Punching shear code provisions examination against the creation of an opening in existed RC flat slab of various sizes and locations

Abstract

Punching shear is a critical problem in flat slabs directly supported at columns resulting in a high-stress concentration area, increasing the probability of brittle punching shear failure. However, the capacity is reduced by creating an opening that affects the overall behavior of the slab based on its size and location with respect to the loaded area. Furthermore, the design and analysis of the various structural elements are based on international regulations that have major differences in their basis and executions. In this study, the different code provisions in punching shear of RC two-way flat slab without shear reinforcement are examined under various opening sizes and locations using the Nonlinear Finite Element Analysis (NLFEA) procedure using ABAQUS software. A total of twenty-one model has been simulated for examining the prediction accuracy by the ACI318-19, MC2010, and EC2 under the effect of opening size (100, 200, and 300) mm, and locations (zero, 0.25d, 0.50d, 2.0d, 4.0 h, 5.5d, and 6.0d) under two main categories; the critical punching perimeter, and the critical opening location. However, it has been revealed that the proposed value of 0.50d as the critical punching perimeter is the most reliable one; besides, the value of 4 h is enough for defining the position where the effect of an opening could be neglected regardless of its size. Furthermore, it has been found that the column-to-opening ratio (C/O) is a very significant factor in controlling the punching shear capacity prediction accuracy by the different codes. Predictions get more overestimated under larger (C/O) values where increasing the C/O ratio by half increases the ultimate deflection percentage by an average of 22 %, except for those with smaller C/O values of less than 0.5, where it only reaches a maximum value of 13 %. Moreover, code prediction of the ACI318-19 and the MC2010 was found to be overestimated in all cases. In contrast, the EC2 was underestimated with an accurate prediction for an opening location of 2.0d from the column's face. However, it has been found that ACI318-19 is the most accurate one regarding the critical punching perimeter (0.5d) and critical opening location (4.0d).