Practicability of Large-Scale Reinforced Concrete Beams Using Grade 80 Stirrups

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Title: Practicability of Large-Scale Reinforced Concrete Beams Using Grade 80 Stirrups

Author(s): Jung-Yoon Lee, Jae-Hoon Lee, Do Hyung Lee, Seong-Jun Hong, and Ho-Young Kim

Publication: Structural Journal

Volume: 115

Issue: 1

Appears on pages(s): 269-280

Keywords: diagonal crack width; Grade 80 stirrups; large-scale reinforced concrete beams; shear strength; size effect

Date: 1/1/2018

Abstract:
ACI 318-14 specifies that the yield strength of shear reinforcement is limited to 420 MPa (60 ksi) for shear-strength calculation of reinforced concrete beams to control failure mode and diagonal crack width for such members. However, in the case where high-strength shear reinforcement is employed in such members, the amount of the shear reinforcement can be reduced and wider spacing is feasible. This may lead to an easy placement of concrete and, thus, improved durability. Thus, the use of high-strength shear reinforcement can be particularly effective for structures having large-scale members such as skyscrapers, long-span bridges, and nuclear power plants. To investigate the practicability of the high-strength shear reinforcement, shear tests are carried out for large-scale reinforced concrete beams using Grade 80 stirrups. For this purpose, a total of 16 reinforced concrete beams are tested and categorized into four groups according to the parameters: two levels of stirrup yield strength and four levels of cross section depth. Current test results reveal that all large-scale beams fail in shear tension, experiencing yielding of stirrups prior to concrete web crushing. Measured shear strength is greater than theoretical shear strength calculated by ACI 318-14 in all members. However, the margin between the two strengths is reduced as the cross section depth increases. The diagonal crack width is influenced by the stirrup yield strength and spacing, and the cross section depth. The crack width increases as the cross section depth and stirrup spacing increase.