桥式起重机的主梁通常用箱形梁。参看图1,组装时先将上盖板1平置在地上,在横向左右两侧放置腹板2,在腹板2与上盖板1之间焊接焊缝4、5、6、7,并将腹板2与长加劲板10和短加劲板11焊接。再将下盖板3放置在腹板2上,在左右两外侧焊接焊缝8和 The girders of overhead traveling cranes usually use box girders. Referring to Fig. 1, the upper cover 1 is laid flat on the ground during assembly, the webs 2 are placed on the left and right sides of the transverse direction, the welds 4, 5, 6, 7 are welded between the web 2 and the upper cover 1 The web 2 is welded to the long stiffening plate 10 and the short stiffening plate 11. Then the lower cover 3 is placed on the web 2, welded on the left and right outside the weld 8 and