Drift Capacity of Concrete Columns Reinforced with High-Strength Steel

The use of high-strength steel bars with a yield stress of 80 ksi (550 MPa) or more as reinforcement for concrete columns has the potential to reduce steel congestion and lower construction costs. Current standards prohibit the use of these steels for most applications by imposing upper limits on yield stress. In this study, those limits are reconsidered for columns resisting lateral loads induced by earthquakes. Eight columns were tested under displacement reversals. Columns reinforced longitudinally with high-strength steel (Grades 80 to 120) had drift capacities between 4 and 8%. The drift capacities of these columns were comparable to the drift capacities of similar columns reinforced with Grade 60 steel. Columns with high-strength steel dissipated less energy than comparable columns with Grade 60 steel, but numerical analyses indicate that multi-story moment-frame buildings with columns reinforced with high-strength steel are not likely to experience consistently larger drifts than buildings with columns reinforced with Grade 60 steel.