SHEAR BEHAVIOR OF STEEL FIBER REINFORCED PRECAST PRESTRESSED CONCRETE BEAMS

Precast industries constantly look for better alternative solutions to reduce the secondary reinforcement to speed up the production process. Addition of fibers in concrete helps in reducing the use of secondary reinforcement. Presence of fiber reinforcement has proven to enhance the ductility and energy dissipation capacity of the concrete under flexure and shear. Shear behavior of concrete members mainly depends on the compressive strength of concrete, shear span to depth ratio (a/d), amount of stirrups, aggregate interlock and dowel action of longitudinal reinforcement. The present study focuses on the shear behavior of steel fiber reinforced PSC beams with different volume fractions i.e., 0.50% and 1.00%. Fiber reinforced prestressed concrete (FRPC) beams were cast using long line method and tested with a shear span to depth ratio of 2.4 to simulate shear dominant behavior. Strain gauges were attached to the strands at loading point and at the center of shear span (a/2) to measure strain variation at different stages such as prestressing, de-tensioning and testing. During experimentation, load-deflection and strand strain was recorded. Test results indicate that the addition of steel fibers improved the shear resistance and ductility of the prestressed concrete beams

SHEAR BEHAVIOR OF FIBER REINFORCED HIGH STRENGTH PRESTRESSED CONCRETE BEAMS

Precast industries look for better alternative solutions to reduce the secondary reinforcement to speed up the production process. Addition of fibers to concrete helps in reducing the use of secondary reinforcement. Presence of fiber reinforcement has proven to enhance the ductility and energy dissipation capacity of the concrete under flexure and shear. The present study focuses on the shear behavior of steel fiber reinforced prestressed concrete (PSC) beams with different volume fractions i.e., 0.50%, 1.0% and 1.50%. Fiber reinforced prestressed concrete (FRPC) beams were cast using long line method and tested at a shear span to depth ratio of 2.4 to simulate shear dominant behavior. The effect of fiber addition on overall load-displacement, load- strain, ductility of PSC beams is analyzed. Other parameters such as shear span to depth ratio (a/d), compressive strength of concrete, longitudinal reinforcement ratio were kept constant. The test results portray that the addition of steel fibers arrested the crack propagation and the changed the failure from shear to ductile flexure-shear at higher dosages of steel fibers. Moreover, effect of other fiber type and its dosage on shear behavior was studied using structural synthetic (polyolefin) fiber and hybrid fiber (combination of steel and synthetic fiber). Effect of fibers on the flexure-shear interaction was studied using modified compression field theory (MCFT). MCFT is a space truss model which is used for modelling of cracked concrete sections. Cracked concrete is treated as a material with its own stress-strain characteristics. Equilibrium, compatibility and stress-strain relationships are formulated in terms of average stresses and average smeared strains. In the current study, the model developed by Vecchio and Collins (1986) for predicting the Shear-flexure interaction has been presented and discussed. The constitutive laws in MCFT algorithm were varied and shear-flexure interaction of fiber-reinforced members were analysed at the membrane and section level