Experimental research and finite element analysis on the axially loaded composite concrete-filled square steel tubular columns

Through the axial compression tests of two common concrete-filled square steel tubular (CFSST) short columns and six composite-sectioned CFSST short columns, the influence factors were section types, steel ratio and concrete strength, the working mechanism and failure mode for the two kinds of CFSST columns were studied. Based on the appropriate material stress-strain relations and failure criteria, finite element program ABAQUS was used to carry on the whole-process analysis on the CFSST short columns. The results show that compared with the ordinary columns, the cooperative work ability between the steel tube and core concrete are improved effectively in the composite CFSST columns, the restraint effect of the steel tube on the core concrete are enhanced, the development of inclined cracks are delayed or inhibited and ultimate bearing capacity are increased significantly under the same steel ratio. The element analysis results coincide well with the experiment results, furthermore, the whole deformation of the composite columns is uniform due to the confinement of the ribs, and the effective confinement areas of the composite columns are larger than the ordinary columns.