SIMULATION OF PUNCHING FAILURE IN REINFORCED-CONCRETE STRUCTURES

A numerical model has been developed to reproduce the punching failure in reinforced-concrete structures. It is characterized by an efficien t triaxial strength criterion for concrete, a nonassociated flow rule reproducing the concrete dilatancy observed experimentally, and a crac king model accounting for the brittleness of concrete failure under va rious states of stress. The simulation of punching failure in a circul ar slab is successfully performed as the localized mode of failure-cha racterized by an inclined crack-is reproduced. It is shown that punchi ng failure is initiated by the coalescence of microcracks inside the s lab, followed by a crack propagation towards the corner of the slab-co lumn intersection. A parametric analysis of the punching failure demon strates that (1) punching failure is due to tensile failure of concret e along the inclined punching crack and is not due to compressive fail ure; (2) increasing the percentage of reinforcement reduces the state of internal cracking resulting in an increase of the failure load and a reduction of the ductility; and (3) the size effect observed experim entally is reproduced and a size-effect law is proposed.