Concrete-Filled FRP Tubes: Manufacture and Testing of New Forms Designed for Improved Performance

This paper reports on the development and testing of three new concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) systems. These CFFT systems were designed to enhance the effectiveness of square and rectangular FRP tubes in confining concrete. In the design of the rectangular CFFTs two different enhancement techniques were considered; namely, corner strengthening and provision of an internal FRP panel. The technique used in the development of the square CFFT system involved the incorporation of four internal concrete-filled FRP cylinders as an integral part of the CFFT. The performance of these systems was investigated experimentally through axial compression tests of 10 unique CFFTs. The results of the experimental study indicate that the new CFFT systems presented in this paper offer significantly improved performance relative to conventional CFFTs with similar material and geometric properties. Examination of the test results have led to a number of significant conclusions with respect to the confinement effectiveness of each new CFFT system. These results are presented and a discussion is provided on the parameters that influenced the compressive behavior of these CFFT systems.