PSI - Issue 28

Jamal A. Abdalla et al. / Procedia Structural Integrity 28 (2020) 1295–1302 Author name / Structural Integrity Procedia 00 (2019) 000–000

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and Ahmad, 1990; Chen and Teng, 2001; Aprile et al., 2001; Teng, 2002; Teng et al., 2003; Lu et al., 2005; Chen and Pan, 2006; Naser et al., 2012; Hollaway, 2010, Chaallal et al. 2016; Abdalla et al., 2017; Mirghani et al., 2017; Naser et al., 2019; Augusthus Nelson et al., 2020). Recently, the use of steel plates was discouraged due to its susceptibility to corrosion and other shortcomings. Currently, FRP composites are the most widely used EBR materials in shear and flexure due to its superior properties; however it has some shortcomings including its high cost, low temperature resistance, and its degradation due to other environmental factors. Carbon-Glass composite hybrid materials have also been used to enhance the performance of the FRP strengthened RC beams (Hawileh et al., 2014; Hawileh et al., 2016; Yuan et al., 2019; Choobbor et al., 2019; Yuan et al., 2020). Recently, the behavior of galvanized steel mesh (GSM) as a strengthening material has also been studied through a number of investigations (Abdalla et al., 2018; Hawileh et al., 2018; Al Nuaimi et al., 2020; Douier et al., 2020) investigated the flexural and durability performance of RC beams externally strengthened with GSM laminates. Recent advancement in aluminum alloys (AA) plates holds the potential of making them one of the alternatives as externally bonded strengthening materials, since AA has the capability of overcoming the deficiencies of steel and FRP in shear (Abdalla et al., 2011; Abu-Obeidah et al., 2015; Abdalla et al., 2016) and in flexure (Rasheed et al., 2017; Abuodeh et al., 2019). Mainly, the efficiency of the EBR method depends precisely on the bond between the EBR plate and concrete via the adhesive material. The adhesive layer in the EBR method works as an interface to transmit shear stresses between the EBR plate and concrete. Hence, the EBR failure could occur prematurely by plate de-bonding (Al-Tamimi et al., 2011; Ko et al., 2014). The peak load, fracture energy of the interface, and FRP effective bond length increase whereas the peak shear stress reduces drastically when soft adhesives are adopted in FRP- concrete joints. Deeper concrete cracks and lengthier FRP effective bond length are the main factors impacted the higher bond capacity of FRP-to concrete joints with softer adhesives (Shi et al., 2019). Various investigations have concluded that the EBR plates to concrete bond is affected by a number of factors. As stated by Pan and Leung (2007) and Yuan et al. (2019) the bond between the FRP to concrete is influenced by the properties of coarse aggregates in the concrete mix in addition to the tensile strength of concrete surface bonded to the FRP laminate. The distribution of shear stresses along the bonded length is expected to be influenced by such factors. Additionally, Chen and Pan (2006) concluded that the plate thickness affects the stress distribution along the bonded length along with the type and thickness of adhesive. Overall, the shear stress differs along the FRP plate bonded length with lowest stresses towards the plate edges and highest stresses in the middle of the bonded zone (Ferracuti et al., 2007; Pellegrino et al., 2008). In addition, a number of researches proven that the surface treatment of the concrete and plate type and surface also affects the bond behavior. It was also shown that concrete with high surface roughness performs better than untreated surface in terms of load-carrying capacity and bond strength. Toutanji and Ortiz (2001) and Zhang et al. (2020) stated that the concrete and GFRP surface treatment impacts the bond strength. Consequently, several bond stress-slip models, that consider these factors, have been established during the past few years. These models were based on analytical, numerical, and experimental studies (Alhassan et al., 2020; Biscaia et al., 2013; Cao et al., 2007; Jiang and Wu, 2013; Mazzotti et al., 2008; Nakaba et al., 2001; Savoia et al., 2003; Sayed-Ahmed et al., 2009; Zhao and Wu, 2012; Zhou et al., 2020). According to a previous study conducted by the authors Abdalla et al. (2017) on the behavior of AA plates with different surface textures to concrete, it was concluded that the AA surface treatment affects the bond between AA plates and concrete surface significantly. AA plain plates (AA-P) with untreated surface has a weak bond strength and failure load when compared to AA plates with different surface arrangements, specially the randomly roughened AA plates (AA-R) as presented in Abdalla et al. (2017) and Mirghani et al. (2017). The aim of this study is to examine the bond slip behavior of AA plates bonded to concrete using different AA plate lengths and surface roughness with different concrete strengths to analyze its capability as a new EBR material besides the

commonly used FRP plates. 2. Experimental Program 2.1. Test specimens

In this study, thirty two prisms with 2 duplicate samples from each group were cast from four typical concrete mixes with a targeted cubic concrete strength of 20, 30, 40, and 60 MPa, respectively. Standard cubes and cylinders were also cast for each mix and tested after 28 days of curing. The prisms were strengthened with treated and untreated AA plates (AA-R) and (AA-P) using epoxy adhesive and tested up to failure. AA plates were externally bonded to