Han, Tao, and Yao 2010
This paper tests eight fiber reinforced polymer (FRP) concrete- steel double-skin tubular columns under axial load and cyclical flexural loading, where the main parameters were axial load and number of polymer layers. For the test, a combination of circular and square columns were tested, both with circular inner steel tubes. The polymers consisted of CFRP and Epoxy and were formed according to ASTM D3039. The steel tubes were made of cold-formed steel tubes, followed by a mold installed for concrete, which was poured and vibrated with a poker vibrator. The tubes were cured and then wrapped in FRB using a hand lay-up method. Eight strain gauges were used to measure the strain at mid-span of the columns, and the specimens were pinned-pinned. In conclusion, it was found that FRP-concrete-steel columns displayed a large amount of energy dissipation, however display a sudden decrease in lateral load capacity after rupture. No debonding was seen between the concrete and the FRP, local buckling was seen in the steel tube, however there were cracks in the concrete at the location the FRP ruptured.
Han, L., Tao, Z., Liao, F., and Xu, Y. (2010) “Tests on Cyclic Performance of FRP-Concrete-Steel Double-Skin Tubular Columns.” Thin-Walled Structures, 48 (6), pp. 430–439. doi:10.1016/j.tws.2010.01.007