SCL-020108: Seismic Performance of Hybrid FRP-Concrete Pier Frame System
As an alternative to transverse spiral or hoop steel, fiber reinforced polymers (FRPs) have been introduced to the construction industry. The concept of concrete-filled FRP tube (CFFT) has raised great interest amongst researchers in the last decade. FRP tube can act as a pour form, protective jacket, and shear and flexural reinforcement for concrete. However, the seismic performance of concrete-filled FRP tube (CFFT) as new construction for bridge substructure is not fully investigated. In this research, four specimens were built and tested under constant axial load and reverse cyclic lateral loads. One was control RC frame and other three were hybrid FRP-Concrete pier frames. One of the FRP tubes was off-the-shelf product made by filament winding of ±55 degree E-glass fibers (Specimen GFF), and the other four FRP tubes were made in the laboratory. One type of FRP tubes was made using 2 layers of bi-directional carbon FRP sheets (Specimens CFF). Specimen HFF a hybrid lay-up of 2 layers of longitudinal uni-directional carbon FRP sheets and 3 layers of transverse uni-directional glass FRP sheets. Test results showed that Specimen GFF remained uncracked when drift ratio reached 15% without axial force while others had cracks at the top and bottom of the FRP tubes in hoop direction even a vertical one. Specimen HFF showed the highest load capacity and initial stiffness with considerable ductility, while GFF performed outstanding ductility with high load capacity. Specimen CFF had similar load capacity to Specimen GFF, however, hoop direction cracks appeared in early stage and one vertical crack happened in last loading cycle when the ductility factor was 7. As for the energy dissipation, Specimen HFF had the highest one and Specimen GFF had similar performance with Specimen CFF. From the readings of the strain gauges, the pier cap beam behaved like as a rigid beam and rotated small. The columns had linear deformation for the middle part and had larger deformation at the top and bottom parts.
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