The main material of steel structure is steel. The performance index of steel can be judged from steel strength, steel plasticity, cold bending performance, impact toughness, welding performance, durability, etc.

1. Strength

The strength index of steel is determined by the elastic limit σ e. Yield limit σ y. Tensile limit σ  U composition, the design is based on the yield strength of steel. High yield strength can reduce the dead weight of the structure, save steel and reduce costs. tensile strength σ U is the maximum stress that the steel can withstand before it is destroyed. At this time, the structure loses its serviceability due to large plastic deformation, but the structure will not collapse due to large deformation, meeting the requirements of resisting rare earthquakes. σ  u/ σ  The value of y can be used as a parameter of steel strength reserve.

2. Plasticity

The plasticity of steel generally refers to the obvious plastic deformation without fracture after the stress exceeds the yield point. The main index to measure the plastic deformation capacity of steel is the elongation δ And area shrinkage ψ。

3. Cold bending property

The cold bending property of steel is a measure of its ability to resist cracking when plastic deformation occurs during bending at room temperature. The cold bending performance of steel is to inspect the bending deformation performance of steel under specified bending degree through cold bending test.

4. Impact toughness

The impact toughness of steel refers to the ability of steel to absorb mechanical kinetic energy in the process of fracture under the impact load. It is a measure of the mechanical properties of brittle fracture of steel due to impact load. This brittle fracture may be caused by low temperature and stress concentration. The impact toughness index of steel is obtained through the impact test of standard sample.

5. Weldability

The weldability of steel refers to the welding joint with good performance obtained under certain welding process conditions. Welding performance can be divided into two types: welding performance in the welding process and welding performance in service.

6. Durability

There are many factors that affect the durability of steel. First of all, the corrosion resistance of steel is poor, and protective measures must be taken to prevent corrosion and rust of steel. Secondly, since the failure strength of steel under high temperature and long-term load is far lower than the short-term failure strength, the endurance strength of steel under long-term high temperature should be determined.