Performance of GFRP-RC circular columns under monotonic loads

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Date
2020-03
Authors
BARUA, SHISIR
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Abstract
In this study, a total of thirteen full-scale reinforced concrete (RC) circular columns were constructed and tested to failure. The columns were divided into Series I and Series II, based on the slenderness ratio. All columns had a 355-mm diameter and were reinforced with six longitudinal bars and continuous spirals. Series I included seven short columns, 1,750-mm long, while Series II included six slender columns, 2,450-mm long. The test variables were reinforcement type (GFRP and steel), GFRP spiral pitch (50 and 85 mm), and eccentricity of axial load (0, 30, 60, and 120 mm) in addition to flexural loading. In each series, one steel-RC column having 85-mm spiral pitch was tested under an eccentric axial load with 30-mm eccentricity. The columns were tested to failure under either axial or four-point bending loads. The obtained capacity of the GFRP-RC short column tested with 30-mm eccentricity was approximately 17% less than the steel-RC counterpart. However, the GFRP-RC short column tested with a lesser spiral pitch (50 mm) exhibited approximately 10% more capacity than that with a larger pitch (85 mm). However, for the slender columns with same eccentricity (30 mm), the obtained capacity was approximately 3% higher than the steel-RC counterpart. Interaction diagrams for GFRP-RC short and slender circular columns were developed from experimental results in which axial capacity decreased and flexural capacity increased until the inflection point was reached, then both axial and flexural capacity decreased simultaneously. For short columns (Series I), as the axial load eccentricity increased from 0 to 30, 90 then to 120 mm, the axial capacity decreased by 32, 39, and 70% from the capacity of the concentric column, respectively. Similarly, for slender columns (Series II), these reduction percentages were 30, 37, and 70% from the capacity of the concentric column, respectively. As an effect of slenderness ratio, the GFRP-RC slender columns showed a peak load of approximately 21 to 25% less than the short counterpart columns.
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Circular column, GFRP reinforcements, Axial load, Four-point bending load
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