Novel testing and characterization of GFRP bars in compression

Glass fibre reinforced polymer (GFRP) bars have now been increasingly used as longitudinal reinforcement in concrete columns. In column design and analysis, the contribution of GFRP bars to compression is often ignored or is estimated as a fraction of its tensile strength due to the limited understanding on their compressive behaviour. Moreover, there exists no standard test method to characterise the properties of GFRP bars in compression. This study implemented a novel test method to determine and characterise the compressive properties of high modulus GFRP bars. During the preparation of test specimens, hollow steel caps filled with cementitious grout were used to confine the top and bottom ends of the GFRP bars. The effects of the bar diameter (9.5, 15.9, and 19.1 mm) and the unbraced length-to-bar diameter ratio, L-u/d(b) (2, 4, 8, and 16) were investigated on the compressive strength of the bars. The results showed that the increase in bar diameter increases the micro-fibre buckling and decreases the compressive-to-tensile strength ratio. Similarly, the failure mode changed from crushing to fibre buckling with the increase of L-u/d(b) ratio. Simplified theoretical equations were proposed to reliably describe the compressive behaviour of GFRP bars with different bar diameters and L-u/d(b) ratios. (C) 2019 Elsevier Ltd. All rights reserved.