There isn't a unified standard to determine whether a structure is heavy steel or light steel. Many experienced designers or project managers often can't fully explain the difference, but we can make a judgment based on several factors:

 

　　1. Factory crane lifting weight: Greater than or equal to 25 tons can be considered heavy steel structure.

 

　　2. Steel usage per square meter: Greater than or equal to 50 KG/M2 can be considered heavy steel structure.

 

　　3. Thickness of main structural steel plates: Greater than or equal to 10 MM, less common in light steel structures.

 

　　4. Additionally, there are other reference values: such as cost per square meter, maximum component weight, maximum span, structural form, eave height, etc. These can provide empirical data when judging whether a factory building is heavy steel or light steel. Of course, many buildings now incorporate both light and heavy steel. However, some can be confidently identified as heavy steel: such as petrochemical plant facilities, power plant buildings, large-span stadiums, exhibition centers, high-rise or super-high-rise steel structures.

 

　　5. In actuality, national standards and technical documents do not have a definition for "heavy steel." To distinguish it from light steel structures, perhaps calling general steel structures "general steel" would be more appropriate. Because the scope of general steel structures is very broad, it can include various steel structures, regardless of load size, even including many aspects of light steel structures. The technical specifications for light steel structures only specify more detailed content due to its "light" characteristics, and its scope is limited to single-story portal frames.

 

　　6. "Light steel" is also a rather ambiguous term, generally understood in two ways. One is the eleventh chapter of the current "Steel Structure Design Code" (GBJ 17-88), "Light steel structure of round steel and small angle steel," which refers to light steel structures made of round steel and angle steel smaller than L45*4 and L56*36*4. It was mainly used in the era of steel scarcity for small structures unsuitable for reinforced concrete structures and is rarely used now, so it is basically tending to be removed in this revision of the steel structure design code. Another is the single-story solid-web portal frame structure with light roofing and light exterior walls (with the conditional use of masonry exterior walls) specified in the "Technical Specifications for Light Steel Structures of Portal Frames." Here, "light" mainly refers to the use of lightweight materials for the enclosure. Since the first type is almost being eliminated, the current meaning of light steel mainly refers to the latter.

 

　　7. Therefore, the distinction between light steel and heavy steel lies not in the weight of the structure itself, but in the weight of the enclosure materials, while the structural design concept remains consistent.

 

 

　　Pre-fabrication and assembly of steel components should be carried out on the steel platform according to the installation sequence and process requirements, ensuring welding quality.

 

　　The spacing between the splice seams of the flange plates and the splice seams of the web plates of the steel should be greater than 200㎜. The splice length of the flange plate should not be less than twice the plate width; the splice width of the web plate should not be less than 300㎜, and the length should not be less than 600㎜.

 

　　For convenient welding and to ensure welding quality, try to assemble and weld the stiffeners, connecting plates, gusset plates, cantilevered beams (beams), etc., on the ground steel platform according to the construction drawing dimensions.

 

　　In addition to being fabricated and assembled according to the construction drawings and specifications, prefabricated steel components on the steel platform should also consider the processability of on-site installation and changes in installation dimensions.