Experimental studies on reinforced concrete columns laterally prestressed by the shear reinforcements have indicated that the performance in shear behaviors can be improved by the active confinement. To investigate the mechanics of the lateral confinement, the 3D finite element analyses were performed on RC columns with prestressed transverse hoops under axial and shear loadings. The equivalent confining pressure and the degree of damage were used as a measure to evaluate active confinement and shear failure quantitatively. The FE analyses revealed that an increase in the resistance against shear failure as well as shear cracking with increasing prestress in the shear reinforcements could be explained by the triaxial state of stress in the core concrete.
