Gantry crane (also known as gantry crane) is a bridge type crane whose bridge is supported on the ground track by two side legs. in structure, it is composed of gantry, crane running mechanism, lifting trolley and electrical part. Some gantry cranes only have legs on one side, and the other side is supported on the workshop or trestle, which is called half gantry crane. The gantry crane consists of upper bridge (including main beam and end beam), support leg, lower crossbeam and other parts. In order to expand the scope of crane operation, the main beam can extend beyond the outriggers to one or both sides to form a cantilever. The crane trolley with boom can also be used to expand the operation range of the crane through the pitch and rotation of the boom.