Verification of spread footing for punching shear
Verification of spread footing for punching shear
The critical section loaded in shear u is distant from the column edge by one half of the footing thickness. It is loaded by the prescribed moments Mx, My and by the shear force NSd provided by:
where: | A | - | area of footing |
V | - | assigned vertical force developed in column | |
At | - | hatched area in fig. |
Dimensioning of shear reinforcement area At
The program computes the maximal shear force NSd developed in the critical section, the shear force transmitted by concrete with no shear reinforcement NRd1 and the maximal allowable force NRd,max:
For NSd < NRd no shear reinforcement is needed.
For NSd >NRd and NSd < NRd,max the shear reinforcement must be introduced. The ultimate shear force is given by:
where: | u | - | critical cross-section span |
α | - | is angle of crooks | |
Asw | - | overall area of crooks in footing |
For NSd >NRd,max the shear reinforcement cannot be designed. It is therefore necessary to increase the cross-section height.
