PSI - Issue 42

Jamal A. Abdalla et al. / Procedia Structural Integrity 42 (2022) 1231–1238 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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2. Experimental Program 2.1. Beam specimens

The cross-sectional dimensions of the beam specimens were 150 mm (width) x 260 mm (height) x 2000 mm (length). The specimens were reinforced in flexure with two 12 mm and two 8 mm steel rebars in the tension and compression zones, respectively. The concrete cover was 30 mm, and the effective depth was 216 mm. The shear span-to- depth ratio was 2.84. All specimens did not include internal steel reinforcement, except at the locations of the supports and at the center of the beam to prevent premature failure at these locations and to hold the flexural steel bars in place. The reinforcement details of the beam specimens are shown in Fig. 1.

Fig. 1. Beam reinforcement detailing (dimensions are in mm)

2.2. Strengthening details and test matrix A total of four RC beams were tested in this study, two specimens were cast with NAC and two were cast with RAC. One NAC specimen (NC) and one RAC specimen (RC) were unstrengthened to act as benchmark specimens. The other two specimens were strengthened with 100 mm wide CFRP U-wraps that were spaced at 150 mm center to-center, as shown in Fig. 2. The U-wraps spanned along the length of the beam between the supports and were placed 50 mm from the top of the beam, as shown in Fig. 2. In addition, to prevent flexural failure, the specimens were strengthened with a single layer of CFRP laminate that was bonded to the soffit of the beam between the supports. The total length and width of the flexural CFRP layer was 1850 mm and 150 mm, respectively. The designation of the specimens includes N and R for NAC and RAC, respectively. In addition, the C in the designation refers to control specimen and the U refers to U-wrapped specimen. The surface of the beams was first prepared by grinding and cleaning the surface to provide better bonding with the CFRP sheets and remove any impurities. Next, flexural CFRP sheets (150 x 1850 mm) and U-wraps (100 x 510 mm) were cut and the location of the U-wraps were marked on the beams. Then, the two-part epoxy adhesive was mixed in the ratio of 4:1, as specified by the manufacturer. The epoxy was placed onto the CFRP locations and was also used to impregnate the CFRP sheets. After placing the CFRP laminates at the desired locations, grooved rollers were used to remove entrapped air. The beams were left to cure for one week prior to testing.

Fig. 2. Strengthening detailing (dimensions are in mm)