Roofs made of Sheet Steel

Abstract

A NOVEL application of electric arc welding has recently been begun in the United States. Roofs are made of long strips of sheet steel which are assembled and welded on the ground and then hung up between the top and bottom of the roof. The shape in which they hang is approximately that of a catenary and they are welded together. In the Electrical Review of August 25 a description is given of the ‘self-supporting’ roofs erected on four huge grain elevators at Albany, New York. These roofs are watertight and have no columns or stanchions to support them. Maximum storage capacity is thus obtained. Each roof measures 288 ft. wide with a total span of 140 ft. and is composed of 76 steel sheets 140 ft. in length and 50 in. wide. The lower support of the roof starts approximately 22 ft. above ground level and extends upward at an angle of 30-40. Both the top and bottom supports were constructed at an angle to conform with the slope of the roof. By welding in various ways, expansion and contraction troubles are avoided. Small expansion joints were welded at suitable places over the longitudinal spans so as to allow free expansion for the roof. On completion, the roofs were given two coats of red lead and one of aluminium paint. With eight operators the speed of welding averaged 50 ft. per hour. More than 400 tons of sheet steel of No. 12 gauge were used.