Abstract
This paper aims at investigating the general axial behavior of long circular concrete-filled, fiber-reinforced polymer (FRP) tube (CFFT) columns internally reinforced with different longitudinal rebars. A total of seven CFFT and three reinforced concrete (RC) columns served as control specimens for comparisons and were constructed and tested under cyclic axial loading until failure. The test parameters were: (1) internal reinforcement type (steel, glass fiber-reinforced polymer (GFRP) or carbon fiber-reinforced polymer (CFRP)) and amount; (2) GFRP tube thicknesses; and (3) nature of loading. All columns had 1900-mm in height and 213-mm in diameter. Examination of the test results has led to a number of significant conclusions in regards to the trend and ultimate condition of the axial stress-strain behavior, mode of failure of tested CFFT columns, and plastic strains. As expected, an increase in the FRP tube thickness (or stiffness) resulted in an increase in the strength and strain enhancement ratios. The validity of the available design provisions for predicting the ultimate load-carrying capacity of tested columns is also highlighted.
Highlights
Over the past couple of decades, fiber-reinforced polymer (FRP) composites have been used for enhancing the behavior of reinforced concrete (RC) members, including several advantages such as favorable strength-to-weight ratio, non-corrosive characteristics, and reduced long-term maintenance costs
The FRP tube acts as a stay-in-place structural formwork, a noncorrosive reinforcement for the concrete for flexure and shear using the multidirectional fiber orientation, which provides confinement to the concrete in compression, and the contained concrete is protected from the intrusion of moisture with corrosive agents that could otherwise deteriorate the concrete core [1]
This paper presents the test results of seven concrete-filled FRP tubes (CFFTs) and three reinforced concrete (RC) columns reinforced longitudinally with steel or glass ffiiber-reinforced polymer (GFRP) and CFRP bars tested under monotonic and cyclic axial compression loads
Summary
Over the past couple of decades, fiber-reinforced polymer (FRP) composites have been used for enhancing the behavior of reinforced concrete (RC) members, including several advantages such as favorable strength-to-weight ratio, non-corrosive characteristics, and reduced long-term maintenance costs. It is worth mentioning that the existing stress-strain models of FRP-confined concrete were developed almost exclusively based on results of specimens with height-to-diameter ratio (h/d = 2) [14] It is, important to examine the stress-strain behavior of full-scale CFFT columns reinforced with and without internal bars with high (h/d) ratios and to develop new analytical models to describe this behavior under axial cyclic compression loading. Previous experimental studies indicated that the compression behavior of concrete columns reinforced with GFRP reinforcements has been similar to that with steel, but with less contribution of FRP longitudinal bars to strength capacity [16,17,18,19,20]. The validity of the available design provisions for predicting the ultimate load capacity of tested columns is highlighted
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