Experimental investigation of the behavior of concrete-filled high-strength glass fiber-reinforced polymer tubes under static and cyclic axial compression

This experimental study investigated the load–displacement behavior, ultimate strength, and failure modes of hollow and concrete-filled high-strength glass fiber-reinforced polymer (GFRP) tubes under static and cyclic axial compression. For this purpose, pultruded GFRP tubes were used which contained fibers oriented at 0^°, +45^°, and −45^° to the longitudinal axes of the tubes. Self-compacting concrete (SCC) was used for in-filling the hollow GFRP tubes. The main parameters considered in the test program were the tube cross-section, column length, and cyclic loading range. A total of 28 specimens of lengths equal to either 0.5 or 1.5 m were tested under static and cyclic axial compressive loading. The experimentally obtained load–displacement and load-axial/hoop strain behaviors are discussed in this paper. It was verified that in-filling the GFRP tubes with concrete can enhance their axial strength and stiffness, though it is not able to prevent the brittle nature of the failure. Hollow GFRP tubes displayed linear-elastic behavior with a constant axial stiffness up to failure under both static and cyclic loading, while the concrete-filled specimens exhibited a bilinear load–displacement behavior with the change in stiffness occurring at the point at which the GFRP tube starts to act as a confining jacket. Under cyclic loading, the concrete-filled specimens suffered degradation in axial stiffness with the rate of deterioration decreasing with increasing number of cycles. However, a consistent relationship between the cyclic load range magnitude and number of cycles to failure could not be found using the experimentally obtained data.