A simplified design approach to corbels made with high strength concrete

Design procedures for corbels are given in various Codes of Practice e.g. ACI 318-89 [1]. These codes give equations based on research on corbels made with normal strength concrete. Consequently, they tend to limit the value of concrete strength to be used in these equations. This will result in an underestimation of the load carrying capacity of corbels made with high strength concrete (HSC) as will be shown later. In the present paper, a semi-empirical equation for the design of corbels made with high strength concrete is derived. In the derivation, an empirical factor K is used, the value of which was determined from experimental data based on thirty tests made by Foster et al. [2]. This factor is assumed to be dependent on the shear span/effective depth ratio a/d. The expression found for K was then used to calculate the theoretical load carrying capacity of corbels made with high strength concrete. Twelve more tests were carried out, in-house, on corbels made with high strength concrete and the experimental results were compared with the theoretical values based on K as obtained from the empirical expression. It was found that the expression for K resulted in good correlation between theoretical and experimental values for the load carrying capacity of corbels made with high strength concrete. Comparison of the ACI Code values was made with both experimental and theoretical data and it was found the Code greatly underestimates the load capacity of corbels made with high strength concrete.