In 2004, Hamad et al.1,2 reported on the first two phases of this research program designed to examine the effectiveness of FRP sheets to confine steel reinforcement in tension lap splice regions anchored in high-strength reinforced concrete beams.1,2 Ten full-scale high-strength concrete (HSC) beam specimens were tested in positive bending. Each beam was designed with three 20 mm (No. 6) bars spliced in a constant moment region at midspan. The variables used in the investigation were the type of the unidirectional FRP U-shaped sheets wrapping the splice region (glass or carbon), area of the FRP sheets (one or two layers), and the design configuration of the sheets. Glass fiber-reinforced polymers (GFRPs) and carbon fiber-reinforced polymers (CFRPs) were used in this study. It was concluded that the presence of FRP sheets confining the splice region considerably increased the bond strength of the splices and improved the ductility of the mode of failure. Results were used to propose a new FRP confinement parameter Ktr,f that accounts for bond strength contribution of the FRP sheets to the overall bond strength of tension lap splices in HSC beams.2 The parameter Ktr,f takes into account the area of the transverse FRP in the splice region, effective stress in the FRP laminates, number of spliced bars, bar diameter, and the spacing between the FRP sheets.
Hamad et al.3 reported on the third phase of the AUB study to verify the trend of the results of the first two phases and the validity of the proposed confinement parameter Ktr,f , if normal-strength concrete (NSC) is used instead of HSC. Ten beams with a nominal concrete strength of 28 MPa (4 ksi) were tested in positive bending. Each beam was designed with a tension lap splice in a constant moment region in the midspan of the beam. The main test variables were the configuration of the unidirectional U-shaped CFRP sheets (one strip, two strips, or continuous strip) and the number of layers (one layer or two layers) of the FRP sheets wrapping the splice region. The test results demonstrated that FRP wraps were effective in enhancing the bond strength and ductility of failure mode of tension lap splices in NSC in a very similar way to HSC. In addition, the FRP confinement index Ktr,f, proposed previously for HSC, was proven to be valid in case of NSC.
Hamad et al.4 reported on the fourth phase of the AUB program to assess the effect of CFRP sheets in improving the serviceability and ultimate response of NSC and HSC beam anchorage specimens. Ten beam anchorage specimens were tested in positive bending in two series. To simulate the flexural cracks, two 50 x 50 mm (2 x 2 in.) pockets were introduced along the entire width of the beam. The tension reinforcement was unbonded between the two pockets and extended 150 mm (5.9 in.) outside the beam on both sides. The variables were bar size: 20 or 25 mm (No. 6 or No. 8), anchorage length, and the concrete strength: 28 or 56 MPa (4 or 8 ksi). For each bar size, anchorage length, and concrete strength, two companion specimens, which were identical except for whether the anchorage zone was wrapped with FRP sheets or not, were tested. The test results demonstrated that CFRP sheets were effective in enhancing the bond strength and ductility of anchorage zones in beam anchorage specimens where splitting failures were imminent.
Hamad et al.3 reported on the third phase of the AUB study to verify the trend of the results of the first two phases and the validity of the proposed confinement parameter Ktr,f , if normal-strength concrete (NSC) is used instead of HSC. Ten beams with a nominal concrete strength of 28 MPa (4 ksi) were tested in positive bending. Each beam was designed with a tension lap splice in a constant moment region in the midspan of the beam. The main test variables were the configuration of the unidirectional U-shaped CFRP sheets (one strip, two strips, or continuous strip) and the number of layers (one layer or two layers) of the FRP sheets wrapping the splice region. The test results demonstrated that FRP wraps were effective in enhancing the bond strength and ductility of failure mode of tension lap splices in NSC in a very similar way to HSC. In addition, the FRP confinement index Ktr,f, proposed previously for HSC, was proven to be valid in case of NSC.
Hamad et al.4 reported on the fourth phase of the AUB program to assess the effect of CFRP sheets in improving the serviceability and ultimate response of NSC and HSC beam anchorage specimens. Ten beam anchorage specimens were tested in positive bending in two series. To simulate the flexural cracks, two 50 x 50 mm (2 x 2 in.) pockets were introduced along the entire width of the beam. The tension reinforcement was unbonded between the two pockets and extended 150 mm (5.9 in.) outside the beam on both sides. The variables were bar size: 20 or 25 mm (No. 6 or No. 8), anchorage length, and the concrete strength: 28 or 56 MPa (4 or 8 ksi). For each bar size, anchorage length, and concrete strength, two companion specimens, which were identical except for whether the anchorage zone was wrapped with FRP sheets or not, were tested. The test results demonstrated that CFRP sheets were effective in enhancing the bond strength and ductility of anchorage zones in beam anchorage specimens where splitting failures were imminent.
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