Cyclic pushout tests on high‐performance concrete‐filled steel tube columns for seismic applications

Concrete‐filled double steel tube columns (CFDST) made from high‐performance materials represent an advanced type of prefabricated composite components with excellent fire performance, enabling a slender design under high loading compared to traditional concrete‐filled steel tubes (CFST). CFST have been proven to be a viable solution under seismic loading, as they can achieve improved load‐carrying capacities (improved stiffness, strength, ductility, and energy dissipation capabilities) compared to conventional concrete columns. However, there is currently a lack of experimental and numerical investigations on CFDST.

This paper presents experimental results on five load‐reversal pushout tests on high‐strength CFDST columns. The objective was to investigate the bond behavior between steel and concrete, as well as the accompanying adhesion, micro‐, and macro‐locking effects under cyclic loading in order to better assess the seismic performance of such structures. The results showed a continuous decrease for the interface carrying capacity as well as for the overall bond stress behavior for each new loading cycle. However, macro‐locking represents the dominant mechanism for composite strength and is strongly influenced by the geometric shape of the high‐strength steel tubes. Even in post‐interface carrying capacity range, significantly higher bond stress states were reached.