Gantry crane (also called gantry crane) is a bridge type crane supported on the ground track by legs on both sides. In the structure by the gantry, large car running mechanism, lifting trolley and electrical parts and other components. Some gantry cranes only have legs on one side, the other side supported on the plant or bridge operation, called semi-gantry crane. Portal crane gantry upper bridge (including the main beam and end beam), outriggers, lower crossbeam and other parts of the composition. In order to expand the scope of crane operations, the main beam can be extended to one or both sides beyond the outriggers to form a cantilever. The lifting trolley with jib can also be used to expand the crane operation range by pitching and rotating the jib.