Axial compressive bearing capacity of high-strength concrete-filled Q690 square steel tubular stub column

Concrete-filled high-strength steel tubular (CFHSST) column is a kind of composite structure that uses highstrength steel instead of ordinary steel to strengthen the transverse restraint of concrete. In this work, in order to investigated the axial bearing capacity of CFHSST square column, a series of 22 CFHSST square stub columns were prepared by using two kinds of Q690 high-strength steel plates with different thickness of 3 mm and 6 mm with the strength of 741-749 MPa and 819-871 MPa, respectively. The static axial compression tests were carried out to understand the confinement effect of high-strength steel tube on concrete of different strength under static axial pressure and the influence of local buckling on the specimen. The axial compressive performances of CFHSST square stub columns are analyzed, including the failure mode, the relationship between load and deformation, and the stress-strain relationship. The test results show that the core concrete strength and area are major factors which have affected on bearing capacity of CFHSST square stub columns. Furthermore, widthto-thickness ratio exhibits significantly improving the failure mode and ductility of CFHSST square stub columns, while width-to-thickness ratio, the ratio of steel or the coefficient of hoop determine confinement effect. Q690 steel tube has good confinement effects, but the confinement effects on low strength concrete is small, especially for the specimen with relatively small width-to-thickness ratio. Finally, the calculation method of the ultimate bearing capacity of CFHSST square stub columns under axial compression is proposed, which can effectively evaluate the ultimate bearing capacity of CFHSST square stub columns.