Seismic behavior of concrete-filled steel tubular flat columns with large steel ratios

Concrete-filled steel tubular columns (CFSTC) have received extensive attention in practical engineering applications. To meet the need for bearing capacity and address the problem of columns protruding from inner walls, concrete-filled steel tubular flat columns (CFSTFC) with a large steel ratio were proposed in this study. Compared with traditional rectangular CFSTC, the aspect ratio of CFSTFC is usually greater than 2.0. The effects of the aspect ratio and thickness of the steel tubular on the seismic performance of 12 CFSTFC were studied. The failure mode, hysteretic curve, skeleton curve, ductility, strength degradation, stiffness degradation and equivalent viscous damping coefficient of the specimen were analyzed in detail. The test results show that the CFSTFC still exhibited good seismic performance during the cracking process and that the ductility indices of all the specimens are between 2.24 and 2.79. The finite element model was established and verified on the basis of the test results. The parameters were analyzed, and the influences of the axial compression ratio and material strength were discussed. Finally, by comparison with the N-M interaction curves specified in the GB 50936, EC4 and AISC 360 codes, the accuracies of the different methods in the CFSTFC design were evaluated.