Steel structure design should ensure the load-bearing capacity of the load-bearing structure and prevent brittle failure under certain conditions. Considerations should be given to the importance of the structure, load characteristics, structural form, state of stress, connection method, steel bar thickness, and working environment. Select the appropriate steel type and material properties.

The structural steel used for load-bearing should be Q235, Q345, Q390, and Q420 steel, with the quality conforming to the current national standards. When using steel with other grades, the relevant standards and requirements must still be adhered to. Q235 steel is recommended to use镇静 steel or semi-镇静 steel.

The structural steel for load-bearing should have guaranteed tensile strength, elongation, yield strength, and sulfur and phosphorus content. The carbon content of the welded structure should also be guaranteed.

Steel for welded load-bearing structures and important non-welded load-bearing structures should also have a cold bending test pass guarantee.

Welded structural steel subject to fatigue inspection must guarantee adequate impact toughness at room temperature. When the structural working temperature is equal to or below 0℃ but higher than -20℃, Q235 and Q345 steel must guarantee 0℃ impact toughness; Q390 and Q420 steel must guarantee -20℃ impact toughness. When the structural working temperature is equal to or below -20℃, Q235 and Q345 steel must guarantee -20℃ impact toughness; Q390 and Q420 steel must guarantee -40℃ impact toughness.