SCL-071201: Seismic Performance of Hybrid FRP-Concrete Pier Columns
While repair and rehabilitation of existing concrete bridges constitute the largest application of fiber reinforced polymer (FRP) in infrastructure, hybrid construction of FRP with concrete in the form of concrete-filled FRP tube (CFFT) is perhaps the most promising application for new bridge substructures. Previous studies have shown exceptional performance for CFFT columns under reverse cyclic loadings. This study focuses on the effects of fiber architecture and shear span to depth ratio on the cyclic behavior of CFFT columns. One control reinforced concrete (RC) and five single CFFT columns were tested as cantilever columns under constant axial load and reverse cyclic lateral loads. One of the FRP tubes was off-the-shelf product made by filament winding of 17 layers of ±55 degree E-glass fibers (Specimen Y), and the other four FRP tubes were made in the laboratory. Two carbon FRP (CFRP) tubes with different shear span to depth ratios were made using 2 layers of bi-directional CFRP sheets (Specimens SC and LC). Specimen G had a tube made with 3 layers of bi-directional E-glass FRP (GFRP) sheets. Specimen H had a hybrid lay-up of 2 layers of longitudinal uni-directional CFRP sheets and 3 layers of transverse uni-directional GFRP sheets. Test results showed that Specimens Y, G and H remained intact throughout the cyclic load tests, while Specimens SC and LC suffered cracks in the FRP tubes. In general, Specimen H demonstrated the highest capacity and initial stiffness with comparable ductility, while Specimens G and Y exhibited superior ductility with considerable capacity. At the same drift ratio, Specimen H was considered as the best in terms of energy dissipation. Moreover, the influence of shear span ratio is insignificant for concrete filled FRP tubes. Last, the combined effects of high moment and high shear on seismic behavior of CFFT columns are also insignificant.
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