Abstract
Experimental data are presented for six concrete specimens subjected to displacement reversals. Two specimens were reinforced longitudinally with steel bars Grade 410 (60 ksi), two with Grade 670 (97 ksi), and two with Grade 830 (120 ksi). Other experimental variables included axial load (0 or 0.2fc′ Ag) and volume fraction of hooked steel fibers (0 or 1.5%). All transverse reinforcement was Grade 410, and the nominal concrete compressive strength was 41 MPa (6 ksi). The loading protocol consisted of repeated cycles of increasing lateral displacement reversals (up to 5% drift) followed by a monotonic lateral push to failure. The test data indicate that replacing conventional Grade-410 longitudinal reinforcement with reduced amounts of Grade-670 or Grade-830 steel bars did not cause a decrease in usable deformation capacity nor a decrease in flexural strength. The evidence presented shows that the use of advanced high-strength steel as longitudinal reinforcement in frame members is a viable option for earthquake-resistant construction.
Highlights
For many years, the earthquake-resistant design of reinforced concrete structures in the USA has been dominated by the use of steel reinforcement with specified yield strength, fy, of 410 MPa (60 ksi)
Observations on the nonlinear cyclic response of concrete frame members reinforced with advanced high-strength steel (AHSS) are summarized as follows
Column failures in reinforced concrete (RC) specimens were due to buckling of the longitudinal reinforcement while failures in high-performance fiber-reinforced concrete (HPFRC) specimens were due to fracture of the longitudinal reinforcement
Summary
The earthquake-resistant design of reinforced concrete structures in the USA has been dominated by the use of steel reinforcement with specified yield strength, fy, of 410 MPa (60 ksi). Current version of ACI 318 [2] maintains the above limits but allows designs with fy of 690 MPa (100 ksi) only if used for confining reinforcement. The terms advanced high-strength steel (AHSS) [3] or ultrahigh strength steel (UHSS) [4] are used to designate high-performance steel bars with a yield strength in excess of 550 MPa (80 ksi) and a fracture strain, εsu, of 6% or more measured in a 203-mm (8-in.) gage length. After the introduction of ASTM A1035 in 2004 [5] and their acceptance as confining reinforcement in the 2005 version of ACI 318, there has been growing interest in AHSS bars. Are nearly proportional to the increase in yield strength used in design
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