A new approach to the confinement of R/C columns

A new constitutive law is presented, valid for confined concrete. The transversal stresses induced by a hoop, either of square or of circular shape, in the cross section of r.c. members (columns or beams) axially loaded, are evaluated through Airy's functions relevant to plain strain states. The results, valid for square or circular hoops, are then extended to hoops of polygonal shape, with or without bindings, and to a combination of hoops of different shapes. The formulation, valid for the cross section containing the hoop, is finally extended to the overall volume of the member through the interaction among hoops and longitudinal reinforcements. The results suggested by the proposed model for members of circular and square cross section are compared with experimental data and with the results of other researchers. The proposed model, in comparison with other models, shows a better agreement with xperimental results.