Extended Rankine failure criteria for concrete

As possible failure criteria MC2010 refers to those of Rankine, Drucker-Prager and Mohr-Coulomb, respectively, and to modifications or combinations of them. After a brief overview of these failure criteria the characteristics of Mohr-circle are described. Next chapter discusses why the Modified Mohr–Coulomb failure criterion fails in case of concrete. Displaying the Mohr-circles of different bi- and triaxial test series reveal that neither the straight nor the parabolic failure criteria fit. The failure patterns of uniaxial compressive and tensile test specimens prove that concrete fails due to principal tensile stresses/strains in separation and concrete is not a frictional material. The proposed Extended Rankine failure criteria are based directly on the principal stresses. The criteria limit the greatest- and the actual smallest principal stress, respectively. This latter is function of the two other principal stresses. It is shown that the Ultimate Strength Surface cannot be properly described as stated by CEB Bulletin Nr. 156.