commonly used are reviewed, although the principlesare applicable to other prestressed concrete members.

7 . 2 D r a w i n g sIn addition to the drawings showing the general arrange-ment of the prestressed concrete structure and reinforce-ment details, a separate set of drawings should be prepareddetailing the prestress to be applied. This set of drawingsshould include the fol lowing information for each pre-stressed concrete member:

layout and arrangement of tendonssetting-out data for each tendon profile and tolerancestendon and duct types and sizesanchorage recess dimensions (if any)the prestressing system that is detailed (if any)f o r c e t o b e a p p l i e d t o e a c h t e n d o n a n d t e n s i o n i n g

sequencelocation of grouting points and ventsfor pretensioned members any tendons to be debonded

should be marked on sections and elevations and themethod and length of debonding specified as illus-trated in Fig. 35

Strands fully bonded

Strands debonded for 1700 from each end of beam

Strands debonded for 4500 from each end of beam

Fig. 3.5 Debonded tendons

tendons to be deflected should be clearly indicated anddimensioned both horizontally and vertically see (Fig.36) (radius of curvature to comply with the recom-mendations of the manufacturer of wire or strand)

concrete grade and minimum strength required at trans-fer of prestress

relevant design parameters assumed:

relaxation of prestressing steelfriction characteristicsanchorage draw-inmodulus of elast ici ty of s teel and expected tendon

extensionsmovements of permanent structure at stressingvariations in camber

Elevation

Section A-A

60

50

50

60 Section B-B

Fig. 36

Straight strands

Deflected strandsStrand positions not used

for precast members: test arrangements, handling andstocking requirements.

It should be clearly stated that the choice of prestressingsystem is left to the contractor where no system is shown onthe drawings or where an alternative system to that detailedis permitted.

I t s h o u l d a l s o b e s t a t e d o n t h e d r a w i n g s t h a t a n yalternative proposed by the contractor should be checkedby the original detailer/designer, particularly any reinforce-ment modifications that may be required.

7 . 3 C o m p o n e n t s7.3 .1 Pretensioned unitsPretensioned units must be suitable for precasting. Bearingplates or similar components should not project below theelement in to the soffit form to allow elastic shortening tothe member to take place.

T e n d o n sTendons should be in vertical rows with spacing and edgecover compatible with the maximum size of aggregate toallow placing and compaction of the concrete. For symmet-rical concrete sections, the centroid of the tendons shouldlie on the vertical centroidal axis (see Fig. 37).

7.3.2 Post-tensioned unitsT e n d o n s a n d a n c h o r a g e s(a) Tendons may consist of wires, strands or bars, pro-

duced in accordance with BS 5896 or BS 4486. Severaldiameters and types of wire and strand are in commonuse, but it is recommended that only one particulartype should be employed on a specif ic project toobviate errors during installation. Prestressing bars are

IStructE Detailing Manual l l 3

A

A

B

B

X m X m

Debondedlength

T e n d o nl o c a t i o n s

D i m e n s i o n s t o s u i tagg rega te s i ze andc o n c r e t e c o m p a c t i o n

P r e t e n s i o n e d s e c t i o n

Fig. 37 Symmetrical tendon locations

also available in several diameters (see Tables 24, 25and 26).

(b) Post-tensioning anchorages should be of proprietarymanufacture and meet the requirements of BS 4447.They may be e i t he r l i ve ( s t r e s s ing ) , dead -end o rpassive anchorages or anchorage couplings. Eachmanufacturer produces a range of suitable anchorages.

T e n d o n d u c t s(a) A tendon duct should be identif ied by i ts internal

diameter, which should be that recommended by theprestressing equipment supplier for each size and typeof tendon.

Fig. 38 Symmetr ical tendon locat ions (mul t ip le- layertendons)

tendon. Very small radii may require the use of speciallymade preformed rigid sheathing. In some circumstances,larger diameter sheathing may be required locally.

(b) Ducts may be formed in several ways, most commonlyby using semi-rigid corrugated steel sheathing, whichmay be bent to sui t the tendon profi le . Rigid s teelsheathing is occasionally used on special projects ,sometimes pre-bent to radius.

(c) External diameters of sheathing vary, depending onthe type and depth of corrugat ions , for which dueallowance should be made when considering spacing,clearances and reinforcement details.

(d ) The detai l ing should enable the sheathing or ductfarmers to be adequately fixed or supported to preventdisplacement.

D u c t s p a c i n g a n d c o v e r

Minimum straight length of tendonIn order to ensure that the elements forming the tendonbear an equal proportion of the prestressing force at theanchorage, it is necessary for the duct to be straight where itconnects to the anchorage. The recommended length ofstraight tendon may usually be obtained from the anchor-age manufacturer (see Fig. 39).

Straight length f roma n c h o r a g e m a n u f a c t u r e r

The minimum spacing and cover to ducts are specified inCodes of Practice and Standards, taking account of theg r o u p i n g o f t e n d o n s , t h e e x p o s u r e c o n d i t i o n s o f t h estructure and the maximum size of aggregate. Tolerancesr e l a t i ng t o t he pos i t i on o f duc t s shou ld be s t a t ed i naccordance with the relevant Codes of Practice.

Mult iple layer tendonsMultiple layer tendons should be arranged in vertical rowswith sufficient space between the rows to facilitate properplacing and compaction of the concrete without damage tothe sheathing (see Fig. 38).

Fig. 39 Minimum straight length of tendon

G r o u t i n g p o i n t s a n d v e n t s

Curved tendonsWhere tendon profiles are curved, vertically and/or hori-zontally, sufficient concrete must be provided to give fullsupport to the duct to prevent the radial force from pullingthe tendon through the wall of the duct. The spacing ofducts may need to be adjusted to comply with Codes ofPractice. The radial stresses on the insides of curves ofsmall radius are considerable. Increased duct spacing andtensile reinforcement will normally be required (see alsosubsection 7.4).

Grouting points (see Fig. 40) are associated with anchor-ages and should have faci l i t ies for connect ion to high-pressure grouting equipment. Vents are required at all highpoints to prevent air-locks. For long tendons, intermediatevents may be advisable at low points, and in an emergency,these can be used as intermediate grouting points.

Grout vents may be combined with sheathing couplers inwhich a short steel tube is riveted to the coupler. Alterna-tively, a plastic saddle vent is placed in the desired positionagainst a compressible gasket to prevent leakage and wiredto the sheathing.

Recommendations on the minimum radius of curvatureof tendons may be obtained from the prestressing equip-ment suppl ier who wil l take into account the bending,without damage, of the sheathing and the installation of the

A hole is punched in the sheathing through the vent pipe,using a soft steel punch so as not to damage the tendon. Aplast ic pipe is connected to the vent pipe and placedvertically to protrude above the surface of the concrete; aninternal diameter of not less than 20mm is recommended.


Tendon

Dimensions to suitaggregate s ize andconcrete compact ion

P o s t - t e n s i o n e d s e c t i o n

Ancho rage

TangentDuct

Table 24 Dimensions and properties of cold-drawn wire from Table 4 of BS 5896: 1980

nominal diameter nominal tensile strength nominal cross-section nominal mass specified characteristic breaking loadmm N/mm 2 mm2

g/m kN

7 1570 38.5 302 60.47 1670 64.3

6 1670 28.3 222 47.36 1770 50.1

5 1670 19.6 154 32.75 1770 34.7

4.5 1620 15.9 125 25.8

4 1670 12.6 98.9 21.04 1770 22.3

Table 25 Dimensions and properties of strands from Table 6 of BS 5896: 1980

type of strand

7-wire standard

7-wire super

7-wire drawn

nominal diameter nominal tensile strength nominal steel areamm N/mm 2 mm2

15.2 1670 13912.5 1770 9311.0 1770 71

9.3 1770 52

15.7 1770 15012.9 1860 10011.3 1860 75

9.6 1860 558.0 1860 38

18.0 1700 22315.2 1820 16512.7 1860 112

specified characteristicnominal mass breaking load

g/m kN

1090 232730 164557 125408 92

1180 265785 186590 139432 102298 70

1750 3801295 300

890 209

Table 26 Dimensions and properties of hot-rolled and hot-rolled-and-processed high-tensile alloy steel bars from Table 1 ofBS 4486: 1980

type ofbar

hot rolled

nominalsizemm

20253240

nominaltensile

strengthN/mm2

1030

hot rolled 20and 25 1230processed 32

nominal cross-sectional area nominal masssmooth ribbed smooth ribbed

surface bar bar bar barmm2 mm2 kg/m kg/m

smooth 314 349 2.47 2.74or 491 538 4.04 4.22

ribbed 804 874 6.31 6.861257 1348 9.86 10.58

smooth 314 349 2.47 2.74or 491 538 4.04 4.22

ribbed 804 874 6.31 6.86

characteristicbreaking load

kN

325505830

1300

385600990


Plast ic vent pipes should be adequately supported —possibly by the insertion of a loose-fitting reinforcing bar orlength of prestressing strand.

The grouping of grouting and vent pipes at a single pointshould be avoided.

Min

Angle

Min

Grout A Vent pipespipes

A

a c

b d

100 minFig. 40 Grouting points and vents

D u c t p r o f i l eThe duct profile should preferably be given in tabular form,the horizontal and vertical dimensions being based on adatum that is easy to identify on site. The profiles for eachvertical row of ducts should be tabulated separately, withx-, y- and z-coordinates (see Fig. 41).

Dimensions should be to the centre of the duct or ductsand should be sufficiently frequent to define adequately theprofile, taking account of its radius of curvature.

Tendony

x Elevation of duct profi les

Distance alongmember ( in te rva ls 0 0.05 0.10 0.15 0.20at 1

10 or 1 20 of span)

Ordinate above sofit, y mm

Tendon

Tendon

x

z

Plan of duct prof i les

Distance alongmember. 0 0.05 0.10 0.15 0.20Dis tance f romoutside face,z mm

Tendon

Tendon

C

Note : Al l dimensions to duct centre l ines

Fig. 41 Duct profiles

AnchoragesIf the s tructure is detai led for a part icular prestressingsystem, an outline of the anchorage should be shown; itshould be axially in line with the last straight length oftendon. The spacing and edge distance should not be lessthan those recommended by the manufacturer.

If the structure is not detailed for a particular system thena general outline should be drawn that would generallyencompass approved system.

Anchorage recesses (see Fig. 42) should be dimensionedto provide adequate working clearance to the s t ressing

Sect ion End elevation

Part plan

*Key dimesions required

Fig. 42 Anchorage recesses in end block

equipment and sufficient depth to ensure that they can besubsequently f i l led with mortar or concrete to providecorrosion protection. Reinforcement may be required toretain the concrete or mortar filling; a convenient method isto screw small diameter bars into sockets provided in thefaces of the recess.

Working clearancesSpace should be provided in front of the anchorages toenable the stressing jack to be lowered into position with itsoil pipes, to be extended in line with the tendon and to beremoved af ter s t ressing (see Fig. 43) . There must be

B

A T o t a l c l e a r a n c e r e c o m m e n d e d t o a l l o w r e m o v a l o fe q u i p m e n t a f t e r c o m p l e t i o n o f s t r e s s i n g

B O v e r a l l l e n g t h o f s t r e s s i n g E q u i p m e n t i n c l u d i n g e x t e n s i o n

C O v e r a l l l e n g t h o f e q u i p m e n t b e f o r e s t r e s s i n g

Fig. 43 Jack clearances


a c

b d 100 min

S o f f i t

1340 1203 1061 938 833

888 771 679 602 536

560 300 150 105 105

1020 770 600 570 570

A

A

B


Fig.

b/k50

(min)

ktHorizontal burstingreinforcement(extends to depth b)

(a)

(b)

118

sufficient space for the operators to stand alongside the (c) Tensile stresses occurring on the faces of end

Where the permanent works cause a temporary obstruc-tion the stressing operations, they should be detailed toallow for the completion of construction after stressing,e . g w i n g and facing walls.

blocks adjacent to the anchorages To resist these stresses and prevent concrete spalling,reinforcement should be placed in two directions atright-angles as close to the end face as cover considera-tions permit.

7 . 4 R e i n f o r c e m e n t d e t a i l i n gEnd blocks distribute high forces requiring large quan-

It is necessary to identify the areas in the structure that aretities of reinforcement in relatively small spaces. This has

subject to tensile forces, and the clauses in this subsectiontwo consequences:

relate to the detailing of reinforcement in these areas. As

h

B C B C

A

Shear

Compression Tension

h Forcedistribution

44 Overall equilibrium of end block

for reinforced concrete, all the reinforcement in any onepart of a concrete member should be detai led on onedrawing.

7.4.1 End blocks in post-tensioned members (seereference 10.4.1)An ‘end block’ is that zone of a prestressed concretemember in which the prestressing force is dispersed fromthe tendon anchorages to an approximately linear distribu-tion across the section.R e i n f o r c e m e n t i n e n d b l o c k s s h o u l d b e d e t a i l e d t oensure satisfactory behaviour of the end block under thefollowing effects:

Overall internal equilibrium of the end blockB0th vertical and horizontal equilibrium should beconsidered and reinforcement provided to resist thetensile forces induced (see Fig. 44).

Tensile bursting forces behind the anchorageThese forces act normally to the line of the prestressingforce in all lateral planes. The reinforcement to resistthese forces is normally provided as closed hoops orspirals. Because the tensile forces act in all lateralplanes the reinforcement will be stressed throughoutits length, and it is essential that any hoops or links aredetailed with full tensile laps (e.g. BS 4466, shape code74, but with large radius bends to avoid crushing theconcrete).

To restrain the bursting forces effectively the rein-forcement should be positioned as near as possible tothe outer edge of the largest prism whose cross-sectionis similar to and concentric with that of the anchor platehaving regard to the direction in which the load isspreading, and at least 50mm outside the edge of theanchor plate (see Fig. 4.5).

Re in forcement links for adjacent anchorages shouldbe overlapped and longitudinal bars positioned in thecorners. Where spirals are provided with some prop-rietary anchorages as part of the anchorage system,additional reinforcement may be required to resist thebursting forces.

b Theoretical prismassociated withhorizontal bursting

Prism associated withvertical bursting

Anchorage

End elevat ion

Vertical bursting reinforcement(extends to depth t)

Zone for posi t ioning ver t icalb u r s t i n g r e i n f o r c e m e n t

t

b

Zone for posi t ioning hor izontalburst ing re inforcement

Side elevat ion t = Least d imensionof member

Fig. 45 Location of bursting reinforcement

(i) The forces in the reinforcement build up quickly overrelatively short lengths, and great care should be takento ensure that the bars are anchored effectively. At allcorners, the bars should have large radius bends toavoid crushing the concrete or should pass round alongitudinal bar or tendon of at least the same dia-meter .


Resultant ofdistributedforce

b/2

t

D

*Forces required to maintainequilibrium of block ABCD

DA

(ii) As well as the tensile forces described above there aresignificant compressive forces in end blocks, particu-larly immediately behind the anchorages, which mustbe resisted by the concrete. The reinforcement shouldbe detailed to allow the concrete to be properly placedand compacted.

7.4.2 Secondary reinforcementWhile prestress is normally introduced into a member toenable it to resist bending moments and axial loads, it mayalso contribute to the shear and torsion capacity. However,secondary reinforcement may be required to enhance shearand torsion resis tance, for crack control and for f i reresis tance.

Shear reinforcement in post- tensioned beams shouldconsist of open links or pairs of lapping U-bars so that thetendons can be easily positioned (see Fig. 46).

Position ofducts vary

Fig. 46 Shear reinforcement

The detailer should be aware that Codes of Practice mayrequire that:• minimum areas of reinforcement be provided to control

cracking in end blocks or shear requirements for• reinforcement be provided longitudinally to resist tensile

forces caused by restraints to early thermal movement(e.g. by the falsework) before the member is stressed.

7.4.3 Additional reinforcement around holesWhen holes occur in prestressed concrete members, thecompressive stresses in the direction parallel to the line ofaction of the prestress may be significantly increased (seeFig. 47). Tensile stresses of the same order as the longitu-dinal stresses are also induced normal to the line of actionof the prestress. Reinforcement may be required to resistthe tensile forces and the enhanced compressive stresses.T h e r e i n f o r c e m e n t s h o u l d b e f u l l y a n c h o r e d i n t o t h esurrounding concrete.

Local reductions in cross-sectional area also occur atcoupler positions and at ducts for transverse, vertical ordiagonal tendons. These reductions may lead to substan-tially increased stresses that require additional reinforce-ment .

Compressionp

anchoragelength

3p

Compression

p p

Tension

Fig. 47 Stress distribution and additional reinforcementaround circular hole

7.4.4. Reinforcement to resist the normal componentof the prestressAngular deviation of the tendon line causes forces normalto the tendon. Although these lateral forces are in equilib-rium when the member is considered as a whole, local shearforces and moments are induced, and these should beresisted by reinforcement,

As an example consider an anchorage bl is ter on theflange of a box girder (see Fig. 48). The radial componentof the prestress force (PR) is applied to the concrete alongthe curved length of the tendon and is balanced by theforces a t the end of the tendon (PV1, PH1 and PH2) .Reinforcement should be provided to resist the forces andmoments induced.

Possible crack

Additional reinforcement

A–A

Additional reinforcementfor local bending

Fig. 48 Forces acting at anchorage blisters

Where the radial prestress component PR is applied nearthe face of the concrete it may cause spalling. Reinforce-ment links should be provided to transfer this force into theconcrete f lange. They should be dis t r ibuted along thecurved part of the tendon. Addit ional l inks should bep r o v i d e d b e y o n d t h e t a n g e n t p o i n t s t o a l l o w f o r a n ymisalignment of the tendon.

A

A

P lan

A – A

Forces acting on Longitudinal stress pcross section Moments around box

Fig. 49 Forces in box girder curved in plan


A

PV1

PH1e

PR

PH2

A

Tensionanchoragelength

Lo

ng

itu

din

al

stre

ss

p

Fig

Fig

120

When tendons are located in the webs of beams that arecurved in plan (see Fig. 49), the lateral force from thetendon is balanced by the combined lateral forces from thecompressions in the web and flanges. The distribution offorces induces bending in the web that should be resisted byreinforcement .The radial component of the prestress force increaseswith decreasing radius of curvature. In looped anchoragesthe dial force is large, and local reinforcement similar tothat in end blocks is required (see Fig. 50).

7.4.5 Reinforcement against grouting pressureIt is usually specified that tendon ducts should be grouted toa pressure of 0.7N/mm2 (7 bars). In some circumstances,higher pressure may be used in order to force grout throughthe duct . Sheathing, anchorages and couplers are notdesigned to resist grouting pressure, which is consequentlytransmitted to the concrete where it can induce tensilestresses.Fig. 51 shows areas where tensi le s t resses are inducedwhen the ducts are grouted. It may be necessary to providereinforcement links around the ducts.

A l te rna t i ve l y : -

Tensi le burst ing forces

P l a n

R a d i a l f o r c e s

E l e v a t i o n

50 Forces at looped anchorages

Ducts in thin members

Local reduction in concrete sectiona t c o u p l e r s

Local bending at rectangular ducts

51 Tensile forces due to grouting pressure

7.4.6 Intermediate anchoragesFig. 52 shows an anchorage within the body of a concretemember. Under the localized action of the prestress force,an imaginary line AA will tend to deform to A’A’ creatingtensile forces parallel to the tendon. These tensile forcesmay occur even when there is an overall compression in themember from, for example, other prestressing tendons.

A A ’

A A ’

X X

A A ’

Y Y

A A’

X–X

Y–Y Large radius bend

Fig. 52 Tensile forces and additional reinforcement atintermediate anchorages

Reinforcement fully anchored into the surrounding con-c r e t e s h o u l d b e p r o v i d e d e a c h s i d e o f t h e a n c h o r a g eparallel to the prestressing tendon.

Local tensile forces can also occur at anchorage coup-lings (see Fig. 53). When the coupled tendon is stressed theforce between the previously s t ressed concrete and theanchorage decreases, and the local deformation of thisconcrete is reduced. Increased compressive forces areinduced adjacent to the anchorage and balancing tensilef o r c e s b e t w e e n a d j a c e n t a n c h o r a g e s . C r a c k i n g i n t h etensile zones should be controlled by distributing tendonsaround the cross-sect ion, by providing ful ly anchoredreinforcement to resist the tensile forces or by providings o m e u n c o u p l e d t e n d o n s a c r o s s t h e j o i n t ( r e f e r e n c e10.3.1.4).

7.4.7 Pretensioned membersIn p r e t ens ioned member s t he ax i a l p r e s t r e s s fo r ce i stransferred from the tendons to the concrete over a finitelength. When the tendons are released from the casting bedthe stress within the transmission length is reduced leading


Large radiusbend

to an increase in the diameter of the tendon because of thePoisson effect.

T h i s t r a n s m i t s a r a d i a l c o m p r e s s i v e f o r c e i n t o t h econcrete that is balanced by circumferential tensile forces.Adequately anchored reinforcement should be providedover the whole transmission length to resist these forces. Ifthe tendons are distributed both vertically and laterally inconformity with the linear prestress distribution remotefrom the transmission zone effects, then the transmissionzone will be in internal equilibrium without the need forany additional reinforcement. If the tendons are concen- Stage 1

t ra ted in groups the overal l internal equi l ibr ium of thetransmission zone should be considered and reinforcementprovided (see Fig. 54).

I t i s r e c o m m e n d e d t h a t t h e e n d z o n e o f a b e a m i sdesigned and detai led as a reinforced concrete memberwith longitudinal and shear reinforcement as necessary (seereference 10.3.3.13).

It is normal practice to provide sets of standard stirrups ata closer spacing (e.g. 75 mm) in transmission zones that notonly occur at the end of members but also where tendonsare debonded. This reinforcement is usually sufficient toresist the Poisson effect and equilibrium forces, as well as Stage 2

providing adequate shear capacity (see Fig. 55).Fig. 53 Tensile forces at anchorage coupling

S t r e s s t r a j e c t o r i e s

Note :P,e ident ical

C h a n g e in force d is t r ibut ion over length of end zone

S t r e s s t r a j e c t o r i e s

F o r c ed i s t r i b u t i o n

E n d z o n e Forced i s t r i b u t i o n

Fig. 54 End zones in pretensioned members

7.4.8 Construction jointsDetailing reinforcement should allow for possible locationsof vertical and horizontal construction joints, which shouldavoid cast-in components such as anchorages and couplers.Where construction joints intersect the planes of tendonduc t s , t hey shou ld be pos i t i oned t o avo id a r ea s w i threstr icted access for vibrat ion equipment and scabblingtools.

“ B a l a n c e d ”

N o r e i n f o r c e m e n t

A d d i t i o n a l r e i n f o r c e m e n tr e q u i r e d

Debonded tendon

Bonded tendon

T r a n s m i s s i o n z o n eof bonded tendon

Transmiss ion zoneof debonded tendon

Fig. 55 Transmission zones in pretensioned members7.5 Other effects of prestressingInformation of the aspects below should be provided on the ments due to the induced prestress will take place. The

drawings. movements will be transmitted to supporting falsework,w h i c h i n t u r n w i l l t e n d t o m o v e i n s y m p a t h y . C l e a r

7.5.1 Movements of the permanent structureindications of the expected movements and the method ofarticulation should be given to avoid overstressing both

During application of the prestressing forces to the perma- permanent and temporary structures. In particular, tem-nent structure, horizontal movements arising from elastic porary restraints to movements should be identified, e.g.shortening of the concrete members and vertical move- anchored sliding bearings.


7p

p

p

2 p

4 p

7 p

p

p

2 p

4 p

7 p

p

p

2 p

4 p

9 p

p

5 p

(see schedule)

Length of debonding

Where prestressed concrete s t ructures are formed onlong-span falsework that has greater flexibility than that ofthe permanent structure, consideration should be given tothe effect of any residual deflect ion of the falseworki m p o s i n g a d d i t i o n a l u p w a r d f o r c e s o n t h e p e r m a n e n tstructure on completion of the stressing operations (seeFig. 56).

Stage 1

∆ 1

Concretestructure

Long spanfalsework

Initial falsework deflection = ∆ 1

Stage 2

∆2

Tendons stressed

Deflection reduces to ∆2 < ∆1

Stage 3

∆2

Residual reactions on structure fromfalsework left in position

Fig. 56 Effect of leaving falsework in position – case A

Stage 1Previouslystressed

Concretestructure Joint

∆1Long spanfalsework

Stage 2Tendonsstressed

Stage 3

Fig . 57 Effect of leaving falsework in position – case B

122

Deflection reduces to ∆ 2 < ∆1

Residual concentrated reactions on structurefrom falsework left in position

Corresponding concentration of forces on falsework

To ensure that these temporary upward forces do notoverload the permanent structure it may be necessary torelease falsework in phase with the appl icat ion of theprestress. Any tendency during stressing for the permanentworks to impose additional vertical downward forces onfalsework should be clearly stated on the drawings (see Fig.57).

7.5.2 Variations in camberIn defining the dimensional tolerances of prestressedconcrete members, variations in the modulus of elasticityand elas t ic shortening of the concrete should be con-sidered. The effects of variations in camber are of greatsignifiance at the detailing stage. As an example, variationsin camber will occur between the adjacent units of a floor,which in turn wil l inf luence the average thickness ofsubsequent floor screeds.

7 . 6 T y p i c a l d e t a i l sFigs. 58 to 66 i l lustrate typical detai ls in prestressedconcrete members and incorporate the recommendationsmade in this manual.

Transverse reinforcement in post-tensioned box girderFig. 58 shows the variation in reinforcement along a beamto accommodate the changes in level of the tendons.

Post-tensioned end block, reinforcementFigs. 59 to 62 illustrate reinforcement in an end block. Eachfigure highl ights reinforcement that is provided for aspecific function as described in this manual.

Anchorage details for prestressed silo wallFig. 63 illustrates typical anchorage reinforcement, whichextends over the full height of the silo. The tendon shouldextend from the tangent point to the anchorage in a straightline, the buttress being dimensioned such that the mini-mum concrete cover is maintained to the tendons at thejunction of the silo wall with the buttress and that adequatejack clearance is provided.

Flat-slab prestressing with unbonded strandFigs. 64, 65 and 66 show the typical three-drawing methodof detailing by which the tendon layout, the tendon supportbars and the additional bonded reinforcement are shownseparately. A typical example of the legend by whichgroups of tendons and anchorage types and the tendonplacing sequence are indicated is shown in Fig. 64, whileFig. 65 shows a typical support bar layout . The actuallayout may be modified by the contractor depending on thesuppo r t sy s t em adop t ed so t ha t t he spec i f i ed t endonprofiles are attained and adequate support provided. Fig.66 shows the reinforcement that is always required in thetop of the slab at columns, the end-block reinforcement andthe reinforcement needed in the bot tom of the s lab atm i d - s p a n i n s o m e design10.4.4, 10.4.5 and 10.4.6).

applicat ions (see references

In addition to the flat plate shown, other types of flat-slabare used — with drops, coffered or ribbed. The principlesof detailing are however applicable to all.


Initial falsework deflection = ∆ 1

∆2

E

Elevat ion of tendon prof i les

A - A B - B C - C

D - D E - E

Fig. 58 Transverse reinforcement in post-tensioned box girder

D C

B

A

D C

A - A

B - B

C - C D - D

Fig. 59 Post-tensioned end block – bursting reinforcement


E

C

C

D

D

B

B

A

A

B

A

Fig. 60 Post-tensioned end block – spalling reinforcement

Note:Some of this reinforcementres is ts shear forces

Fig. 61 Post-tensioned end block – vertical equilibrium reinforcement


AA

A-A

D C

B

C

B

D

B-B

C-C D-D

AA

A-A

D C

B

B

B-B

D C

C-C D-D

124

Note :Some of this reinforcementres is ts d iaphragm bendingmoments

1000

25

1000

25

16090 Anchorage

Note:

Detail repeats over fullheight of silo

Fig. 62 Post-tensioned end block – horizontal equilibrium reinforcement

200Circumferentialstrand tendons

Tangentpoint

450

Buttress

Plan

LinksA

2 No. per

anchorage

2 No. straight A

per anchorage Silo wallreinforcement

Strandtendon

Fig. 63 Anchorage detail for prestressed silo wall


AA

A-A

D C

B

C

B

D

B-B

C-C D-D

Red 15000

White 43000

20 no.

30

00

White 43000

35

00

18 no.

20

00

0.400.801.201.602.00

1x10 67 (added)

Red ∆ = 75

3 x 24 50 (thru)

Blue ∆ = 165

Tendon l ayou t

Dimensions from reference lineto centreline of tendon group

One st randTwo st randsThree s t randsFour s t randsFive st rands

Dead endadd st rands

will be marked withone of the aboves y m b o l s

Edge of slab

Note :When more than one symbol appears on a tendongroup, the number of s t rands equal the sum of

t he symbo l des i gna t i ons .

Fig. 64 Flat slab – tendon layout


Black 26000122 no.

2 no.

05

00

15

00

25

00

35

00

45

00

0 16

50

0

15

50

0

14

50

0

13

50

0

12

50

0

11

50

0

10

50

0

95

00

85

00

75

00

55

00

65

00

A

A

14 no

Blue 9000

2.402.80

Placing sequence (when required)

Tendon quantity, length, color-code, elongation

Gre

en

∆ =

21

5

15

x3

1. 5

m

A-A

Note :1. Height given is from soffit of slab to underside of tendon

2. Diameter of suppor t bar is 10mm

Fig. 65 Flat slab – tendon profile and typical support bar layout


128 IS

tructE

Detailing

Manual

Fig. 66 Flat slab – reinforcement layout

8

Detailing of precast concrete work requires special disci-plines that do not occur with in situ concrete. The reason forthese are:

The precast unit is, by definition, transported after it ismade before it can be incorporated in the works.The unit is often incorporated into a ready built or partbuilt structure. In these cases, consideration of toler-ances is important.The unit is often made by a third party who may nothave visited the site and will not have all the drawings.Clarity of instruction to the precaster and preliminarydiscussions are therefore vital.Precast concrete structures usually require special con-sideration of joints. Sound detailing of these areas leadsto attractive, serviceable and safe structures.

Precast units are often cast in a different orientation fromthat of their final use. The decision of how to cast is oftenbest left with the precaster or should at least be discussedand agreed with him. At the detailing stage the designershould make his intention clear on surface finish and ont o l e r a n c e . A r e a s w h e r e t o l e r a n c e s d i f f e r e n t f r o m t h especification are required for particular reasons should beclearly noted. Remember that unnecessarily rigid specifica-tions may not be economic in the long run.

It is particularly difficult to form re-entrant or protrudingcorners without having breakage or an unsightly finish.Acute re-entrant corners are to be avoided as it is difficultto remove the formwork without damage. Acute protrud-ing corners are often broken in handling and are oftendiscoloured because the large aggregate cannot get into thecorner. Fig. 67 shows how a notched skew-ended beamshould be detai led to overcome these problems. Alsos h o w n i s a r e c o m m e n d a t i o n o n t h e d i m e n s i o n i n g o fskew-ended beams.

T h e n e e d t o t r a n s p o r t a p r e c a s t c o n c r e t e e l e m e n trequires that consideration should be given not only to itsphysical size and weight so that transportation is possiblebut also to the specification of permissible lifting positionsand angles of lifting.

These basic rules are not exhaustive but give a guide forthe detailer in proportioning elements:

length <gross and < 3m wide

> Depar tment of Transport

height>

width 2.9m no restriction2.9 up to 4.3m possible with notification to

police4.3 up to 6 .1m special dispensat ion re-

quired from the Department of Trans-port

Precast concrete

weight < 20 tonne no restriction on normal 32 tonnetruck

< 38 tonne no restriction on special 38 tonnetruck

20 < weight < 60 tonne on low loader orsteerable bogie

60 < weight < 160 tonne pol ice escor trequired, possible special routing, useof air-cushioned vehicle or hydraulicbogies possible.

The most f requent ly used loads are wi th a 20 tonnepayload on a 32 tonne gross truck. In these cases, withmultiple numbers of units on a load, significant savings canbe made if weight of whole number of units approaches butdoes not exceed 30 tonne, i.e. 2 no. 9.8 tonne per load asagainst 1 no. 10.2 tonne units.

Permissible support points and packing materials shouldalso be noted.

Lifting strengths for the concrete should be stated on thedrawing, remembering that the maximum mould use on arepetitive job will bring all its economies only if the veryminimum lifting strength is specified.

The weight of the unit for craneage and for the estima-t ion of t ransportat ion should be clear ly s tated on thedrawing.

According to BS 4449, ordinary reinforcement is notsuitable for use as lifting hooks. Some precast manufac-turers do use reinforcement for lifting purposes, but it ispresumed that they do so with proper care and attentionto details and lifting practices and on the basis of practicaltests and the risks involved.

A range of proprietary inserts are marketed, both forfixing and lifting. It is important that these are used to themanufacturer’s instructions with adequate factors of safety.It is also important that secondary load effects or structuralmovements do not put forces on inserts for which they havenot been tested or designed. In these cases, means shouldbe sought to isolate the fixings so that only the correctforces may be applied.

Where a drawing not only shows a part of a unit that iscast on to another precast unit, the drawings of each shouldclearly state where the weights are noted that the weightsare only for part units.

Units of complex shapes should be discussed with aprecaster before their details are finalized. Units with arequirement for a high quality of finish may be required tobe cast in one piece moulds. In these cases, a drawing fordemoulding is necessary, and the unit and its surroundingstructure should be detailed accordingly.

T h e d e s i g n o f j o i n t s a n d t h e r e q u i r e m e n t s f o r t h edetai l ing of reinforcement and concrete (binding l inks,chamfers, etc.) are covered in the Institution of StructuralEngineer’s report Structural joints in precast concrete,1 9 7 8 ( r e f e r e n c e 1 0 . 3 . 3 . 1 2 ) .

For precasting, the detailer needs to be fully aware of themethod of moulding and the assembly and handling of thereinforcement cage, but such expert knowledge is normallyavailable only in the office of the specialist precaster.


27.4m no restriction if also < 32 tonne

27.4m special dispensation required from

<4.0m special rout ing necessary4.0m total load no restr ict ion

Notes:-

Unless otherwise specified all concrete units to be

manufactured in accordance with BS 8110

1. Cube strengths: 15 N/mm2 before demoulding

40 N/mm2 at 28 days

2. Cover : 25mm nominal

3. Finishes : Type C except as noted on drawing

4. Cement type : R.H.P.C.

5. Aggregate type : 20mm max

6 Weight of unit : 3.44 tonnes

7. Units to be lifted using special cast - in sockets

in top. Lift to be vertical where possible or angle

of lift from vertical

not to exceed 45°45° max

8. Tolerances : To BS 8110 except as noted on drawing

Fig. 67



9 Water-retaining structures

9.1 General Table 27 Tension anchorage lengths for structural re-Water-retaining structures will in general be detailed inaccordance with the recommendat ions for normal re in-forced concrete s t ructures except that the provis ion ofreinforcement, spacing of reinforcement, cover and dura-bility requirements are generally more onerous. BS 8007dea l s w i th t he de s ign o f r e in fo r ced conc re t e s e rv i cereservoirs and tanks used for the s torage of water and concreteother aqueous l iquids . In normal s t ructures the mostcritical aspect of design is generally the ultimate limit state

grade

( s t r e n g t h ) , w h e r e a s f o r s t r u c t u r e s d e s i g n e d t o r e t a i nl iquids not only is s trength to be considered but i t isessential to restrict the width of cracks in the concrete. 35/40The provision and spacing of reinforcement to satisfy thelimit state of cracking may therefore control the design 45and in many cases exceed that required for strength.

Water-retaining structures designed to BS 8007 requirereinforcement to resist tensile forces caused by:

(a)(b)

structural actions due to applied loads andrestraint to thermal contraction and drying shrinkage

The reinforcement to be provided in all slabs and walls ina particular direction is the larger of the amounts requiredseparately for ( a ) and ( b ).

Unlike normal structures where the construction jointsare not normally shown on the detailed drawings but aredescribed in the specification, the positions of all construc-tion joints and movement joints must be shown on thedrawings (see Fig. 68).

I t is the responsibi l i ty of the designer and not thecontractor to position all joints as the amount of reinforce-ment to resis t the tensi le forces ar is ing from thermalcontract ion and drying shr inkage is dependent on thefrequency and spacing of all types of joints.

9 . 2 C o v e rDurability is considered to depend on the concrete grade,cement content , crack width and cover . For reinforcedconcrete the maximum design surface crack widths fordirect tension and flexure or restrained temperature andmoisture effects are:

(1) severe or very severe exposure: 0.2 mm(2) critical aesthetic appearance: 0.1 mm

The nominal cover to any reinforcement given in BS 8007should not be less than 40 mm. This is satisfactory forsevere exposure. For very severe exposure the cover andmix should empty with BS 8110; Part 1. A greater covermay be necessary at a face in contact with aggressive soilsor subject to erosion or abrasion.

9 . 3 S p a c i n g o f r e i n f o r c e m e n tF o r t e n s i l e r e i n f o r c e m e n t t h e b a r s p a c i n g s h o u l d n o texceed 300 mm.

9 . 4 B a r a n c h o r a g e l e n g t h sTable 27 gives anchorage lengths in terms of bar size,according to the allowable steel stress in service conditionsfor horizontal bars in members in direct tension (e.g. hooptension).


q u i r e m e n t s ( a )

member in direct tension

deformedbar type plain (type 2)

design crack 0 .1 mm 0 .2 mm 0 .1 mm 0 .2 mmwidth

allowablestress, ƒS, N/mm2

85 115 100 130

anchoragelength, mm 30φ 40φ 20φ 26φ

ancoragelength, mm 26φ 35φ 18φ 23φ

N o t e s :

1. If A sprov exceeds Asreq multiply by Asreq

A sprov

2. If in flexure, multiply anchorage length by 0.7

Table 28 gives anchorage lengths in terms of bar sizefor members in flexure in which the steel area provided isno more than the steel area required for the ultimate limitstate.

Table 28 Tension anchorage lengths for s tructuralrequirements (a)

member in flexure – ultimate limit state

bar typeconcre te s tee l s t rength , ƒy

grade N/mm2

35/40 anchorage length, mm45 anchorage length, mm

N o t e :If A sprov exceeds Asreq multiply by Asreq

Asprov

plain250

3 3 φ2 9 φ

deformed

(type 2)460

3 4 φ3 0 φ

Table 29 gives anchorage lengths in terms of bar sizefor slabs and walls in which the steel ratio provided is nomore than the critical steel ratio.

Table 29 Tension anchorage lengths for thermal andshrinkage requirements (b)

concretegrade

bar typesteel strength, ƒy

N/mm 2plain250

deformed

(type 2)460

35/40

45

ρcrit 0.0064 0.0035lap length, mm 3 9 φ 4 8 φ

ρcrit 0.007 0.0038lap length, mm 3 6 φ 4 4 φ

Notes:

1. ρ crit is the critical steel ratio, i .e. the minimum ratio of steel area to the grossarea of the whole concrete section required to distribute cracking.

2 . I f A sprov exceeds Ascrit multiply by Ascrit

A sprov

where A scrit = ρcrit × gross area of whole concrete section.

General noteTables 28, 29 and 30 give tension anchorage lengths: The lap length = a factor ×ancho rage l eng th . The f ac to r may be 1 .0 , 1 . 4 o r 2 . 0 , and t he va lue t o u se w i l ld e p e n d o n c o v e r , p o s i t i o n a n d s p a c i n g o f b a r s ( B S 8 1 1 0 , c l a u s e 3 . 1 2 . 8 . 1 3 ) .However in many situations the value will be 1.0 or 1.4. The minimum lap lengthfo r ba r r e in fo rcemen t shou ld no t be l e s s t han 15 t imes t he ba r s i ze o r 300 mm,whichever is greater.

133


Fig. 68 Examples of movement joints

S e a l i n g c o m p o u n d o n

o n e o r b o t h f a c e s

Non - abso rben t

jo in t f i l le r S e a l i n g c o m p o u n d

N o n - a b s o r b e n tj o i n t f i l l e r

F l o o r

No steelc o n t i n u i t y

W a l l

N o s t e e lc o n t i n u i t y

C e n t r e b u l b Initial gap for

w a t e r s t o p e x p a n s i o nE x p a n s i o n t y p ew a t e r s t o p

In i t i a l gap f o re x p a n s i o n

( a ) E x p a n s i o n j o i n t s


one o r bo th f aces

N o c o n c r e t e c o n t i n u i t yand no initial gap

Joint seal ingc o m p o u n d

No concrete cont inui tyand no in i t ia l gap

F l o o r


W a l l


F o r m e d

W a t e r s t o p

S e a l i n g c o m p o u n d o none o r bo th f aces Induced crack

W a t e r s t o p

W e t - f o r m e d o r s a w n

I n d u c e d c r a c k s l o t s e a l e d l a t e r

No s tee lc o n t i n u i t y

I n d u c e d

Centra l cracki n d u c i n g w a t e r s t o p

( b ) C o m p l e t e c o n t r a c t i o n j o i n t s

W a t e r s t o p w i t hc r a c k i n d u c i n g u p s t a n d

S e a l i n g c o m p o u n d o none o r bo th f aces

N o c o n c r e t e c o n t i n u i t yand no in i t ia l gap

J o i n t s e a l i n gc o m p o u n d

N o c o n c r e t e c o n t i n u i t ya n d n o i n i t i a l g a p

W a l l

S t e e lc o n t i n u i t y 5 0 %

F l o o r

S t e e lc o n t i n u i t y 5 0 %

F o r m e d

W a t e r s t o p

J o i n t s e a l i n gc o m p o u n d

I n d u c e d c r a c k

W a t e r s t o p


one or both facesInduced crack

S tee lc o n t i n u i t y 5 0 %

Stee lc o n t i n u i t y 5 0 %

Induced

C e n t r a l c r a c ki n d u c i n g w a t e r s t o p W a t e r s t o p

( c ) P a r t i a l c o n t r a c t i o n j o i n t s



1 0 References

10.1 Essential references for detailers10.1.1 BS 4466 Specification for bending dimensions

and scheduling of reinforcement for concrete10.1.2 BS 1192 Construction drawing practice

Part 1: Recommendations for general prin-ciples

Part 2 : Recommendat ions for archi tec tura land engineering drawings

Part 3 : Recommendat ions for symbols andother graphic conventions

P a r t 4 : R e c o m m e n d a t i o n s f o r l a n d s c a p edrawings

10.2 Important reference documents10.2.1 BS 8110 Structural use of concrete

Part 1: Code of pract ice for design and

10.2.2construct ion

BS 8007 Code of pract ice for the design of

10.2.310.2.4

concrete s tructures for retaining aqueousliquids

BS 5400 Steel, concrete and composite bridgesConcrete Society Standard reinforced concrete

details, Technical report no. 6, ref. 51.066

10.3.1.210.3.1.3

10.3.1.4

10.3.1.5

10.3.1.6

10.2.1.710.3.9

10.3.1.10

10.3.1.11

10.3.1.12

10.3.1.13

10.3 Other useful references10.3.1 Standards and Codes10 .3 .1 .1 BS 6100 Glossary o f bu i ld ing and c iv i l en-

g ineer ing termsSect ion 6.2: ConcreteSection 6.3: Aggregates

BS 8004 Code of practice for foundationsBS 4210 Specification for 35mm microcopying

of technical drawingsBS 4449 Specifications for hot rolled steel bars

for the reinforcement of concreteBS 4482 Specification for cold reduced steel wire

for the reinforcement of concreteBS 4483 Specification for steel fabric for the

reinforcementof concreteBS 5395 Stairs, ladders and walkwaysISO 128 Technical drawings: general principles

of presentationISO 1046 Architectural and building drawings:

vocabularyISO 1047 Architectural and building drawings:

presentation of drawings, scalesISO 3098-1 Technical drawings: Le t ter ing ,Part 1: Currently used charactersISO 5455 Technical drawings: scales 10.4 Prestressed concrete

10.4.1 Construction Industry Research & Information

10.3.2.3

10.3.2.4

10.3.3.10.3.3.1

10.3.3.2

10.3.3.3.

10.3.3.4

10.3.3.5

10.3.3.6

10.3.3.7

10.3.3.8

10.3.3.9

Green, J . Kei th . Detai l ing for s tandard pre-stressed concrete bridge beams, 1973, no. 46.018McKelvey, K. K. Drawings for the structural

concrete engineer, 1974, no. 14.008

Other standards and manualsAmerican Concrete Inst i tute Manual o f s tan-

dard practice for detailing reinforced concrete,1988, ACI 315-88

Concrete Reinforcing Steel Inst i tute, I l l inoisManual of standard practice, 1988, MSP-1-80(3rd ed.)

British Reinforcement Manufacturers Associa-tion Reinforced concrete ground slabs, 1973

Canada National Standard of Canada, CAN3-B78.3-M77

New Zealand New Zealand Standard, NZs 5902Part 2: 1976

Concrete Institute of Australia Code of practicefor reinforced concrete detailing manual, 1975

South African Bureau of Standards Detailing ofsteel reinforcement for concrete, 0144-1978

Whit t le , R. Rein forcement de ta i l ing manual ,Viewpoint Publications, 1981

Dal t ry , C. D. , & Crawshaw, D. T. , Bui ldingResearch Establ ishment Work drawings inuse, CP18/73, 1973

10.3.3 .10 Ins t i tu t ion of Structural Engineers /ConcreteSociety joint report Design and detailing ofconcrete structures for fire resistance, 1978

10.3.3.11 Building Research Establishment Work draw-ings and their use on building sites, CP60/76,1976

10.3.3.12 Institution of Structural Engineers report Struc-tural joints in precast concrete, 1978

10.3.3.13 Construction Industry Research & InformationAssociation Design of deep beams in rein-forced concrete, Guide no. 2

10.3 .3 .14 Comite European du Beton/Federat ion Inter-nationale de la Precontrainte Model code forconcrete structures, 1978

10.3.3.15 Leonhardt, F., Federation Internationale de laPrecontra inte 9th Congress ‘Prevent ion ofdamage in bridges’, Proc., 1, 1982

10.3.3.16 Birt, J. C. Large concrete pours: a survey ofcurrent practice, CIRIA report no. 49, 1974

10.3.3.17 Paterson, W. S. & Ravenshill, K. R. Reinforce-ment connector and anchorages, CIRA reportno. 92, 1981

10.3.2 Cement & Concrete Association publica-tions

10.3.2.1 Balint, P. S., & Taylor, H. P. J. Reinforcementdetailing of frame corner joints with particularr e f e r e n c e t o o p e n i n g c o r n e r s , 1 9 7 2 , N o .42,462

10.3.2.2. Higgins, J. B., & Rogers, B. R. Designed anddetailed, 1986, no. 43.501

10.4.2

10.4.3

Association A guide to the design of anchorblocks for post-tensioned prestressed concretemembers, Guide no. 1, 1975

Federat ion Internat ionale de la PrecontrainteGuide to good practice: practical construc-tion, 1975

Federat ion Internat ionale de la PrecontrainteGuide to good practice: basic reinforced andprestressed concrete construction, 1978



10.4.4 Federat ion Internat ionale de la PrecontrainteRecommendations for the design of flat slabsin post-tensioned concrete, 1980

10.4.5 Concrete Society Flat slabs in post-tensionedconcrete with particular regard to the use ofunbonded t endons – des ign recommenda-t i o n s , T e c h n i c a l r e p o r t n o . 1 7 , r e f e r e n c e51.079

10.4.6 Concrete Society Post-tension flat slab designhandbook, Technical report no. 25, reference53.044, 1984

10.4.7 BS 4447 Specification for the performance ofprestressing anchorages for post-tensionedconstruction

10.4.8 BS 4486 Specification for hot rolled, and hotrolled and processed high tensile alloy steelbars for the prestressing of concrete

10.4.9 BS 5896 Specification for high tensile steel wireand strand for the prestressing of concrete

10.4.10 Concrete Society Steel for prestressed concrete,Digest no. 4, reference 53.048, 1985


concrete detailing handbook

Documents

theistructe

istructe detailing

sectional

detailing

nominal maximum

large radius

reinforced

high wire