Punching shear checks to EC2
Aspects of Tekla Structural Designer's punching shear design that are specific to EC2.
Limitations and assumptions
Applicability of wall punching checks
Punching checks of walls on slabs are made but should be viewed with particular caution.
In particular there is some debate regarding the applicability of a punching check from a long wall  the check doesn’t consider the potential for stress concentrations at the ends of the wall.
Columns and walls not perpendicular to slabs
EC2 only provides specific design guidance for rectangular columns which are perpendicular to slabs. The program treats all columns and walls that are not perpendicular to slabs as if they are for the punching areas developed.
This is conservative as the punching area/perimeter will be smaller than that for the angled column or wall.
Overlapping control perimeters
 If two control areas touch then both areas are set to Beyond Scope.
 If an edge or corner area contains another column or wall then both areas are set to Beyond Scope.
The exception to this is the pile pair check in the design of pile caps.
Loaded perimeter near slab edges
EC2 only provides specific design guidance for rectangular columns with this guidance being further limited, for the case of edge and corner columns, to those cases where the edge(s) of the slab coincide with the edge(s) of the column. In the program the equations for other column shapes and scenarios are therefore obtained by modifying those equations presented in EC2. It is considered that the modified equations result in either the correct perimeter length being obtained or a conservative value i.e. an underestimate of the perimeter length.
Punching shear perimeters
 Loaded perimeter, u_{0}  perimeter around the loaded area  e.g. face of the wall or column
 Basic control perimeter, u_{1}  is the check punching shear perimeter 2d from the loaded perimeter
 Outer perimeter  the first perimeter at which the punching check passes with no need for shear reinforcement  equal to or outside the basic control perimeter (equal to if the check passes at the basic control perimeter).
d is the effective depth to tension reinforcement in the slab. If a slab around the check position changes depth, the thinnest slab and its d values are used. (Note this definition changes in the presence of a drop panel. )
Loaded, control and outer perimeters
 Loaded perimeter

The Loaded perimeter, u_{0} is the minimum length perimeter enclosing the loaded area, which for a regular column will be the column section perimeter.

In some cases of irregular column shapes, such as the L, T, and elbow shapes below, it will be different (shorter) than the actual column section perimeter.

In the case of columns with drops there are two loaded perimeters  one for the column and one at the edge of the drop, (uses each effective depth).

The maximum allowable stress limit is checked at the loaded perimeter.

 Control perimeter

There will only be one control perimeter, u_{1} at check positions without drops.

At positions with drops there will be one control perimeter outside the drop and possibly one inside if the drop is large enough for it to fit.

Is of circular shape and located at two times the effective depth from column face for columns with circular cross section.

Is of rectangular shape with rounded corners and located at two times the effective depth outside the perimeter equivalent rectangular section for all other shapes.

 Outer Perimeter

Is the punching shear perimeter with enough length to allow for concrete to resist shear stress on it’s own.

Reinforcement is no longer required at this perimeter.

No other perimeters are required to be checked beyond the outer perimeter.

The distance from bounding rectangle section to the outer perimeter is used to calculate the required length of reinforcement.

Its shape follows the control/critical perimeter shapes but changes with the use of nonuniform reinforcement arrangements (i.e.: orthogonal).

Length of the loaded perimeter u_{0}
Loaded perimeter for columns
The length of the loaded perimeter, u_{0} at the column face is calculated in accordance with clause 6.4.5(3) of EC2.
Each possible column shape also has a bounding rectangle or circle calculated to aid in the design calculations.
For a rectangular column:
u_{0} = 2 x (D + B)
Bounding rectangle properties:
D_{Bound} = D
B_{Bound} = B
Bounding Perimeter, u_{0Bound} = 2 x (D_{Bound} + B_{Bound})
For circular columns
Loaded perimeter, u_{0} = π x D
Bounding circle, D_{Bound} = D
Bounding circle perimeter, u_{0Bound} = π x D_{Bound}
u_{0} = shortest distance around the column, as shown above.
Bounding rectangle properties:
D_{Bound} = D
B_{Bound} = B
Bounding Perimeter, u_{0Bound} = 2 x (D_{Bound} + B_{Bound})
Loaded perimeter for walls
The length of the loaded perimeter at the wall face may be calculated in accordance with clause 6.4.5(3) of EC2 as determined below.
u_{0} = 2 x (D + B)
Bounding rectangle properties:
D_{Bound} = D
B_{Bound} = B
Bounding Perimeter, u_{0Bound} = 2 x (D_{Bound} + B_{Bound})
Loaded perimeter for point loads
The length of the loaded perimeter at the point load may be calculated in accordance with clause 6.4.5(3) of EC2 as determined below.
u_{0} = 2 x (D_{load} + B_{load})
Bounding rectangle properties:
D_{Bound} = D_{load}
B_{Bound} = B_{load}
Bounding Perimeter, u_{0Bound} = 2 x (D_{Bound} + B_{Bound})
Additional loaded perimeter drops
The additional loaded perimeter for a column/wall with a drop is defined by the perimeter of the rectangular drop
u_{0drop} = 2 x B_{drop} x D_{drop}
The equivalent perimeter
For “circular” shapes of column (circle and polygon with n sides), the equivalent perimeter 

D_{Equiv} = D_{Bound} x u_{0} / u_{0Bound}

B_{Equiv} = B_{Bound} x u_{0} / u_{0Bound}
For “rectangular” shapes of column (all except circle and polygon of n sides) and walls, the equivalent loaded perimeter 

D_{Equiv} = D_{Bound} x u_{0} / u_{0Bound}

B_{Equiv} = B_{Bound} x u_{0} / u_{0Bound}
The equivalent perimeter is used in three situations

adjustment of the loaded perimeter length/shape u_{0} for edge and corner columns/walls

in calculation of β for edge and corner columns/walls.

Reduction in V_{Ed}
Length of the basic control perimeter u_{1}
For all internal column/wall shapes and point loads the length of the basic control perimeter is
u_{1} = u_{0} + 4 π d
Where d is the effective depth to tension reinforcement in the slab.
Modification of control perimeters to take account of slab openings
If any openings have been defined in the slab and if the nearest opening edge is not greater than 6d from the face of the column then the length of the loaded perimeter at the column face, u_{0}, and the length of the basic control perimeter, u_{1}, are both reduced to take account of the presence of the opening(s) in accordance with fig. 6.14 of EC2.
User Modification of control perimeters
 u_{0}  user reduction
 u_{1}  user reduction
When applied, the length of the respective shear perimeters (except that at the column/wall face) are reduced by the specified amount.
 adjust the length of perimeters of irregular section shapes
 obtain the reduced loaded perimeter for edge and corner cases as suggested by EN199211:2004 clause 6.4.5(3)
Magnification factor, beta
The magnification factor β is used to increase the basic transfer shear force V_{Ed} to take account of the increase in shear stress across part of the control perimeter due to the moment transferred into the column. It is calculated differently depending on whether the column is internal, at an edge or at a corner.
For internal columns,

EN 199211 clause applicability: 6.4.3(3) and 6.4.3(6),

β is always calculated by the rigorous method using equation (6.38) modified for a stress distribution from biaxial bending,

The value for internal columns in braced structures with approximately equal spans from figure 6.21N can be optionally used as a minimum,

For edge columns,

EN 199211 clause applicability: 6.4.3(3) and 6.4.3(6),

β is calculated as the minimum between the values obtained by the rigorous method using equation (6.39) modified for biaxial bending and the simplified value for edge columns from figure 6.21N with an added allowance for unequal spans equivalent to the portion of stress calculated by the rigorous method from moments acting about an axis perpendicular to the slab edge. The minimum is used because exclusively using the rigorous method becomes overly conservative where both experience and guidance from BS 8110 shows that regardless of column contribution to lateral stability using the simplified method produces satisfactory results,


EN 199211 clause applicability: 6.4.3(3) and 6.4.3(4),

EN199211 6.4.3(4) introduces the special case of moment eccentricity being towards the exterior of the slab. And in this special case β is calculated solely by the rigorous method using equation (6.39) modified for biaxial bending,

For corner columns,

EN 199211 clause applicability: 6.4.3(3) and 6.4.3(6),

β is calculated as the minimum between the values obtained by the rigorous method using equation (6.39) modified for biaxial bending and the simplified value for corner columns from figure 6.21N. The minimum is used because exclusively using the rigorous method becomes overlyconservative where both experience and guidance from BS 8110 shows that regardless of column contribution to lateral stability using the simplified method produces satisfactory results,


EN 199211 clause applicability: 6.4.3(3) and 6.4.3(5),

EN199211 6.4.3(5) introduces the special case of moment eccentricity being towards the exterior of the slab. And in this special case β is calculated solely by the rigorous method using equation (6.39) modified for biaxial bending,

Pad base punching shear checks
When working to EC2, punching shear checks are carried out for pad foundations using STR load combinations.
Punching shear should be checked at the face of the column and clause 6.4.4(2) of EC2 states that punching shear should also be checked at perimeters within 2d from the column face where d is the average effective depth of the tension reinforcement in the two orthogonal directions.
In Tekla Structural Designer punching shear is checked at 9 locations i.e. at the column face and at the control perimeter located at 0.25d, 0.5d, 0.75d, d, 1.25d, 1.5d, 1.75d and 2d from the face of the column. Design checks being reported for all perimeters that fall within the dimensions of the foundation.
 Checks at multiple perimeters up to 2d are required in pad base punching checks.
 Column Local axes are always parallel with the pad base edges in the pad base punching checks.
 Loads from the column are always above the pad base (one direction).
 No openings can be placed in pad bases.
 No shear reinforcement is used in pad bases.
Pile cap punching shear checks
When working to EC2, punching shear checks are performed for the column and the individual and paired piles.
 the shear force at a perimeter uses the value from the column reduced by pile loads within the perimeter
 a single additional perimeter based on the location of the pile closest to the column will be checked, only if located in the region between the loaded perimeter and the perimeter at 2d
 variable d is replaced with d_{red} where d_{red} =min (h – “pile penetration depth”, average reinforcement effective depth)
 no moments act on top of the pile, only axial load considered
 shear stress at the column face is checked only for the pile with the largest
pile load:
 v_{Ed,0} = β * P_{n,max} / (u_{0} x d)