Punching-shear design of Eurocode 2: a model still in progress

ABSTRACT. Punching-shear is a failure mechanism typical of slabs and footings subjected to concentrated loads applied on very small contact areas. Punching resistance is mainly a function of concrete compressive strength and flexural reinforcement ratio, but it also depends on aggregate size and column side-to-slab depth ratio (size effect). Moreover, in shear-reinforced slabs, punching strength depends also on bond conditions in the transverse reinforcement, which in turn depends on slab depth and reinforcement type. Because of punching-shear complexity, in Eurocode 2 (as in other Codes) the verification rules refer to a conventional failure surface, and the design parameters are chosen to fit the experimental evidence. Nevertheless, the calibration of some parameters looks inadequate, since - for instance - neither size effect nor bond conditions for different transverse-reinforcement types are introduced, and some design rules are hardly exhaustive, like those concerning the design of transverse reinforcement in footings. Last but not least, both EC2 and EC8 are limited to static loading, while the effects of cyclic loading in slab-column connections under seismic excitation are never mentioned, something that is dealt with in other Codes (like ACI), whose provisions are briefly commented.