The Punching category manages the parameters relevant for the punching shear design.
The control perimeter is determined by an iterative calculation. If you select the “Define iterative critical section for foundation” check box, you can manually specify the distance to the load surface lw,it.
kred is a factor for taking into account the relieving effects of soil pressures within the punching cone. This factor determines what percentage of the soil pressure in the punching cone is included as a load relief in the calculation of the resulting shear force. A value of kred = 1.00 means that the soil pressures within the punching cone are fully taken into account and thus have a maximum relieving effect. A value less than 1.00 reduces the soil pressure taken into account accordingly, resulting in a higher resulting shear force.
The parameter β can be determined in various ways. There are three options to select from in the list. The load increasing factor can be determined by assuming a fully plastic shear stress distribution according to EN 1992-1-1 [1] 6.4.3(3) or from constant factors according to 6.4.3(6). Additionally, it is possible to enter a user-defined value.
For a stepped foundation, two separate punching shear design checks are performed: one at the first step and one at the foundation plate:
Design of the foundation plate
The first punching shear design concerns the foundation plate. The loaded area is the column cross-section. The control perimeter is therefore designed at a defined distance from the column edge and covers only the area immediately surrounding the column.
Design at the first step
The second design check concerns the first step. The column first transfers its load to the first step before the step distributes the load over the entire foundation plate. The governing loaded area is therefore not the column cross-section, but the base area of the first step.
