Shear behavior of concrete beams reinforced with CFRP sheet strip stirrups using wet-layup technique

Abstract

Fiber-reinforced polymers (FRP) are being used in reinforced concrete structures featuring their lightweight, high tensile strength, nonmagnetic, and corrosion resistance properties, contrasting conventional steel reinforcement. However, low bend strength, anisotropic and non-plastic nature of FRP composites are the major concerns for their assertive applications in construction industry. Pultruded FRP bar stirrups are characterized by premature failure either due to slippage at overlapping region or rupture at bend portion due to kinking of fibers. In this experimental study, close-type direct wound rectangular cross-section CFRP sheet strip stirrups (CSS) were proposed to mitigate the shortcomings of pultruded CFRP bar stirrups (CP). Total of seven full-scale beam specimens reinforced with steel longitudinal bars and CFRP stirrups were cast and tested to investigate the performance of proposed stirrups. The main study parameters include shear reinforcement material type, the cross-sectional geometry of CFRP stirrups, and the inclination angle of CSS stirrups with the beam axis. Specimens reinforced with CSS stirrups provided better shear capacity and crack control ability compared to steel and CP stirrups for same shear reinforcement ratios. Shear capacity of beam corresponding to serviceability limit state was improved up to 13% by changing the inclination of CSS stirrups from 90° to 45°.