A Close to Reality Method for Determining the Resistance of RC Structures under Eccentric Compression

The paper presents the derivation of analytical formulae determining the resistance of the cross-sections of RC structures subjected to eccentric compression. It takes account of the effect of the concrete softening and the mean compressive strength of concrete. The stress-strain relationship for concrete in compression for uniaxial loading is assumed according to Eurocode 2 for nonlinear analysis. This stress-strain relation closely to reality represents the behavior of the concrete by introducing four parameters. For reinforcing steel linear-elastic model with hardening in the plastic range is applied. The resistance of the cross-section of RC structure is reached when either the ultimate compressive strain in concrete or the ultimate tensile strain in steel is reached anywhere in that section. The formulae determining the section resistance are derived by integrating the equilibrium equations of the cross-section taking account of the physical and geometrical relations as well as the conditions of the ultimate state. Using the derived formulae the interaction diagrams with the values of the ultimate normalized cross-sectional forces have been obtained for the ring cross-sections. The calculated results have been compared with those obtained by testing on RC columns with ring cross-sections subjected to the eccentric compression. The performed analysis confirmed a good conformity between theoretical and experimental results.