Experimental and analytical study of shear strengthening of deep RC beams using externally bonded CFRP system

Carbon fibre reinforced polymer, CFRP, has emerged an appealing solution for the rehabilitation and strengthening of structures. Numerous studies have been done to investigate the behaviour of CFRP-strengthened slender reinforced concrete (RC) beams under shear and many design methods has been adopted by the different codes of practice. On the other hand, there are currently no design guidelines offered by any code, and only a few research have been conducted to analyse the behaviour of deep beams strengthened with CFRP. Due to the lack of provisions, the current design specifications applicable to the slender beams are followed. In the present study, the behaviour of RC deep beams strengthened with CFRP of variable modulus and fibre orientation was examined analytically and experimentally. Seven shear-deficient deep RC beams were constructed and tested to failure. Out of seven, two were control beams, and the other five were strengthened with CFRP sheets in shear. The results demonstrate that shear capacity enhancement depends on the modulus of elasticity and the fibre orientation of CFRP sheets. A simple design procedure based on the strut-and-tie model was developed to evaluate the shear capacity of deep beams strengthened by CFRP, and outcomes were compared with the current experimental results as well as experimental results from the literature. The result indicates that the proposed model provides more accurate and consistent results than the commonly applied design codes ACI 440.2R-17 and TR55. Also, a parametric study was done to determine how different design parameters affect the shear strength of RC deep beams strengthened with CFRP.