A nonlinear material model of corroded rebars for seismic response of bridges

A generalized cyclic steel model characterized by isotropic and kinematic hardening, inelastic buckling in compression and corrosion for the rebar in reinforced concrete (RC) structures is presented. This model has been implemented in in-house fiber program CY.R.U.S.-M developed in MATLAB, to perform the seismic analysis of RC sections. The model is especially accurate, with respect to experimental cyclic behavior of rebars with buckling in compression, in case the strain in compression does not exceed 1.2 - 1.5 %. Four RC sections were selected as the case studies for a single concrete geometry and different steel configurations assumed representative of RC bridge piers (in a suitable scale) and subjected to a cyclic curvature history representative of a severe seismic load, not far from collapse. Different rebar characteristics (yielding stress, maximum stress, hardening ratio), axial loads, corrosion percentages have been selected to perform some cyclic parametric analyses. The numerical results have shown that the maximum strain of the rebar in compression is always smaller than 1.2 - 1.5 % and therefore the simple model for the steel is a valid tool for the structural assessment. Finally, corrosion of the rebars reduces the section capacity in term of strength and energy dissipation.