CEE498
Lisheng Yang
Classification
1) Full Gantry Crane
This type of crane has the most typical shape of a gantry, which maintains high rigidity in its structural configuration and thus very suitable for lifting giant components. The lifting capacity for this type of crane can reach an astonishing 20000 tons, and the lifting height can exceed 150m (490ft). The general span of the full gantry crane ranges from 10m to over 100m. When performing massive components lifting usually there will not be trolleys mounted on top of the beam which is the common practice of gantry cranes in small and medium sizes, instead giant gantry crane usually adopts multiple hooks along the beam direction to accommodate more complex lifting requirements.
The world’s largest gantry crane is under construction in Qidong City, China, with a lifting capacity of 22000 metric tons and a lifting height of over 700ft. This crane will be used to construct ocean oil drilling platform. From the right picture we can see it also adopts the full gantry shape but uses arches instead of straight beams to resist more torque and produce less deformation. Generally, for cranes like this size, the gantry legs are fixed to a structural base rather than movable along a track rail.
2) Semi-Gantry Crane
Under some circumstances, we don’t need to build a full gantry crane because there is some existing structure we can use as supporting legs. Such situations include using walls or columns as legs on one side, or the terrain is not flat so the leg on one side is shorter than the other side. Although such methods can reduce the cost of building a gantry crane, however, we need to realize using this method needs careful design and monitoring to ensure the structural strength of the whole system since the structural components in this case are not as integral as those in a full gantry crane.
Due to its integral strength limitations, this type of gantry is not preferable unless encountering certain site environment limitations.
3) Double-cantilevered Gantry Crane
This type of gantry is the commonest one with efficient structure configuration and the best site coverage. It is mostly used in shipyard or quayside to help move objects on ships in the water. But it can also have amazing functions in building construction, for the cantilevered beams on two sides can lift objects simultaneously, so when lifting heavy symmetrical components we can use this type of crane to avoid the utilization of counterweights, which is especially convenient in the case of high-rise building. It can also be applied in long and narrow construction sites where the transportation of heavy objects need to travel a long distance form unloading area to operation region.
4) Single-cantilevered Gantry Crane
This structure form includes both those only cantilevered at one side and those cantilevered at both sides unevenly. Apparently this structure layout is not as reasonable as double-cantilevering but it can overcome specific site limitations like the situations of the left pecture. For the strictly single-cantilevered type, usually the purpose of the crane is to lift components from staging area to far working region which is not accessible in regular methods, for instance a deep strip excavation area just beside a cliff. Aided by track rails, a single-cantilevered gantry crane can easily move along the working area, which may require multiple rotation cranes to cover. However, since the lifting destination more focuses on cantilevered side, the straddling gantry part is relatively short and requires additional bracing to guarantee safe operation at the far end.
5) Rubber Tyred Gantry Crane
Unlike previous types this kind of gantry has tires at the bottom of its legs so can be very flexible in work positions. Correspondingly its lifting capacity is limited to medium weight and its tires need regular maintaining and changing. Although this type of gantry crane is mostly used in quayside, it can also have a role in construction situations as long as there are enough flat areas, and its straddling structure is particularly compatible with flatbed transportation vehicles like SPMT (Self Propelled Modular Transporter), since it can straddle the transporter and place objects precisely and stably.