Mechanical properties of CFDST column under eccentric compression after exposed to fire

This paper investigates the experimental behaviour of ten square concrete-filled double skin steel tube (SCFDST) columns subjected to eccentric compression after 60 min of fire time. The test parameters included slenderness ratio, eccentricity and hollow ratio. It was found that the slenderness ratio and eccentricity have significant influence on the residual deformation and bearing capacity. However, when the hollow ratio (chi) was 0.72, slenderness ratio has little effect on the bearing capacity. The accuracy of finite element analysis (FEA) models were verified by the presented test results, and they were in good agreement. A FEA model was established to conduct a parameter analysis of CFDST members, and the working mechanism was analyzed in depth. Based on the parametric analysis, it shows that nominal steel ratio, eccentricity and strength of external steel tube have significant influence on the member's residual bearing capacity under eccentric compression after fire: The residual bearing capacity decreases with the increase of nominal steel ratio. When the eccentricity increased from 0 to 0.6, the bearing capacity can decrease about 42 % after fire. The hollow ratio and concrete strength have little effect on the bearing capacity after fire. With the increase of fire time from 0 min to 120 min, the proportion in bearing capacity of internal and external steel tube gradually increases 16.8 %. Finally, compared with the relevant codes, the results of the T/CCES 7-2020 code were in good agreement with the FEA results.