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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effective strain of the CFRP U-wraps was depicted in the anchored specimens. Overall, test results showed that anchoring the CFRP U-wraps enhances the shear capacity, deformability and CFRP strain utilization. It is clear from Table 5 that the embedment depth has a significant effect on the performance of the anchors. This can be shown by comparing the shear values of specimens BAU 75/12/45 and BAU 50/12/45 that had embedment depths of 75 and 50 mm, respectively. Increasing the embedment depth by 25 mm improved the pullout capacity of the anchors and delayed the debonding failure. Hence, more CFRP strain was utilized, and higher capacity was attained in specimen BAU 75/12/45. As for the anchor diameter parameter, test results indicated that increasing the dowel diameter from 10 to 12 mm did not affect the shear capacity, when all other anchor parameters were kept constant. This could be attributed to the anchor hole diameter to embedment depth ratio. Studies showed that increasing this ratio reduces the capacity of the FRP spike anchors (Kim and Smith (2009); Mhanna et al. (2021b)). In this study, specimen BAU 75/12/45 had higher hole diameter-to-depth ratio than specimen BAU 75/10/45. Therefore, even if the anchor material was higher in the 12 mm anchors, the higher hole diameter-to-depth ratio resulted in similar capacity as the 10 mm anchors. Tests results showed that the insertion angle had no significant effect on the capacity of the anchors, as both specimens BAU 50/12/90 and BAU 50/12/45 had similar shear capacities. Theoretically, due to the high bend of the 90 º insertion angle compared to the 45 º , the anchors in specimen BAU 50/12/90 should have lower tensile capacity, as the anchors are subjected to shear force that reduces its tensile capacity. However, the capacity of the anchors in this study could be limited by the choice of embedment depth or dowel diameter. Therefore, based on the experimental results, it is recommended to increase the embedment depth of the anchors up to a minimum of 75 mm. In addition, it is advisable to use straight anchors (IA=0) instead of bent anchors (IA=90) to maximize the tensile capacity of the anchors. More research is needed to investigate the effect of dowel/hole diameter with respect to the embedment depth on the capacity of the anchors. 4. Conclusions In this study, the effect of strengthening RC T-beams with CFRP U-wraps and spike anchors was investigated. The parameters studied were anchor embedment depth, dowel diameter, and insertion angle. The following conclusions were drawn based on the experimental results: • Strengthening of RC T-beams with CFRP U-wraps enhanced the shear capacity of the beam by 45%. Anchoring the U-jackets improved the FRP contribution to shear capacity by 27-55% compared to the unanchored U-wraps. • The primary failure mode of the strengthened specimens was debonding of the middle U-wraps that intersected the critical shear crack. The main advantage of the CFRP spike anchors was in mitigating the debonding failure mode and enhancing the deformation capacity of the anchors. • Increasing the embedment depth from 50 to 75 mm enhanced the CFRP contribution to shear capacity by 19%, due to the increased tensile capacity of the 75 mm depth anchors. • Increasing the dowel diameter from 10 to 12 mm did not affect the capacity of the anchors as both specimens with 10 mm and 12 mm anchors attained similar shear capacity. The results may have been affected by the ratio of hole diameter to embedment depth. Therefore, it is recommended in future studies to investigate the effect of variable anchor and hole diameters with various embedment depths to study the relation between these three parameters. • Reducing the insertion angle from 90 to 45 º resulted in the same shear capacity. The capacity of the anchors in this study could have been limited by the choice of embedment depth (50 mm), where the anchors experienced a partial pullout due to its insufficient embedment depth. Acknowledgements The support for the research presented in this paper had been provided, partially, by Riad Sadek Endowed Chair in Civil Engineering at the American University of Sharjah. Additionally, the authors would like to acknowledge Structural Technologies for providing the CFRP and epoxy and for strengthening the beams. The support is highly appreciated. The views and conclusions expressed or implied, in this study, are those of the authors and should not be interpreted as those of the donor or the institution.