Shear and Bending Behaviour of Short-span Steel-reinforced Concrete-filled FRP Tubes with ±55◦ Fiber Orientation

Abstract

In this study, steel-reinforced concrete-filled ±55◦ glass-fiber-reinforced-polymer (GFRP) tubes (CFFT) are examined under monotonic loading to understand their shear behaviour. A total of three test specimens with three different nominal pressure ratings (50, 100 and 150 Psi) were tested under three point bending. The pressure ratings are associated with the tube wall thickness. The shear span to depth ratio (a/D) was adopted as 1 for this study. The applied load for each test was measured using a 1.5MN load cell. The deflection at mid-span and the bond-slip measured with the help of a string potentiometer and linear potentiometers. The strains at the compression and tension regions were measured using strain gauges with a gauge length of 6mm. The test results show that the increase in the ultimate strength of the concrete-filled GFRP tubes was due to the increase in the wall thickness. All specimens failed in flexure: initial stretching of the tensile fibers with minor compression fracture development at the top and ultimately failed due to fracture at the tension fibers at mid-span. No significant amount of slip between concrete core, GFRP tube and steel reinforcement were recorded, which shows that the superior compositeness between the components of the test specimens. The importance of this study is to improve the understanding of shear and flexural behaviour of the CFFTs with ±55◦ fiber orientation.