Cyclic Response of Concrete Frame Members Reinforced with Ultrahigh Strength Steel

For many years, the design of reinforced concrete structures in the U.S. has been dominated by the use of steel reinforcement with a specified yield strength, f_y, of 60 ksi. Using steel reinforcement with a higher yield strength would introduce several benefits to the architectural, engineering, and construction industry. Not only would it allow for members with reduced cross sectional area, saving on material, shipping, and placement costs, but it would also help to overcome steel congestion, and facilitate concrete placement. This would directly lead to a better quality of construction, improved durability, and shorter construction times. One of the primary obstacles to the use of concrete members reinforced with ultrahigh strength steel (f_y greater than 80 ksi) is the paucity of experimental data. The applicability of using steel with f_y up to 120 ksi as primary reinforcement in concrete members is explored in this experimental study by subjecting beams and columns reinforced with ultrahigh strength steel to a cyclic loading protocol. The mechanical behavior of these members is compared to similar members reinforced with conventional steel. Test data from this study show that the use of ultrahigh strength steel is a viable option for earthquake-resistant construction.