PART A: Discrete Event Simulation model
Description of the port operation (simplified)
As you can imagine, operations at a port container are extremely complex, but for the sake of simplicity in this project, only some important features will be considered here.
The main steps in the operation of the terminal are the following:
- Once a vessel arrives to the port, it has to wait for an empty berth AND a tug to be available before it can be moved to the unloading area.
- When the vessel reaches the berth, it has to wait until there are cranes AND a gang available to unload it.
- As soon as the number of cranes required (as explained below) and the gang to operate them are available, the vessel is unloaded.
- The next step is loading the vessel. As for the unloading, this activity requires one or more cranes (more on this below) and a gang.
- Upon finishing the loading, the vessel will not leave the berth until a tug is available to pull it out of the port.
Resources
For the container port being analysed, there are four different resources:
- Berths - this terminal consists of 13 berthing points
- Cranes - there are at present 23 cranes
- Tug boats - there are at the moment 2 tug boats
- Gangs - these are sets of usually 10 - 15 workers with different skills but for the simulation project you can consider a gang as a unit and do not need to be concerned by the number of workers forming a gang. The number of gangs available depend on whether it is a day shift or a night shift and this is discussed in detail in the following section.
What is required of you:
1. Start with an Activity Cycle Diagram as management wants to be sure your interpretation of the problem is correct. If needed, don't hesitate to ask management (aka "Alicia").
2. Develop an initial model for scenario 1, where vessels are allocated the first berth that is available.
3. Calculate parameters such as:
- total time from arrival to the port to departure for the ship.
- time waiting for a berth, time waiting for a gang and a tug.
- time waiting for a crane.
- Utilisation of berths, tugs, cranes.
- Identification of bottlenecks (if any) and in this case, you should suggest a possible solution.
- Comment on the utilisation of the expensive resources (as mentioned above).
4. Develop a second model for scenario 2 where 8 berths are allocated to feeders only and 5 berths to mother-type vessels. Calculate similar parameters to those you estimated for scenario 1. Comment on your results and compare both scenarios.
PART B:
Operating a container terminal efficiently is difficult as shown in the many studies of this area. The main problem is that the obtaining the "balance between the shipowners who request quick service of their ships and economical use of allocated resources is not easy. Since both container ships and container port facilities are very expensive, it is desirable to utilize them as intensively as possible."(Dragovic, 2007)
Let's assume a fixed number of ships arriving per month as the variability of arrivals per month is not an important factor in this analysis. This is shown in Table 1:
|
Month
|
Ships Arriving
|
|
Month
|
Ships Arriving
|
|
Jan
|
249
|
|
July
|
222
|
|
Feb
|
237
|
|
Aug
|
272
|
|
Mar
|
260
|
|
Sep
|
266
|
|
Apr
|
258
|
|
Oct
|
264
|
|
May
|
268
|
|
Nov
|
233
|
|
1,June
|
239
|
|
Dec
|
222
|
Of these 40% are feeders while 60% are mothers. The analysis of the costs requires some information on the number of containers carried in these vessels. Containers are usually 20 ft (6.1 metres) long. Although containers vary in height, the most common height for ship containers is 2.59 metres. This container is called TEU. Then the capacity of the vessel or the container terminal is measured in units of TEU's.
For our project, it has been established that feeders have a capacity between 1,000 and 2,000 TEU's with the most likely value being 1,420. For mothers the capacity is in the range 3,001 to 5,200 with the most likely value being 4,200.
Another important factor regarding costs is the time taken to unload/load the vessel. We know the time taken by a crane to unload a container and this is 0.072 hours (independent of the type of vessel). Therefore, the time to unload/load a vessel will depend on the number of cranes used. From part A we know that mother-type vessels, being larger, require between 3 and 5 cranes to be unloaded (you can assume equal probability of requiring 3, 4 or 5 cranes). On the other hand, feeder-type vessels require only between 1 and 3 cranes for their operation.Given this information you should be able to work out the time to unload/load a vessel. Assume for this part of the exercise that the number of cranes used to unload is the same as the number of cranes needed to later load the vessel. The cost of using a crane per hour is given by $38.80.
There is also the cost per hour of having a ship in port. This is given by $1,161. See NOTE 3 below.
As mentioned previously, there can be delays due, for example, to having to berth the vessel far from where the containers that will be loaded into it are stored. The cost of waiting per container per hour (or fraction) is $1.40. We know the proportion of vessels that are delayed and this is shown in Table 2:
|
Hours
|
Percentage Delay
|
|
On time
|
50.00%
|
|
0-1
|
25.00%
|
|
1-2
|
20.00%
|
|
2-3
|
5.00%
|
This table applies equally to mother and feeder vessels.
a. You need to calculate the total cost of operation of the terminal. We will ignore fixed costs since they are not affected by the number of vessels visiting the terminal. Comment on which variables are most important.
b. It's also known that when more personnel is hired at an annual cost of $50,000 per gang there is a 10% reduction in the number of hours (or fraction) the vessel is delayed. This means that if for example, at the moment and for a given month there are (on average) 15.6 vessels waiting between 1-2 hours and 2.6 vessels waiting between 2 and 3 hours and one gang is added, then the number of vessels that will wait between 2-3 hours will be reduced by 10%. This 10% will now wait between 1 and 2 hours. This means that 2.34 (= 2.6 x 0.90) vessels on average wait between 2 and 3 and (2.6 x 0.10) + 15.6 x 0.90 = 14.3 will wait between 1 and 2 hours. Management (aka "Alicia") would like to know if the addition of more gangs would decrease the total cost. Modify your model to incorporate the addition of one, two or three more gangs and comment on your findings.
For the cost analysis, we are told that the cost of having a vessel in the port is $1,161 per hour. We are not given any more information on how long the vessel is in the port but you can make the following two approximations:
a. The time taken to load the vessel will be 15% longer than the time it takes to unload the vessel. Notice as well that the time to unload a vessel is a function of the number of cranes used and the number of containers. You are told that the time taken to unload a container per crane is 0.072 hours. You can assume the time is a linear function of the number of cranes used, which means that if you have one container and one crane, it will take 0.072 hours to unload this container, but if you have two cranes then it will take 0.072 (hours)/2 (cranes) = 0.036 hours to unload the container. Considering this, you can calculate the time taken to unload the vessel and the time that it takes to load it will be 15% larger.
b. Note as well that there is a delay that can be calculated from the delay table (think of a discrete distribution to obtain this time). This delay will be added to the time taken to unload and then to load the vessel and this will give you the total time the ship is in port.
c. Notice that as far as this part of the model you can ignore the time taken by the tug to pull the vessel in and out of the quay.
Attachment:- Final project 2015-2016.rar