Experimental Investigation into the Seismic Performance of GFRP Tube–Confined Concrete-Encased Cross-Shaped Steel Columns

Modern structures constructed from steel and concrete face two key challenges. Steel corrosion, a major shortcoming, leads to the deterioration of structural performance and can even cause premature failure. The other challenge is the structural damage caused by disasters such as earthquakes. To overcome these drawbacks, a novel composite structure has been proposed. This novel approach is called fiber-reinforced polymer (FRP) tube–confined concrete-encased cross-shaped steel column (FCCSC). Ten specimens were tested under a combined axial compression load and cyclic lateral displacement to investigate the seismic performance of the FCCSCs. The test variables included the axial compression ratio, glass fiber–reinforced polymer (GFRP) tube thickness, steel flange thickness and width, and loading direction. The FCCSCs demonstrated better ductility and energy-dissipation capacity than concrete-encased cross-shaped steel columns without FRP tubes. Additionally, the lateral loading direction was rotated by 45° to simulate bidirectional seismic action. The results revealed that, at low axial compression ratios, the rotated loading direction enhanced the seismic resistance of the FCCSC specimens. However, at high axial compression ratios, it was found to be unfavorable.