Joist girders, also known as steel joist formwork, are a composite structural system that involves manufacturing the main steel reinforcement into a joist girder using special equipment in a factory, and then welding the joist girder with galvanized steel plate to form an integrated structure. During the construction of structural slabs, this system replaces the construction formwork with galvanized steel plates, which are welded to the steel reinforcement within the structure to bear the self-weight of the concrete slab and construction loads. After the concrete is poured, a reinforced joist girder concrete slab is formed, which withstands service loads during use.