Multi-scale mechanism of steel tube restraint effect on concrete of CFST

A multi-scale numerical model was used to study the mechanism of steel tube restraint effect on the concrete of concrete-filled steel tube (CFST) columns under compression. In the developed model, aggregates, mortar, and interfacial transition zones (ITZ) of concrete core were fabricated in meso-scale; however, steel tube was considered to be in macro-scale to investigate the interactions of all phases. Parametric analyses with different diameters and steel ratios were conducted to evaluate multi-scale model. The developed multi-scale numerical simulation could be employed to provide a better understanding on cracking processes of concrete and stress paths of steel tubes in CFST.