Hysteretic behavior of multi-cell T- Shaped concrete-filled steel tubular columns

• Some improvements on T-shaped concrete-filled steel tubular (CFST) columns are presented.
• Nine T-shaped CFST columns under cyclic loading are experimented.
• Multi-cell layout, concrete strength and load radio effects on hysteretic behavior are studied.
• Hysteretic behavior of T-shaped CFST columns is asymmetrical in different loading directions.
• Some improved multi-cell T-shaped CFST columns are shown to have better hysteretic behavior.

Several multi-cell improvement methods for solving existing problems of conventional T-shaped concrete-filled steel tubular (T-CFST) columns and for determining steel׳s optimal distributions for increasing the strength and ductility of the columns are presented. An experimental study with eight multi-cell T-shaped concrete-filled steel tubular (MT-CFST) columns and one conventional T-CFST column under low frequency cyclic loading was conducted. Effects of the multi-cell layout and the concrete strength on the hysteretic behavior of the specimens were investigated. Experimental results showed that the lateral load-displacement hysteretic curves of the columns were generally saturated with a slight pinching effect. Owing to the asymmetry of the T-shaped cross section, the hysteretic behavior of the composite columns is asymmetrical in different loading directions. The improved MT-CFST columns showed better seismic behavior due to high load bearing capacity, ductility and energy dissipation capacity. Furthermore, the non-linear finite element analysis was performed to simulate the hysteretic behavior of the specimens and the numerical results agreed well with the test results. In conclusion, with an increasing axial load ratio, the ultimate lateral load in the pushing direction gradually decreases and is reached earlier, whereas the ultimate lateral load in the pulling direction increases slightly under low axial ratio and decreases under high axial load ratio.