Verification of Spread Footing for Punching Shear
The program allows us to verify spread footing for punching shear or for the design of shear reinforcement. The critical section loaded in shear bo is distant from the column edge by one half of the footing thickness. It is loaded by the prescribed moments M*x, M*y and by the shear force V* 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 V* developed in the critical section, the shear force transmitted by concrete with no shear reinforcement Vc, and the maximal allowable force Vmax:
where:
where αs: | 20 | - | for interior column |
15 | - | for edge column | |
10 | - | for corner column |
βc c is the ratio of the long side to the short side of the critical section
For V* < ϕVc no shear reinforcement is needed.
For V* > ϕVc and V* < ϕVmax the shear reinforcement must be introduced. The ultimate shear force is given by:
where: | bo | - | critical cross-section span |
α | - | is angle of bends | |
Av | - | overall area of bends in footing |
For V* > ϕVmax the shear reinforcement cannot be designed. It is therefore necessary to increase the cross-section height.