Abstract: Abstract: Double concrete-filled steel tubular composite column is provided with internal steel tube on the basis of ordinary concrete-filled steel tubular column. Because the inner tube is protected by outer concrete, its fire resistance will be improved. In this paper, the fire resistance of this kind of double steel concrete composite column is studied by refined numerical simulation method, the effects of internal diameter thickness ratio, external diameter thickness ratio and internal and external tubular diameter ratio are comprehensively analyzed, and the different section combination types (inner circle and outer circle, inner square and outer circle and inner circle and outer circle) under the same steel content are compared and fire resistance of concrete filled double steel tubular short columns are analyzed. The results show that increasing the thickness of the inner steel tubular when the diameter is constant and increasing the diameter of the inner steel tubular when the thickness is constant are conducive to the improvement of the fire resistance；Under the condition of keeping the overall steel content unchanged, the fire resistance limit of concrete-filled double steel tubular columns with different section combinations is almost the same, but on the whole, the fire resistance of concrete-filled double circular steel tubular short columns is better; In addition, the fire resistance of double concrete-filled steel tubular composite columns is much higher than that of ordinary concrete-filled steel tubular columns.

Key words: Key words: double steel tubular column, temperature field, fire resistance limit, steel content