Reliability of models aimed at evaluating the punching resistance of flat slabs without transverse reinforcement

Abstract

Reinforced concrete flat slabs are structural members frequently used in building construction. Despite their many advantages, such structural systems suffer from several drawbacks. From a safety point of view, the concentration of shear forces at the vicinity of local supports, e.g., columns, edges and corners of walls, can lead to possible structural failure from punching. Punching is a dangerous phenomenon due to its brittle mode of failure and its ability to spread over a whole structure, which can be followed by a progressive collapse. Several models for the assessment of punching capacity have been developed and calibrated using experimental results from laboratory tests. Some models are fully empirical, e.g., EC2 (2004), while other models reflect the physical nature of the phenomenon; however, their safety level was calibrated using experimental data, as the model presented in Model Code 2010 or the CSCT-based model, which is expressed in a closed form. This paper deals with a statistical evaluation of the safety level of the previously mentioned models for punching resistance without transverse reinforcement. A database which includes the results of more than 600 experimental tests of flat slab specimens has been used. The relations between the safety of the model and the quality of the concrete used, the amount of the bending reinforcement, and the effective depth were found using advanced statistical methods.