STR232-1 CSCE 2021 Annual Conference Inspired by Nature – Inspiré par la Nature 26-29 May 2021 SHEAR AND BENDING BEHAVIOUR OF SHORT-SPAN STEEL- REINFORCED CONCRETE-FILLED FRP TUBES WITH ±55 ◦ FIBER ORIENTATION Roy, Subharajit 1,3 , Sadeghian, Pedram 2 1,2 Dalhousie University, Canada 3 subharajit.roy@dal.ca 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. 1 INTRODUCTION Efficient infrastructure systems such as highways, bridges, buildings, pipelines, flood control systems (waterways) and utilities are all necessary for a healthy economy and comfortable standard of living. The long-term structural durability of reinforced concrete structures has been a long-term issue for the infrastructure industry. Corrosion of steel reinforcement causes major degradation problems to the structures worldwide. In the last decade, a hybrid system such as concrete-filled fiber-reinforced-polymer (FRP) tubes (CFFTs) are promising for various structural applications such as structural columns, piles, poles, pipes, signalling post, bridge components, etc. Their fascinating features include durability, concrete confinement, resistance towards chemical attacks, etc. grabbed the attention of researchers and the infrastructure industry. Due to their resistance to corrosion, internal pressure and axial loads, ±55 ◦ filament wound GFRP tubes are readily available and popular among the oil and gas and municipal sector (Betts et al. 2019). Although the behaviour of CFFTs (Mirmiran and Shahawy 1997; Fam and Rizkalla 2002) have been studied substantially under various loading conditions (Fam et al. 2003; Fam and Cole 2006; Burgueño and Bhide 2006; Fam et al. 2007; Mirmiran et al. 2008), very few studies have been executed to understand the shear behaviour of CFFTs, especially with ±55 ◦ fiber orientation. From those studies, it has been noticed that depending on the fiber orientations of FRP tube, longitudinal reinforcement ratio and composite action