Softening in stress–strain curve for Drucker–Prager non-associated plasticity

This paper is devoted to proving some features of the non associated flow rule such as a softening phenomenon in the stress–strain curve and the decrease of limit load. Based on the non-associated Drucker–Prager model, the analysis is investigated by means of a soil specimen subjected to traction and compression actions on its edges. To obtain the stress–strain curve, a semi-analytical approach provides an incremental relation between stresses and strains. The plastic limit load is calculated analytically by direct static and kinematic methods. The kinematic one is determined on the basis of the bipotential concept.