This Architectural Drawing is AutoCAD, 2d drawing of Girder axis and levels details in AutoCAD, dwg file. girder, in building construction, a horizontal main supporting beam that carries a vertical concentrated load. Girders are the main supports of a large structure and will support the smaller beams. Girders are intended to be the primary structural supports, and they have a much larger load-bearing capability. They can carry dynamic and rolling loads. For more details and information download the drawing file.