Once you've chosen your steel, what do you do with it? Steel engineers are also designers. They're responsible for creating structures that make the best possible use of the steel they've selected. For instance, they can plan where lighter steel is useful to save weight. They'll use heavier and more durable steel to make a structure strong, and they'll place girders and struts to make the construct as durable and safe as possible. http://www.ty-industrial.com/light-steel-structure/