Answer:
In the (common) situation of a slab with the upper and lower pillars located at one point, the axial compression actions cancel out the punching effects in the reinforced concrete plate. As a result, their difference will only be considered as the determined punching shear force (Image 01). The punching direction depends on which side of the slab the pillar with the greatest axial action is located.
However, for the internal actions of the result combination (envelope), it is only possible to obtain the difference between the axial actions on the pillars if they belong to the same case or load combination. In the punching shear design of a result combination in RF‑PUNCH Pro, two extreme cases are then considered on the safe side:
- Design punching shear force equal to the difference between the maximum axial action of the upper pillar and the minimum axial action of the lower pillar (Image 02);
- Design punching shear force equal to the difference between the maximum axial action of the lower pillar and the minimum axial action of the upper pillar (Image 03).
If it is not strictly necessary to perform the punching shear design of a result combination (as in the case of seismic loads) instead of the result combination, it is also possible to only select the relevant load combinations for the design in RF‑PUNCH Pro.
