Publication: Experimental and theoretical investigations of shear strength and repair of high-strength concrete deep beams using near-surface mounted gfrp rebars
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Date
2024-09-01
Authors
Azhar Ayad, Jaafar Farajallah
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Abstract
Shear failure in reinforced concrete (RC) deep beams is a critical structural
concern. There has been a rapid adoption of glass fiber-reinforced polymer (GFRP)
sheets and bars for reinforcing structural concrete elements, including deep beams.
This study investigated the behavior of RC deep beams strengthened and repaired
using near-surface mounted (NSM) GFRP bars. Four groups of deep beams—G1,
G2, G3, and G4—were examined, each with a shear span to effective depth ratio of
1.26. These groups included deep beams that were either strengthened or pre-crack
repaired using various NSM GFRP bar arrangements and orientations. The study
utilized two types of concrete: normal high-strength concrete (NHSC) and high strength concrete with special additives (SHSC). The NSM GFRP bars were oriented
at either 0°/90° or 45°/135° with a spacing of 150 mm. Ten RC deep beams, each
measuring 400 x 150 x 1700 mm, were tested. The experimental results were
validated using the finite element software ABAQUS V.20, with simulations
conducted using standard mechanical properties (SMP) and core mechanical
properties (CMP). Results showed that NHSC and SHSC RC deep beams
strengthened or repaired with NSM GFRP bars experienced a 12% to 22.5% increase
in shear capacity compared to control specimens. The ACI standard model aligned
well with the experimental results. Additionally, two modified empirical equations
were proposed to calculate the shear capacity contribution (𝑉𝑓) of NSM GFRP bars
in NHSC and SHSC RC deep beams, using different effective strain values. According to the experimental results, the enhancements in shear strength for Groups
G1 & G3 and G2 & G4 ranged from 13.3% to 22.5%, 15.5% to 20.4%, 12% to
18.25% and 12% to 16.3%, respectively. In contrast, the numerical simulation results
of the FE models compared to the experimental results showed an increase in
maximum shear strength ranging from 2-3% for Groups G1 & G3 and 3-4% for
Groups G2 & G4. Additionally, two empirical equations have been proposed with
the effective strain values used for Groups G1 and G3 with NHSC were 0.0050 and
0.0038, respectively. For Groups G2 and G4 related to SHSC, the values 0.0061 and
0.0042 were employed, respectively.