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Title: Effect of Low Reinforcement Ratio on Reinforced Concrete Wall with 700 MPa Reinforcing Bars

Author(s): Sung-Hyun Kim and Hong-Gun Park

Publication: Structural Journal

Volume: 120

Issue: 2

Appears on pages(s): 171-189

Keywords: cyclic loading; Grade 700 MPa (101.5 ksi) bar; minimum reinforcement ratio; shear strength; shear wall

DOI: 10.14359/51737142

Date: 1/1/2023

Abstract:
High-strength reinforcing bars can be used for the economical design of reinforced concrete shear walls by reducing the reinforcement ratio. However, current design codes require the minimum reinforcement ratio regardless of the yield strength of reinforcing bars. In this study, to investigate the adequacy of the minimum reinforcement ratio of Grade 700 MPa (101.5 ksi) reinforcing bars, seven wall specimens were tested under cyclic lateral loading. The test parameters were the failure mode (shear or flexural mode), reinforcing bar yield strength (Grade 400 and 700 MPa [58 and 101.5 ksi]), and reduced minimum reinforcement ratio (ρv = 0.14 to 0.27% and ρh = 0.14 to 0.25%). The test results showed that the peak strengths of walls with 700 MPa (101.5 ksi) reinforcement were greater than the nominal flexural and shear strengths, even with a lower minimum reinforcement ratio (ρv = 0.14% and ρh = 0.14%). However, the safety margin and ductility decreased with increasing flexural and shear crack widths. Additionally, the strengthening of existing walls (Grade 400 reinforcing bars) with high-strength reinforcing bars (Grade 700) was studied. The test results showed that the shear contribution of extended wall segments with Grade 700 reinforcing bars was limited by the early yielding of Grade 400 reinforcing bars.