BEHAVIOUR OF CONCRETE-FILLED FRP CIRCULAR TUBES (CFFTs) SUBJECT TO COMBINED AXIAL COMPRESSION AND BENDING LOADS

This paper presents the results of an experimental study aimed at investigating the effect of important parameters on the behavior of circular concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs). The experimental program consisted of nine half-scale specimens that were constructed and tested to failure. The tested specimens were divided into two groups. The first group was composed of three plain concrete core tubes without outer confinement (PCTs) that were subjected to different levels of prestressing; there was also a control specimen. The second group consists of six CFFTs that were confined with different FRP tube thicknesses and different levels of prestressing. All specimens had a cir-cular cross section with a diameter of 200 mm and a total length of 2000 mm, which was tested in three-point bending over a simply supported span of 1800 mm. The studied parameters are the confinement effect of using FRP tubes, the FRP tube thickness, and the effect of prestressing level. The test results showed that CFFTs can achieve substantially higher strength, serviceability, ductility, and energy absorption capacity than PCTs without FRP tubes. Furthermore, the significant effect of prestressing is the activation of the confinement mechanism of the concrete core restrained by the FRP tube.