Effect of Reinforcement Grade and Ratio on Seismic Performance of Reinforced Concrete Columns

Reinforcement grades higher than 75 ksi (520 MPa) are not allowed in members that form plastic hinges due to a lack of information on material characteristics and on the seismic performance of columns constructed with high-strength steel (HSS) reinforcement. This research investigated the performance of reinforced concrete columns containing Grade 80 (minimum yield strength of 80 ksi [550 MPa]) HSS reinforcement. Four columns were subjected to lateral cyclic loading to determine the effects of the steel reinforcement grade and longitudinal reinforcement ratio. Results indicate that columns constructed with Grade 80 (550) HSS reinforcement achieved similar resistances, similar maximum drifts, and similar curvature ductility values when compared with the control columns. Results also indicate that the effect of the longitudinal reinforcement ratio on column performance is similar for columns constructed with either Grade 60 or 80 (420 or 550) reinforcement. Columns constructed with Grade 80 (550) reinforcement exhibited lower energy dissipation than the control columns.