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Structural design knowledge: What are the applications of steel?

Structural design knowledge: What are the applications of steel?

What are the applications of steel?
(1) heavy-duty construction and long-span structures;
(2) a multi-layer, high-rise and high-rise building construction;
(3) light steel structure;
(4) and other high-rise tower mast structure;
(5) steel - concrete composite structures.