Shear strength of reinforced concrete beams with precast High-Performance Fiber-Reinforced Cementitious Composite permanent form

As a structural and constructional element, a thin-walled U-shaped precast permanent form consisting of High-Performance Fiber-Reinforced Cementitious Composites (HPFRCC) and steel wire mesh is considered. Prior to casting, transverse steel threaded bars are installed, as well as longitudinal reinforcing bars, connecting two sides of the U-shaped form for shear transfer between the precast and in-filled concrete sections and for fresh concrete pressure resistance. The present study investigated the effect of precast U-shaped HPFRCC section on the shear strength of the composite beams. As parameters for full-scale three-point bending tests, the type or materials of precast section, spacing of shear reinforcement, and shear span-to-depth ratio were considered. The test results showed that the precast U-shaped HPFRCC permanent form increased the shear contributions of in-filled concrete and shear reinforcement in the composite beam substantially. From the experimental and analytical assessment, the coefficients related to the composite action between precast HPFRCC and in-filled concrete sections, shear reinforcement along diagonal cracks, and shear span-to-depth ratio were proposed, which were applied to a previous shear strength model for the simplified shear design of proposed precast U-shaped HPFRCC-in filled concrete composite beams.