Design Information: BS EN 1992-1-1:2004 (Eurocode 2)
The design of punching shear reinforcement should be carried out in accordance with the recommendations contained in BS EN 1992-1-1:2004. Shearfix designed to BS EN 1992 can also be applied to structures designed to BS 8110.
The shear stress in the concrete is calculated at the column face and at the basic control perimeter (2d from the column face) to determine whether punching shear reinforcement is required.
If reinforcement is required, the position of the outer control perimeter at which shear reinforcement is no longer needed (uout) is then calculated. Studs are arranged to start between 0.3d to 0.5d from the column face to within 1.5d of the outer control perimeter (uout); intermediate studs are positioned at 0.75d centres. The Ancon software defaults to a stud start point of 0.5d, although 0.3d is available as an option.
A radial layout will normally provide the most cost-effective solution and rails can be arranged with either 30º or 45º between them. The tangential spacing between studs is kept to within 1.5d for studs within the basic control perimeter (u1) and 2d for studs outside the basic control perimeter; additional secondary rails are added as necessary to comply with this requirement.
For internal, edge and corner columns where lateral stability does not depend on frame action between slabs and columns, and where adjacent spans differ by less than 25%, the recommended ß values from BS EN 1992 can be applied to the design shear load VEd.
Internal columns can also have moments applied in two directions in which case the ß value is calculated, but for all other cases and for all re-entrant corner columns the design effective shear stress Veff should be entered which must include a value for ß calculated in accordance with the guidance within BS EN 1992.
Openings in the slab
Where there are openings in the slab within 6d of the column face a section of the slab will be ineffective and the perimeter lengths will be reduced. A series of rectangular openings can be added around each column using the Ancon design program which then calculates the required punching shear reinforcement.
An Ancon Shearfix manual to EC2 is available. Contact Ancon for a copy.
Other Design Codes
In addition to BS EN 1992 (Eurocode 2), the Ancon program enables design of a Shearfix system to BS 8110 and AS3600.
When forming a cross brace using tie bars, the new Ancon Cross Coupler offers a streamlined alternative to an anchor disc.
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