Although steel structures have many advantages, such as light weight, high strength, good plasticity, and good seismic resistance. Moreover, it has a short construction period, is recyclable, meets environmental protection requirements, etc., and has been widely used in various fields. It has occupied a pivotal position in the construction industry. However, the steel structure has a weakness: poor fire resistance. Once a fire occurs in a steel structure without fire protection treatment, the steel structure building will collapse within 15 minutes. It causes great losses to people’s lives and property safety. Therefore, steel structure buildings often adopt a variety of fire protection measures.

Steel itself will not catch fire, but it will deform when exposed to high temperatures. At high temperatures of 250°C, the impact toughness of steel will decrease; above 300°C, the yield point and ultimate strength will decrease significantly. Under actual fire conditions, the critical temperature at which the steel structure loses its static balance stability is about 500°C, while the load conditions remain unchanged. However, the general fire temperature reaches 800 to 1000°C. Therefore, under the high temperature of fire, the steel structure will quickly undergo plastic deformation, causing local damage, and ultimately causing the overall collapse of the steel structure.

Therefore, steel structure buildings need to take fire prevention measures to achieve sufficient fire resistance limits to prevent the building from rapidly heating up and causing large deformation and collapse of the building. This will buy time for fire extinguishing and evacuation of personnel, avoid casualties, and reduce losses caused by fires.

Fire protection measures for steel structure buildings generally include the following two methods:

1. Fire retardant coating: Spraying fire retardant coating on the surface of steel structural parts is the most commonly used fire prevention measure. Fire retardant coatings create a protective film on steel in the event of a fire. When the coating thickness is 2-7mm, it expands and thickens at high temperatures, and the fire resistance limit can reach 0.5-1.5 hours. When applying 30mm thick fire retardant coating, the fire resistance limit of steel components is 2 hours. Gain valuable rescue time for fire extinguishing and disaster relief. Thin-coating or thick-coating steel structure fire-retardant coatings can be selected according to needs.
2. Outsourcing fire protection layer: The outsourcing fire protection layer generally uses fireproof boards or fireproof bricks to wrap the steel components along the outer boundary of the steel components. The steel components can also be wrapped by pouring concrete to completely seal the steel components. Its advantages are high strength and impact resistance, but its disadvantages are that the concrete protective layer takes up a lot of space and construction is troublesome, especially on steel beams and diagonal braces.

Of course, there are other fire prevention methods, such as water cooling method, arranging automatic or manual sprinkler systems on the upper part of the steel structure or filling the hollow steel components with water. Through the circulation of water in the steel structure, the heat of the steel itself is absorbed, thereby making the Steel structures can maintain a lower temperature during a fire and will not lose their load-bearing capacity due to excessive temperature rise. However, this method requires high design capabilities and requirements, and the cost is high, so it is not suitable for ordinary steel structure buildings.

Fire retardant coatings and outsourced fire retardant layers are both commonly used and effective methods of fire protection. If you do not have high fire protection requirements, you can choose fire retardant coatings. The construction is simple and is not limited by the shape. The appearance of the component will not change significantly after spraying. The main advantages of the outsourced fireproof layer are lower cost, better fireproof performance and durability, but the construction is complicated and takes up a lot of space. The two methods can also be combined according to needs.