Abstract: An apparatus and method for fabricating plate web girders of the ind comprising two flanges spaced apart by a web. The apparatus comprises a plurality of welding devices each mounted on respective spaced apart guides to follow a respective portion of a welding path defined by the intersection of the web and a flange and an arrangement to move the girder longitudinally relative to the welding devices at a substantially constant rate. The guides bear against the web adjacent the respective welding paths and against the flange to maintain the welding devices at predetermined distances from the web and flange respectively. The apparatus can also include a member to follow the corrugations of a corrugated web and operate limit switching devices when the crests and troughs of each corrugation are encountered. The limit switches operate a modulating motor which adjusts the welding device to maintain the welding angle between the welding path and welding device substantially constant for each point along the path.