Cyclic behavior of thin-walled square steel tubular columns filled with demolished concrete lumps and fresh concrete

This study is part of a comprehensive project concerned with research and advocacy of the structural elements containing demolished concrete lumps (DCLs) or demolished concrete segments (DCSs) with a distinctly larger size than the recycled aggregates. Previous studies showed that the steel tubular columns filled with DCLs/DCSs and fresh concrete (FC), recycling demolished concrete in a simplified manner, have properties similar to the conventional concrete filled steel tubular columns. This research is aiming to study the cyclic behavior and to evaluate the strength and ductility of the thin-walled square steel tubular column filled with DCLs and FC. Fifteen specimens, including 10 columns filled with DCLs and FC and 5 reference columns filled with FC alone, were tested under constant axial compression and cyclic lateral loading. The main variables are: replacement ratio of DCLs, thickness of steel tube, and axial load ratio. The design codes are employed to predict the lateral strengths of the specimens. The findings indicate that: (1) the cyclic behavior of thin-walled square steel tubular columns filled with DCLs and FC is similar with that of the reference columns filled with FC alone; (2) the lateral strength of the columns filled with DCLs and FC is slightly lower than those filled with FC alone; and (3) the thin-walled columns filled with DCLs and FC exhibit acceptable deformation and energy dissipation capacities.

► Reusing of DCLs with large size in steel tubes is briefly introduced.
► Cyclic behavior of the proposed columns is experimentally addressed.
► Using DCLs and FC in very thin-walled square steel tubes is acceptable.