Title: CONCRETE BEAMS REINFORCED WITH HIGH-STRENGTH STEEL SUBJECTED TO DISPLACEMENT REVERSALS

Author(s): Hooman Tavallali, Andres Lepage, Jeffrey M. Rautenberg, and Santiago Pujol

Publication: Structural Journal

Volume: 111

Issue: 5

Appears on pages(s): 1037-1048

Keywords: advanced high-strength steel; crack width; cyclic test; deformation capacity; earthquake; high-performance fiber-reinforced concrete; seismic; ultra-high-strength steel

DOI: 10.14359/51686967

Date: 9/1/2014

Abstract:
The use of concrete members reinforced with high-strength steel bars (with a yield strength greater than 80 ksi [550 MPa]) in earthquake-resistant structures has been limited by the U.S. building codes since the introduction of strength design in 1963. This investigation aimed to reexamine that limit by providing benchmark data for studying the cyclic response of concrete beams reinforced with steel bars having yield strengths approaching 100 ksi (690 MPa). Seven specimens were subjected to large transverse displacement reversals: three specimens were reinforced with conventional steel bars (Grade 60 [415]) and four specimens were reinforced longitudinally with high-strength steel bars (Grade 97 [670]). All transverse reinforcement was Grade 60. Other experimental variables were: volume fraction of steel-hooked fibers (Vf = 0 or 1.5%), spacing of transverse reinforcement (s = d/4 or d/2), and ratio of compression-to-tension longitudinal reinforcement (?'/? = 0.5 or 1). The nominal concrete compressive strength was 6000 psi (41 MPa). Test beams reinforced with Grade 97 (670) steel bars had cyclic drift ratio capacities in excess of 5%, comparable to the deformation capacities of similar beams reinforced with conventional bars. The evidence presented shows that the use of high-strength steel (Grade 97 [670]) as longitudinal reinforcement is a viable option for earthquake-resistant construction.