EXPERIMENTAL STUDY ON DIAGONAL SHEAR CRACKS OF CONCRETE BEAMS WITHOUT STIRRUPS LONGITUDINALLY REINFORCED WITH GFRP BARS

An experimental study on diagonal shear cracks of concrete beams without stirrups was carried out. A total of twenty four reinforced concrete beams, consisted of twelve beams reinforced with GFRP bars and twelve beams reinforced with conventional steel bars, were tested up to failure. Test variables in this study were: (1) concrete compressive strength; (2) longitudinal reinforcement ratio; and (3) shear span-effective depth ratio. Beam capacities, slope of the diagonal shear cracks, strains at the maximum concrete compression fiber and selected position of longitudinal reinforcement were observed during the test. The diagonal shear cracking loads obtained from the test were compared to that calculated using empirical equations available in ACI code and Eurocode 2. The test results showed that shear strength of beams reinforced with GFRP bars was lower than that of the beams with conventional steel bars. It was found that the ratio of longitudinal reinforcement significantly influences the failure type and crack pattern in the shear span zone. In addition, the tensile strain of longitudinal reinforcement at the support considerably increases after the occurrence of diagonal cracks.