Finite-element bond-slip model for concrete columns under cyclic loads

The hysteretic behavior of reinforced concrete structures depends in large measure on the transfer mechanism between reinforcing steel and concrete through bond and the resulting slip. This paper presents a finite-element model developed to investigate the response of reinforced concrete columns subjected to cyclic loading, considering in an explicit way the relative displacement at the interface. The novel aspect of the model is its capability of modeling three-dimensional effects as concrete confinement, the softening response of concrete, and to take into account the gradual deterioration of the bond between reinforcing bars and concrete. Numerical results are compared to experimental results on rectangular bridge columns with lapped starter bars subjected to cyclic loading. The numerical model reproduces the physical phenomena observed experimentally, as the gradual stress transfer from one bar to the other. The numerical results show the effect of damage in concrete on the steel stress distribution, as long as the coupled effect of damage in concrete and bond-slip constitutive law on the general behavior of the structural element.