PART4 (1)

The CARES Guide to Reinforcing Steels Part 4

Fabrication of Reinforcement

Fixing on-site

Notation for reinforcing steels (from BS 8666:2005 including amendment)

Table 1 Note 1 In the Grade description B500A, etc., B indicates reinforcing steel.Note 2 Within the ranges given, the grade(s) supplied for notations H and

B are at the suppliers discretion.

1.0 Introduction

The fabrication of reinforcing steels,into shapes suitable for fixing into theconcrete formwork, is normallyperformed 'off-site' in the UK, byspecialist reinforcement fabricators,although it is recognised that thisdiffers globally. Very littlereinforcement is cut and bent on-sitein the UK today. Although the cuttingand bending of reinforcement appearsrelatively straightforward, thespecialist reinforcement fabricator iswell equipped to do so in aconsistently accurate manner and, byworking within a defined set of qualitymanagement criteria, as provided bythe CARES Scheme, provides animportant link in the reinforcementsupply chain. The accuracy of cuttingand bending operations is vital toensure proper fit on site, and tomaintain required lap lengths,anchorage lengths and cover.

Part 4 of the CARES Guide describesthe cutting and bending operations,providing an understanding of theprocesses involved, as well as therole that the CARES scheme forfabricators plays in providingassurance of the quality of fabricatedreinforcement.

2.0 British Standards

Within the UK and abroad, BS 8666,Specification for scheduling,dimensioning, bending and cutting ofsteel reinforcement for concrete,specifies requirements for scheduling,dimensioning, bending and cutting ofreinforcing steels. It is of vitalimportance that the standard beingused, e.g. BS8666:2005, is clearlystated on the cutting and bendingschedule. A helpful fact sheet entitledPublication of British StandardBS8666:2000 is available fromCARES, explaining the differencesbetween BS8666 and its predecessorBS4466 which may still be in use bysome practices. BS 8666 also includesrequirements for the scheduling andfabrication of welded fabric. This iscovered in Part 5 of this Guide.

Type of steel reinforcement

For diameters 12mm, Grade B500A, B500B or B500Cconforming to BS 4449:2005For diameters 12mm, Grade B500B or Grade B500Cconforming to BS4449:2005

Grade B500A according to BS 4449:2005

Grade B500B or grade B500C according to BS 4449:2005

Grade B500C according to BS 4449:2005

A specified grade and type of ribbed stainless steelconforming to BS 6744:2001

Reinforcement of a type not included in the above list havingmaterial properties that are defined in the design or contractspecification

Notation

H

A

B

C

S

X

Courtesy of COSTAIN Ltd

>

Table 2 Note: For all practical purposes, this table must be used in conjunction with BS 8666, latest issue. Should you have any queries regarding the use of this standard, please contact your CARES approved fabricator, or CARES directly.

BS 8666:2000 Shape Codes

BS8666, and the now supersededBS4466, are the basis for the UKCARES scheme for reinforcementfabricators. Under CARES approval, allapproved reinforcement fabricatorsare required to fully understand therequirements of their customers andto provide reinforcement to thespecified standards and relatedbending schedule.

The scheduling standard defines thebar schedule used to transmitrequirements for cut and bent shapesfrom the designer/detailer to thecontractor and reinforcementfabricator. Bending schedules havespecified notations for calling up thedifferent reinforcing materialsavailable on the market, including thedifferent grades of conventional

carbon steels (BS4449), stainlesssteels (BS6744) and any otherspecial steels. The Notations aregiven in Table 1.

The scheduling standard BS8666and the product standard BS4449were both revised in 2005, and BS8666 has been further amended todefine a specific notation

Shear line

Figure 1 Courtesy of Stema/Pedax

Minimum Radius for Scheduling in BS 8666

Table 3

Bar Size (mm) Grade Notation

R T, B, S F, D, W

< 16mm 2d 2d 2d

> 16mm 2d 3.5d 2d

requirement for Grade A steel. It isimportant that the specific revisions ofboth standards be used.

Bent shapes are defined by means of standard shape codes (Table 2).When non-standard shapes are required,guidance is given as to how theseshould be referenced (as shape code99s), and specified by an appropriatedrawing. For each standard shape, thestandard gives the overall length of barused, as a function of the principledimensions.

BS 8666 specifies various restrictionson the bending of shapes as follows:

The minimum bend radius is specifiedfor the different material grades (seeTable 3).

The minimum dimension from a bendto the end of the bar (bob length) isspecified as a function of bardiameter and grade.

The maximum limit for which a pre-formed radius is required.

The restrictions on dimensions ofparticular shapes.

BS 8666 specifies the format for theschedule in which the requirements forcut and bent reinforcement are to bespecified. Schedules are often suppliedto fabricators in the form of faxed copiesof rather poor quality, leading to errors intranscription of data. An alternative is forschedules to be e-mailed by means ofcommercially available softwarepackages. This saves significant time forthe fabricators, and improves theaccuracy of information. In some cases,this electronic schedule information can

be linked directly to the computercontrol system of the productionequipment. There are also significantbenefits for designers andcontractors in terms of reducederrors, fewer queries, and easierchange procedures. The subject ofelectronic handling of datathroughout the supply chain forreinforcement is covered in Part 9 ofthis Guide.

3.0 Fabricationprocesses

The basic fabrication processesconsist of cutting and bending thereinforcing steel. The actualprocesses employed in the bendingand cutting of reinforcing steeldepend principally on the form ofmaterial being processed, whetherbar or coil.

Generally reinforcing bar is suppliedto the fabricator from the mill inbundles of straight lengths. Stock lengths are normally 12m,14m and 15m, and can be up to18m. Non-standard lengths can alsobe supplied, usually subject to aminimum tonnage requirement. Bar is fabricated by cutting on shearlines, and subsequently by bendingon power bending machines.

Reinforcing bar, in coil form, is also supplied from the mill in acontinuous length. This may be in a 'spooled' form. Coil is normallyavailable in sizes 8-16mm, although larger diameters are being developed.

Coil weights may typically be two tothree tonnes, so that for the smallerdiameters, the coil can be severalkilometres in length. Coil can beunwound and cut to length in a singleoperation, called either decoiling orstraightening. Coil can also bestraightened, bent and cut to mostshapes, in continuously operatingmachines commonly referred to asAutomatic Link Benders (or ALBs).

3.1 Cutting

Bars will normally be cut to therequired length in machines calledShear Lines (Figure 1). Thesemachines normally consist of anunscrambler, where bundles of steelare split and loaded into the shear line,a roller table which presents the barsto the cutting shears, a hydraulicallyactivated set of shear blades, a run-outtable to take the cut bars, and pocketsinto which the cut lengths of steel aredeposited. In an automated line, thedifferent cuts required from each milllength can be programmed into themachine, improving efficiency andaccuracy, and decreasing wastage.The minimum length that can normallybe processed by a shear line is around600mm. The tolerance specified in BS8666 for cutting is 25mm, which iseasily achieved by these machines.


Power bender


b) The ribs on the bar surface mayresult in a cross section which isnot exactly round. This means thatresistance to bending depends onbar orientation.

c) The hot rolling process mayintroduce a degree of twist alongthe length of the bar, thusexacerbating the problems of a) and b) above.

d) The degree of spring-back whenthe bending load is released is afunction of bar profile, steel type,and cast characteristics. Suitable allowance must be made for this.

Bar shape requirements, e.g. in termsof twist or straightness, which canaffect consistent bendingperformance, are not covered by BS4449. It is the responsibility of steelmills, to supply product that is fit forpurpose in this respect. This iscovered in the CARES scheme,whereby the CARES assessments ofsuch steel mills, which includesprocess control requirements,ensures that bar shape is beingcontrolled.

It is not uncommon for designers tospecify shapes which are outsidethe bending specifications ofBS8666. In particular, bends tighterthan allowed are often specified,particularly on small size links. This should be avoided whereverpossible. If unavoidable however,designers will normally be asked toauthorise the fabrication outsidespecified limits.

3.3 Decoiling

The processes of decoiling and/orstraightening of coil have alreadybeen described in Part 2 of thisGuide. From the perspective of thereinforcement fabricator, processingcoil instead of bar has manybenefits, including increasedproductivity, increased material yieldand increased flexibility. The use of coil in sizes up to 16mm hasincreased markedly, particularly in the UK but also elsewhere, and many fabricators prefer to use coil exclusively on these sizes.The decoiling process must beproperly controlled to ensure properstraightness of the product, and tominimise any damage to the ribs, or change of mechanical properties.The quality of the ingoing coil interms of consistency of geometryand mechanical properties isimportant in enabling reinforcementfabricators to process steelefficiently.

3.4 Automatic LinkBenders (ALB's)

ALBs process coil directly to bent shapes. These machinesincorporate a roller straighteningsystem, a shear and a bending table(Figure 3). ALBs increase efficiencyof fabrication, compared toconventional cutting and bending.Because of the continuous natureof the operation, there are aspectsof the bending, which cannot be asclosely controlled as for a slower,manual operation however. Inparticular, problems may be createdsuch as links bending out of plane.This is principally a function of theconsistency of the ingoing coil.

3.2 Bending

Bending of reinforcing bar is invariablycarried out on power bending machines.These are normally driven by an electricmotor, through a gearbox with a numberof selectable speeds. Bending isachieved by placing the bar across arotating turntable. The bending mandrelis placed at the centre of the turntable. Acarrier pin, placed off-centre of the tabledeforms the bar continuously as theturntable is rotated, whilst the back endof the bar is restrained by a resistanceroller or stop. (Figure 2). All deformingrollers are normally free rotating, so asnot to offer resistance to the bar, whichcould cause stretching. Benders may besingle-headed or double-headed, thelatter used to speed up production ofshapes having bends at both ends.

Although the concept of bending ofreinforcing steel is simple, it does requiresome skill and experience. Ribbedreinforcing steel is not a consistentproduct to bend for the followingreasons:

a) The hot rolling process employed inthe steel mill may produce significantvariation in dimensions along thelength of bars/coils.


Carpet reinforcement being rolled out on site

Figure 4 Courtesy of Hy-Ten Reinforcements

Automatic Link Bender (ALB)


3.5 Developments

Although the basic processes ofcutting and bending haveremained relatively un-changed,reinforcing fabricators areincreasingly seeing the benefits ofincreased automation, computercontrol, and electronic datainterchange (see Part 9 of thisGuide).

Fabricators are increasingly usingwelded pre-fabrication tomanufacture assembledreinforcement cages, ready forfast assembly on site (see Part 6of this Guide).

A relatively recent innovation isthe development of carpetreinforcement, consisting of aseries of reinforcing bars weldedto a thin steel strip. This productcan be rolled up like a carpet, andthen simply unrolled on site forvery rapid fixing. It is claimed thatthese systems can give 80-90%reduction in fixing costs, and a 20-40% material saving. The systemsare suitable for reinforcement ofmany types of slabs (see Part 8 ofthis Guide).

Other developments includeContinuity Strips and bespokeShear reinforcement.

The element of the scheme provides for:

Independently verified compliancewith the specified standard (BS8666).

Quality management systemassessment using ISO 9001 as abasis.

Verification that raw material is onlypurchased from CARES approvedmanufacturers, thus ensuringapproval for the whole processroute, from steel making, rolling,processing, fabricating to deliveryto site.

Full traceability throughout thesupply chain. All batches offabricated reinforcement can betraced back to the original mill testdata.

Verification of the long-term qualitylevel as defined in BS 8666.

Resolution of any complaints madeto CARES approved suppliers.

Removing the need for purchasersto have their own testing andinspection regime on site, savingconsiderable time and cost.

4.0 The CARES Schemefor Fabricators

Appendix 2 of the CARES Scheme forSteel for the Reinforcement of Concretecovers Quality and operationsschedule for the processing and/orsupply of steel products for thereinforcement of concrete.


UK CARESPembroke House, 21 Pembroke Road, Sevenoaks, Kent TN13 1XR

Phone: +44(0)1732 450000 Fax: +44(0)1732 455917E-mail: [email protected]

URL: www.ukcares.com

Copyright UK CARES

This guide is available in pdf format. If you wish to receive a pdf copy and receive future updates, please send an e-mail to the address above

manufacturers. The product can beused without the need for furtherproduct testing. Where CARESapproved fabricators are not specified,the onus is on the purchaser to verifycompliance, which may requireinspection and testing involving bothsignificant cost in both testing and theassociated site delays.

4.2 CARES list ofapproved fabricators

CARES maintains, in an updated form, alist of approved firms. This is publishedon the CARES Website atwww.ukcares.com in an easilysearchable form and includesreinforcement fabricators. The listdescribes the firms scope of approvaland useful contact information. Thescope of certification allocated to eachCARES approved firm will include theproduct standards for which thatfabricator is approved to cut, bend anddistribute. If there are any doubts aboutthe scope of approval of areinforcement fabricator, the CARES listof approved firms should be consulted,or alternatively, the CARES office canbe contacted for advice.

5.0 References

11.. Improving rebar information andsupply Best Practice Guide for In-Situ Concrete Frame Buildings.British Cement Association 2000.

CARES approval is gained by afabricator only after demonstratingthat its quality management systemmeets the requirements of ISO9001and additional product-specificCARES requirements. This includeschecking the fabricated shapesagainst the requirements of BS 8666.

Once approval has been granted, it ismaintained by twice-yearlysurveillance audits conducted byCARES specialist auditors. At theseinspections, the quality system isaudited, dimensional checks aremade to ensure product isconsistently complying with BS 8666and customer requirements, andtraceability systems are examined.

It should be emphasised that thefabricator plays a vitally important rolein the reinforcing steel supply chain.Some fabricators have claimed thatthey do not need themselves to beCARES approved, because they onlypurchase steel from CARES approvedsources. This is not the case, sinceonly CARES approved fabricatorshave independent verification of theirquality systems, bending capabilityand traceability systems.

4.1 The CARES Scheme-verified compliance

When using CARES approvedfabricators, specifiers can beconfident that all steel supplied willbe from CARES approved

P4/REV1/2011/AARON

22.. BRITISH STANDARDSINSTITUTION. BS 8666:2000Specification for scheduling,dimensioning, bending andcutting of steel reinforcement forconcrete.

33.. BRITISH STANDARDSINSTITUTION. BS 8666:2000Specification for scheduling,dimensioning, bending andcutting of steel reinforcement forconcrete.

44.. BRITISH STANDARDSINSTITUTION. BS 8666:2005Scheduling, dimensioning,bending and cutting of steelreinforcement for concrete -Specification.

55.. Publication of British StandardBS 8666:2000 CARESInformation Sheet.

66.. CARES Reinforcement Guide No. 5 Welded Fabric.

77.. Steel for the reinforcement ofconcrete Appendix 2 Qualityand operations assessmentschedule for the processingand/or supply of steel productsfor the reinforcement of concrete.UK CARES.

88.. CARES Reinforcement Guide No. 2 CARES approvedreinforcing steels; processes andproperties.

99.. CARES Reinforcement Guide No. 6 Welded Pre-fabrication.

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PART4 (1)