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Punching ShearReinforcementfor the Construction Industry
CI/SfB (29) Et6
June 2012
UK CARES Technical Approval
2 Tel: +44 (0) 114 275 5224 www.ancon.co.uk
Shearfix Punching Shear Reinforcement
Ancon Shearfix 4
Comparison with Shear Links 4
System Components 5
Design Information: BS EN 1992-1-1:2004 6
Design Program 7
Design and Technical Support 8
Design Sheet 9
Typical Rail Arrangements 10
Installation Procedure 10
Applications 11
Other Ancon Products 11
Contents
The weight of a slab supportedon a column induces shearstresses in the slab. Thesestresses, if sufficient and whereadditional reinforcement has notbeen provided, would result in thecolumn ‘punching’ through theslab. This punching shear issimilarly induced in the footingon which the column bears.
Although punching shear can berelieved by localised thickening ofthe concrete with downstand
beams and enlarged columnheads, the construction of flatslabs offers many advantages.A consistent head space canreduce the overall height of abuilding and provide significanttime and material savings.
Used within a slab to provideadditional reinforcement aroundcolumns, Ancon Shearfix is theideal solution to the design andconstruction problems associatedwith punching shear.
The system consists of double-headed studs welded to flat rails,positioned around the columnhead or base. The shear loadfrom the slab is transferredthrough the studs into thecolumn.
3
Established, trustedname in concrete
reinforcement
Technical ApprovalTA7-5041
Free EC2 designprogram &
technical support
In-house manufacturefrom CARES-approved
B500C rebar
Full materialtraceability
In-house, traceablebatch testing
Rounded rail ends for safer handling
ISO 9001, ISO 14001 & OHSAS 18001
Shearfix Punching Shear Reinforcement
Technical ApprovalShearfix has been evaluated by UK CARES for use inreinforced concrete slabs and footings designed in accordancewith BS EN 1992 (Eurocode 2). Although British Standard BS 8110has now been withdrawn, shear reinforcement can be safelydesigned and detailed to EC2 where a structure, including theflexural reinforcement of its floor slabs, has been designed to thisprevious design code.
Comparison with Shear LinksAncon Shearfix offers many advantagesover loose shear links. Links can be time-consuming to both design and install.A Shearfix system is easily detailed withAncon’s free calculation program whichgenerates a layout drawing for inclusion in thebuilding plans and, rather than being installedindividually, these studs are supplied to sitewelded to rails at the appropriate spacing.
When comparing links with studs, researchhas shown that any additional material costsincurred when purchasing a prefabricated studsystem, such as Shearfix, are generally faroutweighed by the savings from a significantlyreduced fixing time; these systems being up toten times quicker to install (source: BritishCement Association: Prefabricated punchingshear reinforcement for reinforced concrete flatslabs. BCA, Camberley, 2001).
Details for Specifying/OrderingShearfix systems are designed to suit thespecific load conditions at individual columnsand are therefore manufactured to order. Tospecify and order an Ancon Shearfix system,download the free design program atwww.ancon.co.uk or contact Ancon fortechnical support.
Project ManagementPlease contact Ancon if you would like help increating a Shearfix schedule and a programmefor delivery to suit progress on site. If advisedat the time of ordering, pallets can be packedin priority order e.g by pour number.
Ancon’s ‘Products for Structural Concrete’division offers a dedicated service to theconcrete sector. Contact the team on +44 (0) 114 275 5224 with your Shearfixenquiry.
Corner column
4 Tel: +44 (0) 114 275 5224 www.ancon.co.uk
Ancon ShearfixUsed within a slab to provide additional reinforcement around columns, Ancon Shearfix is the idealsolution to the design and construction problems associated with punching shear.
The system consists of double-headed studs welded to flat rails, positioned around the column heador base. The shear load from the slab is transferred through the studs into the column.
Shearfix is suitable for all column shapes and is easy to install either ‘top down’ or ‘bottom up’,depending on user preference.
Shearfix StudsStuds are manufactured in five diameters (10,12, 16, 20 and 25mm) from CARES-approvedB500C reinforcing bar. The heads are hotforged to three times the diameter of the bar.Studs are manufactured in virtually any lengthto suit the depth of slab, but are normallyformed in increments of 5mm within the 100-1000mm range. The bar used in this systemhas a characteristic yield strength of500N/mm2. The first and last stud from eachproduction batch is tested in-house to ensurethe correct mechanical properties aremaintained.
Shearfix RailsThe studs are welded to the rail at the centresdetermined by Ancon’s software or a designcalculation. The rail performs no structuralfunction but ensures stud alignment andpositioning within the slab.
Shearfix rails are manufactured from stripsof steel which are 16mm wide x 3mm thickon studs up to 16mm in diameter and20mm x 5mm on the larger two studdiameters. The rails feature rounded ends toreduce the risk of injury during handling. Thegap between the strips allows for the passageof concrete during pouring and also enablesthe rail to be nailed through spacers toformwork when fixed ‘bottom up’ i.e. priorto all other reinforcement.
Spacer Bars (Optional)Spacer bars should be used with ‘top down’fixing of an orthogonal rail layout, when railsrun parallel to T1 reinforcement. The spacerbars are tied to the main T2 reinforcementwhere it is necessary to raise the level ofthe studs as if placed on T1 bars.
Double-headed Stud 10, 12, 16,20 and 25mm diameters
Rail
‘Top down’ installation. Rail is tied tothe main reinforcement
Orthogonal Layout Radial Layout
5
System ComponentsThe Ancon Shearfix system comprises double-headed studs welded to flat rails. It ismanufactured to suit the specific requirements of eachapplication. The quantity of each component, thedimensions and spacings, and the layout pattern aroundthe column are determined by calculation. Ancon providesfree software to determine the optimum system design(see pages 6-7).
Product IdentificationEach rail of studs carries an identification codegenerated by the Ancon design program. Toensure the products and documentation can becross-checked, these 16 digit reference codesare used throughout the process from design toinstallation. They appear on the calculationsummary sheet, the DXF layout file and on eachphysical rail when delivered to site.
Rails also include other references such ascolumn number or floor level if provided at thetime of ordering.
Shearfix Punching Shear Reinforcement
u0
u1
Uout
2.0d
≤2.0
d
≤1.5d
0.3-0.5d
1.5d max 0.75d0.75d 0.75d
Ineffective shearperimeter
Opening
Any opening within 6d of columnface must be considered
Openings in the slabWhere there are openings in the slab within 6dof the column face a section of the slab will beineffective and the perimeter lengths will bereduced. A series of rectangular openings canbe added around each column using theAncon design program which then calculatesthe required punching shear reinforcement.
Design ManualAn Ancon Shearfix manual to EC2 is available.Contact Ancon for a copy.
Slab
dep
th
Stud
leng
th
d
Top cover Top reinforcement
0.3dto 0.5d
0.75dmax.
0.75dmax.
0.75dmax.
Stud diameter
Bottom cover Face of loaded area
0.3dto 0.5d
= =
U0 2.0d 1.5d max.U1 Uout
6 Tel: +44 (0) 114 275 5224 www.ancon.co.uk
The shear stress in the concrete is calculatedat the column face and at the basic controlperimeter (2d from the column face) todetermine whether punching shearreinforcement is required.
If reinforcement is required, the position of theouter control perimeter at which shearreinforcement is no longer needed (uout) is thencalculated. Studs are arranged to startbetween 0.3d to 0.5d from the column face towithin 1.5d of the outer control perimeter (uout);intermediate studs are positioned at 0.75dcentres. The Ancon software defaults to a studstart point of 0.5d, although 0.3d is availableas an option.
A radial layout will normally provide the mostcost-effective solution and rails can bearranged with either 30º or 45º between them.The tangential spacing between studs is keptto within 1.5d for studs within the basic controlperimeter (u1) and 2d for studs outside thebasic control perimeter; additional secondaryrails are added as necessary to comply withthis requirement.
For internal, edge and corner columns wherelateral stability does not depend on frameaction between slabs and columns, and whereadjacent spans differ by less than 25%, therecommended β values from BS EN 1992 canbe applied to the design shear load VEd.Internal columns can also have momentsapplied in two directions in which case the βvalue is calculated, but for all other cases andfor all re-entrant corner columns the designeffective shear stress Veff should be enteredwhich must include a value for β calculated inaccordance with the guidance within BS EN1992.
Design Information: BS EN 1992-1-1:2004The design of punching shear reinforcement should be carried out in accordance with therecommendations contained in BS EN 1992-1-1:2004. Shearfix designed to BS EN 1992 can also beapplied to structures designed to BS 8110.
Design ProgramShearfix is designed to suit thespecific requirements of eachapplication. Ancon provides afree design program to simplifythe specification and ordering ofa Shearfix system. This easy-to-use program allows the optimumsystem design to be determined andgenerates a printable data sheet and a DXF fileof the specified layout. Solutions can becreated for all column sizes, shapes andlocations including columns offset from edgesand corners.
The program allows analysis to BS EN 1992(Eurocode 2), BS 8110-1 and AS 3600.
Where there are openings close to the column,a section of the slab will be ineffective andperimeters will need to be reduced; the Ancondesign program allows these reductions to beapplied to each perimeter.
The program requires the following information:
• Column shape(circular, rectangular or ‘L’ shape)
• Column dimensions
• Column location (interior, edge, externalcorner, re-entrant corner)
• Dimension to concrete edge(for offset corner and edge columns)
• Slab thickness
• Concrete grade
• Reinforcement size and spacing
• Cover to reinforcement
• Shear load
• Applied moments
This free program can be downloaded fromwww.ancon.co.uk or emailed on request.Contact Ancon on +44 (0) 114 275 5224 [email protected].
Technical Alliance with Bentley SystemsIn addition to the Ancon design program, theShearfix design method has been integratedinto RAM Concept, the market leadingmodelling tool for reinforced and post-tensioned concrete floor slabs supplied byBentley Systems. An alliance between Anconand Bentley means users of RAM Conceptcan perform an automated punching shearanalysis and detail shear stud rails in theirbuilding models. This enhanced functionalitysaves precioustime at thedesign stage.
Screen shot of a circular column offset fromone edge, with a radial stud layout
The DXF file generated
Screen shot of a rectangular column at are-entrant corner, with a radial stud layout
The DXF file generated
7
The datasheet generated
The datasheet generated
Shearfix Punching Shear Reinforcement
Design and Technical SupportIn addition to the Shearfix design program shown on page 7, Ancon’s Technical Services Team offers freedesign and technical support. A design sheet is available which allows engineers to summarise the criticaldetails of their project and request technical assistance with a Shearfix design. This form is shown onpage 9.
Guidance for Completion of BS EN 1992 (EC2) Design SheetTo ensure we receive all necessary design information Ancon requires the design information foreach column to be compiled together. Unfortunately we are unable to offer a Shearfix designservice based upon sets of separate drawings; the design sheet on the following page has beendeveloped for the transfer of this information. Following receipt of the design information for eachapplication you would like us to consider, calculation sheets will be returned to you detailing therequired Shearfix rails.
LoadsPlease note, that whilst there is a column on the design sheet for moments, these cannot be used in all applications. For different column types the following options are avaliable forspecifying loads:
Rail ArrangementsAncon provides solutions in either orthogonal or radial layouts, therefore please remember to indicateyour preference on the design sheet. In the absence of this information we will provide what weconsider to be the best i.e. most economical solution for each case which will inevitably mean a mix ofthe two in the overall design.
ReinforcementPlease indicate the reinforcement diameter and spacing on the sheet. Where additional reinforcementis being used, please provide both sizes i.e. for main reinforcement of Ø16mm @ 200mm spacingsplus additional reinforcement of Ø20mm @ 200mm spacings, please write 16 + 20 @ 200.
Edge DistancesEdge distances are restricted to three times the effective depth where the effective depth is:
slab depth - top cover - ( )
Column Type Load Specification Options for EC2
Interior Specify VEd and Moments or Specify VEd with set factor of 1.15 or Specify Veff
Edge - Specify VEd with set factor of 1.4 or Specify Veff
Corner - Specify VEd with set factor of 1.5 or Specify Veff
Re-entrant Corner - - or Specify Veff
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8 Tel: +44 (0) 114 275 5224 www.ancon.co.uk
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Shearfix Punching Shear Reinforcement
Installation ProcedureAncon Shearfix is quick and simple to install.It can be fitted either ‘top down’ (after all otherreinforcement) or ‘bottom up’ (prior to otherreinforcement).
‘Top down’ Fixing
• Fix all main reinforcement in position
• Place Shearfix rails around the column tothe layout detailed on job drawings bypassing the studs through thereinforcement grid and resting the carrierrails on the top layer of reinforcement. Usespacer bars where required in orthogonallayouts - see page 5 for details
• Tie rails with wire to main reinforcementand pour concrete
‘Bottom up’ Fixing
• Tie rails with wire to concrete spacers inorder to maintain cover
• Place rail and spacer units around thecolumn to the layout detailed on jobdrawings
• Hammer nails through gap in rails to fix thesystem to formwork
• Fix main reinforcement in position and pourconcrete taking care not to displace thestuds
‘Top down’ fixing
‘Bottom up’ fixing
Typical Rail ArrangementsShearfix is suitable for all column shapes and locations. Some typical arrangements are shown here.
Orthogonal Layouts
Radial Layouts
10 Tel: +44 (0) 114 275 5224 www.ancon.co.uk
Applications Other Ancon ProductsReinforcing Bar CouplersThe use of reinforcing bar couplers can providesignificant advantages over lapped joints.Design and construction of the concrete canbe simplified and the amount of reinforcementrequired can be reduced. The Ancon rangeincludes parallel threaded, tapered threadedand mechanically bolted couplers.
Reinforcement Continuity SystemsReinforcement Continuity Systems are anincreasingly popular means of maintainingcontinuity of reinforcement at constructionjoints in concrete. Ancon Eazistrip is approvedby UK CARES and consists of pre-bent barshoused within a galvanised steel casing. Onceinstalled, the protective cover is removed andthe bars are straightened.
Insulated Balcony ConnectionsAncon Isolan connectors join external concretebalconies to internal concrete floor slabs. Usedto minimise cold bridging, they providecontinuity to the thermal insulation. Standardsystems, comprising rigid CFC-free polystyreneinsulation and duplex stainless steel shearreinforcement, suit most depths of cantileverand simply supported balconies. Conventionalreinforcing bars are used to provide the tensionand compression reinforcement.
Shear Load ConnectorsAncon DSD and ESD Shear Load Connectorsare used to transfer shear across expansionand contraction joints in concrete. They aremore effective at transferring load and allowingmovement to take place than standard dowels,and can be used to eliminate double columnsat structural movement joints in buildings.
Channel and Bolt FixingsAncon offers a wide range of channels andbolts in order to fix stainless steel masonrysupport, restraints and windposts to structuralframes. Cast-in channels and expansion boltsare used for fixing to the edges of concretefloors and beams.
Special Fabrications
Ancon designs and manufactures high integrity
steel components for a wide range of
industries including Civil Engineering, Building,
Infrastructure, Water Treatment, Nuclear and
Mining. Projects are supplied worldwide and
range from small-scale residential
developments to major infrastructure projects.
Markeaton Street, Derby, UK
Phot
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nive
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erby
Kings Dock Mill, Liverpool, UK
Victoria Point, Melbourne, Australia
11
ISO 9001: 2008FM 12226
ISO 14001: 2004EMS 505377
OHSAS 18001: 2007OHS 548992
© Ancon Building Products 2012
The construction applications and details provided in this literature are indicative only. In every case, project workingdetails should be entrusted to appropriately qualified and experienced persons.
Whilst every care has been exercised in the preparation of this document to ensure that any advice, recommendations orinformation is accurate, no liability or responsibility of any kind is accepted in respect of Ancon Building Products.
With a policy of continuous product development Ancon Building Products reserves the right to modify product designand specification without due notice.
These products are available from:
Masonry Support Systems
Lintels
Masonry Reinforcement
Windposts and Parapet Posts
Wall Ties and Restraint Fixings
Channel and Bolt Fixings
Tension and Compression Systems
Insulated Balcony Connectors
Shear Load Connectors
Punching Shear Reinforcement
Reinforcing Bar Couplers
Reinforcement Continuity Systems
Stainless Steel Fabrications
Flooring and Formed Sections
Refractory Fixings
Ancon Building Products114 Kurrajong AvenueMount DruittSydneyNSW 2770AustraliaTel: +61 (0) 2 8808 1111Fax: +61 (0) 2 9675 3390Email: [email protected]: www.ancon.com.au
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Ancon Building ProductsPresident Way, President ParkSheffield S4 7URUnited KingdomTel: +44 (0) 114 275 5224Fax: +44 (0) 114 276 8543Email: [email protected]: www.ancon.co.ukFollow on Twitter: @AnconUK
Ancon (Middle East) FZEPO Box 17225Jebel AliDubaiUnited Arab EmiratesTel: +971 (0) 4 883 4346Fax: +971 (0) 4 883 4347Email: [email protected]: www.ancon.ae
