Considerations for Large Cranes

by Arun Bhimani

Just as we are getting used to beyond post-Panamax dockside container cranes, a new generation of larger cranes is here. Where cranes normally serve ships with 16 containers on deck, the ports of Oakland and Norfolk have ordered cranes to service 22 containers on deck.

The larger cranes raise questions and problems for the designer. Can the existing wharf support them? If a new wharf is being planned, should it be built to accommodate these cranes? Does the size affect choice of rope trolley vs machinery trolley? Are there other considerations?

Solutions to the problems involve innovative uses for existing technology. Some of our innovation creates new problems. Larger cranes mean longer trolley runways and increased hoist travel distance. Speeds are increased to maintain productivity. Larger cranes and faster equipment create a challenge for the operator. The electronic anti-sway is provided to assist the operator with positioning the container, but this modern load control method can create a larger problem if the crane structure is not properly designed.

The presentation discusses the design considerations associated with these larger cranes. A case study where recently purchased cranes experienced excessive vibration is presented along with the structural solution developed to correct the dynamic resonance problem.