Interventi di miglioramento e adeguamento sismico di edifici in c.a. dell’Azienda Ospedaliera Universitaria Policlinico “Paolo Giaccone” di Palermo

The paper shows the results of an experimental investigation on the behaviour of compressed concrete columns subjected to the overcoring technique. Extraction of cylindrical concrete cores in perpendicular direction to the column surface, was achieved by rotary drilling using a diamond tipped hollow barrel. Core is gradually isolated from the stress field in the surrounding concrete and at every advancing step the re-equilibrium deformation response is measured by means of four strain-gauges, placed on its external surface and near the hole. Finally the original stress state is computed in the elastic phase on the basis of recorded strains, knowing the elastic properties of concrete and by means of expressions deduced from the theory of elasticity. The stress state near the hole is after compared with the actual one, that is the stress state induced in the column by loading it with a fixed load level. After that, specimens were tested to failure in order to evaluate the loss of load-carrying capacity due to the presence of the hole, for both reinforced and plain concrete columns. Furthermore, such results were compared with those relative to columns core-bored before compressive test.