The Effect of GFRP Bar Diameter on the Compressive Behaviour of Hollow Circular Concrete Columns with Hollow Composite Section

Anderson, Liam Jacob Frylink (2019) The Effect of GFRP Bar Diameter on the Compressive Behaviour of Hollow Circular Concrete Columns with Hollow Composite Section. [USQ Project]

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Glass Fibre Reinforced Polymer (GFRP) is a composite material with emerging popularity as a replacement for steel in reinforced concrete structures, due to its higher strength, better corrosion resistant properties, and more compatible modulus of elasticity with concrete than steel. Currently there is no Australian Standard for GFRP-reinforced concrete structures, and the research into GFRP bars in circular hollow concrete columns is ongoing. It has been shown that hollow columns with internal steel confinement display enhanced concrete strength, greater ductility and yield strength due to the triaxial confinement of the concrete, compared to columns without internal confinement.

This study aims to investigate experimentally the interaction of GFRP bars and a proprietary GFRP hollow composite reinforcing system (CRS) on the compressive behaviour of hollow concrete columns.

A total of four hollow concrete columns of 1m in height, 250mm outer diameter with 65mm inner hollow core were prepared using 34.4MPa concrete and tested under concentric axial load. All samples were laterally reinforced with GFRP spirals, with the hollow core being reinforced with CRS. Three columns were additionally reinforced vertically with 6 GFRP bars of increasing size, resulting in GFRP bar reinforcement ratios of 1.64%, 2.58%, and 3.72% respectively. The control column was reinforced with spirals and CRS only.

All four columns exhibited linear elastic behaviour until their initial peak load, at which point the cover concrete spalled, exposing the spiral reinforcement. The initial peak load for all columns was found to be on average 13% lower than estimated by theoretical modelling. By adapting the theoretical model’s assumptions to suit the experimental strain data, this model was brought to within the margin of error of the study. The three columns with vertical GFRP bar reinforcement continued to support increasing load, peaking at an average of 36% higher load than the initial peak load, whereas the control column did not support significantly increased load. Increasing the reinforcement ratio was found to increase the efficiency of the confinement provided by the GFRP spirals. Furthermore, increasing the reinforcement ratio was found to decrease the ductility of the columns.

The results confirm that the combination of GFRP bars and CRS reinforcement enhances the strength of hollow concrete columns after the initial peak load, due to triaxial confinement of the concrete. Due to the small sample size and other limitations of this project, further testing and theoretical analysis will be required to develop a theoretical model which can accurately predict the peak load capacities and deformation behaviour of hollow circular concrete columns.

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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; Alajarmeh, Omar
Qualification: Bachelor of Engineering (Honours) (Civil)
Date Deposited: 12 Aug 2021 01:12
Last Modified: 26 Jun 2023 05:38

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