Punching ShearReinforcementfor the Construction Industry
CI/SfB (29) Et6
July 2009
22
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Ancon designs and manufactures high integrity steel products for
the construction industry. Through continuous programmes of
new product development, inward investment and employee
advancement, the company is committed to maintaining the
highest level of customer service within a dynamic and
challenging industry.
Masonry Support Systems
Masonry Reinforcement
Windposts and Lintels
Wall Ties and Restraint Fixings
Channel and Bolt Fixings
Tension Systems
Stainless Steel Fabrications
Flooring and Formed Sections
Shear Load Connectors
Reinforcing Bar Couplers
Reinforcement Continuity Systems
Punching Shear Reinforcement
Insulated Balcony Connectors
Refractory Fixings
3
Used within a slab to provide additionalreinforcement around columns, Ancon Shearfixis the ideal solution to the design andconstruction problems associated withpunching shear. The system consists of double-headed studs welded to flat rails, positionedaround the column head or base.
Punching Shear 4
The Shearfix Solution 4
Comparison with Shear Links 4
Sizes and Configurations 5
Product Identification 5
Design Program 6-7
System Design to BS8110 8
Design Sheet 9
Typical Rail Arrangements 10
Installation Procedure 10Applications 11
Other Ancon Products 11
ISO 9001: 2008FM 12226
ISO 14001: 2004EMS 505377
Shearfix Punching Shear Reinforcement
4
PUNCHING SHEARThe weight of a slab supported on a columninduces shear stresses in the slab. Thesestresses, if sufficient and where additionalreinforcement has not been provided, wouldresult in the column punching through theslab. This punching shear is similarly inducedin the footing on which the column bears.
THE SHEARFIX SOLUTIONUsed within a slab to provide additionalreinforcement around columns, Ancon Shearfixis the ideal solution to the design andconstruction problems associated withpunching shear.
The system consists of double-headed studswelded to flat rails, positioned around thecolumn head or base. The shear load fromthe slab is transferred through the studs intothe column.
Shearfix is suitable for all column shapes andis easy to install either top down or bottomup, depending on user preference (page 10).
Punching Failure
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 withAncons 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).Although punching shear can be relieved by
localised thickening of the concrete withdownstand beams and enlarged columnheads, the construction of flat slabs offersmany advantages. A consistent head spacecan reduce the overall height of a building andprovide significant time and material savings.
Corner column using anorthogonal rail arrangement
Top down installation. A row of studs is passed through the reinforcement grid as aunit and the rail is tied to the main reinforcement
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Sizes and ConfigurationsThe Ancon Shearfix system comprisesdouble-headed studs welded to flat rails. It ismanufactured to suit the specific requirementsof each application. The quantity of eachcomponent, the dimensions and spacings,and the layout pattern around the column aredetermined by calculation. Ancon providesfree software to determine the optimumsystem design (see pages 6-7).
Studs are manufactured in six diameters (10,12, 14, 16, 20 and 24mm) from high strengthsteel bar. The heads are hot forged to threetimes the diameter of the bar. Studs aremanufactured in virtually any length to suit thedepth of slab, but are normally formed inincrements of 10mm within the 100-500mmrange. The bar used in this system has acharacteristic yield strength of 500N/mm2.
The studs are welded to the rail at the centresdetermined by Ancons software or a designcalculation. The rail performs no structuralfunction but ensures stud alignment andpositioning within the slab.
Shearfix rails are manufactured from strips ofsteel, 16mm wide. The gap between the stripsallows for the passage of concrete duringpouring and also enables the rail to be nailedthrough spacers to formwork when fixedbottom up i.e. prior to all other reinforcement.
Double-headed Stud 10, 12, 14,16, 20 and 24mm diameters
Rail
0.5d 0.75d 0.75d 0.5d
Studdiameter
Stud
leng
th
Ove
rall d
epth
Note: d=effective slab thickness
Tel: +44 (0) 114 275 5224 Web: www.ancon.co.uk
0.5d
120mm
0.75d
180mm
0.75d
180mm
0.5d
120mm
Studdiameter12mm
Stud
leng
th
230m
m le
ngth
AS12-3-230-600
Product IdentificationEach rail of studs carries the following identification:
Shearfix Code and Stud Diameter - Number of Studs - Stud Length - Rail Length
Column/Grid Reference
Floor Level
e.g. AS12-3-230-600
K15
Level 2
All dimensions are in millimetres.
PROJECT MANAGEMENTPlease contact Ancon if you would like helpin creating a Shearfix schedule and aprogramme for delivery to suit progress onsite. If advised at the time of ordering,pallets can be packed in priority order e.gby pour number.
Ancons Products for Structural Concretedivision offers a dedicated service to theconcrete sector. Contact the team on +44 (0) 114 275 5224 with your Shearfixenquiry.
Shearfix Punching Shear Reinforcement
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DESIGN PROGRAMShearfix is designed to suit the specificrequirements of each application. Anconprovides a free design program to simplify thespecification and ordering of a Shearfixsystem.
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 8110-1,DIN 1045-1 and AS 3600. For a Eurocode 2version please contact Ancon.
Users can design a radial or an orthogonal raillayout. This feature, which is unique to theAncon program, allows the most economicaldesign (fewest number of studs) to beachieved for each application.
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 followinginformation:
Column shape(circular, rectangular or L shape)
Column dimensions Column location (interior, edge, external
corner, 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 momentsThis free program can be downloadedfrom www.ancon.co.uk, emailed onrequest or supplied on CD. Contact Anconon +44 (0) 114 275 5224 for your copy.
A hard copy of the calculation method toBS 8110 is available on request.
Screen shot of a circular column offset from one edge, with a radial stud layout
The datasheet generated
The DXF file generated
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Tel: +44 (0) 114 275 5224 Web: www.ancon.co.uk
Screen shot of a rectangular column, offset from a re-entrant corner, with an orthogonal rail layout
The datasheet generated
The DXF file generated
8
Shearfix Punching Shear Reinforcement
DESIGN INFORMATION:BS 8110-1:1997The shear stress is checked at a perimeter1.5d (d = effective slab thickness) from theface of the column (u0), further checks arecarried out at successive intervals of 0.75d (u1,u2 etc) until a perimeter is reached which doesnot require shear reinforcement (un).
The first stud is positioned 0.5d from the faceof the column, with the spacing betweenindividual studs taken as 0.75d with amaximum limit of 500mm. The maximumspacing between parallel rails is 1.5d.
When using the Ancon design program acheck is carried out for over-reinforcement; ifthis check fails, a warning message states thatfailure due to punching shear is possible andan increase in slab thickness will be required.
Two layouts are available, radial and orthogonal.
Radial LayoutRails are positioned on the two main axes toall available column faces with diagonal rails atthe corners; all perimeters have radiusedcorners, circular columns have circularperimeters. The spacing between theoutermost studs on the diagonal rails is kept toa maximum of 3d.
Orthogonal LayoutRails are positioned on the main axes to allavailable column faces, additional rails arepositioned in lin
