There is indeed no unified standard for judging the structure as heavy steel or light steel by Waiguangxin Heavy Industry, and many experienced designers or project managers often cannot fully explain it. However, we can consider and judge based on some data comprehensively:

1. The lifting weight of the factory crane is 25 tons or more, which can be considered as a heavy steel structure.
2. The steel consumption per square meter is greater than or equal to 50KG/㎡, which can be considered as a heavy steel structure.
3. Main component steel plate thickness: ≥ 10mm, less commonly used for light steel structures.

What are the differences between heavy steel structures and light steel structures (Figure 1)
In addition, Guangxin Heavy Industry also has some reference values, such as cost per square meter, maximum component weight, maximum span, structural form, eaves height, etc. These can provide empirical data when determining whether the factory building is made of heavy steel or light steel. Of course, many buildings are made of both light and heavy steel. But there are some that we can confidently say are heavy steel, such as petrochemical plant facilities, power plant buildings, large-span sports venues, exhibition centers, high-rise or super high-rise steel structures.

In fact, there is no mention of heavy steel in national regulations and technical documents. To distinguish light steel structures in buildings, it may be more appropriate to refer to general steel structures as "ordinary steel". Because the scope of ordinary steel structures is very wide, it can include various steel structures, regardless of the size of the load, and even many aspects of lightweight steel structures. The technical specifications for lightweight building steel structures only specify some more specific content based on their "lightweight" characteristics, and the scope is limited to single-layer portal frames.

Light steel is also a relatively vague term, which can generally be understood in two ways. One type is Chapter 11 "Light steel structures with round steel and small angle steel" in the current "Code for Design of Steel Structures" (GBJ 17-88), which refers to light steel structures made of round steel and angle steel smaller than L45 * 4 and L56 * 36 * 4.