Splicing of Precast Concrete-Filled FRP Tubes

This paper reports on a feasibility study of splicing techniques for precast concrete-filled fiber-reinforced polymer (FRP) tubes (CFFT). A total of four spliced beams were tested. Three were internally spliced using grouted steel bars, grouted FRP bars, or unbonded posttensioning bars, and the fourth was spliced with FRP socket, commonly used in the piping industry. A control CFFT beam with no internal reinforcement was also tested as a reference. The experiments showed the superior effect of FRP tube continuity on system performance. Although initially stiffer, none of the spliced beams tested in this program was as strong as the control specimen. This may be primarily attributed to the lack of continuity of the FRP tube, as well as the quality of the cement grout for dowel reinforcement. Posttensioning proved to be efficient in improving system performance. The system may benefit from FRP continuity through either a longer and more effective socket or a threaded coupler insert or sleeve. Internal reinforcement can further increase the stiffness and strength of the connection, if grouting quality is controlled. Splicing may be improved by combining the methods tested in this program. Further understanding of the implications of composite action between FRP and concrete was achieved. Finally, the behavior of spliced CFFT beams was closely described using a combination of beam theory and rigid body deformations; the extent of the latter depends on joint stiffness.