Effect of Post Shear Reinforcing Methods with Plate and Head Anchored Shear Reinforcing Bars

Abstract

Some reinforced concrete (RC) structures in Japan which were built before 1980’s had low shear reinforcement and actually failed in shear. Accordingly, various shear strengthening methods, such as steel jacketing, FRP sheet jacketing, have been applied for existing RC structures. A new post shear reinforcing method with a plate and head anchored shear reinforcing bars (PHB method) has also been developed and widely used on site. In this study, some influential factors on this new method were experimentally investigated. A total of seven RC slender beams were tested under a four-point bending loading with the parameters of the spacing, the diameter and the embedded length of plate and head anchored shear reinforcing bars (PHBs). All beams had a rectangular cross section and a fixed a/d ratio of 3.2. The experimental results showed that PHB method improved the shear capacity of RC beams and the shear capacity of RC beams was affected by the spacing of PHBs, whether the PHBs were crossed by the diagonal crack or not. However, the magnitude of the shear capacity became smaller when the effective coefficient (β aw ) was reduced. With the increase in the spacing of PHBs, the shear capacity of RC beams decreased. This result suggests that the shear capacity can be controlled by increasing the shear reinforcement ratio. Furthermore, the shear reinforcement effect can be also promoted by shorter embedment length.