Title:
Reinforced Concrete Coupling Beams with High-Strength Steel Bars (Prepublished)
Author(s):
Andrés Lepage, Rémy D. Lequesne, and Alexander S. Weber-Kamin
Publication:
Structural Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
chord rotation capacity; confining reinforcement; deformation capacity; force-deformation envelope; hoop spacing; reinforcement grade; reversed cyclic displacements
DOI:
10.14359/51745464
Date:
12/17/2024
Abstract:
Eleven large-scale reinforced concrete coupling beam specimens were tested under reversed cyclic displacements of increasing magnitude. The main variables included: yield stress (fy ) of the primary longitudinal reinforcement, span-to-depth (aspect) ratio, and layout of the primary longitudinal reinforcement (diagonal [D] or parallel [P]). Specimens had the same nominal concrete strength and cross-section and were designed for nominal shear stresses for D-type beams and P-type beams. Transverse reinforcement was Grade 80 (550) in all but one beam with Grade 120 (830) reinforcement.
Test results show that, on average, D-type beams had chord rotation capacities in excess of 5, 6, and 7% for beams with aspect ratios of 1.5, 2.5, and 3.5, respectively. P-type beams with Grade 80 or 100 (550 or 690) longitudinal bars, tested only for an aspect ratio of 2.5, had chord rotation capacities of approximately 4%. Based on these results, the authors recommend permitting the use of high-strength steel, Grade 80 (550) and higher, in D-type and P-type coupling beams for earthquake-resistant design. The spacing of confining reinforcement should be limited to 5db for fy = 80 ksi (550 MPa) and 4db for fy = 100 or 120 ksi (690 or 830 MPa). Consistent with prior findings, the results show that deformation capacity correlates with the span-to-depth ratio and is more sensitive to the spacing of the confining reinforcement than to the uniform elongation of the reinforcement. Finally, the test results illustrate the effects of reinforcement grade on stiffness and energy dissipation of pseudo-statically loaded coupling beams.