Investigation of bond slip effect on the P-M interaction surface of RC columns under biaxial bending

The nonlinear behavior of reinforced concrete columns subject to biaxialbending and consideration of bond-slip at the steel-concrete interface are investigated.separate degrees of freedom are used for the steel and concrete parts to allow for thedierence in displacement between the reinforcing bars and the surrounding concrete. theeect of bond-slip is investigated on the numerical bearing capacity of a reinforced concretecolumn subject to axial and biaxial bending forces. the axial force-bending moment (pm)interaction surface of the reinforced concrete column under two conditions (with andwithout bar slip) is calculated, and compared also with aci criteria. the results show thatalthough aci criteria is based on perfect bond assumption, the results are conservativeanyway, due to the fact that the benecial eect of stirrup connement on concretecompressive strength is neglected, and the use of reduction factor ' does not make anymodication necessary for considering the bond-slip eect on the ultimate capacity of therc section.