| Extensive studies in the past decade have shown superior performance of concrete-filled fiber reinforced polymer (FRP) tube (CFFT) under axial compression, as the system utilized both high tensile strength of FRP tube and high compressive strength of concrete core. FRP provides lightweight formwork during construction and life-long protection for concrete in harsh environments. Despite significant advances in the research of CFFT, still for the system to be used in either bridge or building construction, appropriate connections need to be developed. Considering unique mechanical properties of FRP, connections of the CFFT members are considered critical components of the entire system.; Four sets of experiments were carried out to better understand and improve CFFT joint performance. Analytical model were developed and verified with each set of test.; Initially, two pilot CFFT pier cap frames were precast and assembled with five joint concepts. The pier caps were tested under two cases of loading, which simulated various bridge traffic patterns. The pier cap was modeled with a general finite element analysis software, ANSYS, to investigate the relationship between its performance and the joint stiffness.; Subsequently, four CFFT beam splices were tested. Various joint methods were developed with different internal reinforcement or external socket. In general, rigid body rotation dominated the CFFT beam performance, since joint stiffness was significantly lower than the member itself.; To verify axial confinement model for large scale CFFT columns with internal reinforcement, a total of six CFFT column stubs were tested under uni-axial compression. Test results confirmed the validity of Samaan's confinement model.; Finally, a set of CFFT column-footing assemblies were prepared to investigate construction feasibility and performance of joint methods that were developed through the previous experiments. The CFFT columns were subjected to a constant axial load and reverse cyclic load in lateral direction. The CFFT columns exhibited significant improvement over traditional RC columns in both ultimate capacity and deformation. An open software, OpenSees, was used to model the CFFT columns. The analysis showed a close agreement with test results. A detailed parametric study was conducted to identify important design variables for CFFT columns.; CFFT system, with its superior performance over its RC counterpart under both static and earthquake loads, proved to be compatible with the civil engineering practice both in construction methods and in structural analysis techniques. |
