Seismic behavior of double-cell CFST columns with table tennis racket-shaped cross section

Abstract

Multicell concrete-filled steel tube (CFST) columns with excellent mechanical performance have been used in super high-rise buildings in recent years. According to the requirements of a 265-m tall building, the double-cell CFST columns with an innovative cross section of table tennis racket were applied. Hence, six columns were designed according to the prototype columns and subjected to low-frequency cyclic loading. The impacts of different shear-span ratios (SSRs), axial load ratios (ALRs), and steel ratios on the seismic behavior were elaborated and clarified. The test results indicated that the seismic performance varied in different loading directions owing to the asymmetric cross section, and the columns performed better in the positive loading direction resulted from earlier and more sufficient confinement of the circular steel tube, which was also reflected by the measured strain development. With SSR deceasing from 2.5 to 1.7, earlier and more severe damage was recorded. The resisting capacity and stiffness were significantly improved at a cost of ductility loss. Increasing ALR from 0.2 to 0.4 brought about more damage and worse deformability. However, a proper increase in axial load was beneficial to the resisting capacity and stiffness, and its influence on the restoration capacity was associated with SSR. Increasing the steel ratio (by 33.36%) could effectively postpone and alleviate the local buckling of steel tube, thereby comprehensively improving the seismic performance. A finite element (FE) analysis of such columns was performed to carry out the damage evolution and parametric study, and provide references for their application in practical engineering.