The present paper deals with a uniaxial member involving strain localization, making emphasis on deformational characteristics and stability analysis. Localization phenomena are classified into the semi-localization for concrete in compression and the perfect-localization for concrete in tension. Equivalent constitutive equations are formulated for both cases. An incremental calculation method to incorporate the snapback behavior is then presented. Stability/Instability condition is analytically derived based upon second variation of total potential energy for inelastic materials. In addition, an kinetic energy to evaluate snapdown instability of a localized member is proposed.
