Seismic deformation capacity indices for concrete columns: model estimates and experimental results

The transition to displacement-controlled methods for seismic design relies on explicit measures of deformation capacity. Although conceptually clearly defined, the various alternative indices such as displacement ductility, drift and plastic rotation capacity calculated with the available analytical tools in the literature are marked by excessive scatter when tested with well-controlled experimental results, indicating that the validity of the underlying physical models is questionable. This problem is explored systematically in the current paper, by evaluating the parametric performance of the analytical models, as well as through comparison with the experimental trends. An important result of the present study is that well-confined members designed as per the ATC-32 requirements have large dependable deformation capacities regardless of the axial load ratio, a finding with significant implications in practical bridge seismic design.