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 M_x, M_y and by the shear force N_sd provided by:

where:	A	-	area of footing
	V	-	assigned vertical force developed in column
	At	-	hatched area in fig.

Dimensioning of shear reinforcement area A_t

The program computes the maximal shear force N_sd developed in the critical section, the shear force transmitted by concrete with no shear reinforcement N_rd1 and the maximal allowable force N_max:

For N_{sd  <} N_rd no shear reinforcement is needed.

For N_{sd  >} N_rd and N_{sd  <} N_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 N_{sd  >} N_max the shear reinforcement cannot be designed. It is therefore necessary to increase the cross-section height.