Efficiency of steel and macro-synthetic structural fibers on the flexure-shear behaviour of prestressed concrete beams

The efficiency of steel and structural synthetic fibers on the performance improvement of prestressed concrete (PSC) beams under combined flexure-shear is studied. Results of eleven PSC beams tested at a shear span (a) to depth (d) ratio of five are presented. Discrete steel and macro synthetic structural polyolefin fibers of varying dosages of 0.35%, 0.7% and 1.0% by volume of concrete were used. The effect of fiber addition on overall load - displacement, load- strain, and strain energy absorption capacity of PSC beams is analysed. Other parameters such as shear span to depth ratio (a/d), compressive strength of concrete, prestressing reinforcement ratio were kept constant. The test results portray that the addition of steel fibers stiffens the post cracking response, increases the strain energy absorption capacity more efficiently when compared to macro synthetic fibers (Polyolefin). The failure mode changed from less ductile flexure-shear to more ductile flexure dominant mode at 0.35% and 0.70% volumetric dosage of steel and synthetic fibers, respectively. The strain energy absorption capacity increased by more than 100% at 1.0% fiber addition for both steel and macro-synthetic fibers.