The single beam gantry crane is mainly composed of a bridge (main beam), four outriggers, lower beam, cart drive device, electrical control, electric hoist, etc. The bridge frame (main beam) of a single-beam gantry crane is generally a box-shaped structure welded by steel plates. The bottom of the main beam is equipped with an I-beam track for electric hoist operation. It can also be used for the main beam of large-span gantry cranes working outdoors. The truss structure formed by welding of section steel has strong stiffness (especially the horizontal stiffness), light weight, small windward area, and has high economic benefits. However, the production and welding of this structure is more complicated and difficult than the box-shaped structure.