Verification of spread footing for punching shear
Verification of spread footing for punching shear
The program allows 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 Mx, My and by the shear force Vu 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 Vu developed in the critical section, the shear force transmitted by concrete with no shear reinforcement Vc as minimum of values (Art. 11.11.2.1):
where βc is ratio of log side to short side od column.
where αs = | 40 | - | inner column |
30 | - | edge column | |
20 | - | corner column |
and the maximal allowable force Vmax (Art. 11.11.3.2):
For Vu < ϕ×Vc no shear reinforcement is needed.
For Vu > ϕ×Vc and Vu < ϕ×Vmax the shear reinforcement must be introduced. The ultimate shear force is given by (Art. 11.11.3.1):
where: | bo | - | critical cross-section span |
α | - | is angle of crooks | |
Av | - | overall area of bends in footing |
For Vu > ϕ×Vmax the shear reinforcement cannot be designed. It is therefore necessary to increase the cross-section height.
