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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 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.

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