Evaluation of design concepts for post-installed punching shear retrofitting

Abstract

Punching shear is a brittle and sudden mode of failure observed in reinforced concrete slabs structures. This type of failure typically occurs around the slab-column connections, due to transverse forces being highly concentrated in these areas, thereby causing the column to punch through the slab. Several methods have been proposed for retrofitting and strengthening existing flat slabs against punching shear failure using different reinforcement-types. One of these methods relies on post-installed shear reinforcement for existing flat slab systems. The estimation of the punching shear resistance depends on several variables (geometry, mechanical, material properties, etc.) with some level of uncertainty. This study aims to assess the safety and economic performance of different methods for the design of post-installed reinforcement in an existing flat slab structure endangered by punching shear, using probabilistic analysis. The methods considered include the design procedure according to the American Concrete Institute (ACI) design code, the Canadian Standards Association (CSA) design code, the European Eurocode 2 (EC2) design code and analytical method based on the Critical Shear Crack Theory (CSCT). The probabilistic analysis was conducted based on the Monte Carlo simulation technique implemented using a MATLAB code developed in this study. The reliability index obtained for EC2 design procedure was found to be close to the EN 1990 target reliability level. CSCT and CSA, on the other hand, have a low-reliability index for most of the cases investigated.