Effects of openings on the punching shear strength of RC flat-plate slabs without shear reinforcement

Openings in RC flat-plate slabs are one of the critical factors that influence the punching shear strength of the slab and determine its thickness in the vicinity of the slab-column joint. This study experimentally investigates the effects of openings on the punching shear strength of flat-plate slabs without shear reinforcement. Tests were performed on eight flat-plate slab specimens considering the layout and number of openings as test variables. The failure characteristics of each specimen are examined, and the effects of the test variables on the punching shear strengths of the test specimens are investigated. The measured punching shear strengths of the test specimens are compared with the predictions of several concrete design codes, including the American Concrete Institute (ACI), Comite Euro-International du Beton and Federation Internationale de la Precontrainte (CEB-FIP) model and federation internationale du beton (fib) model codes. This indicates that the reductions in punching shear strength due to the existence of openings are generally proportional to the loss of effective critical sections, and an L-shaped opening layout around the corner of the column may further reduce the punching shear strength and may contribute to the loss of effective critical sections due to the existence of openings. Copyright (C) 2015 John Wiley & Sons, Ltd.