Confinement effects on high strength concrete under axial load: evaluation of International Standards prescriptions

Abstract

Confinement effects on concrete behavior have been evaluated by many authors so far and some relationship is inserted in most of the International Standards and Guidelines in order to let the designers increase the properties of the material. A common behavior is shown by both normal and high strength mixtures, but the request of confinement forces is different and the results, in terms of design detailing and verifications, are different. The main problem shown in concrete is that, in order to obtain a significant increasing of rheological concrete performance, the designer is led to insert a large amount of stirrups in concrete columns. For high strength concrete (HSC) it has been found that a brittle behavior occurs when a great amount of confinement is not provided. This paper, focused on HSC columns, will show the limits of some international standard indications on confinement when this is provided in order to achieve high values of resistance, strain and hence ductility in the concrete.