PURPOSE: To decrease the number of welded parts for producing a crane main girder at a low cost, by forming windows in each of the upper wall of a lower column and the lower wall of an upper column, inserting stiffeners and reinforcing plates from these windows and welding them respectively, and welding the upper column to the lower column as the lower wall of the upper column and the upper wall of the lower column are mated with each other. ;CONSTITUTION: A cylindrical upper column 1 and a cylindrical lower column 2, whose cross sections are squares whose four corners are round, are prepared, and a plural number of rectangular windows 5 are drilled through each of the lower wall 3 of the upper column 1 and the upper wall 4 of the lower column 2, while those window groups being shifted from each other concerning respective walls 3, and 4. Stiffeners 7 are inserted through the windows 5 of the upper column 1 and welded to the frame parts 9 between the windows 5, 5 of the lower wall 3 and the columnar surrounding walls 6 other than the lower wall 3, and reinforcing plates 8 are welded to the column inner walls 6, on the lower face of a lateral rail 11 laid on the upper face of the upper column 1, in those positions between the stiffeners 7, 7 at suitable intervals. Both columns 1, 2 are mutually overlapped with their 2 lower wall 3 and upper wall 4 serving as a mating surface, and the welding parts 15 on both sides of both walls 3, 4 at the mating face are welded together for composing a crane main girder.;COPYRIGHT: (C)1993,JPO&Japio
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