Impact of D/t ratio on circular concrete-filled high-strength steel tubular stub columns under axial compression

Concrete-filled steel tubular (CFST) structures have been widely applied in modern construction industry owing to the composite action between the concrete and the steel tube. The benefits of CFST structures can be further achieved if high-strength materials are used. However, when high-strength steel is applied to CFST structures, the thin-walled steel section may not develop its yield strength owing to the early crushing of the cover concrete. Therefore, this paper presents an experimental study on concrete-filled circular high-strength steel stub tube (CFHST) focusing on the effect of the diameter-to-thickness (D/t) ratio. Fifteen specimens were tested under axial compression, with D/t ratios ranging from 50 to 130. The effects of the D/t ratio on the failure mode, load-versus-deformation relationship, and axial compression strength were investigated. Test results showed that the CFHST with a large D/t ratio can still reach the plastic section design. The fibre element method proposed by Liang et al. was revised to predict the load-axial deformation curves and then validated by using the ultimate bearing strength of CFST columns from 215 collected data. Finally, the bearing capacity of CFHST columns was compared with the present design codes, namely, Eurocode 4, American Institute of Steel Construction standard (AISC 360-10), Architectural Institute of Japan (AIJ) standard, and the proposed model, to evaluate the feasibility of the current codes for predicting the axial compressive strength of CFHST under axial compression.