Shear Behavior of Steel or GFRP Reinforced Concrete Beams Without Stirrups

Abstract

The paper presents results of experimental test carried out on 12 T-shaped concrete beams reinforced with glass fiber reinforced polymer (GFRP) or steel bars without stirrups. The aim of this research was to analyze the influence of a type of longitudinal reinforcement (GFRP or steel) on shear capacity and deformability of concrete beams without stirrups and to investigate a dowel effect of the reinforcement on the shear strength. The beams varied mainly with a type of flexural reinforcement, its reinforcement ratio (ρ l ) corresponding to about: 1%, 1,4% and 1.80%, a number of bars, their diameter and a number of reinforcement layers (1 or 2 layers). All beams failed in shear, but diagonal shear cracking was affected by a type longitudinal reinforcement. The GFRP reinforced beams failed due to gradual development of diagonal cracks, while in beams with the steel reinforcement diagonal cracking developed rapidly leading a brittle failure. Steel reinforced beams indicated higher shear capacity than the GFRP reinforced beams. Beneficial influence of two reinforcement layers was confirmed especially for the high longitudinal reinforcement ratio equal of 1.80%, while for the low reinforcement ratio about 1.0%, no difference in the shear capacity due to number of layers was observed. Due to almost four times lower elasticity modulus of the GFRP bars than steel, the GFRP reinforced beams indicated higher ductility than the steel reinforced beams.