how steel beams are made
A steel I-beam is a type of joist or girder made from structural steel. I-beams are used as major support trusses in building, to ensure that a structure will be physically sound. Steel is one of the most common materials used to make I-beams, since it can withstand very heavy loads, although other materials, such as aluminum, are sometimes used. Composite I-beams are also available, with layers of other materials encasing the outside of the steel to disguise it as something else, such as wood.