Seismic behavior of full-scale PEN FRP-concrete-steel double skin tubular columns

This paper presents the first experimental study of the seismic performance of double-skin tubular columns (DSTCs) with polyethylene naphthalate (PEN) FRP tubes. Fiber-reinforced polymer (FRP)-concrete-steel DSTC represents a new type of combined structure. A DSTC has an external FRP tube with an internal steel tube, and concrete fills the gap between the two tubes. DSTCs limit the outward buckling of their steel tubes and have excellent seismic performance. Previous studies have shown that glass FRP (GFRP) fracture controls the ultimate failure of DSTCs with a GFRP tube. Therefore, the fracture strain of the FRP tube is a critical factor for DSTCs. The fracture strain of large-rupture-strain (LRS) FRPs is greater than 5 %, which gives DSTCs an advantage. Six full-scale DSTCs were tested in the paper to investigate the effects of FRP type, PEN FRP thickness and the axial compression ratio as well as the plastic hinge region is filled with concrete on the seismic performance of DSTCs. The experimental results indicate that the seismic performance of DSTCs with PEN FRP is equal to or slightly better than that of GFRP, and the energy dissipation capacity improved by 41.7 %. In addition, decreasing the axial compression ratio, increasing the thickness of PEN FRP, and filling the plastic hinge region with concrete appropriately increased the DSTC seismic performance.