How to repair and maintain the steel structure?

1.Regular rust and corrosion protection

The design service life of general steel structure is 50-70 years. In the process of steel structure use, the chance of being damaged due to overload is very small. Most of the steel structure damage is caused by rust and corrosion resulting in the reduction of structural mechanical properties and physical properties. The Steel Structure Design Code has certain requirements for the use of steel structures to last for more than 25 years without corrosion. Therefore, it is required that the external painting protection of steel structure should meet the use requirements of steel structure, and in general, the steel structure should be maintained for 3 years (clean up the dust, rust and other dirt in the steel structure and then brush the paint). The varieties and specifications of paint should be the same as the original paint, otherwise, the two paints are not compatible with each other, which will bring more hazards, and the users should do the regular maintenance and upkeep in a planned way.

Methods of preventing steel structure from rusting: In the later process of maintenance and upkeep, the non-metallic coating protection method is especially commonly used. The surface of the component is protected by paints and plastics so that it does not come into contact with the surrounding corrosive medium, so as to achieve the purpose of anti-corrosion. This method is effective, inexpensive, and strongly applicable to many varieties of coatings and a wide range of choices, not subject to the shape and size of the component restrictions. The coating can form a firmly attached film on the surface of any component shape, follow the component expansion and contraction as temperature changes, and thus allow easy use. It can also give the components a beautiful color appearance.

2.Regular fire treatment protection

The temperature resistance of steel is poor, and many of its properties change as the temperature rises or falls. When the temperature reaches between 430-540°C, the yield point, tensile strength and modulus of elasticity of the steel will drop sharply and lose its load-bearing capacity. Necessary maintenance of the steel structure must be carried out with fire-resistant materials. It has not been previously treated with fire-resistant coatings or fire-resistant paints. The fire resistance of the building depends on the fire resistance of the building components, and its bearing capacity should be able to continue for a certain period of time when the fire occurs, so that people have time to safely evacuate, rescue materials and extinguish the fire.

Fire prevention measures: The exposed steel components are brushed with fireproof coating and the specific requirements are that the fire resistance time of steel beam is 1.5h, and that of steel column is 2.5h, so that it meets the requirements of the building code.

3.Regular deformation monitoring and maintenance

Rust-induced damage to the steel structure component is not only manifested in the thinning of the effective cross-section of the component but also manifested in the ‘rust pits’ produced on the surface of the component. The former makes the load-bearing capacity of the member decrease, leading to the decrease of the overall load-bearing capacity of the steel structure, which is particularly serious for thin-walled steel and light steel structures. The latter makes the steel structure produce "stress concentration" phenomenon, and when the steel structure is in the impact load or alternating load, it may cause sudden brittle fracture. This phenomenon occurs without any signs of deformation, and it is not easy to detect and prevent in advance. For this reason, it is very important to monitor the stress, deformation and cracking of steel structures and major components.

Deformation monitoring and treatment: If the steel structure produces excessive deformation in the use stage, it indicates that the bearing capacity or stability of the steel structure can no longer meet the use needs. At this time, the owner should pay enough attention to it and quickly organize the relevant industry professionals to analyze the causes of deformation, put forward the treatment solution and implement it immediately, so as to prevent greater damage.

4. Regular inspection and maintenance of other problems

When carrying out daily management and maintenance of steel structure projects, in addition to the inspection of corrosion problems, attention should also be paid to the following aspects:

• Check for cracks, looseness, breakage and other phenomena in the connections such as welds, bolts, rivets and so on.
• Check excessive local deformation of each rod, web, connecting plate and other components, for any damage phenomenon.
• Check for abnormal deformation of the whole structure, and see whether it exceeds the normal deformation range.