PUNCHING SHEAR OF CONTINUOUS FLAT REINFORCED-CONCRETE SLABS

This paper presents experimental results for the punching shear of a t wo bay-by-two-bay flat reinforced concrete slab. The results show that the interior column slab connection is more critical in punching shea r than the edge and corner column connections in a properly designed m ultibay flat slab. Large flexural cracks indicative of steel yield wer e evident at all connections where punching shear failures occurred. S upplementary supports can increase punching shear capacity by about 30 percent at edge column connections. An empirical method using a shear perimeter around the loaded area is developed. The code provisions of ACI 318-89, BS 8110-85, and the CEB-FIP 1990 Model Code were recalcul ated in terms of mean concrete strength using published experimental r esults to remove their conservatism. Comparison shows that isolated pu nching tests can represent the punching shear behavior of interior col umn slab connections in continuous slab systems. All four methods were adequate to predict the capacity of edge and corner column connection s under gravity loads. Finally, the code format equations and the prop osed equation were recalculated to obtain 95 percent characteristic va lues.