J.C. Paro
Minimizing crane moves by smart stacking of containers
Computer program,
Report 2006.TL.7097, Transport Engineering and Logistics.
The transport of containers all over the world consists of only few steps.
To optimize this process only several steps can be considered. One of those
steps is the stacking of containers which takes place in harbors and at the
ships. This research investigates several methods to stack containers more
efficiently. This will overall lead to less crane movements for picking up
all the containers. The goal is to investigate the relation between the amount
of departure time information available and the amount of restacks needed.
A model has been made in TOMAS to compare four different stacking methods. A
stacking lane of 6 x 40 containers and maximum pile height of 4
containers is used (960 containers total). The first stacking method resembles
random stacking. Containers are stacked at the lowest pile available. The second
method chooses the lowest pile and then also considers the departure time of
both containers. The smallest time difference is preferred as long as the
container to be placed is picked up first. The third method is based on a
procedure called the Remaining Stack Capacity (RSC) described by Duinkerken
[M.B. Duinkerken, J.J.M. Evers, J.A. Ottjes "A Simulation Model for Integrating
Quay Transport and Stacking Policies on Automated Container Terminals",
Proceedings of the 15th European Simulation Multiconference (ESM2001),
June 2001, Prague [SCS], ISBN 1-56555-225-3].
This is a cost-reduction method which considers both pile height and departure
times and calculates the reduction of the RSC. The pile with the smallest
reduction of the RSC is preferred. The method uses time windows to compare
departure times. Method 4 is an improvement of Method 3. In this method the
same calculations are made as with Method 3, but containers with equal time
windows are not allowed to be placed on top of each other. The main parameters
that can be changed in the model are the maximum allowable difference between
the planned departure time and the real departure time (time deviation) and the
rate of containers with this information. The output of the model provides the
total amount of restacks and the amount of containers that could not be placed
according to the chosen method. Method 1 is used as a reference when no
particular stacking method is used. (the Random method)
The main experiment in this report is the analysis of the relation for every
method between the restacks needed and the rate of containers with departure
information. Next to this the influence of the occupancy, the time deviation
(difference between real and planned departure time) and the overall departure
distribution is investigated.
Conclusions
Method 4 performs the best of all methods. The relation between the amount
of restacks and the rate of containers with departure information is almost
linear and show the best result. Also the standard deviation of this method
outperforms Method 2 and 3. The result of all Methods is shown in Figure 1
for a time deviation of 3 hours and an occupancy of 90% of the total stack
capacity.
Figure 1. Results
Reports on Transport Engineering and Logistics (in Dutch)
Modified: 2007.05.13;
logistics@3mE.tudelft.nl
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