PSI - Issue 42

Jamal A. Abdalla et al. / Procedia Structural Integrity 42 (2022) 1223–1230 Abdalla et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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increasing the fan length led to a nonproportional increase in the shear capacity of the tested beams. Furthermore, the order of placing the fan of the anchor (before the sheet or after the sheet) had no effect on the shear capacity if all other parameters were kept constant. Another study by Koutas and Triantafillou (2013) investigated shear strengthening of RC T-beams using anchored FRP U-wrapped jackets. The anchor parameters tested were different anchor alignments, number, spacing and FRP types. Test results showed that the type of fiber has no significant effect on the shear strength of the specimens provided that the anchors have similar geometric characteristics. Furthermore, an increase in the number of anchors resulted in an increase in the shear resistance, but in a nonproportional manner because the anchors below the shear cracks were not activated. In addition, inclined anchors showed better performance in terms of increasing the shear capacity of the specimens than the horizontal anchors. Generally, in most of the preceding literature the anchors significantly increased the effective strain in the FRP laminates, and therefore increased the shear resistance of the beams. It should be also noted that the 0.004 mm/mm strain limit recommended by the ACI440.2R 17 (2017) to design the anchored laminates is considered reasonable and conservative. Despite the numerous research studies on the pullout capacity of isolated FRP spike anchors (del Rey Castillo et al. (2019); Pudleiner et al. (2019); Sun et al. (2018); Villanueva Llauradó et al. (2017)), the literature lacks comprehensive analysis on the effect of varying FRP spike anchor parameters on the shear capacity of RC beams. In addition, most of the current design provisions emphasize the importance of anchorage for FRP shear strengthening applications but do not include guidelines to design the anchors (except fib bulletin 90 (2019)). Therefore, this paper aims at studying the effect of embedment depth, dowel diameter, and inclination angle on the shear capacity of CFRP U-wrapped beams. The experimental study consists of an unstrengthened control beam and five U-wrapped strengthened specimens, four of which were anchored with different anchor configurations. The beams are tested under one-point loading tests and the results in terms of failure modes, shear force-deflection responses, and shear capacity are analyzed. 2. Experimental Program 2.1. Test specimens In this study, six RC T-section beams with dimensions of 2000 mm (length) x 150 mm (width) x 300 mm (height) were tested. The tension zone was reinforced with 3#16 mm bars located at 259 mm from the top of the beam and the compression zone was reinforced with 6#8 mm bars distributed in the flange, as shown in Fig. 1. One half of the beams was heavily reinforced in shear using no.8 stirrups spaced at 80 mm center-to-center to prevent shear failure at the non-tested span. The other half (test span) did not include any internal shear reinforcement to investigate the effect of external strengthening using CFRP U-wraps and spike anchors. The reinforcement details of the tested T-beams are shown in Fig. 1.

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

2.2. CFRP laminates and anchor details All specimens are strengthened at the soffit with two layers of 150 mm wide CFRP laminates that were bonded a long the beams’ length , to prevent flexural failure, as shown in Fig. 2. Five specimens were externally strengthened in shear with 100 mm wide CFRP U-wraps spaced at 150 mm center-to-center, four of which were anchored with different configurations of CFRP spike anchors. All anchors had a fan length of 100 mm and a corresponding fanning angle of 30 º . In addition, all anchors were drilled at the top center on both sides of the U-wraps, as shown in Fig. 2(b). The variables tested in this study were the embedment depth (ED), dowel diameter (DD), and insertion angle (IA).