Flexural Ductility of Concrete Beams Reinforced with High Strength Steel

Abstract

This paper presents preliminary findings of a study of the flexural ductility of beams reinforced with ASTM A615 Grades 60 and 100, A706 Grades 60 and 80, or A1035 Grade 100 longitudinal steel bars. Moment–curvature relationships were generated for beams with reinforcement ratios varying between 0.3 and 1.5% with concrete compressive strengths between 30 and 90 MPa. Curvature ductility factors were computed. Regression analysis techniques were used to assess whether the ductility corresponding to a given mechanical reinforcement ratio were significantly different for the different steel grades. It is concluded that the curvature ductility factor is, in all cases investigated, essentially proportional to the inverse of the mechanical reinforcement ratio. The ductility factors for ASTM A615 Grade 100 reinforcement are markedly less than those for the other grades, suggesting that a more stringent target reliability index should be used to calibrate the resistance factor for ASTM A615 Grade 100 reinforcement.