Modeling Nonductile R/C Columns for Seismic Analysis of Bridges

A stress resultant plasticity-based formulation with shear failure criteria and post-shear failure effects is presented for modeling the response of nonductile reinforced concrete bridge columns subjected to biaxial seismic loading. The formulation consists of a single component model, in which plastic hinges exist at each end of an elastic beam-column. Deterioration in column strength following a shear failure, kinematic flexural strain hardening, and degradation of elastic unloading stiffness under cyclic load reversal are accounted for in the hinges' force-deformation relationships. The degradation of the transverse shear strength in a reinforced concrete column's flexural plastic hinge zone is also accounted for. The formulation is shown to predict reasonably well the cyclic response of nonductile beam-column experimental test specimens that develop either ductile flexural yielding, a brittle shear failure, or a ductile shear failure in the flexural plastic hinge zone when subjected to uniaxial or biaxial nonproportional cyclic lateral loading. Inelastic seismic time-history analysis is also presented to illustrate the significance of including nonductile effects in a model of a bridge structure susceptible to column shear failure during an earthquake.