When a slab is subject to a concentrated load or to a load acting over a small area, the punching shear resistance of the slab should be checked. SCIA Engineer can deal with concentrated loads from columns or supports that are perpendicular to a slab.
You can define holes in the plate and column heads. The program automatically determines the necessary critical parameters and performs the punching check. If necessary, it is also possible to calculate and represent extra punching. The output can be configured, from a very simple to a very detailed calculation report.
Circular and rectangular cross-sections can be analysed. Other cross-section shapes are automatically transformed to rectangles. The procedure of the check consists of several steps:
- Set up - input of default values for parameters used in the assessment procedure;
- Punching data - specification of check parameters for individual members;
- Punching check - execution of the check itself
Design of required reinforcement in critical sections in accordance with following codes:
Punching module checks the plate resistance against punching in critical sections according to codes (concentrated loads from columns or supports perpendicular to the lower surface of the plate) for selected load cases; Check of shear stress in the critical section. There is possibility to define the geometry - support in a corner, along the edge, inside of a plate. Technological openings are taken into account in the calculation of the critical perimeter length of the critical section. There is possibility to define square or prismatic column heads. Data for the punching shear check are taken from the calculation model of the analysed plate. Tension can be taken from the results of the calculation of the model or defined manually.
Punching shear check can be performed for
- an automatically calculated required amount of the main reinforcement in the slab or for
- a user-defined main reinforcement in the slab;
Several points can be checked at the same time.
Types of output:
- Unit check with graphical interpretation.
- Documents and tables
- Document for single check with clear layout
Beta factor for punching
As mentioned in the introduction, you can select from several types of calculation method for beta factor. SCIA Engineer offers the following possibilities:
- Simplified method according to EN 1992-1-1, clause 6.4.3(6), default method
- General method according to EN 1992-1-1, clause 6.4.3(3-5)
- General method according to general formula
- User input of β factor (only if punching data are defined)
The maximum punching shear stress in EN 1992-1-1, clause 6.4.3(3) is calculated according to formula below.
It follows that maximum punching shear stress depends on:
- design ultimate shear force on the perimeter (VEd)
- length of control perimeter (ui)
- mean effective depth of the slab at the control perimeter (d)
- shear factor taking into account moment transfer (b). The calculation of this factor is based on the principle that the moment transferred between the slab and the column must be equal to the moment produced by the shear Dv distributed around the perimeter ui