Experimental study for the slenderness ratio of the axially loaded CFFT columns

ABSTRACT

This paper presents the results of an experimental study carried out to investigate the axial behavior of reinforced concrete filled fibre-reinforced polymer (FRP) composite tubes (CFFT). The application of CFFT for different structural applications (piles, column, girder, bridge piers) has proved to be one of the more favorable systems. The FRP tubes benefits are in confinement, protective jackets, providing shear or/and flexural reinforcement and permanent formwork. Actually most of the experimental investigations which conducted to study the effect of different parameters on the behaviour of the CFFT under compression load were on small dimension specimens (cylinders dimension). The axial load behaviors of short, medium and long height reinforced concrete filled GFRP circular tubes with steel bars were investigated. The aims of this study are to investigate the effect of the slenderness ratio on the confinement, axial stress-strain responses, axial and horizontal deformation, failure mode, and ultimate load capacity of the reinforced CFFT columns. The CFFT columns of different heights, 300, 600, 900,

1200 and 1500 mm were tested under axial compression load. The internal diameter of the GFRP tubes used in this investigation was 152 mm, the tube thicknesses was 2.65 mm, the fibre orientation mainly in the hoop direction of ± 60 degree with respect to the longitudinal axes. The final failure mode for CFFT columns is affected by the slenderness ratio, rupture of the GFRP tube for slenderness ratio equals to 2 and 4, buckling accompanied by rupture of the GFRP tube for specimens slenderness ratio equals to 6, and finally, buckling failure is the final mode for specimens slenderness ratio equal to 8 and 10 without rupture for the GFRP tube. In general, increasing the slenderness ratio of CFFT specimens reduce the ultimate load capacity of the specimens due to the buckling.