Experimental behaviour, FE modelling and design of large-scale reinforced concrete deep beams shear-strengthened with embedded fibre reinforced polymer bars

Reinforced concrete (RC) deep beams are widely used in buildings and bridges. However, research on shear strengthening of RC deep beams with embedded fibre reinforced polymer (FRP) bars is limited. This paper presents the first comprehensive study on the experimental behaviour, nonlinear finite element (NLFE) modelling and design of large-scale RC deep beams strengthened in shear with embedded carbon or glass FRP (CFRP or GFRP) bars. An experimental investigation comprising three large-scale RC deep beams was conducted. Subsequently, a three-dimensional NLFE model was developed and validated against the experimental results. The validated NLFE model was used to perform a parametric study, examining the influence of FRP bar type and steel-to-FRP shear reinforcement ratio on shear strength enhancement. The results of the parametric study were utilized to calibrate and validate a novel design model. The results showed that embedded FRP bars can enhance the shear force capacity of large-scale RC deep beams by up to 40 %. The effect of FRP bar type on the shear strength enhancement was insignificant. However, there was 13 % reduction in shear force gain due to the increase in steel-to-FRP shear reinforcement ratio from 0.77 to 10.0. The novel design model reproduced the NLFE results with a mean ratio of 0.921 and a standard deviation of 0.018. Finally, the ability of the design model to capture the effect of the investigated parameters was demonstrated.