Slenderness Effect on the Behaviour of Hollow Circular Concrete Columns Reinforced with GFRP Bars

Fairhall, Thomas (2018) Slenderness Effect on the Behaviour of Hollow Circular Concrete Columns Reinforced with GFRP Bars. [USQ Project]


A major concern of traditionally steel reinforced concrete structures is the susceptibility to corrosion in harsh environments resulting in loss of capacity and serviceability which ultimately lead to failure. This has led to the focus of glass fibre reinforced polymers (GFRP) being the basis of many recent studies due to their advantageous properties when used as reinforcement in concrete structures. With characteristics of high strength and stiffness to weight ratios, it is an obvious choice for reinforcement where corrosion is a concern. The behaviour of concrete columns with internal GFRP reinforcement has had limited research work conducted, with hollow columns not having been researched before. In addition to this slenderness effects on these columns has not been addressed sufficiently in previous research. Currently solid columns reinforced with GFRP have a slenderness limit of 16.

This study aims to close the research gap by analysing the slenderness effect on hollow circular concrete columns reinforced with GFRP bars concentrically loaded through experimental investigations. Four hollow concrete columns of slenderness ratios of 7.5, 15, 22.5 and 37.7 consisting of 250 mm external and 90 mm internal diameters were cast with successive heights of 0.5 m, 1 m, 1.5 m and 2 m. These were reinforced with six 15.9 mm diameter GFRP longitudinal bars and 9.5 mm diameter GFRP spirals at 100 mm spacing and subsequently tested to failure. The test results were discussed in terms of failure behaviour, axial and deformation capacity, stiffness, longitudinal, axial and concrete strain development, confinement efficiency and ductility.

In the testing, none of the columns failed due to buckling, but it was noted that the proposed slender columns concrete core failed to shear. In comparison the short columns failed from crushing of the concrete core. Based on the experimental results, the slenderness ratio affected the columns capacity by reducing it up to 87% of the shorter column, however greater reductions would have been realised if buckling occurred. In addition, increasing slenderness showed a significant effect on reducing the stiffness as well as GFRP bar and concrete cover strain development. Nevertheless, there was no evidence that slenderness had an effect on confinement efficiency or ductility in the setting of hollow concrete columns with GFRP reinforcement.

Based on the findings, a proposed reduction factor was presented to accurately predict a columns capacity with GFRP reinforcing according to its slenderness ratio. The model takes into account reinforcement ratio, concrete compressive strength, cross sectional area and slenderness ratio. The proposed reduction factor exhibited agreement with experimental results and also previous studies. In contrast when applied to columns with high strength concrete, the predicted value showed less favourable results. Finally, through analysis a proposed slenderness limit of 35 should be considered for hollow columns reinforced with GFRP bars.

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Manalo, Allan
Qualification: Bachelor of Engineering (Honours) (Civil)
Date Deposited: 01 Sep 2022 01:54
Last Modified: 29 Jun 2023 01:31
Uncontrolled Keywords: steel reinforced concrete; corrosion; glass fibre reinforced polymers (GFRP)

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