A gantry crane is a bridge-type crane supported on the ground track by legs on both sides. Structurally, it consists of the gantry, trolley running mechanism, lifting trolley, and electrical components. Some gantry cranes have legs on only one side, supported on a factory or pier on the other side, and are known as semi-gantry cranes. The components of a gantry crane include the upper bridge girder (including the main beam and end beam), legs, lower transverse beam, etc. To expand the crane's working range, the main beam can extend beyond the legs on one or both sides, forming a cantilever. An articulated trolley with a boom can also be used to expand the crane's working range through the boom's pitch and rotation.