RELATIONSHIPS BETWEEN FLEXURAL AND PUNCHING FAILURE

Flexural and punching failure experiments were performed on flat slabs by controlling the vertical displacement under the column. This allow s the monitoring of the descending branch of the load-displacement cur ve, and establishes that flexural failure is characterized by a smooth decrease of the load-carrying capacity whereas punching failure exhib its a sudden reduction of this capacity.It is shown both experimentall y and with force equilibrium that one condition for punching failure o ccurs is that the internal strength of the punching cone is larger tha n the punching strength itself. The punching load was reached for a pu nching crack inclination of about 30 deg to the middle plane of the sl ab. By increasing this inclination, the flexural failure load was appr oached and the sudden decrease of the load-carrying capacity was reduc ed. A smooth transition between punching and flexural failure, which i s controlled by the punching crack inclination, is revealed and an int eraction formula is proposed.