Effect of shear span-depth ratio on mechanical performance of RC beams strengthened in shear with U-wrapping FRP strips

Shear span-to-effective depth ratio (av/d) is well known to affect the shear performance of reinforced concrete (RC) members. However, this effect has not been properly addressed in existing design guidelines for fiber-reinforced polymer (FRP) strengthening structures. This paper focuses on the effect of av/d on behaviors of RC beams shear-strengthened with U-wrapping CFRP strips. A total of six shear-strengthened and six normal beams, with av/d ratios ranging from 1.0 to 3.5, were tested. The test results indicate that FRP shear contribution increases initially with av/d ratio, but decreases slightly when the ratio is beyond 2.0. The distribution of FRP strain along the critical shear crack shows different trends for different av/d ratios. Results of the present study and data collected from the literature with different av/d ratios are compared with predictions from various design guidelines. The comparison indicates a potential risk of overestimating the FRP shear contribution for beams with low av/d ratios (especially in deep beam). Further work is required to better understand the av/d ratio effect so it can be properly incorporated into the design equations.