A company Called Arup has developed technology enabling them to create structural strength steel, which can be used for a variety of construction applications. 3D printing has enabled the company to create all kinds of intricate pieces that traditional casting methods would not allow them to. Also, using 3D printing cuts down significantly on wasted material over the traditional methods used. More details on Arups 3D steel printing can be found here: http://3dprint.com/5505/3d-printed-steel-arup/

Check out one of these steel parts that Arup has been using which has been 3d printed: