Numerical comparison between the thermo-structural behavior of steel and partially encased steel and concrete composite columns in fire

The bare steel structural members have a low fire resistance. However, in steel and concrete composite members, the concrete encasement, besides the contribution to the stiffness of the whole system, reduces the amount of heat that reaches the steel profile, increasing the its fire resistance. The aim of this paper is to conduct a numerical study on the behavior of steel and steel and concrete composite columns in fire, in order to compare their performance based on the variation of parameters such as the stiffness of the surrounding structure, geometric imperfection and load ratio. It has been found that, in general, the intensity of the geometric imperfection and stiffness of the surrounding structure does not affect the fire resistance of steel and composite columns. However, the stiffness of the surrounding structure raised the maximum value of the restraining forces generate throughout the heating. Regarding the load ratio, when increased, the fire resistance and critical temperature decreased.