PSI - Issue 28

Jamal A. Abdalla et al. / Procedia Structural Integrity 28 (2020) 2342–2349 Author name / Structural Integrity Procedia 00 (2019) 000–000

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1. Introduction and Background The strength and stiffness of reinforced concrete (RC) members usually deteriorate with time due to many factors which make them susceptible to shear or flexure failure. Shear failure of RC beams is usually sudden and brittle. Such failure is undesirable and should be prevented or mitigated. Strengthening and retrofitting of such deteriorated RC beams become necessary to avoid shear failure, among other types of failures. The use of carbon fiber reinforced polymers (CFRP) laminates as externally bonded reinforcement (EBR) for strengthening of RC beams has been widely accepted. Several comprehensive reviews about the applications of CFRP and other other types of FRP were given by Bakis et al. (2002), Pendhari et al. (2008), Hollaway (2010), Siddika et al. (2019), Naser et al. (2019). Besides the use of CFRP as EBR, other materials such as high strength Aluminum Alloys (AA) were used as EBR for shear strengthening (Abdalla et al., 2011, Abdalla et al., 2016, Abdalla et al., 2017, Mirghani et al., 2017, Abdalla et al., 2019, Abu-Obeidah et al., 2019) and also for flexure strengthening (Rasheed et al., 2017, Abuodeh et al., 2019). In addition, Galvanized Steel Mesh (GSM) was used predominately for flexural reinforcement by many researchers (Borri and Corradi, 2011, Qeshta et al., 2014, Qeshta et al., 2015, Douier et al, 2019, Douier et al., 2020, Hawileh et al., 2014, Hawileh et al. 2018). As indicated, CFRP had been used successfully for flexural strengthening of RC beams (Ashour et al., 2004, Bahn et al., 2008, Zhou et al., 2013) and also for shear strengthening of RC beams (Khalifa et al., 1998, Khalifa and Nani, 2000). The majority of failures in such strengthening techniques has been usually initiated by premature de-bonding of the CFRP laminates without the full utilization of its strength. To mitigate or prevent the premature de-bonding and therefore increase the effectiveness of full utilization of the tensile strength of CFRP laminates as EBR for shear strengthening systems, several anchorage techniques were introduced. The most common types of anchorage techniques introduced included full wrapping, U-wrapping, FRP-spikes, EBR on Grooves (EBROG), splay anchors, among other (Chen and Teng, 2001, Eshwar et al., 2008, Yalim et al., 2008, Galal and Mofidi, 2009, Deifalla and Ghobarah 2010, Schmidt et al., 2012, Belarbi and Acun, 2013, Grelle and Sneed, 2013, Kalfat et al., 2013, Rasheed et al., 2015, El-Saikaly et al., 2015, Mohee et al., 2016, Mohamed et al., 2018, Mhana et al. 2019, Wang et al., 2020, Al Rousan and Al-Saraireh, 2020, Godat et al., 2020). The most common failure mode noticed in shear strengthening occur from intermediate crack-induced interfacial FRP debonding and FRP tensile rupture (Chen and Teng, 2001). The intermediate crack-induced interfacial FRP debonding starts at the end of a maximum diagonal tension shear crack. As the diagonal tension shear crack becomes wider, high stress concentrations cause debonding of the FRP sheet along with a thin layer of concrete. This mode of failure is common when diagonal tensile shear cracks occur at locations near the top of the beam because it is very difficult to develop the strength of the FRP laminate at this location. Many researchers have conducted experimental investigations to test shear deficient reinforced concrete beams to capture the behavior when strengthened with CFRP sheets and plates with different anchorage techniques. Mostofinejad et al. (2012) and Mostofinejad and Kashani (2013) carried out investigation on the effect of EBR on grooves (EBROG) method as an anchorage system on postponing debonding of FRP sheets used for shear strengthening. They concluded that the use of EBROG is an effective anchorage system that delayed the debonding significantly and increased the shear capacity of the tested RC beams. Eftekhar and Ya’ghubi (2015) applied the boring method as an anchorage system for flexural strengthening of small RC beams using FRP. The bores they used, which were drilled in the desired side of the RC beam, transferred the stresses to a deeper concrete depth. They concluded that the boring method enhanced the rupture strength, the ultimate ductility, and increased the flexural capacity of the tested beams by around 35% over the control beams. Al-Rousan and Al-Saraireh (2020) investigated the use of anchored holes technique for flexural strengthening of RC beams and they concluded that this method enhanced the beam behavior and the ultimate load capacity. In this study, this method is used in shear strengthening of RC rectangular beams. This study explored the use of bore-epoxy anchorage system in shear strengthening of shear deficient beams using CFRPs sheets as externally bonded reinforcements. The significance of this research is to explore the effect of this type of anchorage system in delaying deboning of CFRP sheets and therefore increasing the shear capacity of RC beams.