Experimental investigation into the axial compressive behavior of novel composite columns incorporating steel tube sandwich composite tubes

The novel composite column of GFRP‐concrete‐steel tube sandwich composite tube is a new type of composite column derived from further optimizing the cross‐sectional form by replacing steel tubes with steel sandwich composite tubes. Taking the concrete types, inner and outer diameters of steel tube sandwich composite tubes, and cross‐sectional hollow ratio as test parameters, eight specimens were manufactured in total, and axial compression experiments were performed. The failure modes, load–displacement curves, load–strain curves, and mechanical characteristic indexes were comparatively analyzed, and the relationships among f cc / f co , ε cc / ε co , and confinement effect coefficient λ were established. It is found from the results that reasonable thickness and hollow ratio of the steel tube sandwich composite tube contribute to the optimization and improvement of the mechanical properties of the new composite column. The composite column with a hollow ratio of 0.33 and a steel tube sandwich composite tube thickness of 27 mm achieves the maximum peak load, with an increase of 49.02%. The novel composite column incorporated with ECC does not further improve its bearing capacity, while the unique properties of ECC can still be exerted. In addition, a bearing capacity prediction model was established based on the superposition theory, with theoretical calculations showing good agreement with experimental values.