Main disadvantages of steel structure


The main disadvantages of steel structures include poor fire resistance, poor corrosion resistance, high temperature resistance, and high maintenance costs.

Poor fire resistance. At high temperatures, the material of steel will change greatly, and the strength and elasticity will gradually decrease. Even when the temperature reaches 600 ℃, the steel will enter the plastic state and cannot continue to bear the load.
Poor corrosion resistance. In the environment of wet and corrosive medium, steel is easy to rust, especially in the sea platform structure, need to adopt special anti-corrosion measures.
Not resistant to high temperatures. When the temperature exceeds 250 ℃, the material of the steel will change greatly, and the strength and elasticity will gradually decrease. When the temperature reaches 600 ℃, the steel will enter the plastic state and cannot continue to bear the load.
High maintenance costs. Steel structure must pay attention to protection, especially thin-walled components, therefore, in a strong corrosive medium within the building should not use steel structure. The steel structure shall be thoroughly derusted before painting, and the paint quality and coating thickness shall meet the requirements of relevant specifications. In the design, the structure should be avoided from damp and rain leakage, and the dead angle of inspection and maintenance should be avoided as far as possible in the structure. Newly built steel structures generally have to be repainted at regular intervals, resulting in higher maintenance costs.

Steel structure has three outstanding shortcomings.

The first is the fire prevention of steel structure, steel will become soft deformation at high temperature, so the steel structure of the building in the fire burning moment there is no load force and support.

The second is the rust prevention of steel structure. Steel has an oxidation process. In this process, its volume will expand many times, so its yield strength and mass density are definitely not as good as before.

The third is the anti-corrosion of steel structures. The anti-corrosion of steel structures depends on the pH and use scenarios of each region. The pH corrosion of chemical companies will be relatively high, so the corrosion of steel structures is also very important.

Although the steel itself will not fire and burn, but the material properties of steel will be affected by temperature, the impact toughness of steel decreased at 250 ℃, more than 300 ℃, the yield point and ultimate strength decreased significantly. In general, when a fire occurs, the load situation is unchanged, so that the critical temperature for the steel structure to lose its static equilibrium stability is about 500 ℃, and the maximum fire temperature can reach 800~1000 ℃. Therefore, under the high temperature of the fire, the steel structure will quickly appear plastic deformation, resulting in local damage, and ultimately the overall collapse of the steel structure failure.

Steel is easily corroded in air or humidity. Mainly due to the oxidation of iron atoms on the surface of the steel and the oxidation of the air into the texture of loose rust, especially when the air contains acid and alkali salts such media may be more serious. The occurrence of corrosion not only causes some uneven corrosion on the surface of the steel, but also causes stress concentration due to local corrosion, which promotes the early destruction of the steel structure. The corrosion of steel seriously endangers the safety of steel structure engineering.

All things have two sides, there is good and bad. According to the actual needs to choose the most suitable is the best.