Experimental and Numerical Study of the Behavior of Concrete-Filled High-Strength Steel Tube Columns with Large D/t Ratio under Axial Compression

The thin-wall high-strength (HS) steel tube can provide strong confinement ability for core concrete due to its high yield strength, so it can achieve the purpose of confining concrete lateral deformation. In order to make full use of the mechanical properties of HS steel tube and concrete, it is necessary to study the axial compressive properties of the concrete-filled HS steel tube (CFHST) with a large diameter-to-thickness ratio (D/t). In this study, the axial compressive capacity of 15 CFHST columns with a large diameter-to-thickness ratio was tested. Then, a series of finite element (FE) models were developed to study the interaction mechanism between steel tube and concrete, the load-strain curves of typical specimens, and the effect of the key parameters. Finally, a new design proposal for CFHST compressive capacity is proposed and compared with EC4, GB50936-2014, and AIJ-97 prediction results. The results showed that the CFHST has good compressive capacity and can effectively confine the lateral deformation of core concrete; the contact pressure appears a stable stage because with a steel tube is difficult to effectively restrain the lateral deformation after steel tube yielding and partial failure of concrete; the existing design code is conservative in predicting the axial compression capacity of the CFHST with large D/t ratio.