Crane Double Cycling in Container Ports: Affect on Ship Dwell Time
Loading ships as they are unloaded (double-cycling) can improve the efficiency of a quay crane and thus container port. This paper describes the double-cycling problem, and presents two solution algorithms and simple formulae to estimate reductions in the number of operations, and operating time. The problem is formulated as a scheduling problem. Small problems can be solved to optimality with a standard numerical solver, but problems of typical size are computationally burdensome and terminated after 10 hours with optimality gaps larger than 50%. A formula for an improved lower bound to the optimal solution is developed and shows the optimality gaps are actually below 2.5% in all cases. The paper presents a greedy algorithm that can obtain solutions in seconds. A formula for an upper bound to the greedy algorithm's performance can be used to accurately predict crane performance. The problem is extended to include an analysis of double-cycling when ships have deck hatches. Results are presented for many simulated vessels, and compared to empirical data from a real-world trial. The paper demonstrates that analytical methods can be used in addition to numerical methods to provide greater insight. More importantly, the paper demonstrates that double-cycling can create significant efficiency gains.
|Date of creation:||01 Apr 2005|
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- De Castilho, Bernardo & Daganzo, Carlos F., 1993. "Handling Strategies for Import Containers at Marine Terminals," University of California Transportation Center, Working Papers qt5gr4622f, University of California Transportation Center.
- Notteboom Theo E., 2004. "Container Shipping And Ports: An Overview," Review of Network Economics, De Gruyter, vol. 3(2), pages 1-21, June.
- de Castillo, Bernardo & Daganzo, Carlos F., 1993. "Handling strategies for import containers at marine terminals," Transportation Research Part B: Methodological, Elsevier, vol. 27(2), pages 151-166, April.
- Kim, Kap Hwan & Kim, Hong Bae, 2002. "The optimal sizing of the storage space and handling facilities for import containers," Transportation Research Part B: Methodological, Elsevier, vol. 36(9), pages 821-835, November.
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