Effects of circular openings on the compressive behaviour of R.C. columns

Core-drilling technique is nowadays always more frequently performed in existing reinforced concrete (RC) structures in order to investigate on the mechanical properties of concrete and for structural health monitoring purposes. Even if the engineering practice discourages to drill columns, this can be often unavoidable. In this last case the presence of the circular opening influences the compressive behavior of the column in terms of load-carrying capacity and axial deformability. The goal of this investigation was the experimental evaluation of the effects induced by circular openings on the behavior of RC columns. Twenty-four reinforced and plain concrete prisms in presence of circular openings were tested in compression. The effects of concrete strength, hole diameter and repairing were taken into account. Axial loads and strains were recorded during the tests in order to evaluate the effects of key parameters. Finally, analytical predictions of the load-carrying capacity were made with a strut-and-tie model available in the literature, which was also used to estimate the load-shortening curves showing good agreement with experimental data.