Steel-concrete-concrete is good for the resistance to fire and fire of steel pipe, corrosion resistance is superior to steel structure

Steel-concrete-concrete is good for fire-resistance and fire-prevention of steel pipes. Because steel pipes are filled with concrete, they can absorb a lot of heat energy. Therefore, the distribution of the temperature field in the cross-section of the pipe string is very uneven in the event of a fire, which increases the fire-resistance time of the columns and slows down the steel columns. The heating rate, and once the steel column yields, the concrete can withstand most of the axial load and prevent the structure from collapsing. The fire resistance of the composite beam will also increase because the temperature of the steel beam will be reduced by transferring heat from the top flange to the concrete. The experimental statistics show that the fire-retardant coating can save 1/3 to 2/3 or even more when compared with the steel column in the first-class fire-resistance for 3 hours. With the increase in the diameter of the steel pipe, more paint is saved.
The corrosion resistance of concrete-filled steel tubes is better than that of steel-concrete tubes. The exposed area of steel tubes is reduced, the area of corrosion by external gases is much less than that of steel structures, and the costs for corrosion resistance and corrosion resistance are also saved compared with steel structures. The cross-section form of concrete-filled steel tubular members has a great influence on the performance of steel-concrete-filled concrete structures, the ease of construction, the duration of construction, and the construction cost. The steel pipe concrete compressive component is effectively restrained by the round steel pipe to its internal concrete, so that the concrete inside the steel pipe is in a three-way compression state, so that the concrete has a higher compressive strength. However, the construction of round steel tube concrete structures is difficult and the construction cost is high. In contrast, the construction of concrete-filled square steel tubular structures is more convenient, but the concrete-filled steel tubular concrete is less restrained and the bearing capacity of the structure is lower.