Nonlinear analysis of temperature field of steel-concrete composite beams subjected to natural fire

Numerous studies have been carried out on the temperature field of steel-concrete composite beams exposed to natural fire. The temperature variation process of indoor air, including heating and cooling phase subjected to natural fire, is simulated by using the fire dynamics software FDS, and the elevated temperature curve of air on the fire source is calculated, which is different from ISO834 standard fire curve. According to the curve, the thermal field of composite beams is analyzed by finite element analysis software ANSYS and the thermal field distribution of composite beams is obtained. The web temperature reaches 718.4°C, which is highest in the cross-section. Also, the influence of the thickness of protection layer on the thermal field under natural fire is investigated. The calculated results show that fire-retardant coating has a significant effect on the thermal field and can effectively improve the fireproof time in fire. The climbing rate of the internal temperature in the composite beams will reduce gradually and the peak temperature will decrease obviously with the increment of the coating thickness.