Gantry crane is a variant of bridge crane. Its metal structure resembles a portal frame, with two supporting legs installed under the load-bearing main girder, enabling direct movement on ground-mounted tracks. The ends of the main girder may feature cantilever extensions. Gantry cranes are characterized by high space utilization, large working range, wide adaptability and strong versatility. They are mainly used for material handling and installation operations at open storage yards, shipyards, power stations, ports and railway freight terminals.