DESIGN EQUATIONS TO PREDICT THE ULTIMATE PUNCHING SHEAR STRENGTH OF SLAB-COLUMN CONNECTIONS

Abstract

Flat slabs offer an economic and competitive structural form of building construction, but they sometimes fail in a brittle manner without developing an overall yield mechanism at failure. Steel fibre concrete, on the other hand, possesses characteristics of energy absorption capability and ductility, and can transform a sudden structural failure into a ductile mode. However, the use of steel fibre concrete is hampered in practice by the absence of a reliable theoretical model and design equations. Further, existing Code provisions do not account for the presence of fibre reinforcement in concrete. The aim of this paper is to rectify these two situations. The paper presents two design equations to predict the ultimate punching shear strength of slab-column connections - one for plain concrete slabs and the other, for fibre concrete slabs. The former is applied to 20 test results reported in the literature, and the theoretical predictions are compared to those of ACI, BS, CEB-FIP and EC2 Codes. It is shown that the authors' design equation gives a better prediction of ultimate loads with a smaller standard deviation compared to those of the Codes. The second design equation is applied to 62 fibre concrete slabs with a wide range of test parameters. The theory again predicts the test results extremely well with a mean theory/test ratio of 0.943 and a standard deviation of 0.089. The paper thus provides convincing proof that the design equations presented in this paper are reliable, based on sound engineering principles and reflect the true structural behaviour of slab-column connections.