A strain-consistent approach for determination of bounds of ductility damage index for different performance levels for seismic design of RC frame members

The aspects of a robust and practical damage-based deterministic seismic design approach for reinforced concrete (RC) buildings have been discussed. The proposed performance-based design approach can be used for different structural systems by using fundamentals of reinforced concrete behavior and practical analyses. Several aspects of the proposed design approach need to be tuned including the selection of the damage measure and its quantification for a required performance level. Ductility damage index is a suitable damage measure for performance-based design of RC frame members. Currently, there is no systematic approach for selecting the bounds for a damage index according to the required performance level. The preset values provided in literature are based on engineering judgment and cannot be extended to RC members with all kinds of geometries and detailing. In this article, the correlation of damage level to concrete core and rebar strains is used to establish a procedure for determination of damage index intervals for different performance levels of RC plastic hinges. Then, the developed procedure is illustrated through numerical simulations for square and circular columns. The strain-consistent curvature ductility damage index values are determined for operational, immediate occupancy, life-safety, and collapse prevention performance levels used for seismic design of new columns.