Finite element for anchored bars under cyclic load reversals

The hysteretic behavior of reinforced concrete elements depends in large measure on the interaction between reinforcing steel and concrete through bond. This paper presents a new finite element for reinforcing bars anchored in concrete. The novel aspect of the element is the use of force instead of displacement interpolation functions. The force interpolation functions satisfy equilibrium in a strict sense and ensure the numerical stability of the results, even in the presence of significant strength loss and softening, as might be the case for reinforcing bars with insufficient anchorage length. Another novel aspect of the element formulation is its implementation in a general purpose finite element analysis program that is based on the stiffness method of analysis. Correlation studies with available experimental data demonstrate the ability of the proposed model to simulate the bond deterioration and eventual pull-out of anchored reinforcing bars under severe inelastic excursions.