Punching Shear of Reinforced Concrete Flat Plates with Openings

Punching shear tests were conducted on 13 reinforced concrete flat plates with and without openings or/and shear reinforcement. The openings (one or two) were adjacent to the shorter sides of rectangular supports and had widths equal to those of the supports. The methods of calculating punching shear strengths given in ACI 318-11 and MC90/EC2 are reviewed along with some proposed formulations, and their predictions are compared with the test results. Conclusions are drawn on the influence of plate depth on the unit shear resistance from the concrete; the possibility of using straight projections of openings onto control perimeters, rather than radial ones, to evaluate the effect of openings; and the case for considering eccentricity in a pattern of openings as an influencing factor and the detailing of shear reinforcement. It is shown that for the relatively small openings considered, the provision of continuous bars adjacent to openings-to replace the areas of reinforcement-seems to be an adequate approach to flexural design. It is suggested that the shear stress used for the concrete in ACI 318-11 could be increased for the assessment of strengths at the edges of zones with shear reinforcement (outer control perimeter).