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SOME STUDIES ON THE PRINCIPLES AND MECHANISMS
FOR LOADING AND UNLOADING
A thesis
Submitted in Fulfilment of the Requirements for the Award of the Degree of
Doctor of Philosophy(In Mechanical Engineering)
By
Mudar Dayoub
Under the Supervision of
Prof. Rasheed Ahmad Khan
Dr. Mohammed Sharif
&
Dr. Mohammed Suhaib
Department of Mechanical EngineeringFaculty of Engineering and Technology
Jamia Millia IslamiaNew Delhi
2009
i
Abstract
Containerization of general cargo has been increasing steadily over the last three
decades. The world container turnover increased from 76 million TEU in year 1988 to
544 million TEU in year 2008. As a result of substantial increase in world container
turnover, container terminals have become an important component of the global
transportation network. Container terminals serve the function of delivering containers
to consignees and receiving containers from shippers, loading containers onto and
unloading containers from vessels, trains, trucks, and then temporarily storing the
containers in the storage yard. The productivity of container terminals is often
measured in terms of the time necessary to load and unload containers by cranes and
trucks, which are the most important and expensive equipment used in ports. Most
container terminals have either initiated or in the process of initiating measures to
increase their throughput and capacity by introducing new technologies, reducing
equipment dwell times, and increasing storage density.
Transportation of containers between the quayside and the storage yard can be divided
into a number of sub-processes according to the type of equipment involved. In most
container terminals, trucks are commonly used for transporting containers between the
quayside and the storage-yard. Determining the sequence of containers to be handled
by trucks is one of the major issues in terminal operations. The operation efficiency of
container terminals is directly impacted by the container sequencing decisions.
Therefore, the major objective of this research is to develop generic models that can be
used to solve truck scheduling problem that is the problem of scheduling a fleet of
trucks to handle a set of non-preemptive jobs with sequence-dependent processing
times and different arrival times. This objective is achieved through optimizing the
makespan for loading and unloading containers in the container terminal using mixed
integer programming and greedy search algorithms. The intent behind optimizing the
makespan is (1) to reduce the waiting time of the trucks, (2) to cut down the operation
costs, (3) to find the optimal number of trucks to be used for loading and unloading
containers to and from trains and (4) to contribute towards improvement in the national
economy.
ii
In this research, development and implementation of several studies has been carried
out for optimal scheduling of loading and unloading operations in container terminals.
A generic model based on mixed integer programming (MIP) has been developed and
its effectiveness in scheduling container loading and unloading operations has been
studied. In addition to MIP model, four generic models based on different scheduling
algorithms have been developed in this research. The performance of these models has
been evaluated in terms of the quality of solution achieved by them. Comparison of the
performance of MIP model with that of other models has revealed that although MIP
model is able to produce optimal solutions but its execution time is quite high. Due to
the high execution time requirements, it was concluded that MIP model has limited
practical applicability to real world problems.
Major achievements of the research carried out in this thesis may be summarized as
follows:
A comprehensive review of literature related to application of optimization
techniques for improving container terminal operations has been carried out with a
view to provide ready reference for any future work.
A comprehensive review of processes being followed, and equipment being used in
container terminals has been carried out in order to put the work carried out in this
research in context.
Real-world data pertaining to processing time and travel time for each container has
been procured from CONCOR, and has been used to test the developed models
A generic MIP model that is transportable to any other container terminal with
minimal changes has been developed for the truck scheduling problem
Analysis of several computational experiments carried out using the MIP model has
revealed that the execution time requirements are quite high for solving even
moderate size problems, thereby ruling out the application of MIP model to large
real-world problems
iii
Four generic models based on STF, LTF, FAT, and LBT scheduling mechanisms
have been developed and their practicality in solving complex problems has been
demonstrated through application to four real-world problems.
It has been demonstrated that the application of recommended models for unloading
different number of train could lead to substantial savings in the cost of operations
A distinct practical advantage of the model developed in this work are that they are
transportable to any other container terminal without any difficulty
Models developed in this work can be used by terminal operations managers for
optimizing container terminal processes
Models recommended in this work provide a wider choice to the terminal managers
as well as to customers
Finally, implementation of models developed in this work is straightforward due to
the ease of interfacing
iv
Declaration of Originality
This work reported in this thesis entitled “Some Studies on the Principles and
Mechanisms for Loading and Unloading” was conducted entirely by me in the
Department of Mechanical Engineering at the Faculty of Engineering and Technology,
Jamia Millia Islamia, New Delhi, India. The matter embodied in this thesis has not been
submitted in part or full to any other University/institution for the award of any degree
or diploma.
Mudar Dayoub
01 July 2009
v
Certificate
This is to certify that the thesis entitled “Some Studies on the Principles and
Mechanisms for Loading and Unloading” submitted in fulfilment for the requirement of
award of degree of Doctor of Philosophy is a record of bonafide work carried out by
Mudar Dayoub under our supervision and guidance.
To the best of our knowledge the matter embodied in this dissertation has not been
submitted in part or full to any other University/institution for the award of any degree.
(Rasheed Ahmad Khan, Ph.D)
Professor
Department of Mechanical Engineering
Faculty of Engineering and Technology
Jamia Millia Islamia
New Delhi-110025
(Mohammed Sharif, Ph.D)
Associate Professor
Department of Civil Engineering
Faculty of Engineering and Technology
Jamia Millia Islamia
New Delhi-110025
(Mohammed Suhaib, Ph.D)
Associate Professor
Department of Mechanical Engineering
Faculty of Engineering and Technology
Jamia Millia Islamia
New Delhi-110025
vi
Acknowledgements
I am extremely grateful to my thesis supervisor Prof. R A Khan who has provided
valuable guidance for accomplishing this project work. He has been benevolent enough
to take time out from his busy schedule for this project and supported me in every
respect.
I am deeply indebted to my thesis co-supervisor Dr. Mohammed Sharif for his
continuous support, stimulating suggestions and patience. It would not have been
possible to complete this thesis without his encouragement and trust. I have learned a
lot from his broad and profound knowledge during the long hours that we have spent
together.
I am also grateful to my co-supervisor Dr Mohammed Suhaib for his whole hearted
support , who has guided me at the start of this thesis work and introduced me to the
ICD, Tughlakabad, authorities, where ideas for this Thesis work all got started.
In researching container terminals, loading and loading operations, I have met many
colourful and interesting people from academia and industry that have helped
tremendously. Mr. A. K. Mishra, operation Manager , Mr. Tomar, Supervisor of the
Container Corporation of India Ltd., Inland Container Depot, Tughlakabad, New Delhi
for their valuable suggestion and support. And Mr. Leela Dhar Kala, IIT Delhi,
In the course of the working on this thesis, I had the fortune of meeting many fine
friends who assisted me in various forms. I would like to thank all of them.
Lastly, I would like to thank my family for their unceasing love and support of my
endeavour, in particular, my mother my brothers and my sister. There is no way I have
could have done this without their tremendous sacrifice.
Mudar Dayoub
Date: 01, July 2009Place: New Delhi
vii
Contents
Abstract ii
Declaration of Originality v
Certificate vi
Acknowledgements vii
Contents viii
List of Figures xii
List of Tables xv
List of Abbreviations xviii
1. INTRODUCTION 1
1.1 General 1
1.2 World containerized trade 1
1.3 Port scenario in India 4
1.3.1 Performance of Indian ports 5
1.4 Containers 7
1.4.1 Types of containers 91.4.2 Advantages and disadvantages 121.4.3 Identification system 13
1.5 Container terminal structure and handling equipment 14
1.5.1 Processes at container terminal 151.5.2 Technologies for movement of containers 171.5.3 Container handling equipment 19
1.6 Recent technologies for container loading -unloading 24
1.6.1 Automated guided vehicles 241.6.2 Automated lifting vehicle 251.6.3 Linear motor conveyance system 261.6.4 Overhead grid rail technology 271.6.5 Automated storage/retrieval system 271.6.6 Assisting systems 28
1.7 Participants at container terminals 29
1.8 Problem statement 29
viii
2. LITERATURE REVIEW 32
2.1 General 32
2.2 Optimization techniques 32
2.2.1 Mathematical model 332.2.2 Linear programming 352.2.3 Non-linear programming 362.2.4 Mixed integer programming 372.2.5 Simulation 382.2.6 Branch and bound algorithms 392.2.7 Heuristic models 41
2.3 Literature review of container terminal processes: 41
2.3.1 Arrival of containers 422.3.2 Loading and unloading of containers 442.3.3 Transport of containers from quayside to stack and
vice versa 472.3.4 Stacking of containers 492.3.5 Inter-terminal container transport 532.3.6 Complete container terminals 54
3. CONTAINER TERMINAL OPERATIONS 56
3.1 Operations at Singapore port 56
3.2 Operations at container terminals in India 58
3.2.1 Container corporation of India 593.2.2 Financials 603.2.3 Physical performance 61
3.3 Case study at ICD, Tughlakabad, New Delhi 62
3.3.1 Facilities and Equipment 633.3.2 Loading-unloading operations at ICD, Tughlakabad 653.3.3 Rail Side operations 653.3.4 Storage yard operation 673.3.5 Gate operation 683.3.6 Summary of operations at ICD, Tughlakabad 68
4. MATHEMATICAL MODEL FORMULATION 70
4.1 Introduction 70
4.2 Problem description 70
4.3 Truck dispatching model formulation 72
4.4 Solution of truck dispatching problem 75
ix
5. SOLUTION MECHANISMS 78
5.1 Introduction 78
5.2 Greedy algorithm 79
5.2.1 Elements of a GA 79
5.3 Types of GA 82
5.3.1 Greedy algorithm and scheduling problems 83
5.4 Solution using GA 83
5.4.1 Assumptions 845.4.2 GA for unloading container operation 865.4.3 Greedy algorithm for loading container operation 915.4.4 Reverse greedy algorithm for loading container
operation 925.4.5 Solution using shortest job time first scheduling
algorithm 965.4.6 Solution using largest job time first scheduling
algorithm 98
6. MODEL APPLICATION TO REAL WORLD CASE STUDIES 101
6.1 Case study 1 102
6.1.1 Makespan for unloading operations 1036.1.2 Computation of makespan for loading operations 1046.1.3 Cost of unloading operations 1056.1.4 Cost of loading operation 1066.1.5 Waiting time of unloading operation 1076.1.6 Waiting time of loading operation 108
6.2 Case study 2 109
6.2.1 Makespan for unloading operations 1116.2.2 Makespan for loading operations 1126.2.3 Cost of unloading operations 1136.2.4 Cost of loading operations 1146.2.5 Waiting time for unloading operations 1156.2.6 Waiting time for loading operations 116
6.3 Case study 3 117
6.3.1 Makespan for unloading operations 1206.3.2 Makespan for loading operations 1216.3.3 Cost for unloading operations 1226.3.4 Cost for loading operations 123
x
6.3.5 Waiting time for unloading operations 1246.3.6 Waiting time for loading operations 125
6.4 Case study 4 126
6.4.1 Makespan for unloading operations 1296.4.2 Makespan for loading operations 1306.4.3 Cost for unloading operation 1316.4.4 Cost for loading operation 1326.4.5 Waiting time for unloading operation 1336.4.6 Waiting time of loading operation 134
6.5 Summary of loading and unloading results 135
6.6 Analysis of models results 139
6.6.1 Optimal number of trucks 1396.6.2 Optimal makespan 1416.6.3 Optimal cost 1436.6.4 Optimal waiting time 145
6.7 Recommended Models 147
7. CONCLUSIONS AND FUTURE WORK 153
7.1 Achievement of the thesis 154
7.2 Limitations of the research 157
7.3 Recommendations for further research 157References 159
Appendix A 176
Appendix B 180
Appendix C 183
Appendix D 184
Appendix E 204
xi
List of Figures
Figure 1.1 Growth of world container turnover from 1988 to 2008 2
Figure 1.2 Continent-wise turnover of containers 2
Figure 1.3 Growth rate of real GDP in India 5
Figure 1.4 Traffic handled at major and minor ports of India 6
Figure 1.5 Share of principle commodities handled at major ports: 2005-2006 6
Figure 1.6 Growth of world maritime trade versus containers 1987 to 2004 8
Figure 1.7 Forty feet normal, forty feet high cube, and twenty feet containers 10
Figure 1.8 Example of container ID 14
Figure 1.9 view of containership 15
Figure 1.10 Process of loading –unloading containers 16
Figure 1.11 Different types of handling equipment and their stacking capacity 18
Figure 1.12 Straddle carrier at Singapore port 19
Figure 1.13 Reach Stacker at ICD, Tughlakabad 20
Figure 1.14 Multi-trailers at the port of Rotterdam 21
Figure 1.15 Rail mounted gantry crane at CONCOR, Tughlakabad, New Delhi. 22
Figure 1.16. Quay crane at port of Paranaque, Brazil. 23
Figure 1.17 Automated guided vehicle used at Rotterdam port. 25
Figure 1.18 Linear motor conveyance system 26
Figure 2.1 View of container terminal. 41
Figure 2.2 (a) Single cycling unloading (b) Double cycling unloading and loading. 46
Figure 2.3 Yard crane and a container block 50
Figure 3.1 Container throughput at Singapore 56
Figure 3.2 Total traffic handled at CONCOR terminals 61
xii
Figure 3.3 ICD, Tughlakabad, New Delhi 62
Figure 3.4 Schematic of ICD, Tughlakabad. 64
Figure 3.5 Rail mounted gantry crane 66
Figure 3.6 Truck used for transhipment of containers 66
Figure 3.7 Part of storage yard in CONCOR served with TMGC. 67
Figure 4.1Layout of ICD, Tughlakabad 76
Figure 5.1 Flow chart of scheduling mechanism 78
Figure 5.2 The greedy algorithm for an unloading job sequence using FAT principle90
Figure 5.3 GA for an loading job sequence using FAT principle 91
Figure 5.4. Reverse greedy algorithm for loading containers using LBT principle 96
Figure 5.5 STF scheduling algorithm for unloading containers 98
Figure 5.6 The LTF scheduling algorithm for unloading containers 100
Figure 6.1 Comparison of makespan for unloading one train 103
Figure 6.2 Comparison of makespan for loading one train 104
Figure 6.3 Comparison of cost of unloading one train 106
Figure 6.4 Comparison of cost of loading one train 107
Figure 6.5 Comparison of waiting time for unloading one train 108
Figure 6.6 Comparison of waiting time for loading one train 109
Figure 6.7 Comparison of makespan for unloading two trains 112
Figure 6.8 Comparison of makespan of unloading two trains 113
Figure 6.9 Comparison of cost for unloading two trains 114
Figure 6.10 Comparison of cost for loading two trains 115
Figure 6.11 Comparison of waiting time for unloading two trains 116
Figure 6.12 Comparison of waiting time for loading two trains 117
Figure 6.13 Comparison of makespan for unloading three trains 120
Figure 6.14 Comparison of makespan for loading three trains 121
xiii
Figure 6.15 Comparison of cost for unloading three trains 122
Figure 6.16 Comparison of cost for loading three trains 123
Figure 6.17 Comparison of waiting time for unloading three trains 124
Figure 6.18 Comparison of waiting time for loading of three trains 125
Figure 6.19 Comparison of makespan for unloading four trains 130
Figure 6.20 Comparison of makespan for loading three trains 131
Figure 6.21 Comparison of cost of unloading four trains 132
Figure 6.22 Comparison of cost for loading four trains 133
Figure 6.23Comparison of waiting time for unloading four trains 134
Figure 6.24 Comparison of waiting time for loading four trains 135
Figure 6.25 Number of trucks versus number of trains in unloading process 140
Figure 6.26 Number of trucks versus number of trains in loading process 140
Figure 6.27 Number of trucks versus number of trains in loading-unloading process141
Figure 6.28 Makespan versus number of trains in an unloading process 142
Figure 6.29 Makespan versus number of trains in a loading process 142
Figure 6.30 Makespan versus number of trains in loading and unloading process 143
Figure 6.31 Cost versus number of trains in unloading process 144
Figure 6.32 Cost versus number of trains in loading process 144
Figure 6.33 Cost versus number of trains in combined loading-unloading process 145
Figure 6.34 Waiting time versus number of trains in an unloading process 146
Figure 6.35 Waiting time versus number of trains in loading Process 146
Figure 6.36 Waiting time versus number of trains in combined loading-unloading
process 147
xiv
List of Tables
Table 1.1 Busiest ports in the World in 2004 versus 2007 3
Table 1.2 Average allocation of funds in the Indian public transport sector 7
Table 1.3 Dimensions f ISO and non- ISO containers 10
Table 1.4 Types of containers 11
Table 2.1 Categorization of optimization techniques 33
Table 3.1Characteristics of Singapore Container Port (2007) 57
Table 3.2 Summary of loading/unloading operations at ICD, Tughlakabad 68
Table 4.1 Input data for truck dispatching problem 75
Table 4.2 Output from MIP model 75
Table 4.3 Computational time requirements for combinations of number of trucks and
containers 77
Table 5.1 Performance Comparison of GA and MIP 90
Table 5.2 Schedule obtained using STF algorithm 98
Table 5.3 Schedule obtained using LTF algorithm 99
Table 6.1 Four different real world case studies 101
Table 6.2 Input data for case study 1 102
Table 6.3 Minimum makespan and the corresponding number of trucks of unloading
operation 104
Table 6.4 Minimum makespan and the corresponding number of trucks for loading
operation 105
Table 6.5 Comparison of costs for unloading operations 106
Table 6.6 Comparison of costs for loading operations 107
Table 6.7 Comparison of waiting time for unloading operations 108
Table 6.8 Comparison of waiting time for loading operations 109
xv
Table 6.9 Input data for case study 2 110
Table 6.10 Minimum makespan and the corresponding number of trucks for unloading
operations 112
Table 6.11 Minimum makespan for loading two trains 113
Table 6.12 Operation cost for unloading two trains 114
Table 6.13 Operation cost for loading two trains 115
Table 6.14 Waiting time for unloading two trains 116
Table 6.15 Waiting time for loading two trains 117
Table 6.16 Input data for case study 3 118
Table 6.17 Minimum Makespan for unloading three trains 121
Table 6.18 Minimum makespan for loading three trains 122
Table 6.19 Operation cost for unloading three trains 123
Table 6.20 Operation Cost for loading three trains 124
Table 6.21 Waiting time for unloading three trains 125
Table 6.22 Waiting Time for loading three trains 126
Table 6.23 Input data of case study 4 126
Table 6.24 Minimum makespan for unloading four trains 130
Table 6.25 Minimum makespan for loading four trains 131
Table 6.26 Comparison of operation cost for unloading four trains 132
Table 6.27 Operation cost of for loading four trains 133
Table 6.28 Waiting time for unloading four trains 134
Table 6.29 Waiting time for loading four trains 135
Table 6.30 Summary of minimum makespan for loading-unloading operations 136
Table 6.31 Summary of cost corresponding to the minimum makespan for loading and
unloading operations 137
xvi
Table 6.32 Summary of waiting time corresponding to the minimum makespan for
loading and unloading operations 138
Table 6.33 Recommended models for loading and unloading one train 148
Table 6.34 Recommended models for loading and unloading two trains 149
Table 6.35 Recommended models for loading and unloading three trains 150
Table 6.36 Recommended models for loading and unloading four trains 150
Table 6.37 Computations for savings in cost for one train 152
Table 6.38 Computations for time savings for unloading one train 152
Table 6.39Computations for resource savings for one train 152
xvii
List of Abbreviations
AGVs Automated Guided Vehicles
AISC All India shippers Council
ALV Automated lifting Vehicle
AS/RS Automated Storage and Retrieval Structure
ASCs Automated Stacking Cranes
BAP Berth Allocating Problem
BARSYL Balaji Railroad Systems Limited
CFSs Container Freight Stations
CONCOR Container Corporation of India, Ltd
CT Container Terminal
DGS Directorate General of Shipping
ECT European Container Terminal
EDIFACT Electronic Data Interchange For Administration, Commerce and Transport
ESCAP Economic and Social Commission for Asia and the Pacific
EXIM Export – Import
FAT First Available Truck
xviii
FEU Forty-feet Equivalent Unit
GA Greedy Algorithm
GDP Gross Domestic Product
HC High Cubic
INFORMS Institute for Operations Research and the Management Sciences
ICD Inland Container Depot
ID Identification Details
ITCT Inter-Terminal Container Transport
INSA Indian National Ship-owners Association
ISO International Organization for Standardization
KMI Korea Maritime Institute
KPMG Knowledge Partner Management
LBT Last Busy Truck
LMCS Linear Motor Conveyance System
LP Linear programming
LTF Largest Time First
MBPP Master Bay Plan Problem
MIP Mixed Integer Programming
xix
MT Million Tonnes
MTS Multiple Trailer System
NLP Non-Linear Programming
OHBC Over-Head Bridge Cranes
PPT Pasir Panjang Terminal
PSA Port of Singapore Authority
QC Quay Crane
RMGC Rail-Mounted Gantry Crane
RTGC Rubber Tired Gantry Crane
SCI Shipping Corporation of India
SC Straddle Carrier
SKU Stock Keeping- Units
STF Shortest Time First
T Tonne
TEU Twenty feet Equivalent Unit
TKD Tughlakabad
UNCTAD United Nations Conference on Trade and Development
YC Yard Crane
xx
YoY Year on Year
xxi
1. INTRODUCTION
1.1 General
The loading and unloading of materials is a human activity which has been
performed since time immemorial. Due to rapid globalization of trade, many trade
barriers have broken down during the last the few years. Loading and unloading of
materials have become an important and specialized function in all trade activities.
The importance of port handling and transportation systems has increased due to
globalization of trade. Port handling and transportation systems include a network of
terminals around the globe that allow manufacturers and shippers to deliver goods
quickly to their customers. Increasing global trade has created the need for efficient
container ports wherein the goal is to move containers as quickly as possible and at
the minimum cost. Goods that are delayed at the port are inevitably tardy when
delivered to the customer, and often incur late delivery charges. Two key activities in
the port are (i) unloading of containers from truck and then storage in the export area,
and (ii) removal of containers from storage area and then loading onto the trucks.
Container terminals (CT) primarily serve as an interface between different modes of
transportation, such as domestic rail or truck transportation and deep sea maritime
transport. Worldwide container trade is growing at an annual rate of 9.5%.
Percentage of containerized trade in the world sea borne trade has increased from
5.8% in 1988 to 14.9% in 2006 and it is expected to go up to 35% by 2020
(Sabonge, 2006). It is anticipated that the growth in containerized trade will continue
as more and more cargo is transferred from break-bulk to containers.
1.2 World containerized trade
The use of container as a universal carrier for various goods has increased rapidly
during the last century. It has become a standard in worldwide transportation due to
rapid increase in containerization operations over the recent years. As result of
1
increasing world trade, new container terminals are being built and existing ones are
expanded.
19881989
19901991
19921993
19941995
19961997
19981999
20002001
20022003
20042005
20062007
20080
100
200
300
400
500
600The Growth of world container turnover
Container Turnover
Year
Mil
lion
TE
U
Figure 1.1 Growth of world container turnover from 1988 to 2008
Container Turnover by Continents
Total, 1720028
Total, 2725718
Total, 3738307
Total, 7003479
Total, 8861804
0
1000000
2000000
3000000
4000000
5000000
6000000
7000000
8000000
9000000
10000000
1989 1994 1999 2004 2006YEAR
TEU
Asia
Europe
North\Central-AmericaSouth America
Africa
Austral./Pac.
Total
Figure 1.2 Continent-wise turnover of containers
Figure 1.1 shows the growth of world container turnover. Over the last two decades
(1988 - 2008), the use of containers for intercontinental maritime transport has
rapidly increased. Starting with 76 million twenty feet equivalent unit (TEU) in year
1988, world container turnover has reached more than 544 Million TEU in year 2008
(Drewry, 2007a). A further continuous increase in container turnover is expected in
the upcoming years, especially in Asia and Europe.
2
Figure 1.2 shows the container turnover of different continents. Containerized trade
in 2008 has shown growth of the container turnover more than 5 times since the year
1989 (Etzelmueller, 2006). The world’s top 20 container ports handled 166.7
million TEU in 2004, accounting for 49.6 per cent of the world’s container port
throughput, which is defined as the average number of containers being loaded and
unloaded per hour per quay crane (QC).
Table 1.1 Busiest ports in the World in 2004 versus 2007
Rank
2004
Rank
2007
port Country 2004
(TEU)
2007
(TEU)
Percentage
change
1 3 Hong Kong China 21,984,000 23,881,000 +8.6%
2 1 Singapore Singapore 21,329,000 27,932,000 +31%
3 2 Shanghai China 14,557,000 26,150,000 +79.6%
4 4 Shenzhen China 13,615,000 21,099,000 +55%
5 5 Bussan South Korea 11,430,000 13,270,000 +16%
6 8 Kaohsiung Taiwan 9,714.000 9,774,670 +0.62
7 6 Rotterdam Netherlands 8,281,000 10,790,600 +30.3%
8 -* Los Angels US 7,321,000 7,702,000
9 9 Hamburg Germany 7,003,000 8,861,454 +30.3%
10 7 Dubai United Arab
emirates
7,702,000 8,923,456 +15.9%
*It indicates the port of Qingdao in China which had a rank of 10 in the year 2007
(Source: Drewry, 2007b)
Table 1.1 presents the volume of container traffic in TEU for the most busy container
terminals in the world in the year 2004 versus year 2007. The world’s top 3 container
3
ports in terms of container throughput were Singapore, Hong Kong, and Shanghai.
The port of Singapore is described in chapter 3 of this thesis. In the Asian and Pacific
region, the concentration of port throughput is even more prominent, with the 10
busiest ports handling 110 million TEU or 61.3 percent of the region’s total
throughput in 2004. The world’s six busiest container ports are located in the United
Nations Economic and Social Commission for Asia and the Pacific (ESCAP) region,
handling 27.4 per cent of world container throughput amounting to 51.1 percent of
the ESCAP total. Within the South and South-West Asia sub-region, container
throughput growth for Bangladesh, India and Sri Lanka has been strong. Growth in
Bangladesh reached nearly 20 percent per annum during the second half of the
1990s. While Bangladesh and India suffered only a modest slowdown in 2001, the
Sri Lankan transhipment port of Colombo was severely affected, recording a small
absolute decline in container throughput. However, in 2003 Bangladesh recorded a
comparatively strong growth rate of 19.1 per cent. The port scenario in India is
briefly discussed in next section.
1.3 Port scenario in India
India is one of the world’s fastest-growing economies where the gross domestic
product (GDP) showed a growth of 9.2% in 2006. India has shown an average
growth of 7.6% in the 10th five year plan (2002-2007) compared to a global growth
rate of 3.7%. (Lahiri, 2006). But due to global financial crisis, this growth slowed
down in India from 8.9 % to 7% (Vos, 2008) Figure 1.3 shows that GDP in India has
grown at a fast pace from 4.5 percent in the year 2001 to 11.5 percent in the year
2005. However, the pace of growth has shown a decline in the recent years (2006-
2009). One of the fields where India has made a significant progress is the
transportation and ports facility. Over 95 percent of India's international trade by
volume takes place through ports. However, due to the fast growing rate of the global
container trade, Indian major ports are under the pressure of meeting the international
demand.
4
The concept of ocean going containers was introduced in India for the first time in
1968 in a seminar held jointly by the Indian National Ship-owners Association
(INSA), Directorate General of Shipping (DGS), the Shipping Corporation of India
Ltd. (SCI) and the All India shippers Council (AISC) at Bombay.
2001 2002 2003 2004 2005 2006 2007 2008 20090
2
4
6
8
10
12
14
4.5 4.5
7.3 7.1
11.5
7.3
8.9
7.57
Annual Growth Rate of Real GDP (%) in India
GDP
Year
GD
P
Figure 1.3 Growth rate of real GDP in India
The 7517 km long Indian coastline has 12 major ports and 187 minor/ intermediate
ports out of which 139 are operable (Banger, 2007) Ports serve as the gateways to
the international trade in India and are handling over 90% of foreign trade. The major
ports are located at Calcutta/ Haldia, Chennai, Cochin, Ennore, Jawaharlal Nehru
Port at Nhava Sheva, Kandla, Mormugao, Mumbai, New Mangalore, Paradip,
Tuticorin and Vishakhapatnam, and Mundra port in Gujrat.
1.3.1Performance of Indian ports
The 12 major Indian ports, which are managed by the Port Trust of India under
Central Government Jurisdiction, have handled 463.84 MT (million tonnes) of cargo
in 2006-2007, a growth of 9.1% against the same period of the previous year (Ravi,
2007). As on 13-3-2007, these ports handled 509 MT of cargo with an average
growth rate of 10%. Figure 1.4 shows the performance of major and minor ports in
India in terms of traffic handled between 1990 and 2007. The major ports handled
5.541 million TEU out of which the share of the principle commodities was 12%.
The 187 minor ports are under the jurisdiction of the respective State Governments,
5
and have handled 195 MT (million tonnes) of cargo in 2006-2007. The capacity of
minor ports in India has a capacity of 228 MT as on 13-3-2007 with an average
growth rate of 12.6 %, (Banger, 2007). During 2005-06, major ports handled a
record traffic of 423.41 million tonnes with a growth rate of 10.3 percent over the
previous year, which was higher than the growth in GDP.
1990
1993
1996
1997
1999
2000
2001
2002
2003
2004
2005
2006
2007
050
100150200250300350400450500550600650700
Traffic handled at Minor and Major Port in India between 1990-2007
Minor Ports
Major Ports
Total
Year
Mill
ion
TE
Us
Figure 1.4 Traffic handled at major and minor ports of India
33%
3%
14%14%
20%
16%
POLFertilizerContainerCoalIron OreOthers
Figure 1.5 Share of principle commodities handled at major ports: 2005-2006
Of the total traffic handled at major ports, petroleum products have the largest share
of about 33 percent; iron ore, 20 percent; coal, 14 percent; containers, 14 percent;
fertilizer, 3 % and the rest is shared by general cargo 16 percent as shown in Figure
1.5
6
The performance of Indian ports does not compare favourably with that of efficient
international ports. On three important parameters- capacity, productivity and
efficiency, Indian ports lack in comparison to some of the major international ports.
In international terms, labour and equipment, productivity levels are still very low
due to the use of outdated equipment, poor training, low equipment handling levels
by labour, uneconomic labour practices, idle time at berth, and time loss at shift
change. Containerization is currently at 18% largely due to healthy EXIM (export –
import) growth of 15-20% (KPMG, 2006). However, this is still very low compared
to the levels of 70% in other countries, primarily due to the lack of adequate
infrastructure in terms of ports, roads, and railways.
Table 1.2 Average allocation of funds in the Indian public transport sector
Railway
s
Roads Ports and Shipping Aviation Others
52% 32% 6% 6% 4%
Table 1.2 presents the average allocation of funds in the public transport sector
during the five year plan (2002-2007). With the globalization of the Indian economy
and spurt in imports and exports, the container traffic is expected to grow
exponentially. It has been estimated that the growth will be of the order of 15 %
(Prasad, 2005).The Government of India decided to set up Inland Container Depots
(ICDs) which are also called dry ports and Container Freight Stations (CFSs). ICDs
which are constructed away from the ports and provide all facilities for effecting
containerized shipments; CFSs are smaller than ICDs and constructed near the ports,
limited only for stuffing into and de-stuffing of cargoes from the containers
(BARSYL, 2009). Indian ICDs perform many functions include stuffing, de-stuffing,
locking, sealing, providing trailers chassis, railway flats, repairs, handling
equipment, storage, 'facilities for reefer, customs examination and processing of
customs documents, issuance of combined transport documents by carriers.
7
1.4 Containers
Containerization has been defined by the Containerization Institute, USA as “the
utilizing, grouping or consolidating of multiple units into a larger container for more
efficient movement” (Agerschou et al., 1983). Containerization is an important
element of the logistics revolution that changed freight handling in the 20th century.
Use of containers or other large size boxes to protect the cargo as a single unit
throughout the journey is not new. In 1955 a very important man came into this
business. His name was Malcolm McLean. He bought shipping company called “Pan
Atlantic Steamship Corporation”. Soon he found out that the loading and unloading
of trucks and ships took a lot of time and many people were needed to fulfil these
tasks. McLean came up to an idea that there must be a special box/unit that can
contain goods from the shipper’s house to the receiving party without unloading and
loading again. This must result in less damage and must avoid steeling by thieves.
This concept also results in faster loading/unloading trucks and ships and large
packing materials is not needed (Meersmans, 2002). Nowadays, colourful steel
containers can be seen in every major port. An exclusive overview of history of
containers is given by Rath (1973). Indian railways used the containers for the first
time in 1966 on the Bombay-Ahmadabad route.
Figure 1.6 Growth of world maritime trade versus containers 1987 to 2004
8
A study of containerisation has shown that the saving in the cost of freight to
shippers can be as high as 50% of the cost of freight without using the container
(Khanna, 2005). As shown in Figure 1.6, the strong growth in tonnage moved by
container has been increasing at a rate faster than total maritime trade over the period
betwen1987 and 2006 (Drewry Shipping Consultants, 2007).
Total international maritime trade volumes grew at an average of 4.1 percent per
annum over the period of 1980 to 2004 with the result that by 2004 total seaborne
trade was almost double to that of 1990 volume. The growth of containers grew
seven times from 1980 to 2004. On the other hand, the challenge with containers lies
in two areas: the mismatch between ISO (the International Organization for
standardization) standards and un-standardized domestic container, and the prolific
growth (highly productive) of different types of containers for cargos. Global
production of container boxes in terms of annual output has increased by 76 times
from 40,000 TEU in the year 1966 with a cost of 1,500 US Dollars (75000 Indian
Rupees) to 3,050,000 TEU with a cost of 1,850 US Dollars (92000 Indian Rupees)
per container (Raghuram, 2007).
1.4.1Types of containers
There are three common standard lengths, 20 feet (6.1 m), 40 feet (12.2 m) and 45
feet (13.7 m). There are wide varieties of containers that are being used in practice.
Most of the containers have standard widths and heights, with standard lengths
varying from 20 to 53 feet. After several years of usage, some containers might lose
a few inches due to minor accidents and repairs. The dimensions of ISO and non ISO
containers are presented in Table 1.3 (Source: Kang, 2006).
Container capacity of ships and ports is measured in twenty-foot equivalent units
(TEU). Figure 1.7 shows 1 TEU, and 2 TEU normal, and 2 TEU high cube
containers. A twenty foot equivalent unit is a measure of containerized cargo equal to
one standard 20 ft (length) × 8ft (width) × 8.5 ft (height) container. Most containers
today are of the 40-ft variety and are known as 2 TEU. Two TEU are referred to as
one FEU or "Forty foot equivalent unit”. These two terms of measurement are used
interchangeably. "High cube" containers have a height of 9.5 ft (2.9 m), and half-
9
height containers used for heavy loads have a height of 4.25 ft (1.3 m). The cost of a
20-feet container is approximately $2,000 to $3,000 (1-1.5 lakh Indian Rupees) and a
40-foot container can be anywhere between $3,100 and $4,500 (1.6-2.25 lakh Indian
Rupees).
10
Table 1.3 Dimensions f ISO and non- ISO containers
Figure 1.7 Forty feet normal, forty feet high cube, and twenty feet containers
Containers are also classified on the basis of the type of cargo carried in them. As per
this classification, there are four basic types of containers; dry cargos, liquid cargos,
bulk commodities, and special cargoes requiring protection from the environment.
According to their function containers are classified into general purpose,
refrigerated, high cube, open top, flat top, and tank containers, etc. Table 1.4 shows
these types with their character and applications.
11
20’ container 40’ container 40’ High Cube
Table 1.4 Types of containers
Container Type
Character Application Figures
Standard 20' - Max. Payload: 28,23 Tonne(T) 40' - Max. Payload: 26,7 T 40' HC (High Cubic) - Max. Payload: 26,46 T
Suitable for any general cargo. Has various lashing devices on the top and bottom longitudinal rails and corner post.
Hardtop 20' - Max. Payload: 27,89T40' - Max. Payload: 25,78T.
40'HC-Max.Payload: 25,58 T
Equipped with a removable steel roof. Especially for heavy loads and over height cargo. Loading through roof opening and doorway by swing outdoor header
Open Top 20' - Max. Payload: 28,13 T40' - Max. Payload: 26,63 T
With removable tarpaulin. Used especially for over height cargo. Loading either from top side or door side by swing outdoor header.
Flat Rack 20' - Max. Payload: 31,26 T40' - Max. Payload: 26,28 T40'HC-Max.Payload: 39,30 T
Especially for heavy loads and over width cargo.
Platform 20' - Max. Payload: 31,26 T 40' - Max. Payload: 39,30 T
Especially for heavy loads and oversized cargo.
Ventilated 20' - Max. Payload: 27,99 T
Especially for cargo which needs ventilation.
Refrigerated 20' - Max. Payload: 27,45 T40' - Max. Payload: 29,40 T40' HC - Max. Payload: 29,88 T
Reefer containers do have their own electrically operated cooling / heating unit. The power supply is provided by ship's
12
electrical plant, by terminal or by "clip-on" diesel generator.
Insulated 20' - Max. Payload: 21,45 T40' - Max. Payload: 26,63 T
These containers do not have their own cooling facility. The cooling / heating is supplied by an onboard plant, by terminal or by a "clip-on" reefer unit.
Tank 24000 Litter /Litter Water
For the transport of liquid food, e.g.: Alcohols, Juices, Edible Oils, Food Additives
1.4.2Advantages and disadvantages
There are many advantages of using containers as a packaging unit, some of which
are outlined below:
Use of containers reduces loss, pilferage and damage claims significantly.
It eliminates a great deal of paper work related to shipments.
It expedites door-to-door pick-up and delivery service of cargo by reducing
the time for loading and unloading operations.
It eliminates multiple handling of cargo because a container is handled as a
unit.
The consolidation of small loads into a unit load is possible with a container,
leading to economy in freight cost
Improvement relating to handling, marketing and pattern of packaging is
made possible by the container
It is possible to reduce the cost of packaging because of possibilities of
placing goods without heavy packaging inside the container without any risk
of damage in transit.
A container combines all the advantages of various mode of transport by rail,
road and sea.
13
Containerization has led to improvement in the construction of boxes or
containers, and quick turn-round of modes of transport – whether ship, rail,
road- which leads to economy in the cost of transport.
The main disadvantages of using containers are as follows
Containerization increases the fuel costs of transport and reduces the capacity
of the transport as the container itself must be shipped around not just the
goods. For certain bulk products this makes containerization unattractive.
When transporting containers through railways, containers cannot be stacked
in layers due to vertical height limitations. As a result transportation through
railways sometimes becomes difficult
Containers occasionally fall from the ships during storms. It is estimated that
over 10,000 containers are lost at sea each year.
1.4.3 Identification system
Like any vehicle, every container has an identification system based on a unique
registration number. The identification system for containers (ID) is based on a series
of letters and numbers that represent the owner’s code, the serial number and the
code for the country of origin. The registration number is given on all four sides of
the container which makes it possible to identify its owner, and to identify the
contents of the container. Other important information about the container is also
provided by these numbers. All containers are, therefore, required to have these
identification numbers and letters. A system also been developed to check this
information, and details of the type and dimensions of containers is also expressed in
figures.
14
Figure 1.8 Example of container ID
The container ID is composed of several fields as shown in Figure 1.8, including the
following fields:
1. The shipping company (e.g., “UXX”)
2. The equipment category (always “U” for freight containers, "Z" or "C" for chassis)
3. The serial number of the container (e.g., “423697”).
4. The check digit of the first 3 fields (e.g.,”0”)
5. The container type (e.g.,”SE4310”)
Only the first 3 fields are relevant to the identification of the container, and represent
a unique identification number for each shipping container. In the above case, this ID
is “UXXU 423687”. The shipping company field ("UXX"in the example) is verified
against a pre-defined list of known companies. Additionally, the second field ("U") is
always verified. The check digit is used in order to verify the entire 10-character
identification number. If the check digit is not identified, only the 10 characters are
compared and reported. If it is recognized and tested for correctness, it will also be
reported (a "0" in the above case). The container type (in the above
example,”SE4310”) is not part of the ID and is not identified or transmitted.
1.5 Container terminal structure and handling equipment
Container terminal is a facility for loading and unloading of containers from ships or
another means of transportation. In general terms, a container terminal is an area
15
designated for the stowage (see appendix A) of cargos in container, usually
accessible by truck, railroad, or marine transportation. At container terminals,
containers are picked up, dropped off, maintained, and housed. Types of container
terminals and typical processes are given in the next section.
1.5.1 Processes at container terminal
Container terminal can be classified mainly into three types:
Sea port container terminal
Rail container terminal (Dry port)
Inland container terminal
Containerships as shown in Figure 1.1Figure 1.9 are nowadays unloaded and loaded
at large sea port container terminals. This loading and unloading of container process
can be divided into different sub-processes as shown in Figure 1.10.
Figure 1.9 view of containership
16
Figure 1.10 Process of loading –unloading containers
When a ship arrives at a port, a berth is assigned for unloading. After the ship is
positioned under the quay crane(s) (QCs), the containers are unloaded by the QC and
are loaded to fleet of trucks and transported to yard area for storage. At the storage
area containers are stacked into blocks. Equipments, like cranes or straddle carriers
(SCs) serve the blocks .On the berth, a necessary number of quay cranes (QCs) are
allocated to unload the containers. A straddle carrier can both transport containers
and store them in the stack. It is also possible to use dedicated trucks to transport
containers. If a truck arrives at the stack, it puts the load down or the stack crane
takes the container off the truck and stores it in the stack.
Containers are stored in blocks for certain period until they are claimed by the
importer. When containers are claimed, containers are retrieved from the stack by
17
cranes and transported by trucks to transportation modes like barges, deep sea ships,
trucks or trains. To load export containers onto a ship, these processes are executed
in reverse order. Figure 1.10 illustrates a summary of the main operations in a
container terminal. Every process is highly dependent on the previous one. Except
for arrival and departure of external trucks all the operations are under the control of
port’s personnel. A large number of highly dependent operations need continuous
coordination and high degree of efficiency.
A complete description of various equipment used, and the operations inside the
terminal have been described by various researchers with a view to facilitate decision
making within the terminal (see Silberholz et al., 1991; Kozen 1997; Nevins et al.,
1998; Lee et al., 2003, Linn, et al., 2003, Steenken et al, 2004; Murty et al.,
2005a; Murty et al., 2005b; Dekker et al., 2006; Petering, et al., 2006; and
Petering 2007).
Most of the terminals make use of manned equipments, like straddle carriers, cranes
and multi-trailer-systems. However, a few terminals, like terminals in Rotterdam, are
semi-automated. At such terminals Automated Guided Vehicles (AGVs) are used for
the transport of containers. Furthermore, the stacking process can also be done
automatically by Automated Stacking Cranes (ASCs). In practice, the number of
containers to be unloaded from or loaded onto a ship is fairly large, ranging from 500
to 2500 containers (Ioannou et al., 2000).
1.5.2Technologies for movement of containers
Since containers are large and heavy, specialized material handling equipment are
required for transporting them within the terminal. A container terminal provides the
location, mechanical devices, space and operating conditions under which the
container transfer takes place. Container yard is a materials handling/storage facility
used for completely unitized loads in containers and/or empty containers (Dirk, et
al., 2004). A great variety of handling equipments are involved in container yard
operation (Ioannou et al., 2000).
18
Figure 1.11 Different types of handling equipment and their stacking capacity
General information as well as particular details of technical equipment for container
handling are provided by engineering oriented journals as well as by specialized
outlets, brochures, or websites of suppliers of material handling equipment and
services in the container sector (e.g., PTI 2006, Kalmar 2006, Noell 2006,and
ZPMC 2006) Common equipment such as the chassis-based transporter, straddle
carriers (SCs), Reach Stacker (RS), Rubber-Tired Mounted gantries (RTMG) crane,
Rail-Mounted Gantries (RMG) crane, are compared in terms of the actual stacking
capacity in Figure 1.11. (source:Kalmar, 2006)
Over the last decade, technology and automation have been introduced into the
container business to improve the efficiency, increase capacity, and meet future
demands. Furthermore the explosive growth of freight volume has greatly increased
the load on container terminals. Recent advances in electronics, sensors, information
technologies and automation have motivated the port authorities to adopt advanced
technologies to cope with the booming growth. In the next section, a brief review of
some of equipment used for moving the containers within the container terminal as
well as details of recent technologies and automation equipment is presented.
19
1.5.3 Container handling equipment
Most of the terminals make use of the equipment, like lift truck (front end loader,
side loader or reach-stacker), straddle carrier, rail mounted and rubber tyred gantry
crane, etc. quay crane at quayside.
Straddle Carrier
Straddle carriers (SCs) are four wheeled vehicles that are able to pick and drop a
container by itself at high speeds. They are available for handling different sizes of
containers and with different vehicle-lifting ability.
SC as shown in Figure 1.12 is often used in medium size multi-modal facilities
where speed of operation is important. They are the most common form used for
manned inter-terminal transport over short distances say, between the quay side and
storage yard. SCs remain popular because of their relatively low purchase cost,
smaller yard development cost and their economic and flexible operations (Ioannou
et al., 2000). However, SCs are less space efficient, have lower operational capacity
and less suited to higher automation and have greater downtime and higher
maintenance cost [for more technical information see Siemens, (2007a)].
Figure 1.12 Straddle carrier at Singapore port
20
Fork lifts
Fork trucks are sometimes used for container handling for small capacity up to 5
tonnes. They are generally considered unsuitable and not recommended for
containers because of lack of visibility to the driver, as a result of which there is
possibility of damage to containers. Forklifts cannot be used for containers that are
not fitted with the pockets for fork truck.
Reach Stacker
A reach stacker (RS) is a type of fork lift with a telescopic boom and top-lift
attachment used for lifting and stacking containers. Its design enables it to reach
beyond the first row to pick up a container. Figure 1.13 shows a reach-stacker that
operates in the container terminal. Its main task is to stack containers and to load
them into trucks, tractors or trains. It is a road vehicle, with a high tonnage capacity.
Its storage capacity is approximately equal to 500 TEU per hectare. It can stack
containers up to 3 containers high and can reach a maximum height equivalent to 5
containers high. The capital cost for a RS is low as compared to other container
handling equipment. RS is recommended for small to medium size operations in
multi-purpose terminals.
Figure 1.13 Reach Stacker at ICD, Tughlakabad
21
Multiple trailer system
A multiple trailer system (MTS) (also called multi-trailer system) is one where a
towing vehicle transports more than one container to and from the container yard. It
is also known as elephant trains, and is shown in Figure 1.14. It can move eight
trailers loaded with container, which can lead substantial reduction in operation and
labour cost (Ioannou et al., 2000).
Development of Multi-Trailer System (MTS) has been carried out by the Technical
University of Delft, Netherland. The demand for (MTS) is growing rapidly. For
example in a Kalmar delivery each MTS will be able to move eight 20ft containers
(or an equivalent mix of 20s and 40s) simultaneously, thus providing significant
benefit over single trailer systems
Figure 1.14 Multi-trailers at the port of Rotterdam
Stacking cranes
Stacking cranes are used for placing and retrieving of containers in stack. These
forms of stacking cranes are known as Rail Mounted Gantry Cranes (RMG) or
Rubber Tired Gantry Crane (RTGC) [for technical information see Siemens, (2007b)
and Siemens (2007c)], and Over-Head Bridge Cranes (OHBC). OHBC requires
huge initial investments in erecting columns sustaining crane rail girds and ground
breaking works. An RTGC moves on rubber tyres over containers and is able to
22
move among blocks. A RMG runs on rails normally serving a single storage block
between the rails. Figure 1.15 shows RMGCs at ICD, Tughlakabad terminal
The RTGC has the flexibility to change stack but in practice this is time consuming
and cannot be done often. Being harder to automate, they are less attractive for the
terminals trying to further increase their throughput by automization. As a result yard
cranes are space-efficient, fast in operation and more suited for automation.
However, they require higher development cost than SCs typically around 3 times
the price, because of their heavy body weight and wheel load. RTGs are typically
cheaper to install, more expensive to operate and more flexible than RMGs.
Comparison of OHBC, RMGC, and RTMC is given in Appendix B.
Figure 1.15 Rail mounted gantry crane at CONCOR, Tughlakabad, New Delhi.
Quay crane
Quay crane (QC) is manned equipment; the maximum capacity to load and unload
containers from or to the ship is 50 containers per hour (Evers et al., 1996). QC is
the most important determinant of the ship operation productivity at the terminal.
The number of quay crane Nqc required to accomplish the proposed task, can be
calculated by
23
Nqc=N containers
Cqc T ship Eq 1.1
Whereas, Ncontainers is the number of containers to be loaded and unloaded. Cqc is the
maximum physical capacity of the quay cranes, Tship is the turnaround time of the
ship. Figure 1.16 shows Quay cranes (QCs) that have trolleys that can move along
the crane arm to transport the container from the ship to the transport vehicle and
vice versa. A spreader, a pick up device attached to the trolley, picks the containers
Figure 1.16. Quay crane at port of Paranaque, Brazil.
The QCs move on rails to the different holds to take/put containers off/on the deck
and holds. Technical specifications of quay cranes can be browsed in (Ceres
Paragon, (2006); Dubini (2007); Corp, (2007); ZPMC (2007a); ZPMC (2007b);
and ZMPC, (2007c).) It can happen that at the same moment one QC is unloading
containers while another QC is loading containers. QCs are manned because
automation of this process encounters practical problems. For example exact
positioning of containers may not be achieved.
24
1.6 Recent technologies for container loading -unloading
Over the last decade, technology and automation have been introduced into the
container business to improve the efficiency of part operations See (Dimitrijevic et
al., 2005) and (Asef-Vaziri et al., 2003). Some of these technologies include:
Automated guided vehicles (AGV)see (Liu et al. 2002) and (Liu et al., 2004),
Automated lifting vehicle (ALV), overhead grid rail system (OHGR), linear motor
conveyance system (LMCs), and high rise automated storage and retrieval structure
(AS/RS) see (Asef-Vaziri et al. 2000) and (Chen, et al., 2003).
1.6.1Automated guided vehicles
Automated guided vehicle (AGV) is driven by an automatic control system that
serves the role of the driver, and moves along guide-paths, which can be modified
easily. AGVs are considered to be the most flexible type of material handling system
(Egbelu, 1984). Their size ranges from small load carriers of a few kilograms to over
125-ton transporters AGV consists of the vehicle, onboard controller management
system, communication system and navigation system. AGVs are now becoming
popular in automated materials handling systems, flexible manufacturing systems
and container handling applications. In this concept the terminal configuration is
similar to that of conventional terminals but instead of using manually operated
equipment, AGVs are used to transfer containers within the yard and automated
cranes are used for loading and unloading. AGVs are very well suited to be deployed
for terminal operations due to the repetitive nature of movements within the
terminals. The promise of deploying AGVs in container terminals lies in their
capability of achieving the following benefits: high container throughput, continuous
operation for 24 hours a day, 365 days a year, high controllability and reliability,
high safety standards, automated and consistent container handling operation,
reduced operational costs, especially labour costs, high position and heading
accuracy (Evers et al. 1996). Unlike, straddle carrier, AGVs are not able to load and
unload containers themselves. A crane is always needed to perform these operations.
However, the system is not cost effective because it does not permit high stacking
and requires wide roads to travel through the terminal.
25
The European Container Terminal (ECT) in Rotterdam is the most advanced
container terminal in the world. It uses a fleet of AGVs (as shown in Figure 1.17 )
between the yard-cranes and ship-cranes at the terminal. The system is considered
successful but the rate of success so far has been less than what was expected. Other
ports considering this technology are watchful of ECT’s success as they recognize it
has been a slow process. In the recent years, there have been substantial
improvements in speed of vehicle as well as in the navigation technology and
communications systems
Figure 1.17 Automated guided vehicle used at Rotterdam port.
1.6.2 Automated lifting vehicle
Automated lifting vehicle (ALV) was launched by Seoho Electric Company and the
Korea Maritime Institute (KMI). The design is a hybrid between a passive AGV and
a low height straddle carrier (Kim, 2006). It is a vehicle which can both load and
unload containers and travel from the ship to the stack during the unloading process
and from the stack to the ship during the loading process under its own power. These
vehicles are capable of lifting containers from the ground by themselves and that is
in fact the main difference from AGV. By using lifting vehicle the loading and
unloading process at the crane and the transportation process can be decoupled. A
crane places a container on the ground and does not have to wait for a vehicle to
26
place the container on. This last action is required in case when non lifting vehicles
are used.
1.6.3 Linear motor conveyance system
Another technological concept that has demonstrated significant promise for the
transfer of containers to and from the yard is based upon linear motor-conveyance
system (LMCS).
Figure 1.18 Linear motor conveyance system
Linear induction motor operates on the same basic principles as a conventional,
rotary induction motor, except that instead of the coils being wound around a shaft,
the entire assembly is “unwound” into a linear configuration. Running current
through the unrolled, flattened stator moves a metal flat blank, which is placed above
the stator (Ioannou et al. 2000). By controlling an array of linear motors that are
placed underneath a platform, one can accurately move the platform given that it is
on a sliding or rolling surface. However, the technology is scalable to larger tasks. A
system such as this could be ideally suited for port and terminal operations.
Prototype of LMCS as shown in Figure 1.18 has been constructed and successfully
tested in Eurokai Container Terminal in Hamburg, Germany (Patrik et al.
2001).Once the necessary infrastructure is in place and the shuttles to carry the
containers are constructed, the system could be operated autonomously without any
constraints on the hours of operation, and at a very low cost. Linear motor driven
27
systems could be proven to be more attractive than AGV systems for marine terminal
applications in terms of maintenance cost and reliability (Ioannou et al. 2000)
However, due to the fixed guide-way associated with linear motor systems, AGV
system could be much more flexible in terms of their ability to travel on numerous
paths depending on the navigation concept used.
1.6.4Overhead grid rail technology
A concept known as Overhead Grid rail technology for optimizing the use of space
and improving the productivity of container terminals (OHGR) has been proposed by
Sea-Land and August Design, Inc (Design, 2005). The OHGR consists of an
overhead rail, passive switches, shuttles, container buffers and a computer control
system. The container handling devices (shuttles) can access any part of the container
yard, eliminating the need for ground vehicles in the terminal and, as a result, the
need for unproductive road areas (Dougherty, 2008). The shuttles could access the
gate area to transfer containers, access a rail spur to transfer to and from trains, and
the shuttles could deliver cargo directly to quay cranes in order to improve
productivity. Alternatively the shuttles could be isolated to operations within the
OHGR and yard vehicles can be used to transfer containers between the OHGR and
the gate, ship, and train buffers (Ioannou et al. 2000). The key advantages of OHGR
are that it provides high density of stacked containers,, near random access to densely
stacked containers, reduction in crane “dancing”, reduction of in-hoisting time,
elimination of crane waiting time, valuable combination of high density and high
productivity, and ability to be modified or moved from port to port (Khoshnevis et
al., 2000).
1.6.5Automated storage/retrieval system
Automated Storage/Retrieval Systems (AS/RS) are a storage system that uses fixed-
path storage and a retrieval machine running on one or more rails between fixed
arrays of storage racks. AS/RS are used to efficiently store cargo awaiting shipment
or awaiting pickup by a customer, also used to increase the packing density of cargo
and containers, and for storage and retrieval with minimal human effort (Asef-Vaziri
28
et al. 2000) and (Khoshnevis et al. 2000). Physical handling systems are used to
move cargo or containers within a terminal, to or from a ship, or to or from a storage
location. AS/RS can also interface directly with an AGV system, further reducing
labour content. These benefits offer more efficient utilization of available space, and
quicker and less labour-intensive storage and retrieval (Liu et al. 2002). AS/RS is
most often used in distribution centres, which stock large number of items, instead of
trans-shipment terminals (such as ports). Like AGV systems, AS/RS require
significant capital investment and skilled labour for operation and maintenance.
Naturally, the benefits of an AS/RS would be greatest in ports where land and labour
costs are especially high or where the space is constrained.
1.6.6Assisting systems
Besides cranes and transport vehicles, assisting systems play an important role for
the organization and optimization of work flow at container terminals. This is valid
especially for communication and positioning systems. The electronic
communication is based on international standards (EDIFACT; Electronic Data
Interchange For Administration, Commerce and Transport). Every change of
container status is communicated between the respective parties. From the point of
view of the terminal operator the most important messages are: the container loading
and unloading lists which specify every container to be loaded or unloaded to/from a
ship with specific data; the ‘bay plan’ which contains all containers of a ship with
their precise data and position within the ship (it is communicated before arrival in
the port); the ‘stowage instruction’ which describes the positions where export
containers have to be located in a ship and which is the base for the stowage plan of
the terminal; container pre-advices for delivery by train and truck, and the schedule
and loading instruction for trains only to name a few. Although only some of these
messages specially the stowage instruction for ships and trains interfere directly with
the operational activities of the terminal, they are very important because they help to
maintain completeness and correctness of container data which is necessary to
optimize the work flow. Besides the communication with external partners, the
29
internal communication systems play a major role in optimizing the terminal
operation.
1.7 Participants at container terminals
There are 6 principal participants at a terminal: 1) the shipper that loads the container
and sends it to the terminal, 2) the inland carrier that transports the container to and
from the terminal, 3) the terminal operator that oversees the terminal operations, 4)
the stevedore who loads and unloads the containerized vessels, 5) the steamship line,
and 6) the consignee or recipient of import cargo. The shipper could be the owner of
the cargo, freight forwarder, or broker. The inland carrier could be a truck or rail
company. The terminal operator might be a public port authority that operates a
facility open to any vessel that makes arrangement to call there, or a steamship line
operating the terminal as a dedicated facility, serving only its own vessels and
customers. The stevedore could be the terminal operator itself or an independent
contractor hired by the steamship line. The steamship line is the one who owns the
vessel and is a key player in the process. It interacts with the shipper, terminal
operator, consignees, and government officials. Lastly, the consignee could be a
retailer who bought the cargo or a subsidiary of the shipper.
1.8 Problem statement
The main functions of the terminals are delivering containers to consignees and
receiving containers from shippers, loading containers onto and unloading containers
from vessels, trains, trucks, and storing containers temporarily. The productivity of
container terminals is often measured in terms of the time necessary to load and
unload containers by cranes and trucks, which are the most important and expensive
equipment used in ports. The truck scheduling problem consists of determining a
sequence of unloading and loading movements for trucks assigned to cranes in order
to minimize completion time as well as the crane idle times. The efficiency of a
container terminal is also measured by the degree of utilization of human resources,
equipment, yard area, and cost of the operations.
30
Most terminals are now taking measures to increase their throughput and capacity by
introducing new technologies, reducing equipment dwell times through increasing
demurrage fees and/or limiting the advance delivery of export cargo, and increasing
storage density by stacking containers four or five levels. However, there are four
major problem faced by container terminal managers.
1. How to manage the flow of containers to and from the terminal
2. How to track the highly dynamic movement of containers in the yard area
3. How to allocate resources to perform loading and loading operations in the
terminal optimally
4. How to schedule loading and unloading operations in an optimal manner
This major objective of this research is to develop generic models that can be used to
schedule loading and unloading operations at container terminals in an optimal
manner. This objective can be achieved through optimizing the makespan for loading
and unloading containers in the container terminal using greedy search algorithm and
mixed integer programming. The intent behind optimizing the makespan is (1) to
reduce the waiting time of the trucks, (2) to cut down the operation costs, (3) to find
the optimal number of trucks to be used for loading unloading containers to /from
trains and (4) to contribute towards improvement in the national economy. Specific
objectives of the thesis include
1. To carry out a literature review of application of optimization techniques to
container terminal operations
2. To carry out literature review of container handling processes in container
terminals
3. To collect data pertaining to container laoding-unloading in Inland Container
Depot in Tughlakabad
4. To develop and evaluate the performance mixed integer programming based
mathematical model
5. To develop and evaluate the performance of scheduling mechanisms based on
different principles using greedy and reverse greedy algorithms
31
6. To identify and recommend models for improving container terminal
operations
The remainder of this thesis is organized as follows. Chapter two presents the
literature review of research related to this work. Chapter three presents
characteristics of container terminal at ICD, Tughlakabad, New Delhi owned by
Container Corporation of India (CONCOR), which is the terminal selected as a case
study for this research work. Chapter four discusses the development of
mathematical model of truck dispatching problem using mixed integer programming
which has been developed using AMPL software.
Chapter five presents heuristic model based on different scheduling mechanisms to
address the problem of this research work.
Chapter six presents application of models based on different scheduling algorithms
to solve four real-world problems. The analysis of results obtained by using the
developed models is also presented in this chapter.
Lastly, chapter seven summarizes key findings from this thesis work, highlights its
contribution, and discusses potential areas for future research.
32
2. LITERATURE REVIEW
2.1 General
The demand on container terminals has increased due to high growth rates on major
seaborne container routes. Terminals are faced with the problem of handling an
increasing number of containers in short time and at low cost. Therefore, container
terminals are forced to increase handling capacities and to achieve gains in
productivity. The problem of dispatching and scheduling of the trucks at the
container terminal has been extensively studied by many researchers. But
unfortunately; most of this research is not directly applicable to container terminals
due to their unique characteristics. This, in turn, requires the development of
algorithm that take into account the special characteristics and constraint associated
with container terminals. Since throughput is the most important objective for a
container terminal thus it is important to minimize the total throughput that is the
handling time of unloading / loading of all containers from / to the ship. In the
following sections, a literature review of terminal operations and logistics has been
presented. The review is broadly divided into two parts. In the first part, literature
related to applications of optimization techniques to container terminals is presented.
The second part presents a review of container terminal processes.
2.2 Optimization techniques
Optimization models are used to obtain best solution of a given problem under given
circumstances. Most optimisation models are based on some type of mathematical
programming technique. Some successful applications of these techniques to
container terminal operation have been reported in the literature. Application of
various optimization models to container terminal problems has been reviewed by
Sirikijpanichkul et al. (2005); Taniguchi et al. (2001); and Russell et al (2003).
Basically, these techniques fall into two categories; namely, classical and heuristic. A
categorization of optimization techniques has been presented in Table 2.5. A brief
33
review of applications of traditional and heuristic techniques to container terminal
operations has been presented in this chapter.
Table 2.5 Categorization of optimization techniques
Technique & Application Advantages Disadvantages
Mathematical programming:
Branch and bound algorithms,
Lagrangian relaxation,
- Branch and cut methods
Provides exact Solution Limited to small scale
simplified problems.
Require many simplified
assumptions
High computation
Cost
Greedy algorithm,
Simulated annealing search,
Local beam search,
Tabu search,
Genetic algorithms,
Expert system
Neural network
Multi-agent system, Etc.
Practical for complex
model formulations.
Flexible regarding the
nature of the objective
function and constraints.
Reasonable computation
cost.
May not sometimes achieve
global optimum solutions
2.2.1Mathematical model
A mathematical model of a system describes system behavior using equations and
logical relationships. Types of mathematical models include probabilistic models,
mathematical programming models, and simulation models. In addition to the
functional and logical relationships that describe system behavior, mathematical
models include several other components.
Decision variables are the variables that affect the performance of a given system.
Examples of decision variables are the number of cranes to be installed at a container
berth, or the number of parking spaces at container terminal.
34
Parameters are values over which the decision-maker has no control. Examples of
parameters are the service rate of an agent at a ticket counter, or the arrival rate of
trucks to a container terminal. Identifying the decision-maker for a system is an
important step in the modeling activity. If the president of a distribution company is
the decision-maker, the location of a warehouse might be a decision variable. If the
decision-maker is the warehouse manager, then the location of the facility is a
parameter.
Constraints are any limitations that may be placed on the decision variables.
Examples of constraints are area limitations for dockside cranes at a container
terminal, budget limitations for operating container terminal, and towing capacity
limitations of the trucks used in an intermodal system. A constraint may limit a
single decision variable or it may involve two or more decision variables.
Performance measures are quantities that capture the level to which the system is
operating. Examples of performance measures are throughput, waiting times,
equipment utilization, operating costs, and inventory levels.
An objective function identifies an important performance measure and the
optimization goal (maximize or minimize) for the measure. For example, an
objective function may maximize utilization of yard tractors, minimize operating
costs of a container terminal, or maximize profit generated from a container terminal.
In a mathematical model, decision variables, parameters, constraints, performance
measures, and objective functions are all captured using equations and/or logical
relationships.
According to Liu (2002), some of techniques being commonly used by the
researchers can be broadly classified as follows:
Linear programming (LP)
Non-linear programming (NLP)
Mixed integer programming(MIP)
35
2.2.2Linear programming
Linear programming (LP) is a most widely used mathematical programming
technique. LP is an optimization problem with a linear objective function, a set of
linear constraints, and nonnegative restrictions imposed upon the underlying decision
variable. LP has been used in the optimization of container terminal operations, and
the optimization model is of the form
Minimize or Maximize∑j=1
q
C T j X jEq 2.1
Subject to ∑j=1
q
Aij Xj=B(i) for all i=1,...pEq 2.2
Xj ≥ 0 for all j=1,...q Eq 2.3
Where is a q dimensional vector of decision variables, C is a q dimensional
vector of objective function coefficients; B is a p dimensional vector of right hand
side o A is a p q matrix of constraint coefficients; and T represents the matrix
transpose operation.
An integer programming model is the one in which all the decision variables assume
integer values. Rajotia et al. (2002) applied a mixed integer linear programming
model to study the deterministic case for finding out the minimum number of
vehicles for loading and unloading a given number of containers. The objective of
the model is to minimize empty trips made by the vehicles by taking into account the
load handling time, empty travel time, and waiting and congestion time. The result of
the model is compared with the result of a simulation study. They conclude that the
vehicle fleet size is underestimated using the analytical methods. Holguin et al.
(1998) presented a linear programming model of an intermodal container terminal.
The model estimates storage charges to maximize a “pricing” function subject to the
storage capacity for containers. They classify containers according to marginal
36
operating costs, space requirements, and price elasticity of dwell times. The objective
function is evaluated according to the storage charges placed on each container
classification. This price function may maximize profit, or profit subject to a
breakeven constraint. The model is constrained by a function of the average stack
height, dwell time, and input rate for each container classification.
Kim et al. (1999a) studied dispatching of containers to AGVs in a container
terminal. The authors proposed a mixed integer linear programming model (MIP)
and heuristics to dispatch containers to AGVs such that the delay of the ship is
minimised Kim et al. (2004) presented a study that tried to synchronize ship
operations with vehicle dispatching using both MIP model and a look ahead
heuristic. In a numerical investigation, their heuristics were shown to outperform
conventional dispatching rules. Ambrosino et al. (2006) studied the impact of yard
organization on the stowage of containers in terms of unproductive export containers
movement in the port. They tackled the problem using a heuristic approach based on
a 0-1 linear programming model. Alessandri et al. (2007b) proposed a linear
discrete-time model and a linear cost function in order to model the flows of
containers through an intermodal container terminal and to optimize problems related
to the strategic planning of maritime terminals. The objective of the proposed
optimal control problem is the minimization of the transfer delays of containers in
the terminal. The entire terminal is decomposed into three sub-terminals for ships,
for trucks and trailers, and for block trains. Handshaking queues are used for
describing delays in transferring containers from one resource to another one. A
receding-horizon strategy is adopted in order to seek a solution of the optimization
problem. The effectiveness of the proposed control scheme is evaluated by numerical
experiments using data from a Mediterranean port in the Northern part of Italy.
2.2.3Non-linear programming
NLP technique can be applied where some of the constraints or the objective
function is nonlinear. NLP can effectively handle a non-separable objective function
and non-linear constraints. A general NLP problem can be expressed in the form
37
Minimise F= f ( x1 , x2 , .. . , xq ) Eq 2.4
subject to gi( x )=0 i = 1........., pEq 2.5
where x j ≤ x j≤ x j j = 1,....... q Eq 2.6
in which F is to be minimised subject to m constraints expressed by function g(x), n
is the number of decision variables, and Eq 2.6 is a bound constraint for the jth
decision variable xj with x j and x j being the lower and upper bounds, respectively.
Alessandri et al. (2007a) generalized the results of Alessandri et al.( 2007b) by
proposing a nonlinear predictive control approach for the allocation of the available
handling resources in a maritime intermodal terminal. A mixed integer nonlinear
problem is formulated for modelling the container flows within the terminal. The
solution techniques developed by them treats decisions expressed by binary variables
as non-differentiable functions. However, NLP requires that both the objective
function and constraints are differentiable functions.
2.2.4Mixed integer programming
A mixed integer programming (MIP) problem results when some of the variables in
the model are real valued (can take on fractional values) and some of the variables
are integer valued the model is therefore “mixed”. When the objective function and
constraints are all linear in form, then it is a mixed integer linear program (MILP). In
common parlance, MIP is often taken to mean MILP, though mixed- integer
nonlinear programs (MINLP) also accrue, and are much harder to solve.
Zhang et al. (2005) presented three mixed binary integer programming models for
dispatching vehicles such as AGVs or yard trucks at the quayside. The models
consider the unloading phase of a vessel in one berth without taking physical settings
such as buffers for vehicles into account. Furthermore, congestion free vehicle traffic
38
is assumed, and continuous operations of quay cranes are not guaranteed since the
number of vehicles is limited. The models determine the starting times of the
unloading operations as well as the order of vehicles for carrying out the jobs. The
objective is the minimization of the overall waiting time of the quay crane (or
container jobs) which is equivalent to minimizing the job ready time of the last job.
Nguyen et al.( 2009) discussed how to dispatch ALVs by utilizing information about
pickup and delivery locations and time in future delivery tasks. A mixed-integer
programming model is provided for assigning optimal delivery tasks to ALVs. A
procedure for converting buffer constraints into time window constraints and a
heuristic algorithm for overcoming the excessive computational time required for
solving the mathematical model are suggested
2.2.5Simulation
Simulation is a modelling technique used to approximate the behaviour of a system
on a computer, representing all the characteristics of the system largely by a
mathematical or algebraic description. Simulation models provide the response of the
system to certain inputs, which include decision rules that allow the decision makers
to test the performance of existing systems or a new system without actually building
it. Optimization models aim to identify optimum decisions for system operation that
maximises certain given objectives while satisfying the system constraints. On the
other hand, simulation models are used to explore only a finite number of decision
alternatives so that the optimum solution may not necessarily be achieved. However,
many simulation models now involve a certain degree of optimisation and the
difference between the optimisation and simulation models is becoming less distinct.
Simulation models have been routinely applied for many years by several
researchers. Legato et al. (2001) and Canonaco et al. (2007) have proposed
methods for integrated berth planning via simulation. Ludwik (1990) simulated a
ship-to-rail intermodal freight terminal using a knowledge base and a set of
algorithms. The knowledge base consisted of the physical elements of the terminal
and the terminal operations processes–specifics about the loading and unloading of
equipment, the type of ships arriving to the terminal, the storage facilities, the type of
39
cargo being handled, and the interactions among these elements. Ludwik (1990),
defined the vehicle, its arrival frequency and time of first arrival, its economic cost,
and its required operations. He described processes by the type of cargo transfer
(storage to vehicle, vehicle to vehicle, etc), the type of cargo, a process efficiency
measure, and the terminal elements required to carry out the process. A microscopic
simulation model based on Automated Container Terminal (ACT) has been proposed
by Ioannou et al. (2001). Data was collected from a conventional terminal and
simulation was carried for the ACT system for the same operational scenario in order
to compare and evaluate their performances. The performance of the model was
assessed by throughput, ship turn-around time, truck turn-around time, gate
utilization, container dwell time, idle rate of equipment.
Liu et al. (2002) and Liu et al. (2004) investigated the impact of two commonly
used terminal layouts and automation using AGVs on the terminal performance. One
layout is characterized by container stacks that are placed in parallel with the berth.
In the second layout, the stacks are arranged perpendicular to the berth. A multi
attribute decision-making method is applied in order to evaluate the terminal
performance and determine the optimal number of deployed AGVs. Three
operational scenarios are considered and compared for both automated yard layouts:
(1) loading, (2) unloading, and (3) combined loading and unloading operations.
Simulation experiments based upon real-life yard operational data from Norfolk in
the United States of America. Results of simulation showed that the performance of a
non automated terminal can be substantially improved by automation using AGVs.
An additional finding was that the yard layout influences the terminal performance as
well as the number of AGVs. It is indicated that the combined operation can increase
the terminal throughput as well as the utilization of equipment in the yard.
2.2.6Branch and bound algorithms
Branch and bound algorithms are methods for global optimization in non-convex
problems. According to Lawler et al. (1966), a branch and bound algorithm searches
the complete space of solutions for a given problem for the best solution. The basic
concept underlying the branch and bound technique is to divide and conquer. Since a
large problem is difficult to solve directly, it is divided into smaller sub-problems
40
until these sub-problems can be conquered. The algorithm is applied recursively to
the sub-problems. If an optimal solution is found to a sub-problem, it is a feasible
solution to the complete problem, but not necessarily globally optimal. Branch and
bound algorithms have been applied successfully in container terminal operations by
several researchers. Peterkofsky et al. (1990) formulated the static allocation model
with the objective to minimize the weighted amount of time that ships spend at the
port. The branch and bound method determines the best possible ship departure
schedule. Dominance of infeasible solutions, boundary points, and construction of
the branch and bound tree were illustrated. Branching procedures such as node
selection, pruning and termination are explained with an example according to the
proposed methodology. In order to determine the feasibility, the set of constraints are
analyzed one by one. The feasibility of a set of constraints that have a capacitated
transportation problem structure is checked through solving a derivative maximum
flow problem by labelling algorithm. Computational performance of the method is
evaluated by ten problems of different sized ships.
Narasimhan et al. (2002) defined the problem of minimizing the time taken to load
and unload the containers from the container stack yard onto the ship as transtrainer
routing problem, where transtrainer is the dedicated equipment to load and unload
containers from/to trucks to/from container stacking yard blocks respectively. They
investigate the theoretical aspects of the problem and prove that the problem is NP-
complete. The problem is formulated as an integer program with the given load and
bay plans. The overall objective was to minimize the total setup and inter-bay
travelling times. A branch and bound based enumerative method was developed to
obtain an exact solution to the problem. The properties of optimum solutions and
related proofs of lemmas are given. The problem is decomposed into enumerating the
degenerate solutions and then arranging the partial sequences in the degenerate
solutions to obtain final route for transtrainer. Several lower bounds to prune the size
of tree were also developed.
41
2.2.7Heuristic models
The other alternatives that can be used for container terminal problems are heuristic
techniques. By their nature, heuristic approaches are flexible regarding the nature of
the objective function and constraints. As shown inTable 2.5, heuristics models
covers several techniques including greedy algorithm, simulated annealing
algorithms, tabu search, genetic algorithms, etc. Greedy algorithm (GA) has been
discussed in details in chapter 3 as it has been applied for optimizing container
terminal operations in this research work.
2.3 Literature review of container terminal processes:
As mentioned in chapter 1, container terminal operations can be divided over various
processes, starting from the arrival of the ship until the departure of the container to
its final destination. Container terminals can be classified into two: automated and
non-automated.
Figure 2.19 View of container terminal.
Automated terminals are preferred in areas where manpower is costly such as the
western Europe and the United States. Non-automated terminals operate in Southeast
Asia, where labour is less expensive. Figure 2.19 represents the basic structure of the
container terminals. Steenken et al. (2004), Vis et al. (2003), and Henesey (2006)
provide an exhaustive overview of methods for the optimization of container
terminal operation operations and logistics. Various decision problems that arise at
42
container terminal can be categorized according to the time horizon involved as i)
strategic, ii) tactical, and iii) operational (Hax et al. 1984).
Strategic level includes long-lasting effect decisions on the terminal (covers
one to several years) concerning terminal layout, the choice of the handling
equipment, and procedures.
Tactical level includes mid-term and short-term decisions (once every week,
every month or once every quarter) regarding which types of equipments are
used and which layout is chosen.
Operational level involves short-term decisions regarding daily and real-time
operations (berth allocation, quay crane scheduling, scheduling routing and
loading unloading of trucks, ship stowage), landside operation (transfer
operation, yard management), and human resources management.
A review of general classification of various decision problems addressed for
container terminal processes are given in the subsequent sections
2.3.1Arrival of containers
Containers arrive at the ports by different means of transportation such as ships,
trucks, and trains. At the strategic level, when ship arrives at the port, it has to moor
at the quay side of the port. As there are a number of available berths, a decision has
to be made to specify the number of berths that should be allocated to the ship. At the
operational level, berth allocation can be done with the objective of maximizing the
berth utilization. Logically when ship arrives at the terminal, assigning it to the
available berth can be done by first arrived first served rule. However, this strategy
may not be good especially when ship's handling time depends on the assigned berth.
In Berth Allocating problem, ships are allocated berths closest to the stacking area
where most containers for these certain ships are located. In this way, the sum of the
waiting and handling time of the ship can be minimized. This problem is equivalent
to a machine scheduling problem (e.g. Lawler et al., 1993 and Brucker et al.,
2001).
43
Edmond et al. (1978) used a queuing model for decisions on investment in berth
construction and cargo handling equipment, and evaluated simple queuing models
for container service. The objective of berth planning by evaluation of congestion
and cost as suggested by Nicolau (1967) is to arrive at an optimum port capacity
while incurring minimum capital cost. Thus, many container terminal managers are
keen to minimize turn-around time with the resources that are available to them.
According to Imai et al. (1997), Imai et al. (2001) and Nishimura et al. (2001)
several versions of BAP are possible. (i) In static BAP, it is assumed that at the
beginning of the planning horizon all ships have already arrived in the port. In this
case, at a specific berth where the ships are to be handled, there is no idle time
between them. The problem can be formulated as two dimensional assignment
problem, which can be solved as polynomial time problem see (Ahuja et al. 1993).
(ii) In dynamic BAP, it is assumed that more than two ships may arrive during the
planning period which makes it difficult for the problem to be solved using
polynomial time anymore. Imai et al. (1997) investigated static BAP under multiple
objectives. Not only the sum of the waiting and handling times of the ships are
minimized, but the ship's dissatisfaction that arises from the berthing order is also
investigated. The multiple objectives are handled by using the weighting method,
which reduces the multiple objectives into a single one. The set of non-inferior
solution is identified by varying the weights. In the dynamic BAP based on a MIP
formulation. Imai et al. (2001) developed a Lagrangian relaxation which was solved
using the sub-gradient method. An application of genetic algorithm to dynamic berth
assignment has been presented by Nishimura et al. (2001) and Cordeau, et al.
(2005) considered both static and dynamic BAP. Two tabu search heuristics are
presented and tasted on realistically generated instances (up to 35 ships and 10
berths), derived by a statistical analysis of traffic and berth allocation data of the port
of Gioia Tauro in Italy. The terminal plans to incorporate the heuristics in its decision
support system in the near future.
44
2.3.2Loading and unloading of containers
At strategic level, quay cranes are often used to load and unload containers from a
ship. Thus the determination of the type of material handling equipments is the
decision involved at this level. At the tactical level, the determination of the number
of QCs that have to work on a ship is the decision involved here. Such a problem is
known as the crane scheduling problem, which can be visualized as a project
scheduling problem. In the crane scheduling model, machines (cranes) work to finish
independent tasks (holds) but the objective function value varies with the completion
time of full job (ships). Daganzo (1989a) provides a description of a static
scheduling problem where a number of quay cranes have to serve a number of ships
such that the delay costs of the ships are minimized. An MIP is given for this
problem, which is only solved for small problems by direct enumeration.
Furthermore, a heuristic procedure is designed which is based on following crane
scheduling principles:
Principle 1: a crane should not be idle if there is some work it can do.
Principle 2: if cranes work on a ship, at least one of them should work on "maximum
hatch" The maximum hatch of the ship corresponds to the hold that requires the most
crane time to be finished.
Principles 3: Assume that when the first hold of a ship is about to be assigned, h
crane-hours are available before time t (the latest departure time of the ships already
assigned).
Daganzo (1989b) studied the effect of crane operations on ship service at port
terminals. In the first step, a simple, approximate approach to calculate the maximum
berth throughput during periods of congestion was proposed. The approach then
examines the effect that two extreme crane operating strategies have on ship delay,
when the traffic level does not exceed the maximum throughput. This is done for an
idealized situation designed to highlight the impact of crane operations while
admitting closed-form solutions. The average ship delay can vary considerably with
the crane operating strategy. Peterkofsky et al. (1990) considered the minimization
of the total delay of ships as the objective function. The problem is decomposed into
45
two stages, namely finding the best departure schedule for the ship and finding a
crane allocation scheme. A branch and bound method was used to solve the static
case of crane scheduling problem.
At the operational level, a decision has to be made to prepare the unloading and
loading of containers. The unloading plan indicates which containers are to be
unloaded and where they are on the ship. Contrary to the unloading process, loading
process is hardly flexible. A loading (stowage) plan indicates for each container
where it is to be placed on the ship. Containers with same destination, weight, size,
content and so on, belong to the same category .Wherein making stowage plan
attention has to be made to find out the sequence in which containers have to be
unloaded. In general the unloading and stowage plans seek to minimize the number
of unnecessary movements to be performed on the ship. According to Shields
(1984), the containers, that will be stowed, have to satisfy a variety of constraints,
which arise as a result of physical limitations of the ship, the containers and the
sequence in which port are visited by ship. The stowage problem is solved with
Monte Carlo method (see Metropolis et al. 1949). Many different possible ships
loading are generated and the most different one is given such that re-handlings are
avoided to a large extent, physical limitations are met and unloading and loading
time is minimized. Wilson et al. (2000) presented a very realistic model, taking into
account all technical restrictions in order to arrive at a commercially usable decision
support system. The approach by Wilson et al. (2000) is based on decomposing the
planning process into two sub-processes, namely a tactical and operational process.
The first process assigns containers with the same characteristics (size, port, etc.) to
blocks of storage space in the ship. The second, assigning a specific container to
specific location in the blocks that determined in the first process. Branch and bound
is used to assign the containers to the blocks in the ship. In the tactical planning
process, packing heuristics together with Tabu Search are used. Avriel et al. (2000)
discussed the container ship stowage problem, its complexity, and connection to the
coloring of circle graphs. The shifting of containers on board is defined as the
temporary removal from and placement back of containers onto a stack of containers.
For instance, if a container placed on a vertical stack has a destination of j, while the
46
containers stacked on it have destinations further than j, the latter containers should
be shifted. Although shifting cost could be considerable for large ships, container
stowage placement decisions are based on port operations efficiency and ship
stability, but not enough attention has been given to minimize the number of shifts
for a particular route. Avriel et al. (2000) showed that the problem is NP-complete,
where a polynomial time algorithm for single column case exists. Also, they derive
upper and lower bounds on the number of columns for which a plan can be found in
polynomial time that will result in zero shifts. Further, they show that finding the
minimum number of columns for which there is a zero shifts stowage plan is
equivalent to finding the coloring number of circle graphs. Avriel et al. (1998)
proposed a binary linear programming formulation to solve the problem of stowage
planning such that the number of unnecessary moves is minimized. It is shown that
the stowage planning problem is NP-hard. Therefore, also a heuristic is developed
for solving the problem.
Figure 2.20 (a) Single cycling unloading (b) Double cycling unloading and loading.
Goodchild et al. (2004) described the double cycling technique that can be used to
improve the efficiency of quay cranes by eliminating some empty moves instead of
using the current method, where often all relevant containers are unloaded from the
ship before any are loaded (single cycling). In double cycling, containers are loaded
and unloaded simultaneously (see Figure 2.20). A solution for this problem has been
presented through simple formulae to determine reductions in the number of
operations and the operating time.
47
Ambrosino et al. (2006) proposed a model for the Master Bay Plan Problem
(MBPP) where the main goal is the minimization of the loading time of all
containers, given that all other ship movements have fixed and known duration. The
authors propose a three phase algorithm based on partitioning procedure of the ship,
an assignment phase of containers to ship portions and heuristic algorithm. They also
propose methods to check and validate the ship stability of the overall stowage plan.
Imai et al. (2004) presented a multi-criteria optimization method to the ship stowage
problem which takes into account two contrasting objectives: the ship stability and
the number of container re-handles. The authors propose a multi-objective integer
programming model and they implement a weighting method to come up to a single
objective function. Computational experiments for instances with up to 504
containers are provided. Sciomachen et al. (2006) formulate the MBPP as a three-
dimensional bin packing problem and present a heuristic solution method which is
based on this relation. Objectives are to minimize the total loading time as well as to
efficiently use the quay equipment. The approach is validated by using real test cases
from the port of Genova (Italy).
2.3.3 Transport of containers from quayside to stack and vice versa
At strategic level, several types of equipment could be used (e.g. truck, straddle
carrier, AGV) to transport containers from quayside to stack and vice versa. One of
the decisions here concerns with the type of material handling equipment, which take
care of the transport of containers. According to Baker (1998) the use of straddle
carriers instead of non-lifting trucks improves QC productivity. For the transport of
multiple containers, multi-trailer systems can be used (see Error: Reference source
not found). This system, in this figure, uses a truck that pulls five trailers, each
capable of carrying 2 TEU.
After deciding which system will be used tactical decision entails determining the
necessary number of material handling equipment needed to carry out day to day
operations. Steenken (1992) developed an optimization system to determine the
number of straddle carriers and their route. Because of the fact that the system had to
be implemented into a radio data transmission system, it had to fulfil the conditions
48
of a real-time application. The problem is solved as a linear assignment problem.Vis
et al. (2001) presented a model and an algorithm to determine the necessary number
of AGVs at an automated container terminal. To solve the problem a network
formulation was presented.
At the operational level it should be decided which vehicle transports which
container and which route is chosen. The objectives are to minimize empty travel
distances, delay of ships, or total travel time of the vehicles. A complete review of
the routing and scheduling of vehicles in general is given by Bodin et al., 1983 and
by Steenken (1992). Steenken et al. (1993) described the more specific problem of
the routing of straddle carriers at the container terminal. The objective is to minimize
empty-travel distances by combining unloading and loading jobs. Routing and
scheduling systems are tested and integrated into a radio data transmission system of
a real terminal. Steenken (1992) obtained savings of 13% in empty drives compared
with the previously existing situation at the terminal, by solving the problem as a
linear assignment problem. Steenken et al. (1993) solve the problem by formulating
it as a network problem with minimum costs. Savings of 20–35% in empty-travel
distances can be obtained within acceptable computation times.
Bish et al. (2001) considered the truck dispatching problem in a container terminal.
They model both the loading and unloading of the ship by a quay crane which is
serviced by a fleet of identical trucks. Their model attempts to minimize the
makespan to complete the entire loading and unloading operation. It was shown that
the problem was NP-hard. Bish (2003) extended this study to examine the problem
of determining a storage location for each discharging container, dispatching vehicles
to containers, and scheduling the discharging and loading operations of quay cranes
to minimize the maximum time needed to serve a given set of ships. The problem
also was shown to be NP-hard and they proposed heuristic algorithms to solve it.
Kim et al. (1999a) discussed dispatching containers to AGVs so as to minimize the
delay of the ship and the total travel time of the AGVs. MIP formulations and a
heuristic method for such a problem is given with numerical experiments. Kim et al.
49
(1999b) investigated the single transfer crane routing problem. They focus on the
minimization of total handling time of transfer crane at the container storage yard by
determining the optimal number of containers to be picked up at each yard bay as
well as the optimal route of the transfer crane. Their modelling approach and optimal
algorithm is applied without major changes to the straddle carrier routing problems
for single and multiple carrier cases as illustrated below. Kim et al. (1999c)
discussed the optimal routing of single straddle carrier, which is the frequently used
transhipment equipment in port container terminals. They propose a MIP model with
the objective of minimizing the total travel time of the straddle carrier and investigate
the properties of optimal solutions to devise a solution procedure. The solution
procedure is decomposed into two stages. In the first stage, the number of containers
to be picked up during a sub tour is determined. In the second stage, the visiting
sequence of yard bays by the straddle carrier is found. Their solution procedure could
be summarized as follows. First, with respect to a set of transportation model
constraints involved in MIP model all basic feasible solutions are generated. Then
the set of basic feasible solutions subject to the whole constraints is constructed by
enumerating the solutions found in the first step. Next, the routing problem is solved
by dynamic programming according to the solution set found in the second step and
the least cost route is selected.
2.3.4Stacking of containers
As already mentioned in chapter 1, there are two ways of storing containers can be
seen in the container terminal, storing on the ground and stacking on chassis. The
stack as shown in Figure 2.21 is an area in the terminal where import and export
containers can be stored for a certain period. The stack covers the major part of the
terminal and it is used for temporary storage of containers, it can be divided into
blocks, each consisting of number of rows, as per terminal the stack's height varies
between two to eight storey high (Cools, 2005). A transfer point at end of each lane
is situated; at this point the crane unloads - loads the container off/on the truck that
transports the container. Empty containers are usually stored in separate area.
50
Figure 2.21 Yard crane and a container block
To stack and retrieve containers, several types of equipment could be used (e.g.
gantry yard crane, reach stacker, top loader, etc). At strategic level one decision is
how to choose the material handling equipment which is best suited for the stack
layout. Another strategic decision which affects greatly the efficiency of stacking is
the stack layout itself. The stack height and strategies for storage and retrieval of
export and import containers are the factors involved in determining the stack layout.
Chen, (1999) described various storage strategies. At the stack, reaching to
demanded container it is necessary to move the containers that are placed on the top
of it. Reshuffling and removing the containers at the idle time, leads to minimize the
delay. Chen (1999) presented a systematic approach to the terminal system which
provides a cornerstone for the empirical study of the terminal operations. Using the
approach presented by Chen (1999) several factors such as terminal management
strategy, shortage of storage capacity, poor quality of container information received,
operational rules, higher container storage which influence operational efficiency and
cause `unproductive container movements’ can be taken into account. Chen (1999)
concluded that improvement of all surrounding conditions has to be carried out to
achieve higher stacking.
Chung et al. (1988) proposed the idea of using a buffer area where the number of
empty chassis is available to store export containers temporarily. They developed
and tested strategies that can reduce the unproductive movements of the stack crane
51
during the loading process and as result reduce the total container loading time. They
developed a simulation model to investigate the effect of buffer area on the port
operation. A reduction of 4% in the loading time can be obtained by utilizing the
buffer area. De Castilho et al. (1993) concluded that for a good configuration of the
stack area, the amount of handling effort required to retrieve a container from the
stacks depends on stack heights and on the operation strategy used. As a result, it is
possible to trade off extra handling effort for higher stacking against space
requirements. Moreover, the best operating strategy can be selected for the chosen
configuration.
Kim et al. (1999d) examined the storage space allocation problem with stack height
and allocation space as the decision variables. The objective was to minimise the
number of reshuffles under the condition that the space requirements are met. First,
the case in which import containers arrive with a constant arrival rate is observed.
The stack height and the amount of space are decision variables. It was concluded
that the optimal height of the stack equals the total number of import containers
during the length of the planning horizon divided by the total number of available
locations in the stack. Secondly, it is assumed that the arrival rate of import
containers follows a cyclic pattern with the period of one week. Thirdly, the case in
which the arrival rate of containers varies in an irregular way on a rolling horizon is
observed. Both problems can be solved by formulating a linear program model. The
solution can be obtained by solving the dual problem and related sub-problems by
applying the sub-gradient optimization technique. The problem is solved for different
cases by determining firstly a formula representing the relationship between the stack
height and number of re-handles and secondly by determining methodologies based
on Lagrangian relaxation.
Taleb-Ibrahimi et al. (1993) obtained results for long-term and operational
planning. They discuss space allocation and storage strategies for export containers.
Given the vessel arrival patterns and workloads they find space requirements. The
minimum amount of storage space needed is determined at the strategic level. At the
operational level, the problem of minimising and predicting the amount of work is
52
discussed. Models are given that reflect the relationship between available handling
effort, storage space and traffic demand.
Kim et al. (2000) discussed the problem of determining storage locations for export
containers with a certain weight with the objective of minimizing the expected
number of re-handles for the loading of containers on the ship. These re-handles
occur for example if containers are stacked on top of heavier containers, which, as
assumed by Kim et al. (2000), are needed first in the ship. A dynamic programming
model is formulated to solve this problem. For making real time decisions, a decision
tree is given, the performance of which is evaluated by comparing its solutions to the
solutions of the dynamic programming model. Maximally, 5.5% of the decisions
made with the decision tree are wrong. One of the decisions that have to be made at
the tactical level is the determination of the number of transfer cranes necessary to
ensure an efficient storage and retrieval process.
Lee et al. (2006) address a yard storage allocation problem in a transhipment hub
with the objective of reducing re-shuffling and traffic congestion. They proposed a
mixed integer programming model to minimize the number of cranes needed to
handle the total workload. Two heuristics, a sequential method and column
generation algorithm, were proposed and tested on generated instances: Other
operational decisions include 1) determining which crane(s) should serve the ship
trucks (seaside) and which crane(s) should serve the road trucks (landside), 2)
determining where to store export containers, and 3) determining the order in which
ship and road trucks are served.
Ng et al. (2005) studied the problem of scheduling a yard crane to perform a given
set of loading/unloading jobs with different ready times. The objective was to
minimize the sum of job waiting times. A branch and bound algorithm was proposed
to solve the scheduling problem optimally. Efficient and effective algorithms are
proposed to find lower bounds and upper bounds. The performance of the proposed
branch and bound algorithm is evaluated by a set of test problems generated based on
53
real life data. The results show that the algorithm can find the optimal sequence for
most problems of realistic size.
2.3.5 Inter-terminal container transport
Inter-terminal container transport (ITCT) means that containers have to be
transported from the stack to other modes of transportation, like barges, rail and road.
In future, there is likely an increased need for container transport between the various
modalities (rail, road, barge, sea),, Also, the transport between these modalities and
other service centres (empty depot, DistiParks) will increase. Kozan (1997a)
developed an analytically based computer simulation model to describe the container
process at a rail container terminal. The major factors influencing the throughput
time of containers, which is a function of cranes, stackers and transfer systems, are
discussed by Kozan (1997a). The simulation model is combined with heuristic rules
to describe the progress of containers in the system. Firstly, a cyclic heuristic rule is
used to assign handling equipment to trains. This rule selects the first available
resource beginning with the successor of the last resource seized. As a result,
workloads are balanced and utilisation of handling equipment and throughput are
higher. Secondly, a new heuristic rule is developed to dispatch trains to tracks. When
a train enters the system there may or may not be a queue for the tracks. If there are
no free tracks, the train will join the queue. Otherwise, the system sends trains first to
track 1 and then to track 2 or 3 if they become available for track 1 and if they
minimise total throughput time. In case more than one track is used, the train with the
fewest number of containers will be unloaded first. A simulation model is developed
by using data from a terminal in Australia. Due to cyclic train schedules a weekly
simulation period was used.
Bostel et al. (1998) studied the allocation of containers on trains. Different models
and solution methods are presented and tested on realistic data. It can be concluded
that the number of container moves and the use and quantity of equipment can be
minimized. Ballis et al. (1996) developed a simulation model that can be used in the
design and evaluation of terminal facilities at the landside. Five heuristics are
incorporated in the model to investigate the performance of the system. To obtain a
54
realistic model, experiences of operations managers are included in the model. The
comparison between different studies indicates that a shorter truck service time is
feasible but this leads to an increase of traffic conflicts in the internal transport
network.
2.3.6Complete container terminals
In previous sections, problems for individual types of material handling equipment
are discussed. Within a container terminal it is obvious that in order to obtain an
efficient terminal, it is also necessary to address all problems in an integrated
manner. The methods and algorithms obtained by optimising the single processes can
be used as a base to the optimisation of processes in the entire terminal.
Gambardella et al. (1998) showed how operations research techniques can be used
to generate resource allocation plans. These plans can be used by terminal managers
to determine the best management strategies. Ramani (1996) develops an interactive
planning model to analyse container port operations and to support its logistics
planning. It is assumed that all unloading operations are completed before loading
operations are started. In the simulation model of Yun et al. (1999) an object-
oriented approach is used. The performance of a simple model, in which many
design parameters affecting the performance are changed, is observed. A decision
support system for the capacity planning of container terminals has been developed
by Van Hee et al. (1988). Several mathematical models, each describing parts of the
complete process, are incorporated in this system. The system can support decisions
at the strategic and tactical level. Kozan (1997b) compared analytical and simulation
planning models for a complete terminal. It was stated that containers arrive at the
seaside in batches, namely on the ship, and not alone. Consequently, a batch-arrival
multi-server queuing model is developed and compared with a simulation model.
The results of this comparison indicate that, at a 95% level of significance, there
exists little difference between the models. However, before implementing the
analytical model, long-term data collection is necessary.
55
Kozan (2000) examined the problem of minimisation of handling and travelling
times of import and export containers from the time the ship arrives at the port until
the time they are leaving the terminal and vice versa. The complete trajectory that
containers go through from the ship to road or rail terminals via storage areas is
included into a network model. Improvements in operational methods are not
incorporated in this model. The objective of the model was to minimise total
throughput time. The model is, however, subject to several constraints. Firstly, the
expected number of containers moved from node i to node j in a time interval larger
than or equal to the minimum amount of containers required in node j within this
time interval. Secondly, space constraints at node j should be met. Further, the sum
of containers moved to each section of the stack should equal the total number of
containers moving into the stack. Also, the sum of containers moved into the stack
should equal the sum of containers moved out of the stack. The incoming flow in
each node should equal the outgoing flow of containers. Finally, the total number of
containers moved should equal the number of containers unloaded from the ship and
no more than the maximum number of equipment available is used. It is shown that
the expected number of moves per container is the average of the maximum stack
height and the minimum stack height. It is explained that this model can be used as
decision tool in the context of investment appraisals of multimodal container
terminals.
56
3. Container Terminal Operations
3.1 Operations at Singapore port
The port of Singapore handled more than 182 million tonnes of cargo in 2007
thereby occupying first rank in the world in terms of throughput, Through continual
infrastructure development and growth in world trade, Singapore has become the
port with the largest container throughput in the world (Chou, 2002 and Singapore,
2009). Singapore has unique geographical position in the terms of having natural
deep water harbour. No other port in the South East Asian region is close to
Singapore in terms of number of ship calls and containers handled. The Port of
Singapore holds the title of world’s busiest container port. The port is set to grow by
12.5% in the year 2008 bringing the total throughput of the port up to 29, 918, 20
TEUs. This growth is largely due to the influx of intra-Asia and Asia-Europe trade.
2001 2002 2003 2004 2005 2006 2007 20080.00
5,000.00
10,000.00
15,000.00
20,000.00
25,000.00
30,000.00
35,000.00
15,571.1016,940.90
18,410.50
21,329.10
23,192.20
24,935.20
27,935.50
29,918.20
container throughput at singapore
Throughput
Year
TEU
s
Figure 3.22 Container throughput at Singapore
Singapore’s strategic location has made it a giant in the shipping industry. 20% of the
world’s transhipment trade passes through the Port of Singapore. In 2007,
transhipments accounted for 5% more than the total of imports and exports of
Singapore. It can be seen from Figure 3.22that the throughput has increased from
15,571.10 TEUs in the year 2001 to 29,918.20 TEUs container in year 2008.
57
The Port of Singapore is one of the busiest ports in the world serving more than 500
shipping routes, and connecting over 700 ports world-wide. The port typically
handles 800 ships on site at any one time.
Table 3.6Characteristics of Singapore Container Port (2007)
Ports/Terminals
Number of Berths
Number of Terminals
GantryCranes
Terminal Area (acre)
Yard capacity (TEUs/day)
Singapore 54 4 118 8 38 75,000
Table 3.6 shows the characteristics of Singapore container port in terms of
throughput, number of berths, terminals, and gantry cranes, terminal area, and yard
capacity (Singapore, 2007). There are four terminals in Singapore; namely Tanjong
Pagar, Keppel, Brani, and Pasir Panjang. In order to handle continuous growth, the
Port of Singapore is in the process of automating the cargo handling process within
its terminals, The Port has developed integrated technology systems and software to
facilitate electronic transfer of trade data and vessel clearance. This has encouraged
international carriers and ship-management companies to set up regional offices in
Singapore. The Port of Singapore Authority (PSA) has become an international
identity in container stevedoring with representation in several major ports including
Italy, China and Belgium.
The Port of Singapore manages the highest volume of containerized cargo than any
other port in the world. Due to technological advances that are utilized within the
Port of Singapore, greater volumes of cargo are able to pass through the Port of
Singapore. The port of Singapore Authority has been investing over $7 billion to
develop 26 berths over four phases at Pasir Panjang Terminal. When fully developed,
the state-of-the-art Pasir Panjang Terminal will be able to handle 36 million TEUs a
year. The terminal has the world’s first remotely operated Bridge Cranes which will
speed up container handling in the yard and further maximise yard utilization by
stacking containers nine storey high. Built by a consortium comprising Mitsui
Engineering and Shipbuilding and Keppel Engineering, these cranes will
substantially boost worker productivity, by enabling each crane operator to manage a
58
number of cranes. The Pasir Panjang terminal can handle an average of 750,000
TEUs a year, 25% more containers than PSA’s other terminals; and one operate can
operate several cranes.
In order to overcome the growing shortage of skilled labor and improve productivity
the Port of Singapore Authority (PSA) is considering the design of the most
advanced automated terminal system. PSA plans to operate hundreds of AGVs under
a sophisticated traffic management schedule for container movements. A contract for
5 prototype AGVs was awarded to Kamag of Germany and Mitsui of Japan. The
vehicles were designed to be able to accelerate from 0 to 5 mph in under 10 seconds,
with the top speed of 15.5 mph – loaded or unloaded. They can accept either 20- or
40-foot containers with 50 tons maximum payload and can operate independent of
the weather conditions. The pilot AGV system started in the late 1994 at Brani
Terminal and was completed in 1997. In May 1998, PSA signed another agreement
for the phase II program to develop and test AGV systems for container terminal
operations. The completion date for phase II is scheduled for 2002. It is expected that
with the use of AGVs each berth will be able to handle 25% or more containers that
the PSA currently handles.
3.2 Operations at container terminals in India
Indian Railway's strategic initiative to containerize cargo transport put India on the
multi-modal map for the first time in 1966. Since then, India has made good progress
in container transportation facilities. Given the continental distances in India (almost
3,000 km from North to South and East to West), rail transport is seen as cost
effective option for all cargo over medium and long distances, especially if the cost
of inter-modal transfers could be reduced (KPMG, 2007). Containerized multi-
modal door-to-door transport provided the ability to deliver variety of cargo at the
doorstep at the clients. Though the first ISO marine container had been handled in
India at Cochin as early as 1973, it was in 1981 that the first ISO container was
moved inland by the Indian Railways to India's first Inland Container Depot (ICD) at
Bangalore, also managed by the Indian Railways. Expansion of the network to 7
ICDs by 1988 saw the increase in the handling of containers, and along the way, a
59
strong view had emerged that there was a need to set up a separate pro-active
organization for promoting and managing the growth of containerization in India.
Presently, containerized cargo represents about 30% by value of India’s external
trade, and this proportion is likely to grow as containerization increasingly penetrates
the general cargo trades and increases its share from the current 68% to levels that
are comparable to international levels. With increased penetration, and growth in
India’s trade, container traffic is projected to grow from 4.5 million TEUs per annum
in 2005 to around 21 million TEUs by 2015 (World Bank, 2007). There is a
movement of 30 percent of EXIM containers by rail, and the remaining is transported
by road.
3.2.1Container corporation of India
Container Corporation of India (CONCOR) is a public sector was set up in March,
1988 with the objective of developing multimodal logistics support for India’s
international and domestic containerised cargo and trade. Its operations are directed
towards efficient, economical and expeditious handling and transit of containerised
goods by rail through India. Although more than 90 per cent of its inland transport
service is by rail. Road and coastal shipping services are also provided according to
the market demand. The company`s core business is characterized by three distinct
activities that of a carrier, a terminal operator, and a warehouse operator. The
company provides a single-window facility coordinating with all the different
agencies and services involved in the containerized cargo trade right from customs,
gateway ports, and railways, to road haulers, consolidators, forwarders, custom house
agents and shipping lines. It has value-added services like linking of road or short
lead rail shuttle services to long lead point-to-point train services (hub and spoke
services), integrated freight terminals, coastal shipping, transportation of perishable
products from source to end-user, and total logistics solutions.
CONCOR terminals are equipped with the most modern, sophisticated and state of
art cargo and container handling equipment like rail-mounted gantry crane (RMGC),
tyred mounted gantry crane (RTGC) and loaded and empty handling reach stackers.
Besides, it has over 5,200 state-of-the-art high-speed bogies, low-height container
60
flat-wagons in service. The company has a total of 57 terminals, of which 48 are
export-import container depots, and there are nine exclusive domestic container
depots. The customs bonded inland container depots are dry ports in the hinterland
and serve to bring all port facilities including customs clearance to the customer`s
doorstep. Till 2005, CONCOR was a sole service provider for rail transportation of
containers The Company has a large fleet (about 8,000) of owned and leased
containers. These are not just general purpose boxes, but include various special type
of containers such as tank containers, open tops, high cube 22ft. containers etc. to
facilitate the carriage of all types of cargo. Over the years, CONCOR has diversified
into several container logistics activities. It has recently partnered with Maersk for
taking up the construction of third container terminal at the Jawaharlal Nehru Port at
Nhava Sheva in Mumbai.
3.2.2Financials
Container Corporation of India registered a 24% growth in net profits to Rs 1,692.40
million for the quarter ended March, 2007 from Rs 1,362.20 million for the quarter
ended March, 2006. Net sales rose 18.74% to Rs 8,081.20 million for the quarter
ended March, 2007 compared with Rs 6,805.60 million for the quarter ended March,
2006. Total income rose 18.12% to Rs 8,229.5 million in the quarter ended March,
2007, from Rs 6,967.1 million for the quarter ended March, 2006. The earnings per
share (EPS) of the company stood at Rs 26.04 in the quarter ended March, 2007.
Container Corporation of India Ltd Company has posted a net profit of Rs 2018.336
million for the quarter ended June 30, 2008 as compared to Rs 1870.923 million for
the quarter ended June 30, 2007. Total Income has increased from Rs 8134.720
million for the quarter ended June 30, 2007 to Rs 8681.145 million for the quarter
ended June 30, 2008.
CONCOR recorded 16.5% rise Year on Year (YoY) in throughput to 618,534 TEU
led by strong growth in domestic volumes at 38.3% YoY to 113,786 TEU. For the
first time in six years, the company has recorded such high growth in domestic
throughput. This is mainly due to premium service of dedicated rakes, that is,
running point to point schedules. Also, an increase in the share of non-bulk cargo
61
triggered an increase in containerization, boosting domestic volumes. On the other
hand, EXIM volume grew by 12.6% to 504,748 TEU, below the expectations mainly
because the company ran empty rakes due to unfavourable import export mix. This
will continue due to appreciation of rupee affecting exports. CONCOR has started
giving lucrative discounts for export volumes to combat higher empty rakes.
3.2.3Physical performance
Company's operations have seen the traffic grow from a level of total 594118 TEUs
in 1995-96 to 2105266 TEUs in 2006-07.where the international traffic have grown
from 349141 TEUs in 1995-96 to 1715661 TEUs in 2006-07 and domestic traffic
have grown from 244977 TEUs to 389605 TEUs in 2006-07. Total traffic handled by
CONCOR, separately for international and domestic streams, during the last decade
clearly brings out the success story of CONCOR's growth as shown in Figure 3.23
(see Raghuram, 2007).
1995
-96
1996
-97
1997
-98
1998
-99
1999
-00
2000
-01
2001
-02
2002
-03
2003
-04
2004
-05
2005
-06
2006
-07
0
500000
1000000
1500000
2000000
2500000
Total Traffic Handeld at CONCOR(TEUs)
International
Domestic
Total
Year
tota
l Tra
ffic (
TEUs
)
Figure 3.23 Total traffic handled at CONCOR terminals
62
3.3 Case study at ICD, Tughlakabad, New Delhi
The ICD Tughlakabad is the largest dry port in South Asia and the leading centre for
importers and exporters of the Northern Region of India. This ICD began functioning
at Tughlakabad, New Delhi in 1993. It is situated near Okhla Industrial Area and is
spread over 44 hectares of land. It has three storied administrative block that houses
Offices of Customs, CONCOR, Bank, and Shipping Lines. Four full length rail lines
are available in the customs area which brings the containers by train from Gateway
ports such as Mumbai, Nhava Sheva, Chennai, besides bringing the containers by
road from other ports such as Haldia, Calcutta and Kandla,
A part of CONCOR terminal at Tughlakabad is shown in Figure 3.24, it can be seen
that there are four rail tracks available out of which three are shown loaded with
trains. Gantry cranes, shuttle trucks, and a part of the storage yard are also shown in
Figure 3.24. Details of equipments and facilities available at CONCOR are given in
the next section.
Figure 3.24 ICD, Tughlakabad, New Delhi
63
3.3.1Facilities and Equipment
ICD, Tughlakabad as shown in Figure 3.24 is equipped with most modern facilities
and it has the following infrastructure facilities for operations located inside the
custom bonded area (CONCOR, 2007).
4 full train-length rail lines can serve full loaded trains with 45 wagons ( the
wagons used here is high speed bogie container flat wagons)
6,000 square meters. covered warehouse space for imports which is sufficient
to accommodate cargo of 160 TEUs
110,000 square meters covered warehouse space for export cargo which is
sufficient to accommodate a cargo of 240 TEUs
1,500 square meters of especially reserved space for LCL consolidation.
Open space for stacking of 5,000 loaded containers
Open space for stacking 6,000 empty containers.
Six hectares parking area to accommodate 400 trailers
Fully computerised import and export documentation
Administrative building of 8,000 sq. mtrs. of built up area housing officers of
CONCOR, customs, bank, shipping lines, CHAs, surveyors, transporters,
Business Centre, etc.
Computerised weighbridge facility
Container repair facilities
Two rail mounted gantry cranes each of capacity of 40 tonnes service at the
rail side
Three Rubber Tier diesel powered Gantry Cranes each with a capacity of 40
tonnes service at the yard side
Eight loaded reach stackers (40 tonnes)
Six empty reach stackers (16 tonnes).
25 internal trucks
With these ultra-modern facilities, ICD, Tughlakabad has developed into the largest
hub of multi-modal centre in the Indian sub-continent. Containers meant for ICDs:
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Patparganj, Faridabad and Gari Harsaru are first brought at ICD, Tughlakabad by rail
and then transported to their respective destinations.
The traffic volume at lCD, Tughlakabad is increasing every year. With the increase
in volumes, the numbers of reach stackers/cranes are also likely to be enhanced.
CONCOR presently owns 3600 Containers. About 8000 containers are taken on
operation lease bringing the total population to about 12000. While acquiring new
containers, CONCOR is also replacing its old containers, which have either out-lived
their life or are beyond repair.
Figure 3.25 Schematic of ICD, Tughlakabad.
65
A schematic of ICD, Tughlakabad, New Delhi is shown in Figure 3.25.
3.3.2Loading-unloading operations at ICD, Tughlakabad
Containers arrive to the terminal by train and trucks, and are stored in the storage
area (yard side). The containers then leave the terminal by the same means to reach
their final destinations. Various operations at ICD, Tughlakabad can be divided into
three parts as follows.
3.3.3Rail Side operations
The rail yards are characterized by the number of available tracks for
unloading/loading, the distribution of load types processed and the rates of arrival for
trains and outgoing loads. A rail mounted gantry cranes provides an important
operation associated with loading and unloading trains. Approximately 7 to 8 trains
are loaded-unloaded in a day. Numbers of trains to be handled varies from time to
time (CONCOR, 2008). Each train consists of 45 Bogie containers flat wagons
(Hadi, 1998). The particulars of Bogie Container flat wagon can be seen in
Appendix B. Each train is described by a line that contains the transport mode, a
unique identity (ID), an arrival day and time, and the numbers of containers to be
loaded and unloaded. Then the attributes of all containers to be loaded and unloaded
follow, that is, a unique container ID, size, destination, weight, information on the
type (empty, refrigerated, dangerous content, oversized), as well as pick-up
information (which mode of transport will pick it up on what day).
Rail mounted gantry cranes are widely used in container loading and unloading. It is
built in the form of a bridge, supported by a trestle at each end. Its fixed horizontal
boom projects over trains being loaded or unloaded. Therefore RMGC works on the
offside of the containers being loaded/ unloaded at the rail siding and position them
in a way so as to be visible to the crane operator. For more technical information
about RMGC used in CONCOR see Appendix B. To unload a train the RMGC as
shown in Figure 3.26 picks up the containers from the train and put them on shuttle
66
trucks that move them to the storage yard in the terminal. To load trains the RMGC
unload containers from shuttle trucks and put them on the train.
Figure 3.26 Rail mounted gantry crane
A reach stacker is used to load unload container to/from trains. It has more flexibility
to move inside the terminal. There are several reach stackers that are being used in
ICD, Tughlakabad to load/unload containers, out of which four are owned by the
CONCOR while the rest are owned by different agencies.
Figure 3.27 Truck used for transhipment of containers
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Trucks as shown in Figure 3.27 are used for transhipment of containers. Each truck
has its own identity number and performs its task according to the available container
to be loaded and unloaded.
3.3.4Storage yard operation
In storage yard, the yard is divided into three parts. The first part is the main storage
area where shuttle trucks move containers from/to the rail side. The storage area has
5 blocks, and each block contains 7 rows and 72 columns except the first and the last
blocks which contain 4 rows and 72 columns, and 7 rows 70 columns respectively.
TMGC serve the main storage yard area as shown in Figure 3.28. Technical
information of TMGC are given in Appendix B. Containers can be loaded unloaded
reshuffled, and staked on the top each other up to 5 storey high. There are some
constraints which impose a sequence to be repeated in storing containers (e.g. size,
weight, port of distinction, series of distinctive characteristics such as hazard class
and the kind of goods transported).
Figure 3.28 Part of storage yard in CONCOR served with TMGC.
The second part consists of storage area for empty containers. It is divided into four
blocks each block consist of 5 rows and 25 columns, except the first block which
consists of 4 rows 6 columns. This part is serviced by reach stackers which can stack
68
containers to 4 storey high. The third part is used for temporary storage of containers
whenever necessary.
To enable online availability of data pertaining to container stacking, CONCOR has
installed a Management Information System (MIS) at ICD, Tughlakabad. As soon as
there is any change in the stack position, it is instantly fed to the computer server by
a Radio Data Terminal operated by the operational task force.
3.3.5Gate operation
At the gate of ICD, Tughlakabad, checking of all in and out containers and trucks is
done by a designated clerk. All the reservations and paperwork are checked at the
“gatehouse” which is a structure at the gate where the clerk inspects and clears the
entrance and exit of all containers and trucks.
3.3.6Summary of operations at ICD, Tughlakabad
The entire operations at ICD have been further divided into micro operations.
Analysis of control, operation and scheduling of container handling operations can
be summarized in Table 3.7. It can be seen that except container stock and booking
position, none of the operations are scheduled or planned using the real time
planning of logistics.
Table 3.7 Summary of loading/unloading operations at ICD, Tughlakabad
Activities Method of control/ operation/ scheduling
Arrival /Departure of container train Information submitted by communication system
Arrival/ departure of container carrier (input/ exit of container)
Information transmitted by communication system
Unloading activity Manually scheduled
Unloading from container train by gantry cranes
Manually scheduled, crane operation
Placing over the shuttle truck Crane operation
Movement of shuttle truck to stack position
Shuttle truck operation
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Direction to the shuttle truck operator to transfer the container to stack position
Manual indication to the shuttle truck operator
Unloading of the container from the shuttle truck to placing on the stack
Reach stacker operation, directed by information from MIS
Any mid course instruction to the truck driver
Delivered manually alone
Loading activity (nearly same as for the unloading)
Nearly same as for unloading
Stock inventory position of containers Available on MIS
Requirement of movement of a particular container
Available on MIS
Availability position of empty container Available on MIS
Custom position of a container pertaining to export/ import Container delivery requirement of client
Available on MIS
Container booking position for onward transport
Available on MIS
Survey and data updating - Gate in / Gate Out of containers / trucks at ICD,TKD
- Rail in / Rail out of containers at ICDITKD
- Internal shifting within the yard
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4. Mathematical Model Formulation
4.1 Introduction
This case study for this work is the inland container terminal (ICD) at Tughlakabad
in New Delhi. ICD, Tughlakabad is a dry port served by trains. The terminal consists
of a rail-side area where trains arrive, get serviced, loaded, unloaded and depart from
the terminal. There is a yard area, where containers are stored until they are
transported to their destination. The terminal handles a number of trains, and each
train is served by variety of equipments that load and unload containers onto and
from trains. Similarly, there are a number of yard cranes in the yard-side that load
and unload containers onto and from trucks. Most containers handled by the terminal
are of standard sizes (e.g. Table 1.3) and the containers are transported in the
terminal area using a fleet of trucks of unit carrying-capacity, each truck can
transport only one container at a time. With the use of MIS, the location of each
container in the terminal can be tracked.
4.2 Problem description
Typically, there are large numbers of containers to be loaded onto or unloaded from
Trains everyday in a terminal. On an average, 7-8 trains arrive to the terminal
everyday to unload 500- 600 containers. The containers are then required to be
loaded to transport them to their destination. Throughout the container handling
operation, trucks, RTMG and YCs need to be available to ensure a continuous
container flow. A truck that finds the RMGC/TMGC at its job location busy with
handling containers for other trucks will join the rail-side crane queue and wait until
the crane becomes available to serve it. Similarly, a RMGC/TMGC that does not find
a truck assigned with a job parking under it will be idle until a truck arrives with a
service request.
In order to reduce terminal turnaround times, it is of utmost importance to ensure an
efficient and effective transportation of containers between the rail-side and the yard-
71
side using a fleet of trucks. A gain in terminal productivity cannot be necessarily
achieved by increasing the number or the speed of trucks operating in the terminal.
This is because the possibility of congestions in the terminal increases with the
number of trucks operating at higher speeds. At the same time, if less number of
trucks are used then it would results in idle cranes. Therefore, an efficient and effective
scheduling mechanism is needed to schedule containers on trucks using some principles
to minimize unnecessary truck waiting times and cutting down capital investment and
operating costs. This can be efficiently achieved by minimizing the makespan.
Similar scheduling problems in container terminals have been analyzed by various
researchers (for example, Bish et al. 2001; Li et al. 2004; and Nishimura et al.
2005). These researchers focused on a class of truck dispatching rules called the
vessel-based truck dispatching policy in which a fleet of trucks is usually assigned to
a specific vessel until their work is completed.
One major issue in terminal planning is how to determine the sequence of containers
to be handled on a fleet of trucks. This sequencing decision affects the operation
efficiency of both the rail-side and the yard-side to a large extent .Unnecessary truck
waiting time would lead to a longer terminal turnaround time. .A few hours before
arrival of an incoming trains the terminal receives detailed information about their
contents; i.e., containers that are to be unloaded into the yard, as well as the list of
containers currently in the yard that should be uploaded onto the trains. This
information allows the terminal dispatchers to generate so-called container sequence.
It is no surprise that managing, controlling and operating such system is a very
complex phenomenon. At the operational level the question is how trucks con be
routed in this complex system, in which mechanism should trucks be dispatched to
containers, and what is an effective traffic control mechanism? Similarly, at the
strategic level, the issues include optimizing the number of cranes, trucks etc. The
truck dispatching problem can be considered similar to the job scheduling problem
on parallel machines. In a truck dispatching problem, the crane operations represent
the setups, crane represents the operator, each container corresponds to job and
trucks correspond to machines. However, the job scheduling problem for container
72
terminals has not been studied in the literature. Therefore, this study aims to develop
models for effective and efficient loading and unloading operations for ICD,
Tughlakabad in New Delhi.
4.3 Truck dispatching model formulation
This section describes the formulation of mathematical model for the truck
dispatching problem by considering one or more number of trains serviced with a
single crane. Let R number of trains to be serviced with a K number of trucks using a
single crane. The number of trains to be considered in the model depends upon the
availability of trains in the terminal. The container loading and loading problem with
a single crane can be formally described as follows: we would like to minimize the
time required to execute a given set of unloading containers in a predetermined
sequence, followed by a given set of loading containers in a predetermined sequence.
The execution time of every job is deterministically known and consists of two
components: (i) the time required for the rail side crane to pick/drop a container
from/onto a truck (during this time both the crane and the truck are occupied); and
(ii) the time required to transport the container between the crane and the appropriate
yard location. Upon completing the last unloading job assigned to truck, the truck
transfers directly to the first loading job assigned to it (if any) without passing
through the crane. Since the loading and unloading sequences of the jobs are given,
the decision problem is to assign the loading and unloading jobs to trucks so as to
minimize the makespan of the schedule. The formulation of truck dispatching problem
as a mixed-integer program is presented below.
Parameters
N number of jobs
M number of trucks available (N¿M)
Si Processing time, where i=1,2,...,N.
d i half travel time where i=1,2,...,N.
t iaarrival time(completion time of job i) where i=1,2...,N.
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t id
departure time of job i, where i=1,2...,N.
K large positive number
Decisions Variables
X ijmis a binary variable number whose value is 1 if truck m (m=1,2,....,M) handles
job j after job i (i=1,2,...,N), otherwise it is zero.
Y ℑ is a binary variable whose value is 1 if truck m (m=1,2,...,M) handles job i
(i=1,2,...,N) otherwise it is zero
T is the makespan for N Jobs.
Denoting the set of X ijmby X, the set of Y ℑ by Y, and the set t iaof by t, the truck
dispatching can be stated as follows
Minimize T
Subject to
t ia≤ T i=1, 2...,N
Eq 4.1
∑m=1
M
Y im=1 i=1, 2 ...,NEq 4.2
∑i=1∧i≠ j
N
Xijm≤Yim i=1,2 , …, N Eq 4.3
∑i=1∧i≠ j
N
Xijm≤Yjm j=1,2, …, N Eq 4.4
Xijm+ Xjim≥Yim+Yjm−1≤ 1
i, j=1,2,…,N and i≠ j , m=1,2,...,M
Eq 4.5
t ia≤ K (1−Xijm )+t j
a
i, j=1,2,...,N ; i≠j ; m=1,2,...,M
Eq 4.6
t id+2 d i=t i
a , i=1, 2 ...,N Eq 4.7
74
t id=∑
a=1
j
S (a ) j=1, 2 ...,MEq 4.8
t id= min
a=i−Mt ( a)
a +| mina=i−M
t (a )a − max
a=i−Mt (a )
d |+S i
i=M +1…,N
Eq 4.9
X ijm∈ {0,1 } i=1,2,...,N; j=1,2,...N+1; m=1,2,...,M Eq 4.10
t ia∧T ≥ 0 i=1,2,...,N Eq 4.11
The objective in the truck dispatching problem is to minimize the makespan of the N
jobs. Constraint (4.1) states the relationship between the arrival times and the makespan.
Constraints (4.2) ensure that each job is handled by only one truck. Constraints (4.3) to
(4-5) give the relationship between X and Y for jobs handled by the same truck.
Constraint (4.3) ensure thatY ℑ must be equal to 1 if truck m handles a job after job i.
Constraints (4.4) ensure that Y jm must be equal to 1 if truck m handles a job before
job i. Constraint (4.5) ensure that if Y ℑ+Y jmequals 2, truck m handles either job i
before job j or job j before job i. Constraint (4.6) gives the relationship between the
completion time of a job and that of its successor job i completes before job j.
Constraint (4.7) states the relationship between a job’s completion time, travel time,
and departure time of job i. Constraints (4.8) give the initial scheduling of M number
of jobs to M Number of trucks . Constraints (4.9) describes the second assignments
of i-m jobs to M number of trucks .constraints (4.10) and (4.11) are simple constraint
to ensure that X, Y, and t are non-negative.
In typical container terminals such as ICD, Tughlakabad, trucks travel at the speed of
15 km/h in the terminal area. The layout of the terminal is shown in Figure 4.29. The
respective times taken by a RMGC and TMGC to handle a container are 1.5 minutes
and 5 minutes. All the locations of containers are uniquely identified by the (x, y)
coordinates with respect to a defined origin. The initial location of each truck is next
to RMGC so that it is ready to be loaded with containers for transhipment to its
predefined location in the storage yard area. The travel time of each container is the
75
distance covered divided by the speed of the truck. The duration of a loading or
unloading time of a container is equal to the sum of the travel time and the total crane
handling time plus waiting time, if any. A terminal operations control system is typically
used to determine the container ready time and truck ready time.
4.4 Solution of truck dispatching problem
A real-world problem of dispatching 2 trucks to transport 5 containers is solved with
the objective to minimize the makespan of the operation. The values of input data
(2 d i , si ) of the problem are given in Table 4.8. The problem is formulated and solved
using the AMPL software (AMPL, 2009) for the input data given in Table 4.8. Using
the mixed integer programming model, the makespan for the problem was found to
be 23 minutes. Table 4.9 gives the truck schedule of problem, including the container
departure timet id and the completion time of each container on each truck.
Table 4.8 Input data for truck dispatching problem
Container Number i Travel time, 2di (minutes) Processing Time, s
(minutes)
1 3 2
2 5 2
3 2.5 2
4 4 2
5 2 2
Table 4.9 Output from MIP model
Container
NumberDeparture time t i
d Minutes Completion time of the jobs
(makespan) t ia minutes
Truck
number
1 2 8 1
2 4 14 2
3 10 15 1
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4 16 23 2
5 17 21 1
Figure 4.29Layout of ICD, Tughlakabad
Several computational experiments were conducted for various combinations of
number of trucks and containers. For each combination, the solutions were obtained
using AMPL on a personal computer with 2.10 GHz CPU. It was found from the
computational results that even for these problems, the average computational time
required to find the optimal schedule is about few minutes while for large problem
the computational time required is over 3 hours, Table 4.10 shows the computational
time for different combinations of number of trucks and number of containers.
77
78
Table 4.10 Computational time requirements for combinations of number of trucks
and containers
NO. Number of Trucks Number of containers Computational time
1 2 5 16 Minutes
2 3 9 23 minutes
3 4 15 31 Minutes
4 5 18 42 Minutes
The results of the computational analysis carried out in this chapter clearly indicate
that AMPL is capable of finding optimal schedule for large container unloading and
loading problem. However, the computational time required for solving large
problems is quite high. In view of large computational time, application to AMPL to
solving real-life terminal operation problems is not practical. Therefore, a heuristic
algorithm is proposed in the following chapter to solve the truck dispatching
problem.
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5. Solution Mechanisms
5.1 Introduction
This chapter describes mechanisms for scheduling a number of containers on a
number of trucks. In such mechanisms, trucks are the players of the mechanism.
According to Noam Nisan (2007), mechanism is a special class of algorithm.
According to Heydenreich et al. (2008), a scheduling mechanism is a scheduling
algorithm on an operating system. A flowchart of the solution mechanism is shown
in Figure 5.30
Figure 5.30 Flow chart of scheduling mechanism
From the flowchart shown in Figure 5.30, the mechanism can be done by applying
scheduling algorithm on operating system through number of principles. to get the
makespan, then finding out the minimum makespan followed by finding number of
trucks , operation cost, and waiting time corresponding to the minimum makespan
The problem of obtaining scheduling mechanism through different algorithms to get
an optimal solution is not new. Many researchers including Gillett et al. (1974),
Aarup et al. (1994), and Zeng et al. (2009 ) have studied the similar problem.
80
Scheduling algorithmsPrinciplesOperating systemMakespanMinimum makespan1. Number of trucks2.Operation cost 3.Waiting time
5.2 Greedy algorithm
One of the first applications of greedy algorithm (GA) to computational optimization
problem was reported by Edmonds (1971). Greedy algorithms are simple and
straightforward. They are short-sighted in their approach in the sense that they take
decisions on the basis of information at hand without worrying about the effect these
decisions may have in the future. They are easy to invent, easy to implement and
most of the time quite efficient. Greedy algorithms are used to solve optimization
problems (for example Kleinberg et al. 2005, and Khuller et al. 2007). GA has
been applied to wide variety of disciplines ranging from stock portfolio management
to choosing a University. GA is easy to code, easy to debug, executes quickly, and is
robust. GA has been applied to a wide variety of problems from several fields of
science, technology, and management.
5.2.1Elements of a GA
An optimization problem involves finding a subset, ∈from a collection of candidates
∁ ; the subset, ∈, must satisfy some specified criteria, i.e. be a solution and be such
that the objective function is optimised by ∈. `Optimised' may mean maximized or
minimized, depending on the precise problem being solved. Greedy methods are
distinguished by the fact that the selection function assigns a numerical value to each
candidate. All GA’s have exactly the same general form. A GA for a particular
problem is specified by describing the predicates `solution' and `feasible'; and the
selection function `select'.
Consequently, GAs are often very easy to design for optimization problems.
The General Form of a Greedy Algorithm is
function select ( ∁ : candidate_set) return candidate;
function solution (∈ : candidate_set) return
boolean;
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function feasible (∈ : candidate_set) return
boolean;
***************************************************
function greedy (C : candidate_set) return candidate_set is
ϑ : candidate;
∈ : candidate_set;
begin
∈ := {};
while (not solution(∈)) and ∁ /= {} loop
ϑ := select(∁);
∁ := ∁ - {ϑ };
if feasible(∈union {ϑ } ) then
∈:= ∈union { ϑ};
end if;
end loop;
if solution(∈) then
return∈;
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else
return e∈;
end if;
end greedy;
One useful concept for proving the correctness of greedy algorithms is the definition
of a promising set ,that is a feasible set is promising if it can be extended to produce
not merely a solution but an optimal solution to the problem . It follows that:
Lemma. If ∈ is promising at every step of the Greedy procedure and the procedure
returns a solution, then the solution is optimal
The working principle of a GA can be understood with the help of an example.
Consider that it is required to count a certain of money using the fewest possible
number of bills. Assume that the following bills are available: Rs. 50, Rs. 20, Rs. 10,
Rs. 5 coin, Rs. 1 coin, and 50 paisa coin.
The set ∁ of candidates is the collection of coins (1; 2; 5; 10; 20; 50), The feasibility
function is that the next coin must not bring the total to more than what is required.
The selection function is the value of the coin. The solution function is whether the
selected coins reach the desired target. A GA would start the solution process by
picking up the largest possible bill or coin that does not overshoot. Suppose, the
problem is to count Rs. 79.50. The choices would be:
a Rs. 50 bill a Rs. 20 bill, to make Rs. 70 a Rs. 5 coin, to make Rs. 75 two Rs. 2 coins, to make Rs. 79 a 50pais coin, to make Rs. 79.50
It is noted that that GA is able to achieve the optimal solution for this problem.
However, GA may not be able to achieve an optimal solution for every monetary
83
system. For example, consider a problem where a vending machine needs to return
41 cents to a customer using the available coins of 25-cent, 10-cent, and 1-cent. The
GA would start he solution procedure in the following manner.
Pick up a 25-cent coin, to make 25-cent Pick up a 10-cent coin, to make 35-cent Pick up six 1-cent coins, to make 41-cent
It can be seen that although the GA was able to achieve the solution but it is not an
optimal one. The total number of coins as determined by GA is 7 while it is a
possible to achieve a better solution that requires only 5 coins. The optimal solution,
can, therefore, be achieved using four 10-cent coins and one 1-cent coin.
5.3 Types of GA
Greedy algorithms are equally applicable to simple problems such as the money
change problems as discussed above to large complex problems that are difficult to
solve using classical techniques. GA can be effectively used as a selection algorithm
to prioritize options within a search, or branch and bound algorithm. GA is
sometimes characterized as being 'short sighted', and as 'non-recoverable'. However,
if a greedy algorithm can be proven to yield the global optimum for a given problem
class, it typically becomes the method of choice because it executes faster than other
optimization methods like dynamic programming. Examples of such GA’s are
Kruskal's algorithm and Prim's algorithm for finding minimum spanning trees,
Dijkstra's algorithm for finding single-source shortest paths, and the algorithm for
finding optimum Huffman trees (Thomas, 2001)
There exist several versions of greedy algorithm. The four most commonly used are:
Pure Greedy Algorithm
Orthogonal greedy algorithm
Relaxed greedy algorithms
stepwise projection algorithms
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5.3.1Greedy algorithm and scheduling problems
Scheduling problem of set of job on one machine
Suppose we have n jobs and every job i has start and finish time (si, fi). The goal is
to schedule the maximum number of non overlapping jobs on a single machine. GA
can be applied to this problem by scheduling jobs successively ensuring that no
assigned jobs overlap with previously scheduled jobs. The decision problem is to
determine the order in which the jobs should be processed so that the scheduling
mechanism is optimal. There are several ways to solve this problem. Suppose for
example, jobs can be picked in increasing order of size. It is easy to see that this does
not necessarily lead to the optimal solution. Likewise, scheduling jobs in order of
their arrivals (start times), or in increasing order of the number of conflicts that they
have, also does not work. Thus the possible greedy algorithms strategies are as
below:
Earliest start time: ascending order of sj.
Earliest finish time: ascending order of fj.
Shortest interval: ascending order of (fj – sj).
Fewest conflicts: For each job j, count the number of conflicting jobs cj. Schedule in
ascending order of cj.
5.4 Solution using GA
Greedy algorithm has been used for solving problems in container terminal by
several researchers (for example Goodchild et al. 2005; Ng, 2005; Günther, 2005;
Froyland et al. 2008; Jinxin et al. 2008).The truck loading and unloading problem
with a single crane can be formally described as follows: it is required to minimize
the time required to execute a given set of unloading jobs in a predetermined
sequence, followed by a given set of loading jobs in a predetermined sequence. The
execution time of every job is deterministically known and consists of two
components: (i) the time required for the rail side crane to pick/drop a container
from/onto a truck (during this time both the crane and the truck are occupied); and
85
(ii) the time required to transport the container between the crane and the appropriate
yard location. Upon completing the last unloading job assigned to a truck, the truck
transfers directly to the first loading job assigned to it (if any) without passing
through the crane. Since the loading and unloading sequences of the jobs are given,
our decision problem is to assign the loading and unloading jobs to trucks so as to
minimize the makespan of the schedule. The following notation is required for
formulating the model.
Let m = number of trucks;
n1 = number of unloading jobs;
n2 = number of loading jobs;
U = {JU1, J U
2…….J U n1} = set of unloading jobs, ordered in the required processing
sequence;
L = {JL 1, JL 2. . . JL n2} = set of loading jobs, ordered in the required processing
sequence;
S (J) = processing requirement of the crane for job.
d(J) = one-way travel time required by any truck to transport a job J between the
crane and the appropriate yard location.
H (λ) = duration (i.e., makespan) of a feasible unloading/loading schedule λ.
Throughout the analysis of this work considered the following assumptions
5.4.1Assumptions
Throughout the analysis each container is referred to as a job.
All trucks are assumed to be located next to the rail-side crane at the end of
all operations.
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All trucks are same in their function and transfer one container at a time.
Each truck travels at unit speed 15 mile per hour.
Congestion among trucks is not considered.
The total travel time of any container (i) is the sum of the travel time from
rail yard to the stack position and back. Irrespective of the position of the
container where it has to be stacked, the total time is equal to 2di.
There is always an available yard crane ready to respond to a service request
of any truck. Thus the time it takes a yard crane to load and unload a
container is assumed to be incorporated into the container travel time between
the rail side area and the yard area. Therefore the term crane will always refer
to a rail-side crane (RMGC).
RMGC and TMGC are required to move a bit to adjust to the position of the
container to be transferred to the truck. Hence crane unloading time also
includes its movement time to position itself for the next container.
The containers in storage yard area can be stacked on top of one another,
therefore the time required to get container from the lower levels needs to be
incorporated in the loading time.
Every truck makes exactly one switch from “unloading” job to a “loading”
job.
All problem parameters (including S (J), d (J)) are non negative.
Scheduling of unloading and loading of containers in a container terminal can be
carried out using the two principles described below.
Principle 1: First Available Truck (FAT): Assign the first unscheduled job in U to the
available truck which first completes the jobs previously assigned to it.
Principle 2: Last Busy Truck (LBT): Select any value [ζ ]. Schedule jobs to trucks so
that the last job completes at time [ζ ], and proceed backwards. Assign the last
unscheduled job in L to the last available truck that became busy with jobs
87
The FAT principle is used to unloading containers from train(s) to fleet of trucks
using RMGC. These trucks transport the containers to their locations in the storage
yard (see Figure 4.29). The GA is applied to unloading operations using the FAT
principle.
5.4.2GA for unloading container operation
Out of the first m jobs (containers) assign one job to each truck. When a truck returns
to the rail side area, the next job is assigned to the truck. The next job is assigned to
the first truck available at the rail side area. The greedy algorithm is the same as the
list scheduling rule in the machine scheduling literature (see, for example Lawler et
al. (1993)). Similarly, when assigning loading job, the first available truck that can
reach the job's location at the earliest time will be dispatched to this job. Consider a
JU job (container) sequence. Once a truck takes a “U” Job, it transports the job to its
location in the storage yard where the yard crane unloads the job. Then this truck has
to make empty trip back to the rail-side area to take the next job. The greedy
algorithm based on FAT principle is applied to schedule containers to trucks.
Notation
Consider that the job sequence consists of jobs {J1, J2 ...Jn}. For any scheduling policy
applied to JU or JL job sequences, the concept of truck arrival time, and truck
departure time have been introduced. For dispatching policy, we refer to the time a
truck in assigned to job (container) Ji, i=1, 2,…,n, as the arrival time of Ji and denote
it as t ia(λ) and it is known as the completion time of all the jobs. Similarly, we refer
to t id(λ) as the departure time for each unloading jobJ i
U , i =1, 2,...,n, by truck to its
location in the storage yard area. For example, initially in an unloading job sequence
all trucks are ready next to the RMGC to transport containers to their locations.
When the crane starts unloading jobs to trucks, the completion time of job (U) is the
time at which the truck returns empty to the rail-side area after dropping off its job at
its location in the yard area.
88
For the sake of simplicity, we will omit the scheduling policy parameter and use t ia
andt id. As mentioned above, job precedence constraints for J_ :{ J1, J2,..., Jn} job
sequence are applied in two stages
1. for i=1,2,…,m
t ia≥ t i−1
a +si i=2 , …, m Eq 5.1
t ia≥ t i
d+2d i+si i=1,2,...,m Eq 5.2
2. for i= n-m, …, n
t ia≥ t i
d+2d i+s i i= n-m,...,n Eq 5.3
The waiting time can be calculated by using the arrival time and the departure time
for m jobs. The waiting time is calculated by taking the difference between the
minimum arrival time and maximum departure time within a set of m jobs.
w=| mina=i−M
t ( ℑ )a − max
a=i−Mt (ℑ )
d | Eq 5.4
To calculate t ia and t i
d we use the following equations
t ijd=Cur min
i=mtℑ
a+sℑ +w Eq 5.5
t ija=tij
d +2×d ij Eq 5.6
The cost C of each job from its starting time to completion time is given in the
following equation
∁=4 × (t ija−tij
d )+0.5× wij+sij Eq 5.7
89
Costs involved in the handling systems are: cost of land, cost of terminal
development, cost of equipment, and cost of labour, administration cost and related
office operation cost etc. The cost of land is equal to the annual rental cost if the
terminal operator does not own the land, or the opportunity cost of the land if the
terminal operator owns the land. The terminal development cost, including the
annual maintenance and amortization cost of the yard is crucial to terminal operator.
The total annual cost of equipment is equal to the capital cost, annual depreciation
charge, operation and maintenance cost tied up with the equipment. The cost of
labour is equal to the annual salaries and benefits for the equipment drivers and dock
foremen.
For any dispatching policy λ ,we refer to the time the last truck returns to the rail-
side area after completing all jobs(containers) in the job sequence as the makespan
under the dispatching policy, which is donated by H(λ).
Theorem 1 For any unloading job sequence, the greedy algorithm is optimal. that is,
the greedy algorithm minimizes the makespan.
Proof
Suppose to the contrary, the schedule obtained by greedy algorithm is not optimal for
JU:{J1,J2,.....,Jn} job sequence. Consider another optimal schedule say γ, as this
schedule is not obtained by greedy algorithm then, there must be a job say job 1 ≤ i
≤ n in the schedule γ, that has not been assigned to the first available truck ,that is ,
job i has been assigned to truck Mi that is available at time T2 instead of truck Mj that
is available at time T1, with T1≤T2, due to the job precedence constraints, the
successors of job i can be taken by trucks only after time T 2+s. Thus, in scheduleγ,
truck M j is idle from time T 1toT 2+s. Now consider schedule λ⋇obtained from
schedule λ by assigning job i to the first available truck, that is, to truck M j at timeT 1
. In schedule λ¿the successors of job i can be taken by trucks after time T 1+s ,where
T 1+s≤ T2+s by principle 1 .Clearly the makespan of the scheduleλ¿ is either same or
less than the makespan of the schedule λ , which is contradiction. Hence the greedy
algorithm generates the optimal schedule for unloading container sequence.
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Remark The greedy algorithm is still optimal even if crane processing times are job-
specific, that is, the crane time associated with job Ji is si, and not a constant s.
Similarly, it is optimal even when the vehicle travel time and quay crane processing
times for each job are random variables.
Corollary1 the greedy algorithm minimizes the completion time of each job in an
unloading job sequence (from greedy algorithm definition).
To explain how greedy algorithm works for unloading job, we consider the following
example of five unloading jobs JU :{J1 , J2 , J3 , J 4 , J 5}
With half travel time d1=¿2 minutes,d2=5 minutes , d3=2.5 minutes , d4=4minutes,
d5=2minutes, with fixed crane processing time s=2 we need to schedule these jobs
on 2 trucks. In this case greedy algorithm has applied where the first m jobs are
assigned, each to a single truck. The greedy algorithm is optimal for any J- job
sequence. Note that the round-trip travel time for each unloading job J is 2d (J). The
greedy algorithm works as follows. First assign T1 to J1 and T2 to J2 after s1 (J1) =2
units, T1 leaves the crane with J1, and starts discharging J2 . After s(J 2 ) =2 minutes , T2
leaves with J2 , waiting time = w
t 11d =s1=2 t 11
a =t 11d +2 d11=¿ 2+ 2 ×2=6
t 22d =s2+w=2+2=4 t 22
a =t22d +2 d2=4+2 ×5=14
By comparing t 11a and t 22
a we find truck 1 return back earlier to the rail-side area so
next container will assign to it, where is
t 31d =t11
a +s13+w=6+2+0=8 t 31a =t31
d +2 d3=8+2×2.5= 13
Now by comparing t 22a and t 31
a we find t 31a =13 and t 22
a =14, then truck 2 reach to the
rail-side earlier, so next container will assign to truck 1, w=0
t 41d =t 31
a +s41+w=13+2+0=15 t 42a =t 42
d +2 d34=15+2× 4= 23
91
By the same way we find T1 reached to the rail side before T2 so the next container
will assign to it
t 52d =t22
a +s52+w=14+2+1=17 t 52a =t52
d +2 d52=17+2× 2=21
The dispatching solution can be represented as T1:{J1, J3, J4}, and T2: {J2, J5}. The
completion time for this unloading job sequence is 23= (6+9+8) minutes. The
schedule generated by the greedy algorithm is depicted in Gantt chart (used as a
visual aid for unloading and scheduling). In Figure 5.31 and in all other figures to
follow, the shaded region represent the crane processing time and the boxes represent
the travel time of the jobs.
Crane processing time (minutes) Truck Travel Time (minutes)
0 2 6 8 13 15 23
Truck1
J1 J3 J5
Waiting time
2 4 14 15 17 21
Truck2
J2 J4Figure 5.31 The greedy algorithm for an unloading job sequence using FAT
principle
The performance of GA has been compared with that of MIP in terms of execution
time and the quality of solution achieved. Both the techniques were able to obtain the
same optimal solution having a makespan of 23 minutes. However, the execution
time taken by GA was only 30 seconds compared to 16 minutes taken by the MIP
model. The results are shown in Table 5.11.
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Table 5.11 Performance Comparison of GA and MIP
MIP GA
Makespan (minutes) 23 23
Computational time(minutes) 16 0.5
5.4.3Greedy algorithm for loading container operation
The problem of loading the containers on to the trains has been solved first by greedy
algorithm and then by using the reverse greedy algorithm. Now, consider a JL job
(container) sequence. For each job sequence, once a truck is assigned to a “L“ job, it
makes an empty trip to the job’s location starting from the train area, takes the job,
and returns back to the train area with the job. The completion time of loading job is
the time at which the RMGC finishes loading the job onto train(s). For loading
sequence JL: {{J1, J2,..,Jn}
t ia≥ t i−1
a +si i=2 , …,n Eq 5.8
the departure time, arrival time, waiting time, and the cost can be computed using the
equations (5-4),(5-5),(5-6),(5-7) Consider again the same five jobs used in the
previous example, but now assume that these are loading jobs and not the unloading
jobs as was the case previously. That is, we have a job sequence JL: {J1, J2, J3, J4, J5}.
In this case, the greedy algorithm suggests the following schedules for each truck: T1 :
{ J1, J3, J5} and T2: {J2, J4 }, which results in 24 units of completion time. This
schedule is given in Figure 5.32. Note that, in this schedule, truck T1 has to wait for 5
minutes after bringing J3 and J5 to the train(s), since the predecessors (J1, J2, J4) in this
case are uploaded. In order to determine whether the solution obtained by GA is
optimal, the same problem has also been solved by using the reverse greedy
algorithm.
Crane processing time (minutes) Truck Travel Time (minutes)
waiting time
93
0 4 6 11 12 14 18 22 24
Truck1
J1 J3 J5
0 10 12 20 22
Truck2
J2 J4Figure 5.32 GA for an loading job sequence using FAT principle
5.4.4Reverse greedy algorithm for loading container operation
Giving a job sequence JL: {J1, J2... Jn}, consider the following polynomial time
algorithm called the reverse greedy algorithm the algorithm works by applying
principle 2 (LBT) for loading jobs as follows:
1. Replace each loading job by an unloading job with same location, that is, if
location P is the pickup point for a specific loading job, the associated
unloading job has location P as its drop-off point.
2. Reverse the order to get the reversed job sequence JRU: { Jn2, Jn2 -1… J2 , J1 }.
3. Apply the greedy algorithm for this reversed list of unloading jobs.
4. Reverse again the sequence of the job assigned to each truck
Following the steps outlined above, the reverse greedy algorithm can be applied for
scheduling loading jobs.
Theorem 2 The reverse greedy algorithm is optimal for any loading job instance
Proof
To prove Theorem 2 the following lemma is needed.
94
Lemma Consider the dispatching policy λL applied to loading job sequence J L with a
makespan of H (λL). There exists policy λUL applied to the reverse job sequence J R .UL
associated with J L that achieve the same makespan, i.e., H (λL) =H(λUL)
Proof Consider loading job sequence J L={J1 , J 2 , …, J n }, and the dispatching policy λL
LetM l: {J1 , J 2, …, J lfl } ,denote the job sequence assigned to vehicle l, l=1, 2,..., m,
under this dispatching policy. The precedence constraints for this J L job sequence
imply that job i=2 ,…, n, can not be completed until all its successors in J L i.e.,
J1 , J 2 , …, J i−1 are completed. Hence the following equation is given
CT i ( λL )≥ CT i−1 ( λL)+s i=2 , …, n Eq 5.9
Clearly the makespan for this dispatching policy is H (λL)=.CT n ( λL ).Now considers the
corresponding reverse unloading jobs sequence, JRU: {Jn2, Jn2 -1…, J2, J1}.the objective
is to find a dispatching policy λL for the reverse job sequence with a makespan H (λL)
such that H (λL) = H (λUL).
For this purpose consider the dispatching policy λL obtained as follows.
Reverse the job sequence M l ,l=1,2, …, k , define as above, and denote the resulting
sequence as M lR : {J lfl
, J f l−1,…, J l1
}. Under this policy, truck l starts with job J lf l
,
continues with job J lf l−1, and so on. Start job Jn, an unloading job now , at time H (λL
)-CT i ( λL )=0, job Jn−1 at H (λL)-CT n−1 ( λL ),..., and job J1 at H (λL)-CT 1 ( λL ).
The question here it can be able to show the schedule obtained by dispatching policy
λL satisfies (a) the precedence constraints for the JUR job sequence, and (b) truck
capacity constraints, when we have dispatching for which
H (λUL) = H (λL)-CT 1 ( λL )+ 2 d1+s= H (λL)
95
Consider jobs J i−1 and J i ,i=2 ,…,n . under dispatching policy λL then it has
ST i−1 ( λUL )−ST i ( λUL )=H ( λL )−CT i−1 ( λL )−¿ H (λL) +CT i ( λL )=CT i ( λL )−CT i−1 ( λL )≥ s from Eq
5.9
And hence the precedence constraints job JUR job sequences are satisfied.next it has to
show that the schedule obtained by dispatching policy λUL is also satisfy the truck
capacity constraints. Truck l, l=1,2 , …, k, can serve jobs {J l fl, J f l−1
, …, J l1 }.under
dispatching policy λUL, since for jobs J lh−1 and J lh, h=2 ,… , f l .
ST lh−1 ( λUL )−ST lh ( λUL )=H ( λL )−CT lh−1( λL )−¿ H (λL) +CT lh ( λL )=CT lh ( λL )−CT hl−1 ( λL )≥ 2 dlh +s
Hence, dispatching policy λULgenerates a feasible schedule for the JUR job sequence
with a makespan of H ( λL) . .This complete the proof of lemma which lead to the
following corollary:
Corollary2: Consider the dispatching policy λUL applied to unloading job sequence,
with a makespan of H (λUL). There exists a dispatching policy λL for the reverse
loading job sequence wth unloading job such that it achieves exactly the makespan,
i.e., H (λL) = H (λUL).
Now it is ready to prove Theorem 2
Proof of Theorem 2 Let λL be the optimal dispatching policy for an unloading job
sequence, with a makespan of H (λL∗¿¿). By Lemma 2 it can be found a dispatching
policy λUL for the corresponding reverse unloading job sequence JUR such that H (λUL
).= H (λL∗¿¿).
Now considering the optimal dispatching policyλUL∗¿¿.for this JUR job sequence with a
makespan of H (λUL∗¿¿) by corollary2 the dispatching policy λL for the corresponding
reverse loading job sequence J L which is the original J L job sequence such that H (
λUL∗¿¿).= H (λL), by optimality of H (λUL∗¿¿) for the JUR job sequence , it has :
96
H (λL∗¿¿). = H (λL)≥ H (λUL∗¿¿). = H (λL), Eq 5.10
On the other hand, the optimality of H (λL∗¿¿). For loading jobs sequence implies that
H (λL∗¿¿).≤ H (λL) and hence Eq 5.10 hold as equality. That is H (λL∗¿¿).≤ H (λUL∗¿¿)
H (λL∗¿¿).≤ H (λUL∗¿¿) Eq 5.11
Finally Theorem 2 tell us that greedy algorithm is an optimal dispatching policy for
JUR job sequence .thus, given a loading job sequence, it can obtain the reverse job
sequence JUR associated with loading job and find the optimal schedule for this JU
R job
sequence , it can be constructed a schedule for the original loading job as done in
proof of lemma 2, that is it can be done by reversing the sequence of jobs assigned
to each truck. Furthermore, this must be one of the optimal schedule(s)for the loading
job sequence ,since H (λUL∗¿¿).≤ H (λL∗¿¿) by Eq 5.11. Observing that this is the
reverse greedy algorithm complete the proof.
The same problem as discussed above was solved using the reverse greedy
algorithm.
loading job J JL: { JL1, JL2 , JL3, JL4, JL5},which become JU (JU1,JU2,JU3,JU4,JU5}
reverse the order JU R :{J5,J4,J3,J2,J1)={2, 4, 2.5, 5, 2}
Apply greedy algorithm on this sequence we get
t 51d =s5=2 t 51
a =t51d +2 d5=¿ 2+ 2 ×2=6
t 42d =s4+w=2+2=4 t 42
a =t 42d +2 d4=4+2×4=12
By comparing t 51a and t 42
a we find truck 1 return back earlier to the rail-side area so
next container will assign to it, where is
t 31d =t51
a +s31+w=6+2+0=8 t 31a =t31
d +2 d3=8+2 ×2.5= 13
97
Now by comparing t 42a and t 31
a we find t 31a =13 and t 42
a =12, then truck 2 reach to the
rail-side earlier, so next container will be assigned to truck 2, w=0
t 22d =t 42
a +s2+w=12+2+0=14 t 22a =t22
d +2d2=14+2×5= 24
By the same way we find T1 reached to the rail side before T2 so the next container
will assign to it and has to wait 1 minute.
t 11d =t 31
a +s1+w=13+2+1=16 t 11a =t 11
d +2 d1=16+2 ×2=20
Reversing the order again yields an optimal makespan of 22 minutes.
Figure 5.33 illustrates the mechanism of reverse greedy algorithm as applied to a J+
job sequence for the problem described above. It can be seen from Figure 5.33 that
application of reverse greedy algorithm resulted in an optimal makespan of 22
minutes for the loading problem described above. The schedule in Figure 5.33 (a) is
obtained by applying the greedy algorithm to the reserved job sequence in the first
step of algorithm. The schedule in Figure 5.33 (b) is obtained by reversing the jobs
assigned to each truck in the first step. Hence, the reverse greedy algorithm obtains a
schedule with a makespan of 22 minutes, which is the optimal makespan for this
loading job sequence. The complexity for both greedy algorithm and reverse greedy
algorithm has running time of O (n2 ) (see Appendix D).
Crane processing time (minutes) Truck Travel Time (minutes)
(a) waiting time
0 2 6 8
13
14 16 20
Truck1
J5 J3 J1
2 4 12 14 24
98
Truck2
J4 J2
(b)
0 4 6 11 12 14 18 20
Truck1
J1 J3 J5
0 10 12 20 22
Truck2
J2 J4Figure 5.33. Reverse greedy algorithm for loading containers using LBT principle
5.4.5Solution using shortest job time first scheduling algorithm
STF is one priority sequencing rule which starts scheduling with the shortest job
completion time (Rose, 2001) It is typically considered a multiclass and non-
preemptive scheduling policy. The STF algorithm starts with shortest job completion
time and then schedule the remaining jobs according to the increasing order of job
completion time. For application of this mechanism to loading and unloading
operations, the exact completion time of different jobs must be known in advance.
However, in a real life situation it is not possible to determine the exact time of
completion of a job in advance.
99
STF does not exhibit the fairness shown in FAT scheduling policy as processes are
given priorities based on job sequence, and handling a job with longer time may
starve or may have to wait too long to get serviced As mentioned above, job
precedence constraints for J :{ J1, J2..., Jn} job sequences are considered in two
stages: In the first stage, the processing time and travel time (which referred as
handling time for simplicity) for each job is summed up. In the second stage, the
scheduling sequence can be obtained by starting from smallest values to the largest
value obtained in the first stage.
si+2d i≤ s i+1+2d i+1 ≤ …≤ sn+2 dnEq 5.12
The working principle of a STF algorithm is as follows: The job with the shortest
completion time are handled and completed first. The driving data for the algorithm
includes the number of jobs, the job names, and the handling time of each job. The
second step involves sorting out the smallest values of the summation of processing
and travel time among the jobs. The order of the jobs to be sequenced is determined
on the basis of summation of processing and travel time. The jobs with smallest sum
are executed first and the job with the largest sum is executed in the end. The
makespan is then determined by using equations (5-4), (5-5), and (5-6). The schedule
obtained using the STF algorithm for the 2 trucks, 5 jobs problem is presented in
Table 5.12.
100
Table 5.12 Schedule obtained using STF algorithm
Job Number Handling time
(minutes)
Handling time in increasing order
(minutes)
Job number according to the new
scheduling
1 2+4=6 6 1
2 2+10=12 6 5
3 2+5=7 7 3
4 2+8=10 10 4
5 2+4=6 12 2
Table 5.12 gives the following job sequence: {J1, J5, J3, J4, J2}. For this job sequence,
the makespan is calculated and the Gantt chart is prepared and shown in Figure 5.34.
Crane processing time (minutes) Truck Travel Time (minutes)
0 2 6 8 13 15 25
Truck1
J1 J3 J2
2 4 8 10 18
Truck2
J5 J4Figure 5.34 STF scheduling algorithm for unloading containers
STF algorithm suggests the following schedules for each truck: T1 :{ J1, J3,J2} and T2:
{J5, J4 }, which results in 25 minutes of completion time . This schedule is given in
Figure 5.34.
101
5.4.6Solution using largest job time first scheduling algorithm
LTF is multiclass scheduling policy that can be pre-emptive or non-pre-emptive. It
works in the same way as STF, but tasks are initially sorted based on expected
execution time. It is possible for a user to have an accurate estimation of the
distribution of times between the tasks of the application, but in practice small
variations will affect the overall efficiency because the order of assignment is fixed
by the user at the beginning. LTF does not exhibit the fairness shown in FAT
scheduling algorithm as processes are given different priorities. Also, shorter job
handling time may have to wait too long to get serviced.
LTF works as follows the jobs with total handling time are handled first and
completed. The algorithm requires the data pertaining to the number of jobs, the job
names, the processing time and the travel time as the input. The second step is
sorting out the largest sum of processing time and travel time among the jobs. In the
third step, jobs are rescheduled and assigned to the trucks according to the sequence
generated through the second step.
si+2d i≥ s i+1+2d i+1 ≥ …≥ sn+2 dn Eq 5.13
In the end, the makespan is computed by using equations (5-4), (5-5), (5-6) used in
FAT.
Table 5.13 Schedule obtained using LTF algorithm
Job Number Handling time (minutes)
Handling time (minutes),in
increasing order
Job number according to the new
scheduling
1 2+4=6 12 2
2 2+10=12 10 4
3 2+5=7 7 3
4 2+8=10 6 5
5 2+2=4 6 1
102
The results of application of LTF algorithm to the 2 truck- 5 jobs problem is
presented in Table 5.13. The job sequence as determined by STF is {J2, J4, J3 ,J5 ,J1}.
LTF algorithm suggests the following schedules for each truck: T1:{J1, J3,J2} and T2:
{J5, J4 }, which results in a makespan of 25 minutes of completion time . This
schedule is given in Gantt chart shown in Figure 5.35.
Crane processing time (minutes) Truck Travel Time (minutes)
0 2 12 14 19 21 25
Truck1
J2 J3 J1
Waiting time
2 4 12 14 16 20
Truck2
J4 J5Figure 5.35 The LTF scheduling algorithm for unloading containers
103
6. Model Application to Real World Case Studies
This chapter describes the application of models described in the previous chapter to
optimize loading and unloading operations in ICD, Tughlakabad. Four real world
case studies based on the data collected from CONCOR for ICD, Tughlakabad are
solved using different mechanisms. The mechanisms considered are greedy
algorithm, reverse greedy algorithm, shortest time first algorithm, and longest time
first algorithm solved on personal computer. Performance of each of the models is
evaluated through application to the four real-world case studies as shown in Table
6.14. The model for the greedy algorithms, reverse greedy algorithm and shortest
time first and longest time first have been coded using Microsoft Visual C++.
Table 6.14 Four different real world case studies
Case study Trains Trucks Jobs
1 1 9 70
2 2 12 145
3 3 15 210
4 4 18 270
Four different combinations of number of containers, number of trucks and number
of trains considered in the computational experiments for each loading and unloading
operation are listed in Table 6.14. For the problems considered here, the number of
containers (N) to be handled ranges from 70 to 270 and the number of trucks (M)
employed ranges from 9 to 18 and number of trains (R) ranges from 1 to 4. The
performance of all the four models for each of the problems has been evaluated on
the basis of the objective function values achieved and the execution time required.
Model runs have been conducted on a personal computer with 2.10 GHz CPU and
2GB RAM.
104
6.1 Case study 1
This section describes the results of application of greedy algorithm model based on
FAT principle, reverse greedy algorithm model based on LBT principle, greedy
algorithm model based on STF principle, and greedy algorithm model based on LTF
principle. In a typical container terminal, trucks travel at the speed of 15 km/h in the
terminal area. The time taken by a RMGC to handle a container is typically between
1.5 minutes and 5 minutes. The initial location of each truck and the location of each
job’s pick-up/drop-off are randomly generated based on a terminal area of 1500
metres by 1500 metres. The travel time is the time that truck takes to travel from rail-
side and return back to the same point. The duration of a job is equal to the sum of
the total travel time from its pick-up location to its drop-off location and the total
crane handling time. A terminal operations control system is typically used to
determine the job ready time and truck ready time. The processing time (s) and travel
time (2d) for each job for case study 1 is given in Table 6.15.
Table 6.15 Input data for case study 1
Job. s (min) 2d(min) Job s (min) 2d(min) Job S(min) 2d(min)
1 3.00 7.00 24 3.00 9.00 47 4.00 5.00
2 4.00 9.00 25 1.00 7.00 48 2.00 3.00
3 4.00 3.00 26 1.00 5.00 49 2.00 5.00
4 3.00 4.00 27 3.00 4.00 50 2.00 7.00
5 2.00 5.00 28 2.00 5.00 51 2.00 4.00
6 3.00 7.00 29 3.00 7.00 52 2.00 3.00
7 2.00 9.00 30 3.00 12.00 53 2.00 12.00
8 3.00 5.00 31 3.00 3.00 54 2.00 5.00
9 3.00 4.00 32 3.00 5.00 55 2.00 7.00
10 2.00 5.00 33 5.00 7.00 56 4.00 3.00
11 3.00 8.00 34 3.00 4.00 57 4.00 9.00
12 4.00 5.00 35 3.00 9.00 58 2.00 5.00
13 4.00 7.00 36 2.00 7.00 59 4.00 12.00
14 3.00 10.00 37 2.00 10.00 60 4.00 5.00
15 2.00 5.00 38 3.00 5.00 61 3.00 7.00
16 3.00 7.00 39 2.00 3.00 62 2.00 5.00
17 2.00 3.00 40 3.00 4.00 63 3.00 6.00
105
18 3.00 5.00 41 4.00 5.00 64 2.00 4.00
19 3.00 9.00 42 3.00 7.00 65 4.00 5.00
20 2.00 6.00 43 4.00 8.00 66 4.00 7.00
21 2.00 5.00 44 3.00 7.00 67 4.00 3.00
22 3.00 3.00 45 3.00 10.00 68 5.00 7.00
23 2.00 5.00 46 3.00 7.00 69 3.00 10.00
70 3.50 4.00
6.1.1Makespan for unloading operations
Three different models namely greedy algorithm based on FAT, STF, and LTF were
used to determine the makespan for the case study 1. Comparison of the makespan
obtained using the three models are presented in Figure 6.36. It can be observed from
Figure 6.36 that the minimum makespan of 201.5 minutes is achieved using the
model based on FAT.
3 4 5 6 7 8 9 10190
195
200
205
210
215
220
STF
LTF
FAT
Number of Trucks
Mak
espa
n(m
inut
es)
Figure 6.36 Comparison of makespan for unloading one train
The number of trucks obtained corresponding to the minimum makespan of 201.5 is
5. For the existing situation, the minimum makespan with 9 trucks is 214.5 minutes.
Therefore, there is a saving of 13 minutes and 4 trucks when the model based on
FAT principle is used. In terms of makespan, the worst performance was obtained by
106
using the STF model. The minimum makespan and the corresponding number of
trucks for the three models and for the existing situation are shown in Table 6.16.
Table 6.16 Minimum makespan and the corresponding number of trucks of
unloading operation
STF LTF FAT Existing
Makespan (minutes) 214.5 201.5 201.5 214.5
Number of trucks 5 9 5 9
6.1.2Computation of makespan for loading operations
Three different models namely greedy algorithm based on LBT, STF, and LTF were
used to determine the makespan for case study 1. Comparison of makespan obtained
using the three models is presented in Figure 6.37. It can be observed from Figure
6.37 that the minimum makespan of 204.5 minutes is achieved using the model based
on STF.
3 4 5 6 7 8 9 10190
195
200
205
210
215
220
225
230
235
STF
LTF
LBT
Number of Trucks
Mak
espa
n (M
inut
es)
Figure 6.37 Comparison of makespan for loading one train
The number of trucks obtained corresponding to the minimum makespan of 204.5 is
6. For the existing situation, the minimum makespan with 9 trucks is 213.5 minutes.
Therefore, there is a saving of 9 minutes and 3 trucks when the model based on STF
107
principle is used. In terms of makespan, the worst performance was obtained by
using the LTF model. The minimum makespan and the corresponding number of
trucks for the three models and for the existing situation are shown in Table 6.17
Table 6.17 Minimum makespan and the corresponding number of trucks for loading
operation
STF LTF LBT Existing
Makespan (minutes) 204.5 213.5 208.5 213.5
Number of trucks 6 7 5 9
6.1.3Cost of unloading operations
The cost of unloading a container from a train and transporting it to its location in the
storage yard depends upon the travel time of the truck, processing time taken by the
crane, and waiting time for the truck. The following equation ( Eq 6.1 )has been used
to compute the cost (C )of unloading a single container.
∁=4 × (t ija−tij
d )+0.5× wij+sij i=1,...n and j=1,...m Eq 6.1
Where t ija is arrival time of job i on truck j, t ij
d is departure time of job i on truck j,w ij
is waiting time of job i on truck j, and sijis the processing time of job i to be loaded
on truck j.
Figure 6.38 gives the comparisons of the cost obtained through three models based
on the SFT, LFT, and FAT principle. It can be seen from Figure 6.38 that the lowest
cost of operation is obtained using the model based on FAT principle while the SFT
model produces the worst results in terms of cost.
108
0 1 2 3 4 5 6 7 8 9 101900
2000
2100
2200
2300
2400
2500
2600
2700
2800
STF
LTF
FAT
Number of Trucks
Cost
(Rup
ees)
Figure 6.38 Comparison of cost of unloading one train
Table 6.18 shows the cost of operation corresponding to minimum makespan
obtained through three different models. The existing operation cost is also given in
Table 6.18.
Table 6.18 Comparison of costs for unloading operations
STF LTF FAT Existing
Cost(Rupees) 2146.5 2732 2164 2674
Number of trucks 5 9 5 9
6.1.4Cost of loading operation
The cost of loading a container onto a train after bringing container from its location
in the storage yard depends upon the travel time of the truck, processing time taken
by the crane, and waiting time for the truck. The Eq 6.1 is used to compute the cost
(C )of loading a single container
Figure 6.39 gives the comparisons of the cost obtained through three models based
on the SFT, LFT, and LBT principles. It can be seen from Figure 6.39 that the lowest
cost of operation is obtained using the model based on LBT principle while the LTF
model produces the worst results in terms of cost.
109
0 1 2 3 4 5 6 7 8 9 101100
1300
1500
1700
1900
2100
2300
STF
LTF
LBT
Number of Trucks
Cost
(Rup
ees)
Figure 6.39 Comparison of cost of loading one train
Table 6.19 shows the cost of operation corresponding to minimum makespan
obtained through three different models. The existing operation cost is also given in
Table 6.19
Table 6.19 Comparison of costs for loading operations
STF LTF LBT Existing
Cost (Rupees) 1684 1869 1563 2176
Number of Truck 6 7 5 9
6.1.5Waiting time of unloading operation
A truck might have to wait before loading could start on it if there are other trucks in
the rail side on which the jobs are being processed. The waiting time of truck
depends upon the arrival time and departure time of a truck. The following equation
(Eq 6.2) has been used to compute the waiting time (w ) of unloading a single
container
w=| mina=i−M
t (ij )a − max
a=i−Mt (ij )
d | i=1,...n and j=1,...mEq 6.2
110
where mina=i− M
t (ij )a
is the minimum arrival time value among set a=i-m, and maxa=i−M
t (ij )d
is
the maximum departure time value within a set a=i-m.
Figure 6.40 gives the comparisons of the waiting time obtained through three models
based on the SFT, LFT, and FAT principles. It can be seen from Figure 6.40 that the
lowest waiting time of operation is obtained using the model based on FAT principle
while the LTF model produces the worst results in terms of waiting time
0 1 2 3 4 5 6 7 8 9 100
200
400
600
800
1000
1200
1400
STF
LTF
FAT
Number of Trucks
Wai
ting
Tim
e (M
inut
es)
Figure 6.40 Comparison of waiting time for unloading one train
Table 6.20 shows the waiting time of unloading operation corresponding to
minimum makespan obtained through three different models. The existing waiting
time for unloading operation is also given in Table 6.20.
Table 6.20 Comparison of waiting time for unloading operations
STF LTF FAT Existing
Waiting time (minutes) 397 1165 322 1165
Number of trucks 5 9 5 9
111
6.1.6Waiting time of loading operation
The waiting time of truck to load a container to a train after coming back from the
storage yard depends upon the arrival time and departure time of a truck. The Eq 6.2
is used to compute the waiting time (w )of loading a single container
Figure 6.41 gives the comparisons of the waiting time obtained through three models
based on the SFT, LFT, and LBT principles. It can be seen from Figure 6.41 that the
lowest waiting time of operation is obtained using the model based on LBT principle
while the LTF model produces the worst results in terms of waiting time.
0 1 2 3 4 5 6 7 8 9 100
200
400
600
800
1000
1200
1400
STF
LTF
LBT
Number of Trucks
Wai
ting
Tim
e(M
inut
es)
Figure 6.41 Comparison of waiting time for loading one train
Table 6.21 shows the waiting time of loading operation corresponding to minimum
makespan obtained through three different models. The existing waiting time for
loading operation is also given. It is found that LBT gives a minimum waiting time
of 333 minutes while LTF gives a worst waiting time of 838 minutes.
Table 6.21 Comparison of waiting time for loading operations
STF LTF LBT Existing
Waiting time(Minutes) 562.5 838 333 1235
Number of trucks 6 7 5 9
112
6.2 Case study 2
In this case study, as shown in Table 6.14, there are two trains, 12 trucks and 145
jobs to be processed. The processing time (s) and travel time (2d) for each job is
given in Table 6.22.
113
Table 6.22 Input data for case study 2
Job. s(min) d (min) Job. s(min) d (min) Job s(min) d(min)
1 3.00 3.50 49 2.00 2.50 97 2.00 2.50
2 4.00 2.50 50 2.00 3.50 98 2.50 3.00
3 4.00 1.50 51 2.00 2.00 99 2.00 3.50
4 3.00 2.00 52 2.00 1.50 100 2.00 2.50
5 2.00 2.50 53 2.00 6.00 101 3.00 3.50
6 3.00 3.50 54 2.00 2.50 102 2.00 1.50
7 2.00 4.50 55 2.00 3.50 103 3.00 4.50
8 3.00 2.50 56 4.00 1.50 104 3.00 4.00
9 3.00 2.00 57 4.00 4.50 105 2.00 2.50
10 2.00 2.50 58 2.00 2.50 106 2.00 2.00
11 3.00 4.00 59 4.00 6.00 107 4.00 4.50
12 4.00 2.50 60 4.00 2.50 108 6.00 2.50
13 4.00 3.50 61 3.00 3.50 109 3.00 3.00
14 3.00 5.00 62 2.00 2.50 110 3.00 2.50
15 2.00 2.50 63 3.00 3.00 111 5.00 6.00
16 3.00 3.50 64 2.00 2.00 112 1.50 3.00
17 2.00 1.50 65 4.00 2.50 113 3.00 3.50
18 3.00 2.50 66 4.00 3.50 114 5.00 4.00
19 3.00 4.50 67 4.00 1.50 115 3.00 2.00
20 2.00 3.00 68 5.00 3.50 116 5.00 3.50
21 2.00 2.50 69 3.00 5.00 117 4.00 4.50
22 3.00 1.50 70 3.50 2.00 118 1.50 3.00
23 2.00 2.50 71 3.00 3.50 119 2.00 3.50
24 3.00 4.50 72 3.00 1.50 120 2.00 2.50
25 1.00 3.50 73 3.00 2.00 121 2.00 4.00
26 1.00 2.50 74 2.00 2.50 122 2.50 3.50
27 3.00 2.00 75 2.50 3.00 123 6.00 2.50
28 2.00 2.50 76 2.00 3.50 124 5.00 3.50
29 3.00 3.50 77 2.00 2.50 125 2.00 3.00
30 3.00 6.00 78 2.50 1.50 126 4.00 3.50
31 3.00 1.50 79 3.00 3.50 127 2.00 4.00
32 3.00 2.50 80 2.00 2.50 128 4.00 2.50
114
33 5.00 3.50 81 2.00 2.00 129 4.00 3.50
34 3.00 2.00 82 3.00 4.00 130 2.00 2.50
35 3.00 4.50 83 3.00 2.00 131 3.00 2.00
36 2.00 3.50 84 3.00 2.50 132 5.00 3.00
37 2.00 5.00 85 2.00 6.00 133 2.00 2.50
38 3.00 2.50 86 3.00 2.00 134 2.00 3.00
39 2.00 1.50 87 2.00 4.50 135 3.00 3.50
40 3.00 2.00 88 1.50 2.50 136 4.00 4.00
41 4.00 2.50 89 1.50 1.50 137 2.00 2.50
42 3.00 3.50 90 2.00 2.50 138 4.00 3.00
43 4.00 4.00 91 2.50 3.00 139 6.00 2.50
44 3.00 3.50 92 5.00 3.50 140 3.00 4.00
45 3.00 5.00 93 3.00 2.00 141 3.00 1.50
46 3.00 3.50 94 2.00 3.50 142 4.00 3.00
47 4.00 2.50 95 1.50 4.50 143 4.00 2.50
48 2.00 1.50 96 2.00 5.00 144 3.00 3.00
145 2.00 3.5
6.2.1Makespan for unloading operations
Three different models based on FAT, STF, and LTF principles were used to
determine the makespan for the case study 2. Comparison of the makespan obtained
using the three models is presented in Figure 6.42. It can be observed from Figure
6.42 that the minimum makespan of 421 minutes is achieved using the model based
on FAT. The number of trucks obtained corresponding to the minimum makespan of
421 is 7. For the existing situation, the minimum makespan with 12 trucks is 437
minutes. Therefore, there is a saving of 16 minutes and 5 trucks when the model
based on FAT principle is used. In terms of makespan, the worst performance was
obtained by using the LTF model. The minimum makespan and the corresponding
number of trucks for the three models and for the existing situation are shown in
Table 6.23.
115
0 1 2 3 4 5 6 7 8 9 10 11 12 13415
420
425
430
435
440
445
450
455
SFT
LFT
FAT
Number of Truck
Mak
espa
n(M
inut
es)
Figure 6.42 Comparison of makespan for unloading two trains
Table 6.23 Minimum makespan and the corresponding number of trucks for unloading operations
STF LTF FAT Existing
Makespan (minutes) 434 422.5 421 437
Number of trucks 5 6 7 12
6.2.2Makespan for loading operations
Three different models namely greedy algorithm based on LBT, STF, and LTF were
used to determine the makespan for the case study 2. Comparison of the makespan
obtained using the three models to load two trains is presented in Figure 6.43. It can
be observed from Figure 6.43 that the minimum makespan of 423.5 minutes is
achieved using the model based on STF. The number of trucks obtained
corresponding to the minimum makespan of 423.5 is 5. For the existing situation, the
minimum makespan with 12 trucks is 432.5 minutes. Therefore, there is a saving of 9
minutes and 7 trucks when the model based on STF principle is used. In terms of
makespan, the worst performance was obtained by using the LTF model. Also, there
is no decrease in the makespan even the number of trucks are increased beyond 7.
The minimum makespan and the corresponding number of trucks for the three
models and for the existing situation are shown in Table 6.24
116
4 5 6 7 8 9 10 11 12 13410
415
420
425
430
435
440
445
STF
LTF
LBT
Number of Trucks
Mak
espa
n(M
inut
es)
Figure 6.43 Comparison of makespan of unloading two trains
Table 6.24 Minimum makespan for loading two trains
STF LTF LBT Existing
Waiting time (minutes) 423.5 432.5 427.7 432.5
Number of trucks 5 6 7 12
6.2.3Cost of unloading operations
The cost of unloading a containers from trains and transporting it to its location in the
storage yard depends upon the travel time of the truck, processing time taken by the
crane, and waiting time for the truck. The Eq 6.1 used to compute the cost (C )of
unloading a single container.
Figure 6.44 gives the comparisons of the cost obtained through three models based
on the SFT, LFT, and FAT principles. It can be seen from Figure 6.44 that the lowest
cost of operation is obtained using the model based on STF principle while the FAT
model produces the worst results in terms of cost.
117
0 1 2 3 4 5 6 7 8 9 10 11 12 134000
4500
5000
5500
6000
6500
STF
LTF
FAT
Number of Trucks
Cost
(Rup
ees)
Figure 6.44 Comparison of cost for unloading two trains
Table 6.25 shows the cost of operation corresponding to minimum makespan
obtained through three different models. The existing operation cost is also given in
Table 6.25.
Table 6.25 Operation cost for unloading two trains
STF LTF FAT Existing
Cost (Rupees) 4400 4695 4861 6375
Number of trucks 5 6 7 12
6.2.4Cost of loading operations
The cost of loading a container onto a train after bringing it from its location in the
storage yard depends upon the travel time of the truck, processing time taken by the
crane, and waiting time for the truck. The Eq 6.1 used to compute the cost (C )of
loading a single container.
Figure 6.45 gives the comparisons of the cost obtained through three models based
on the SFT, LFT, and LBT principles. It can be seen from Figure 6.45 that the lowest
cost of operation is obtained using the model based on LBT principle while the LTF
model produces the worst results in terms of cost.
118
0 1 2 3 4 5 6 7 8 9 10 11 12 132500
3000
3500
4000
4500
5000Cost STF
Cost LTF
Cost LBT
Number of Trucks
Cost
(Rup
ees)
Figure 6.45 Comparison of cost for loading two trains
Table 6.26 shows the cost of operation corresponding to minimum makespan
obtained through three different models. The existing operation cost is also given in
Table 6.26.
Table 6.26 Operation cost for loading two trains
STF LTF LBT Existing
Cost (Rupees) 3574 3935.5 3384 5059.5
Number of trucks 7 8 6 12
6.2.5Waiting time for unloading operations
The waiting time of truck to unload a container from a train after return back to the
rail yard depends upon the arrival time and departure time of a truck. The equation 6-
2 has been used to compute the waiting time (w ) of unloading a single container
Figure 6.46which give the comparisons of the waiting time obtained through three
models based on the SFT, LFT, and FAT principles. It can be seen from Figure 6.46
that the lowest waiting time of operation is obtained using the model based on STF
principle while the FAT model produces the worst results in terms of waiting time.
119
0 1 2 3 4 5 6 7 8 9 10 11 12 130
500
1000
1500
2000
2500
3000
3500
4000
4500
STF
LTF
FAT
Number of Trucks
Wai
ting
Tim
e (m
inut
es)
Figure 6.46 Comparison of waiting time for unloading two trains
Table 6.27 shows the waiting time of unloading operation corresponding to
minimum makespan obtained through three different models. The existing waiting
time for unloading operation is also given in Table 6.27.
Table 6.27 Waiting time for unloading two trains
STF LTF FAT Existing
Waiting time (minutes) 814 1234 1525.5 3856
Number of trucks 5 6 7 12
6.2.6Waiting time for loading operations
The waiting time of truck to load a container to a train after coming back to the
storage yard depends upon the arrival time and departure time of a truck. The Eq 6.2
is used to compute the waiting time (w )of loading a single container.
Figure 6.47 presents the comparisons of the waiting time obtained through three
models based on the SFT, LFT, and LBT principles. It can be seen from Figure 6.47
that the lowest waiting time of operation is obtained using the model based on LBT
principle while the LTF model produces the worst results in terms of waiting time.
120
0 1 2 3 4 5 6 7 8 9 10 11 12 130
500
1000
1500
2000
2500
3000
3500
4000
STF
LTF
LBT
Number of Trucks
Wai
ting
Tim
e (M
inut
es)
Figure 6.47 Comparison of waiting time for loading two trains
Table 6.28 shows the waiting time of unloading operation corresponding to
minimum makespan obtained through three different models. The existing waiting
time for unloading operation is also given in Table 6.28.
Table 6.28 Waiting time for loading two trains
STF LTF LBT Existing
Waiting time (minutes) 1576.5 2117 1151 3779
Number of trucks 7 8 6 12
6.3 Case study 3
This section describes the results of application of greedy algorithm model based on
FAT principle, reverse greedy algorithm model based on LBT principle, greedy
algorithm model based on STF principle, and greedy algorithm model based on LTF
principle. In this case study, as given in Table 6.14 there are three trains, 15 trucks
and 210 jobs to be processed. The processing time (s) and travel time (2d) for each
job for case study 3 is given in Table 6.29
121
Table 6.29 Input data for case study 3
job s(min) 2d(min) job s(min) 2d(min) job. s(min) 2d(min)
1 4.00 5.00 71 3.00 7.00 141 2.00 7.00
2 2.00 7.00 72 2.00 9.00 142 2.00 5.00
3 2.00 8.00 73 3.00 5.00 143 2.50 3.00
4 2.00 4.00 74 3.00 4.00 144 3.00 7.00
5 2.50 6.00 75 2.00 5.00 145 2.00 5.00
6 2.00 5.00 76 3.00 8.00 146 2.00 4.00
7 2.00 6.00 77 4.00 5.00 147 3.00 8.00
8 2.00 5.00 78 4.00 7.00 148 3.00 4.00
9 2.00 10.00 79 3.00 10.00 149 3.00 5.00
10 3.00 5.00 80 2.00 5.00 150 2.00 12.00
11 3.00 6.00 81 3.00 7.00 151 3.00 4.00
12 5.00 7.00 82 2.00 3.00 152 2.00 9.00
13 4.00 3.00 83 3.00 5.00 153 1.50 5.00
14 3.00 7.00 84 3.00 9.00 154 1.50 3.00
15 3.00 6.00 85 2.00 6.00 155 2.00 5.00
16 2.00 5.00 86 2.00 5.00 156 2.50 6.00
17 2.00 4.00 87 3.00 3.00 157 5.00 7.00
18 3.00 8.00 88 2.00 5.00 158 3.00 4.00
19 2.00 5.00 89 3.00 9.00 159 2.00 7.00
20 3.00 4.00 90 1.00 7.00 160 1.50 9.00
21 3.50 6.00 91 1.00 5.00 161 2.00 10.00
22 3.00 7.00 92 3.00 4.00 162 2.00 5.00
23 2.50 8.00 93 2.00 5.00 163 2.50 6.00
24 2.00 5.00 94 3.00 7.00 164 2.00 7.00
25 3.00 3.00 95 3.00 12.00 165 2.00 5.00
26 2.00 5.00 96 3.00 3.00 166 3.00 7.00
27 3.00 8.00 97 3.00 5.00 167 2.00 3.00
28 1.50 4.00 98 5.00 7.00 168 3.00 9.00
29 3.00 7.00 99 3.00 4.00 169 3.00 8.00
30 2.00 5.00 100 3.00 9.00 170 2.00 5.00
31 4.00 7.00 101 2.00 7.00 171 2.00 4.00
32 3.00 4.00 102 2.00 10.00 172 4.00 9.00
33 2.00 5.00 103 3.00 5.00 173 6.00 5.00
34 3.00 8.00 104 2.00 3.00 174 3.00 6.00
122
35 2.00 4.00 105 3.00 4.00 175 3.00 5.00
36 3.00 7.00 106 4.00 5.00 176 5.00 12.00
37 2.00 4.00 107 3.00 7.00 177 1.50 6.00
38 3.00 10.00 108 4.00 8.00 178 3.00 7.00
39 3.50 4.00 109 3.00 7.00 179 5.00 8.00
40 2.00 5.00 110 3.00 10.00 180 3.00 4.00
41 3.00 6.00 111 3.00 7.00 181 5.00 7.00
42 4.00 5.00 112 4.00 5.00 182 4.00 9.00
43 4.00 8.00 113 2.00 3.00 183 1.50 6.00
44 3.00 7.00 114 2.00 5.00 184 2.00 7.00
45 2.00 4.00 115 2.00 7.00 185 2.00 5.00
46 2.00 10.00 116 2.00 4.00 186 2.00 8.00
47 2.00 5.00 117 2.00 3.00 187 2.50 7.00
48 3.00 4.00 118 2.00 12.00 188 6.00 5.00
49 3.00 9.00 119 2.00 5.00 189 5.00 7.00
50 2.00 5.00 120 2.00 7.00 190 2.00 6.00
51 3.00 6.00 121 4.00 3.00 191 4.00 7.00
52 2.00 5.00 122 4.00 9.00 192 2.00 8.00
53 2.00 4.00 123 2.00 5.00 193 4.00 5.00
54 3.00 7.00 124 4.00 12.00 194 4.00 7.00
55 4.00 5.00 125 4.00 5.00 195 2.00 5.00
56 2.00 4.00 126 3.00 7.00 196 3.00 4.00
57 3.00 7.00 127 2.00 5.00 197 5.00 6.00
58 3.00 5.00 128 3.00 6.00 198 2.00 5.00
59 2.00 10.00 129 2.00 4.00 199 2.00 6.00
60 5.00 7.00 130 4.00 5.00 200 3.00 7.00
61 3.00 5.00 131 4.00 7.00 201 4.00 8.00
62 4.00 4.00 132 4.00 3.00 202 2.00 5.00
63 1.50 6.00 133 5.00 7.00 203 4.00 6.00
64 2.00 5.00 134 3.00 10.00 204 6.00 5.00
65 2.00 7.00 135 3.50 4.00 205 3.00 8.00
66 3.00 7.00 136 3.00 7.00 206 3.00 3.00
67 4.00 5.00 137 3.00 3.00 207 4.00 6.00
68 4.00 3.00 138 3.00 4.00 208 4.00 5.00
69 3.00 4.00 139 2.00 5.00 209 3.00 6.00
70 2.00 5.00 140 2.50 6.00 210 2.00 7.00
123
6.3.1Makespan for unloading operations
A comparison of the makespan obtained using the three models STF, LTF, and FAT
is presented in Figure 6.48 It can be observed from Figure 6.48 that the minimum
makespan of 598.5 minutes is achieved using the model based on LTF. The number
of trucks obtained corresponding to the minimum makespan of 598.5 is 8. For the
existing situation, the minimum makespan with 15 trucks is 622 minutes. Therefore,
there is a saving of 23.5 minutes and 7 trucks when the model based on LTF
principle is used. In terms of makespan, the worst performance was obtained by
using the STF model.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16595
600
605
610
615
620
625
630
635
640
SFT
LFT
FAT
Number of Trucks
Mak
espa
n(M
inut
es)
Figure 6.48 Comparison of makespan for unloading three trains
The minimum makespan and the corresponding number of trucks for the three
models and for the existing situation are shown in Table 6.30.
Table 6.30 Minimum Makespan for unloading three trains
STF LTF FAT Existing
Makespan(minutes) 610.5 598.5 601 622
Number of trucks 5 8 7 15
124
6.3.2Makespan for loading operations
A Comparison of the makespan obtained using the three models STF, LTF, and LBT
is presented in Figure 6.49 It can be observed from Figure 6.49 that the minimum
makespan of 599.5 minutes is achieved using the model based on STF. The number
of trucks obtained corresponding to the minimum makespan of 599.5 is 8. For the
existing situation, the minimum makespan with 15 trucks is 608.5 minutes.
Therefore, there is a saving of 9 minutes and 7 trucks when the model based on STF
principle is used. In terms of makespan, the worst performance was obtained by
using the LTF model. The minimum makespan and the corresponding number of
trucks for the three models and for the existing situation are shown in Table 6.31.
3 4 5 6 7 8 9 10 11 12 13 14 15 16570
580
590
600
610
620
630
640
650
660
STF
LTF
LBT
Number of Trucks
Mak
espa
n(M
inut
es)
Figure 6.49 Comparison of makespan for loading three trains
Table 6.31 Minimum makespan for loading three trains
STF LTF LBF Existing
Makespan 599.5 608.5 601.5 608.5
Number of trucks 8 8 6 15
6.3.3Cost for unloading operations
The cost of unloading a containers from trains and transporting it to its location in the
storage yard depends upon the travel time of the truck, processing time taken by the
125
crane, and waiting time for the truck. The Eq 6.1 is used to compute the cost (C )of
unloading a single container.
Figure 6.50 gives the comparisons of the cost obtained through three models based
on the SFT, LFT, and FAT principles. It can be seen from Figure 6.50 that the lowest
cost of operation is obtained using the model based on STF principle while the LTF
model produces the worst results in terms of cost.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 165600
6100
6600
7100
7600
8100
8600
9100
9600
10100
STF
LTF
FAT
Number of Trucks
Cost
(Min
utes
)
Figure 6.50 Comparison of cost for unloading three trains
Table 6.32 shows the cost of operation corresponding to minimum makespan
obtained through three different models. The existing operation cost is also given in
Table 6.32.
Table 6.32 Operation cost for unloading three trains
STF LTF FAT Existing
Cost (Rupees) 6265 7326.5 6908 10057
Number of trucks 5 8 7 15
6.3.4Cost for loading operations
The cost of loading a container onto a train after bringing it from its location in the
storage yard depends upon the travel time of the truck, processing time taken by the
126
crane, and waiting time for the truck. The Eq 6.1 is used to compute the cost (C )of
loading a single container
Figure 6.51 gives the comparisons of the cost obtained through three models based
on the SFT, LFT, and LBT principles. It can be seen from Figure 6.51 that the lowest
cost of operation is obtained using the model based on LBT principle while the LTF
model produces the worst results in terms of cost.
0 1 2 3 4 5 6 7 8 9 10 113500
4000
4500
5000
5500
6000
6500
7000
7500
8000
8500
STF
LTF
LBT
Number of Trucks
Cost
(Rup
ees)
Figure 6.51 Comparison of cost for loading three trains
Table 6.33 shows the cost of operation corresponding to minimum makespan
obtained through three different models. The existing operation cost is also given in
Table 6.33. it is found that STF gave the minimum cost while LTF gave the worst
results.
Table 6.33 Operation Cost for loading three trains
STF LTF LBT Existing
Cost (Rupees) 5356 5510 4746.5 8209.5
Number of trucks 8 8 7 15
127
6.3.5Waiting time for unloading operations
The waiting time of truck to unload a container from a train after return back to the
rail yard depends upon the arrival time and departure time of a truck. The Eq 6.2 has
been used to compute the waiting time (w ) of unloading a single container
Figure 6.52 gives the comparisons of the waiting time obtained through three models
based on the SFT, LFT, and FAT principles. It can be seen from Figure 6.52 that the
lowest waiting time of operation is obtained using the model based on STF principle
while the LTF model produces the worst results in terms of waiting time.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160
1000
2000
3000
4000
5000
6000
7000
8000
STF
LTF
FAT
Number of Trucks
Wai
ting
Tim
e (m
inut
es)
Figure 6.52 Comparison of waiting time for unloading three trains
Table 6.34 shows the waiting time of operation corresponding to minimum
makespan obtained through three different models. The existing operation cost is
also given in Table 6.34
Table 6.34 Waiting time for unloading three trains
STF LTF FAT Existing
Waiting time (minutes) 1139 2908 2225.5 8209.5
Number of trucks 5 8 7 15
128
6.3.6Waiting time for loading operations
The waiting time of truck to load a container to a train after coming back to the
storage yard depends upon the arrival time and departure time of a truck. The Eq 6.2
is used to compute the waiting time (w )of loading a single container.
Figure 6.53 gives the comparisons of the waiting time obtained through three models
based on the SFT, LFT, and LBT principles. It can be seen from Figure 6.53 that the
lowest waiting time of operation is obtained using the model based on LBT principle
while the LTF model produces the worst results in terms of waiting time
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160
1000
2000
3000
4000
5000
6000
7000
8000
STF
LTF
LBT
Number of trucks
Wai
ting
time
(Min
tes)
Figure 6.53 Comparison of waiting time for loading of three trains
Table 6.35 shows the waiting time of operation corresponding to minimum
makespan obtained through three different models. The existing operation cost is
also given in Table 6.35
Table 6.35 Waiting Time for loading three trains
STF LTF LBT Existing
Waiting time(minutes) 2818.5 2969.5 1664 7093
Number of trucks 8 8 6 15
129
6.4 Case study 4
This section describes the results of application of greedy algorithm model based on
FAT principle, reverse greedy algorithm model based on LBT principle, greedy
algorithm model based on STF principle, and greedy algorithm model based on LTF
principle. In this case, as given in Table 6.14 there are four trains, 18 trucks and 270
jobs to be processed. The processing time (s) and travel time (2d) for each job for
case study 3 is given in Table 6.36
Table 6.36 Input data of case study 4
job s(min) d (min) job. s(min) d (min) job. s (min) d (min)
1 4.00 2.50 91 1.00 2.50 181 4.00 2.50
2 2.00 3.50 92 3.00 2.00 182 2.00 2.00
3 2.00 4.00 93 2.00 2.50 183 3.00 3.50
4 2.00 2.00 94 3.00 3.50 184 3.00 2.50
5 2.50 3.00 95 3.00 6.00 185 2.00 5.00
6 2.00 2.50 96 3.00 1.50 186 5.00 3.50
7 2.00 3.00 97 4.00 4.00 187 3.00 2.50
8 2.00 2.50 98 3.00 3.50 188 4.00 2.00
9 2.00 5.00 99 3.00 5.00 189 1.50 3.00
10 3.00 2.50 100 3.00 3.50 190 2.00 2.50
11 3.00 3.00 101 4.00 2.50 191 2.00 3.50
12 5.00 3.50 102 2.00 1.50 192 5.00 3.50
13 4.00 1.50 103 2.00 2.50 193 4.00 1.50
14 3.00 3.50 104 2.00 3.50 194 3.00 3.50
15 3.00 3.00 105 2.00 2.00 195 3.00 3.00
16 2.00 2.50 106 3.00 2.50 196 2.00 2.50
17 2.00 2.00 107 5.00 3.50 197 2.00 2.00
18 3.00 4.00 108 3.00 2.00 198 3.00 4.00
19 2.00 2.50 109 3.00 4.50 199 2.00 2.50
20 3.00 2.00 110 2.00 3.50 200 1.50 4.50
21 3.50 3.00 111 2.00 5.00 201 2.00 5.00
22 3.00 3.50 112 3.00 2.50 202 2.00 2.50
23 2.50 4.00 113 2.00 1.50 203 2.50 3.00
24 2.00 2.50 114 3.00 2.00 204 2.00 3.50
130
25 3.00 1.50 115 4.00 2.50 205 2.00 2.50
26 2.00 2.50 116 3.00 3.50 206 3.00 3.50
27 3.00 4.00 117 2.00 1.50 207 2.00 1.50
28 1.50 2.00 118 2.00 6.00 208 3.00 4.50
29 3.00 3.50 119 2.00 2.50 209 3.00 4.00
30 2.00 2.50 120 2.00 3.50 210 2.00 2.50
31 4.00 3.50 121 4.00 1.50 211 3.00 2.00
32 3.00 2.00 122 4.00 4.50 212 2.00 2.00
33 2.00 2.50 123 2.00 2.50 213 4.00 4.50
34 3.00 4.00 124 4.00 6.00 214 6.00 2.50
35 2.00 2.00 125 4.00 2.50 215 3.00 3.00
36 3.00 3.50 126 3.00 3.50 216 3.00 2.50
37 2.00 2.00 127 2.00 2.50 217 5.00 6.00
38 3.00 5.00 128 3.00 3.00 218 1.50 3.00
39 3.50 2.00 129 2.00 2.00 219 3.00 3.50
40 2.00 2.50 130 4.00 2.50 220 5.00 4.00
41 3.00 3.00 131 4.00 3.50 221 3.00 2.00
42 4.00 2.50 132 4.00 1.50 222 5.00 3.50
43 4.00 4.00 133 5.00 3.50 223 4.00 4.50
44 3.00 3.50 134 3.00 5.00 224 1.50 3.00
45 2.00 2.00 135 3.50 2.00 225 2.00 3.50
46 2.00 5.00 136 4.00 2.50 226 2.00 2.50
47 2.00 2.50 137 2.00 3.50 227 2.00 4.00
48 3.00 2.00 138 2.00 4.00 228 2.50 3.50
49 3.00 4.50 139 2.00 2.00 229 6.00 2.50
50 2.00 2.50 140 2.50 3.00 230 5.00 3.50
51 3.00 3.00 141 2.00 2.50 231 2.00 3.00
52 2.00 2.50 142 2.00 3.00 232 4.00 3.50
53 2.00 2.00 143 2.00 2.50 233 2.00 4.00
54 3.00 3.50 144 2.00 5.00 234 4.00 2.50
55 4.00 2.50 145 3.00 2.50 235 4.00 3.50
56 2.00 2.00 146 3.00 3.00 236 2.00 2.50
57 3.00 3.50 147 3.50 3.00 237 3.00 2.00
58 3.00 2.50 148 3.00 3.50 238 5.00 3.00
59 2.00 5.00 149 2.50 4.00 239 2.00 2.50
131
60 5.00 3.50 150 2.00 2.50 240 2.00 3.00
61 3.00 2.50 151 3.00 1.50 241 3.00 3.50
62 4.00 2.00 152 2.00 2.50 242 4.00 4.00
63 1.50 3.00 153 3.00 4.00 243 2.00 2.50
64 2.00 2.50 154 1.50 2.00 244 4.00 3.00
65 2.00 3.50 155 3.00 3.50 245 2.00 4.50
66 3.00 4.00 156 2.00 2.50 246 1.50 2.50
67 4.00 2.50 157 4.00 3.50 247 1.50 1.50
68 4.00 3.50 158 3.00 2.00 248 2.00 2.50
69 3.00 5.00 159 2.00 2.50 249 2.50 3.00
70 2.00 2.50 160 3.00 4.00 250 5.00 3.50
71 3.00 3.50 161 2.00 2.00 251 3.00 2.00
72 2.00 1.50 162 3.00 3.50 252 6.00 2.50
73 3.00 2.50 163 2.00 2.00 253 3.00 4.00
74 3.00 4.50 164 3.00 5.00 254 3.00 1.50
75 2.00 3.00 165 3.50 2.00 255 4.00 3.00
76 3.00 3.50 166 2.00 2.50 256 4.00 2.50
77 4.00 2.50 167 3.00 3.00 257 3.00 3.00
78 4.00 1.50 168 4.00 2.50 258 2.00 3.50
79 3.00 2.00 169 4.00 4.00 259 3.00 3.50
80 2.00 2.50 170 3.00 3.50 260 3.00 1.50
81 3.00 3.50 171 2.00 2.00 261 3.00 2.00
82 2.00 4.50 172 2.00 5.00 262 2.00 2.50
83 3.00 2.50 173 2.00 2.50 263 2.50 3.00
84 3.00 2.00 174 3.00 2.00 264 2.00 3.50
85 2.00 2.50 175 3.00 4.50 265 2.00 3.50
86 2.00 2.50 176 2.00 2.50 266 2.00 2.50
87 3.00 1.50 177 3.00 3.00 267 2.50 1.50
88 2.00 2.50 178 2.00 2.50 268 3.00 3.50
89 3.00 4.50 179 2.00 2.00 269 2.00 2.50
90 1.00 3.50 180 3.00 3.50 270 2.00 2.00
6.4.1Makespan for unloading operations
A Comparison of makespan obtained using the three models based on STF, LTF, and
FAT principles is presented in Figure 6.54 It can be observed from Figure 6.54 that
132
the minimum makespan of 760 minutes is achieved using the model based on FAT.
The number of trucks obtained corresponding to the minimum makespan of 760 is 7.
For the existing situation, the minimum makespan with 18 trucks is 774 minutes.
Therefore, there is a saving of 14 minutes and 11 trucks when the model based on
FAT principle is used. The minimum makespan and the corresponding number of
trucks for the three models and for the existing situation are shown in . In terms of
makespan, the worst performance was obtained by using the STF model.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19755
760
765
770
775
780
785
790
795
800
STF
LTF
FAT
Number of Trucks
Mak
espa
n (m
inut
es)
Figure 6.54 Comparison of makespan for unloading four trains
Table 6.37 Minimum makespan for unloading four trains
STF LTF FAT Existing
Makespan (minutes) 771 760.5 760 774
Number of trucks 8 8 7 18
6.4.2Makespan for loading operations
A comparison of the makespan obtained using the three models based on STF, LTF,
and LBT principles is presented in Figure 6.55. It can be observed from Figure 6.55
that the minimum makespan of 761.5 minutes is achieved using the model based on
STF. The number of trucks obtained corresponding to the minimum makespan of
133
761.5 is 8. For the existing situation, the minimum makespan with 18 trucks is 770.5
minutes. Therefore, there is a saving of 9 minutes and 11 trucks when the model
based on STF principle is used. In terms of makespan, the worst performance was
obtained by using the LTF model. The minimum makespan and the corresponding
number of trucks for the three models and for the existing situation are shown in
Table 6.38.
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19730
740
750
760
770
780
790
800
810
820
830
STF
LTF
LBT
Number of Truck
Mak
espa
n(M
inut
es)
Figure 6.55 Comparison of makespan for loading three trains
It can be seen from Figure 6.55 that there is no reduction in the makespan even when
the number of trucks are increased beyond 7. This results shows that no further
savings in terms of makespan could be achieved by increasing the number of trucks
beyond 7 with either of the three models considered here. However, the optimal
number of trucks in this case study is 5.
Table 6.38 Minimum makespan for loading four trains
STF LTF LBF Existing
Makespan( minutes) 761.5 770.5 763.5 770.5
Number of trucks 8 7 5 18
134
6.4.3Cost for unloading operation
The cost of unloading a containers from trains and transporting it to its location in the
storage yard depends upon the travel time of the truck, processing time taken by the
crane, and waiting time for the truck. The Eq 6.1 is used to compute the cost (C )of
unloading a single container. The comparisons of the cost obtained through three
models based on the STF, LTF, and FAT principles is presented in Figure 6.56. It
can be seen from Table 6.33 that the lowest cost of operation is obtained using the
model based on FAT principle while the LTF model produces the worst results in
terms of cost.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 197000
8000
9000
10000
11000
12000
13000
14000
STF
LTF
FAT
Number of Trucks
Cost
(Rup
ees)
Figure 6.56 Comparison of cost of unloading four trains
Table 6.39 shows the cost of operation corresponding to minimum makespan
obtained through three different models. The existing operation cost is also given in
Table 6.39.
Table 6.39 Comparison of operation cost for unloading four trains
STF LTF FAT Existing
Cost (Rupees.) 9124 9278 8784.5 13974
Number of Trucks 8 8 7 18
135
6.4.4Cost for loading operation
The cost of loading a container onto a train after bringing it from its location in the
storage yard depends upon the travel time of the truck, processing time taken by the
crane, and waiting time for the truck. The Eq 6.1 is used to compute the cost (C )of
loading a single container.
Figure 6.57gives the comparison of cost obtained through three models based on the
SFT, LFT, and LBT principles. It can be seen from Figure 6.57 that the lowest cost
of operation is obtained using the model based on LBT principle while the STF
model produces the worst results in terms of cost.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 204000
5000
6000
7000
8000
9000
10000
11000
12000
STF
LTF
LBT
Number of Trucks
Cost
(Rup
ees)
Figure 6.57 Comparison of cost for loading four trains
Table 6.40 shows the cost of operation corresponding to minimum makespan
obtained through three different models. The existing operation cost is also given in
Table 6.40.
Table 6.40 Operation cost of for loading four trains
STF LTF LBT Existing
Cost (Rupees) 6780.5 6488.5 5604 11621
136
Number of trucks 8 7 5 18
6.4.5Waiting time for unloading operation
The waiting time of truck to unload a container from a train after return back to the
rail yard depends upon the arrival time and departure time of a truck. The Eq 6.2 has
been used to compute the waiting time (w ) of unloading a single container
Figure 6.58 gives the comparison of the waiting time obtained through three models
based on the SFT, LFT, and FAT principles. It can be seen from Figure 6.58 that the
lowest waiting time of operation is obtained using the model based on FAT principle
while the LTF model produces the worst results in terms of waiting time.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190
2000
4000
6000
8000
10000
12000
STF
LTF
FAT
Number of Trucks
Wai
ting
tim
e (m
inut
es)
Figure 6.58Comparison of waiting time for unloading four trains
Table 6.41 shows the waiting time of operation corresponding to minimum
makespan obtained through three different models. The existing operation cost is
also given in Table 6.41
Table 6.41 Waiting time for unloading four trains
STF LTF FAT Existing
Waiting time(minutes) 3645.5 3694.5 2863 11287.5
Number of trucks 8 8 7 18
137
6.4.6Waiting time of loading operation
The waiting time of truck to load a container to a train after coming back to the
storage yard depends upon the arrival time and departure time of a truck. The Eq 6.2
is used to compute the waiting time (w )of loading a single container.
Figure 6.59 gives the comparisons of the waiting time obtained through three models
based on the STF, LTF, and LBT principles. It can be seen from Figure 6.59 that the
lowest waiting time of operation is obtained using the model based on LBT principle
while the STF model produces the worst results in terms of waiting time
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190
2000
4000
6000
8000
10000
12000
STF
LTF
LBT
Number of Trucks
Wai
ting
time
(min
utes
)
Figure 6.59 Comparison of waiting time for loading four trains
Table 6.42 shows the waiting time of operation corresponding to minimum
makespan obtained through three different models. The existing operation cost is
also given in Table 6.42.
Table 6.42 Waiting time for loading four trains
STF LTF LBT Existing
Waiting time (minutes) 3605 2995 1396.5 11232.5
Number of trucks 8 7 5 18
138
6.5 Summary of loading and unloading results
In this section, summary of results of minimum makespan and related number of
trucks, cost and waiting time is presented in Table 6.43, Table 6.44, Table 6.45. The
results presented here have obtained from models based on STF, LTF, FAT, and
LBT scheduling mechanisms as discussed in the previous sections. The number of
jobs considered in case studies 1 to 4 ranges from 70 to 270. The number of trucks
varies from 9 to 18, and upto four trains have been considered in the four case studies
discussed in the previous sections. Summary of minimum makespan with related
number of trucks obtained with four models based on different scheduling algorithms
for loading unloading operations with different number of trains are given in Table
6.43. The summary of cost related to the minimum makespan with number of trucks
is given in Table 6.44. In same way, the summary of waiting time is given in Table
6.45.
Table 6.43 Summary of minimum makespan for loading-unloading operations
Scheduling Mechanisms
STF LTF LBT FAT
One Train
(loading operations)
Makespan(min) 204.5 213.5 208 -
Trucks 6 7 5 -
One Train
(unloading operations)
Makespan(min) 214.5 204.5 - 201.5
Trucks 5 9 - 5
Two Trains
(loading operations)
Makespan(min) 423.5 432.5 427.7 -
trucks 7 8 6 -
Two Trains
(unloading operations)
Makespan(min) 434 422.5 - 421
trucks 5 6 - 7
Three Trains
(loading operations)
Makspan(min) 599.5 608.5 601.5 -
trucks 8 8 6 -
Three Trains
(unloading operations)
Makespan(min) 610.5 602.5 - 601
trucks 5 5 - 7
139
Four Trains
(loading operations)
Makespan(min) 761.5 770.5 763.5 -
trucks 8 7 5 -
Four Trains
(unloading operations)
Makspan(min) 771 760.5 - 760
trucks 8 8 - 7
Table 6.44 Summary of cost corresponding to the minimum makespan for loading
and unloading operations
Scheduling mechanism
STF LTF LBT FAT
One Train
(loading operations)
Cost (Rs) 1684 1869 1563 -
trucks 6 7 5 -
One Train
(unloading operations)
Cost(Rs) 2146 2180 - 2164.5
trucks 5 5 - 5
Two Trains
(loading operations)
Cost(Rs) 3574 3935.5 3384 -
trucks 7 8 6 -
Two Trains
(unloading operations)
Cost(Rs) 4400 4695 - 4861
trucks 5 6 - 7
Three Trains
(loading operations)
Cost(Rs) 5356 5510 4746.5
trucks 8 8 6 -
Three Trains
(unloading operations)
Cost (Rs) 6265 6319 - 6908
trucks 5 8 7
Four Trains
(loading operations)
Cost(Rs) 6780.5 6488.5 5604 -
trucks 8 7 5 -
Four Trains
(unloading operations)
Cost(Rs) 9124 9278 - 8784.5
trucks 8 8 - 7
Table 6.45 Summary of waiting time corresponding to the minimum makespan for
140
loading and unloading operations
Scheduling mechanism
STF LTF LBT FAT
One Train
(loading operations)
Waiting time(min)
562.5 838 333 -
trucks 6 7 5 -
One Train
(unloading operations)
Waiting time(min)
397 391 - 322
trucks 5 5 - 5
Two Trains
(loading operations)
Waiting time(min)
1576.5 2117 1151
trucks 7 8 6 -
Two Trains
(unloading operations)
Waiting time(min)
814 1234 - 1525.5
trucks 5 6 - 7
Three Trains
(loading operations)
Waiting time(min)
2818.5 2969.5 1664
trucks 8 8 6 -
Three Trains
(unloading operations)
Waiting time(min)
1139 2908 - 2225.5
trucks 5 8 - 7
Four Trains
(loading operations)
Waiting time(min)
3605 2995 1396.5 -
trucks 8 7 5 -
Four Trains
(unloading operations)
Waiting time(min)
3645.5 3694.5 - 2863
trucks 8 8 - 7
141
6.6 Analysis of models results
6.6.1Optimal number of trucks
In this section, analysis of results obtained from models based on STF, LTF, FAT,
and LBT scheduling mechanisms has been carried out. The results have been
presented for optimal number of trucks, makespan, cost, and waiting time for
different number of trains. In each case study, the results have presented for loading,
unloading and combined loading-unloading operations. The optimal number of
trucks required to unload different number of trains is presented in Figure 6.60. It can
be seen from Figure 6.60 that for unloading one to three trains, the best results in
terms of minimum number of trucks required is obtained using STF model. For
unloading four trains, the best results were obtained using FAT model. Results
obtained by FAT model are as good as those obtained by STF model for unloading
one train. The results produced by LTF model are inferior to STF and FAT models
for unloading any number of trains.
Figure 6.61 shows optimal number of trucks required for loading a given number of
trains using STF, LTF, and LBT models. The optimal solution obtained using LBT
model is superior to those produced by other models for loading operations. For
loading one train, the STF model suggests that six numbers of trucks must be used
for loading one train. However, a better optimal solution (five trucks) is obtained
using LBT model. Similarly, LBT model produces the best solution for loading two
to four trains. The worst results are produced by the LTF model.
142
1 2 3 40
1
2
3
4
5
6
7
8
9
10
STF
LTF
FAT
Number of trains
Num
ber o
f tru
cks
Figure 6.60 Number of trucks versus number of trains in unloading process
1 2 3 40
1
2
3
4
5
6
7
8
9 STF
LTF
LBT
Number of trains
Num
ber o
f tru
cks
Figure 6.61 Number of trucks versus number of trains in loading process
143
1 2 3 40123456789
1011121314151617181920
STF
LTF
LBT/FAT
Number of trains
Num
ber o
f tru
cks
Figure 6.62 Number of trucks versus number of trains in loading-unloading process
The optimal results obtained by using different models for combined loading and
unloading operations are presented in Figure 6.62. The STF and LTF model have been
applied to both loading and unloading operations. The LBT model is used for loading
operations only while FAT model can be used for unloading operations. It can be seen
from Figure 6.62 that ten trucks are required for loading and unloading a single train. For
processing both loading and unloading jobs for two and three trains, the best results are
obtained using STF model. For four trains, the best results (12 trucks) are obtained by
using FAT and LBT models. The worst results for combined operations are produced by
the LTF model.
6.6.2Optimal makespan
Figure 6.63 shows optimal makespan for unloading different number of trains using
STF,LTF, and FAT models while Figure 6.64 shows optimal makespan for loading
different number of trains using STF, LTF, and LBT model. Figure 6.65 shows
optimal makespan for combined loading and unloading number of trains using STF,
LTF, LBT, andFAT algorithms. The optimal makespan for combined laoding and
unloading process is shown in Figure 6.65.
144
1 2 3 40
100
200
300
400
500
600
700
800
900
214.5
434
610.5
771
201.5
422.5
598.5
760.5
201.5
421
601
760STF LTF
FAT
Number of trains
Mak
espa
n (m
inut
es)
Figure 6.63 Makespan versus number of trains in an unloading process
1 2 3 40
100
200
300
400
500
600
700
800
900
204.5
423.5
599.5
761.5
213.5
432.5
608.5
770.5
208
427.5
601.5
763.5 SFT
LTF
LBT
Number of trains
Mak
espa
n (m
inut
es)
Figure 6.64 Makespan versus number of trains in a loading process
145
1 2 3 40
200
400
600
800
1000
1200
1400
1600
1800
418.5
857.5
1210
1532.5
415
855
1207
1531
409.5
848.5
1202.5
1523.5STF LTF
FAT/LBT
Number of trains
Mak
espa
n (m
inut
es)
Figure 6.65 Makespan versus number of trains in loading and unloading process
It can be seen from Figure 6.63 that the FAT model produces the best results for
unloading one, two and four number of trains. For unloading three trains, LTF model
produces the best results. For unloading three trains, the results produced by FAT are
only marginally lower than the LTF model. Therefore, FAT model can be considered
as the best model for unloading processes in terms of makespan, This result is
consistent with the theorem 1 which states that greedy algorithm based on FAT
principle produces optimal results for unloading processes. The worst results are
produced by the STF model for unloading any number of trains. For loading jobs,
STF model produces the best results for any number of trains considered. The worst
results in case of loading jobs were produced by LTF as can be seen from Figure
6.64. For combined loading and unloading process, FAT and LBT models together
produce the best results. The worst results for combined loading and unloading of
one, three or four number of trains are produced by the STF model. However, for
combined loading and unloading of a single train, the worst results are obtained by
LTF model.
6.6.3Optimal cost
Figure 6.66 shows optimal cost for unloading different number of trains using STF,
LTF, and FAT algorithms while Figure 6.67 shows optimal cost for loading different
146
number of trains using STF, LTF, and LBT models. For combined loading and
unloading operations, the results are shown in Figure 6.68.
1 2 3 40
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
2146
4400
6265
9124
2732
4695
7326.5
9278
2164.5
4861
6908
8784.5
STF
LTF
FAT
Number of trains
Cost
(Rup
ees)
Figure 6.66 Cost versus number of trains in unloading process
1 2 3 40
1000
2000
3000
4000
5000
6000
7000
8000
1684
3574
5356
6780.5
1869
3935.5
5510
6488.5
1563
3384
4746.5
5604
STF
LTF
LBT
Number of trains
Cost
(Rup
ees)
Figure 6.67 Cost versus number of trains in loading process
147
1 2 3 40
2000
4000
6000
8000
10000
12000
14000
16000
18000
3830
7974
11621
15904.5
4601
8630.5
12836.5
15766.5
3727.5
8245
11654.5
14388.5 STF LTF
FAT/LBT
Number of trains
Cost
(Rup
ees)
Figure 6.68 Cost versus number of trains in combined loading-unloading process
It can be seen from Figure 6.66 that the STF model produces best results for unloading
one, two or three number of trains. For unloading trains, FAT model produces the best
results. The LTF model produces worst results for most cases for unloading operations.
For loading operations, LBT produces the best results for all cases of number of trains.
The worst results for loading operations are produced by LTF for one, two and three
number of trains. For loading four number of trains, STF produces the worst results as
can be seen from Figure 6.67. For combined loading and unloading operations, the FAT
and LBT model produces the best results in terms of cost of operation for one and four
number of trains. For combined loading and unloading operations of two and three
trains, STF model produces the best results. The LTF model produces the worst results
for most of the cases.
6.6.4Optimal waiting time
Figure 6.69 shows optimal waiting time for unloading different number of trains
using STF, LTF, and FAT models. Figure 6.70 shows optimal waiting time for
unloading different number of trains using STF, LTF, and LBT models. Figure 6.71
shows optimal waiting time for combined loading and unloading operations for
different number of trains.
148
1 2 3 40
500
1000
1500
2000
2500
3000
3500
4000
397
8141139
3645.5
1165 1234 1150
3694.5
322
1525.5
2225.5
2863 STF
LTF
FAT
Number of trains
Wai
ting
time
(min
utes
)
Figure 6.69 Waiting time versus number of trains in an unloading process
1 2 3 40
500
1000
1500
2000
2500
3000
3500
4000
2165.5
1576.5
2818
3605
2995
2117
2969.5 2995
1396.51151
1664
1396.5
STF
LTF
LBT
Number of trains
wai
ting
time(
min
utes
)
Figure 6.70 Waiting time versus number of trains in loading Process
149
1 2 3 40
1000
2000
3000
4000
5000
6000
7000
8000
2562.5 2390.5
3957
7562
4160
3351
4119.5
6689.5
1718.5
2676.5
3889.5
4259.5
STF
LTF
LBT/FAT
Number of trains
waiti
ng ti
me(
Min
utes
)
Figure 6.71 Waiting time versus number of trains in combined loading-unloading
process
From the Figure 6.69, it can be seen that the best results are obtained for two and three
number of trains using STF model. For one and four number of trains the best results are
obtained by FAT model. The FAT model produces worst results for two and three
number of trains while for one and four number of trains the LTF model produces result
that are substantially inferior to that produced by FAT. For unloading a single train, the
results produced by LTF model are 3 times inferior to those produced by FAT model.
For loading operations, LBT produces far better results that are produced by other two
models (Figure 6.70). It can be seen from Figure 6.70 that the worst results for loading
operations are produced by LTF models for one, two, or three number of trains. For four
number of trains, STF produces the worst results. For combined loading-unloading
operations, the best results for one, three and four trains are obtained using the LBT and
FAT models together. For combined loading-unloading of two trains, the best results are
obtained using STF. The worst results for all the cases except for four trains are obtained
by LTF. When the numbers of trains are four, the STF model produces the worst results.
150
6.7 Recommended Models
This section presents a summary of recommended models for loading operations,
unloading operations and combined loading and unloading operations for different
number of trains. Table 6.46 presents the recommended models and associated
savings for loading, unloading and combined loading-unloading processes for a
single train. The computation of savings has been carried out with respect to the
existing operation procedures being followed at ICD, Tughlakabad. It can be seen
from Table 6.46 that by using the models recommended in this study, a substantial
savings in operation costs can be achieved. Table 6.47, Table 6.48, and Table 6.49
present a summary of recommend models, cost savings, savings in resources for
loading, unloading, and combined loading and unloading processes for two, three
and four trains respectively. The computations of savings in cost, time and resources
(trucks) is presented in Table 6.50, Table 6.51, and Table 6.52. It can be seen from
these Tables that substantial savings can be achieved by using the models developed
in this study.
Table 6.46 Recommended models for loading and unloading one train
Loading operations
Min
Value
Recommended
Model
Savings (minute) Percentage
savings
Makespan (minutes)
204.5 STF 213.5 – 204.5 = 7 3.4%
Cost (Rs.) 1563 LBT 2176-1563=613 39,2%
Waiting time (minutes)
333 LBT 1235-333=902 270%
trucks 5 LBT 9-5=4 80%
Unloading operation
Makespan (minutes)
201.5 FAT 214-201.5=12.5 6.2%
151
Cost (Rs.) 2146 STF 2732-2146=586 27%
Waiting time (minutes)
322 FAT 1235-322=913 283.5%
trucks 5 FAT, STF 9-5=4 80%
Combined operation
Makespan (minutes)
406 STF(L)FAT(UL) 428-406=22 5.4%
Cost (Rs.) 3709 LBT(L)STF(UL) 4908-3709=1199 32%
Waiting time (minutes)
655 LBT(L)FAT(UL) 2400-655=1745 266%
trucks 10 LBT(5L)FAT(UL
)
18-10=8 80%
Table 6.47 Recommended models for loading and unloading two trains
Loading Operations
Min
Value
Recommended
Model
Savings (minute) Percentage
savings
Makespan (minutes)
423.5 STF 432.5-423.5=9 2.1%
Cost (Rs.) 3384 LBT 5059.5-3384=1675.5 49.5%
Waiting time (minutes)
1151 LBT 3779-1151=2628 228%
trucks 6 FAT 12-6=6 100%
Unloading operation
Makespan (minutes)
421 FAT 437-421=16 3.8%
Cost (Rs.) 4400 STF 6375-4400=1975 44.8%
152
Waiting time (minutes)
814 STF 3856-814=3042 373.7%
trucks 5 STF 12-5=7 140%
Combined operation
Makespan (minutes)
844.5 STF(L)FAT(UL) 869.5-844.5=25
2.9%
Cost (Rs.) 7748 LBT(L)STF(UL) 11434.5-7748= 3686.5
47.5%
Waiting time (minutes)
1965 LBT(L)STF(UL) 7635-1965=5670 288.5%
trucks 12(7+5) LBT(L)FAT(UL) 24-12=12 trucks 100%
Table 6.48 Recommended models for loading and unloading three trains
Loading Operations
Min
Value
Recommended
Model
Savings Percentage
savings
Makespan (minutes)
599.5 STF 608.5-599.5 = 9 1.5%
Cost (Rs.) 4746.5 LBT 8209.5-4746.5=3463 77.2%
Waiting time (minutes)
1664 LBT 7093-1664=5429 326%
trucks 6 LBT 15-6=9 150%
Unloading operation
Makespan (minutes)
598.5 LTF 622-598.5=23.5 3.9%
Cost (Rs.) 6265 STF 10075-6265=3792 60%
Waiting time (minutes)
1139 STF 8209.5-1139=7070 620%
trucks 5 STF 15-5=10 200%
Combined operation
153
Makespan (minutes)
1200.5 STF(L)FAT(UL) 1230.5-1200.5=30 2.4%
Cost (Rs.) 11011 LBT(L)STF(UL) 17325-11011=6314 57.3%
Waiting time (minutes)
2803 LBT(L)STF(UL) 5302.5-2803= 12500 446%
trucks 13(8+5)
or(6+7)
STF(L+UL) or FAT(L)LBT(UL)
30-13=17 130%
Table 6.49 Recommended models for loading and unloading four trains
Loading Operations
Recommended
Model
Savings Percentage
savings
Makespan (minutes)
761.5 STF 770.5-761.5 = 9 1.18%
Cost (Rs.) 5604 LBT 11621-5604 =6017 107%
Waiting time (minutes)
1396.5 LBT 112232-1396=9836 704 %
trucks 5 LBT 18-5=13 260%
Unloading operation
Makespan (minutes)
760 FAT 774-760=14 1.8%
Cost (Rs.) 8784.5 FAT 13974-8784.5= 5189.5 59%
Waiting time (minutes)
2863 FAT 11287.5-2863= 8424.5 294%
trucks 7 FAT 18-7= 11 157%
Combined operation
Makespan (minutes)
1521.5 STF(L)FAT(UL) 1544.5-1521.5=23 1.5%
Cost (Rs.) 14388.5 LBT(L)FAT(UL) 25595-14388 =11206 77.8%
154
Waiting time (minutes)
4259.5 LBT(L)FAT(UL) 22520-4259.5 =18260.5
428.7%
trucks 12(5+7) LBT(L)FAT(UL) 36-12=24 200%
155
Table 6.50 Computations for savings in cost for one train
Saving per train
(Rs.)
Daily Saving for 8
trains (Rs)
Annual saving (Rs.)
Loading 613 4904 1789960
Unloading 586 4688 1711120
Combined 1199 9592 3501080
Table 6.51 Computations for time savings for unloading one train
Saving per train
(minutes.)
Daily Saving for 8
trains(minutes)
Annual saving
(minutes/day.)
Loading 7 56 20440=14.2 days
Unloading 12.5 100 36500=25.35 days
Combined 22 167 60955=42.33 days
Table 6.52Computations for resource savings for one train
Saving per train
(truck)
Daily Saving for 8
trains
Annual saving (truck.)
Loading 4 32 11680
Unloading 4 32 11680
Combined 8 64 23360
156
7. Conclusions and future work
This chapter summarises the research reported in this thesis, outlining the limitations
of the research and providing recommendations for future research. Containerization
of general cargo has been increasing steadily over the last three decades. Starting
with 76 million twenty feet equivalent unit (TEU) in year 1988, world container
turnover has reached more than 544 Million TEU in year 2008. As a result of the
increasing volume of the world container turnover, container terminals have become
an important component of the global transportation network. Due to and rising
competition, handling an enormous volume of containers speedily and accurately is
of paramount importance to a container terminal. To achieve better operations
efficiency, a container terminal needs to address the complicated process of
transporting containers between various containers handling equipment.
The transportation of containers between the quayside and the yard-side can be
decomposed into a number of separate sub-processes according to the type of
equipment involved. In most container terminals, trucks are commonly used for
transporting containers. Determining the sequence of containers to be handled by
trucks is one of the major issues in terminal planning. This sequencing decision
directly affects the operation efficiency of both the quayside and the yard-side to a
large extent. Unnecessary truck waiting times would lead to a longer terminal
turnaround time; terminals need to develop optimal truck schedules to ensure a high
terminal throughput. Scheduling problems have been studied extensively in the
operations research and management science literature but very few studies have
been carried out to study scheduling problems of container transporting equipment
such as trucks.
The research presented in this thesis describes the development and application of
models to solve truck scheduling problem that is the problem of scheduling a fleet of
trucks to handle a set of non-preemptive jobs with sequence-dependent processing
times and different arrival time to minimize the makespan. In this research,
157
development and implementation of several kinds of models for optimal scheduling
of loading and unloading operations in container terminals has been presented. A
generic model based on mixed integer programming (MIP) has been developed and
its effectiveness in scheduling container loading and unloading operations has been
studied. In addition to MIP model, four generic models based on different scheduling
algorithms have been developed in this research. The performance of these models
has been evaluated in terms of the quality of solution achieved by them. Comparison
of the performance of MIP model with that of other models has revealed that
although MIP model is able to produce optimal solutions but its execution time is
quite high. Due to the high execution time requirements, it was concluded that MIP
model has limited practical applicability to the real world problems. It was decided to
apply greedy algorithm for truck scheduling problem in ICD, Tughlakabad. The main
motivation behind using greedy algorithm is that easy to implement in real-world
situations because it is highly efficient in terms of time requirements. Following this
introduction, section 7.1 presents the achievements of the research. section 7.2
describes the limitations and section 7.3 presents a few pointers towards the future
work.
7.1 Achievement of the thesis
The research presented in this thesis is made up of three distinct parts. The first part
of the thesis presents the literature review related to the application of optimization
techniques to container terminal operations. Review of container terminal processes
has also been presented in the first part of the thesis. In the second part, development
of a MIP model has been described. Application of MIP model to a number of
container loading and unloading problems has also been described in the second part
of the thesis. Finally, development and application of models based on different
scheduling mechanisms to several real world problems has been presented. Major
achievements of the thesis highlighting the contributions at each stage are presented
below.
158
Following the introduction to global and Indian port scenario, chapter 2 of the thesis,
presents a review of optimization techniques for improving the efficiency and
productivity of container terminals. A review of container terminal processes is also
presented in chapter 2 of the thesis. Chapter 3 of the thesis describes the
characteristics of the Port of Singapore. The factors that are responsible for making
Singapaore the leading port in the world have been discussed. Operations at
Container Corporation of India’s ICD at Tughlakabad in New Delhi have been
described in chapter 3 of this thesis. Various facilities available at ICD, Tughlakabad
have also been described. A summary of control, handling and scheduling operations
has been presented in tabular form in chapter 3. It was observed that except for
container stock and booking position, none of the operations are scheduled or
planned using the real time planning of logistics. Therefore, there is an urgent need
to develop models for improving the efficiency of terminal operations in ICD,
Tughlakabad.
In Chapter 4 of the thesis, formulation of truck dispatching problem has been
presented. A generic model based on MIP has been developed using AMPL
programming language. Four different problems with combinations of number of
trucks and number of trucks were solved using MIP model. It was concluded that the
execution time requirements are quite high for problems of larger size. Therefore,
application of MIP model to solving real world problems is not practical. In chapter 5
of the thesis, heuristic models based on greedy and reverse greedy algorithms have
been described. Four different models based on shortest time first (STF), longest
time first (LTF), last busy truck (LBT), and first available truck (FAT) scheduling
mechanisms have been developed, and described in this chapter.
Application of models based on STF, LTF, LBT, and FAT to four real-world case
studies based on the data collected from CONCOR for ICD, Tughlakabad has been
described in chapter 6 of the thesis. The data pertaining to job processing and travel
times as obtained from CONCOR is presented in tabular form in the chapter. Using
the real world data, optimal scheduling of container loading and unloading jobs has
been carried out. Comparison of optimal results achieved by each of the four models
159
has also been made. Major achievements of the research carried out in this thesis
may be summarized as follows:
A comprehensive review of literature related to application of optimization
techniques for improving container terminal operations has been carried out with
a view to provide ready reference for any future work.
A comprehensive review of processes being followed, and equipment being used
in container terminals has been carried out in order to put the work carried out in
this research in context.
Real-world data pertaining to processing time and travel time for each container
has been procured from CONCOR, and has been used to test the developed
models
A generic MIP model that is transportable to any other container terminal with
minimal changes has been developed for the truck scheduling problem
Analysis of several computational experiments carried out using the MIP model
has revealed that the execution time requirements are quite high for solving even
moderate size problems, thereby ruling out the application of MIP model to large
real-world problems
Four generic models based on STF, LTF, FAT, and LBT scheduling mechanisms
have been developed and their practicality in solving complex problems has been
demonstrated through application to four real-world problems.
It has been demonstrated that the application of recommended models for
unloading different number of trains as presented in section 6.7 could lead to
substantial savings in the cost of operations
A distinct practical advantage of the model developed in this work are that they
are transportable to any other container terminal without any difficulty
160
Models developed in this work can be used by terminal operations managers for
optimizing container terminal processes
Models recommended in this work provide a wider choice to the terminal
managers as well as to customers
Finally, implementation of models developed in this work is straightforward due
to the ease of interfacing
7.2 Limitations of the research
This section presents the limitations of the research presented in this thesis.
The location for storing containers in the storage yard has not been taken into
account by the models developed in this work. Each container was randomly
assigned to a location in the storage yard. The time taken by the yard crane has not
been separately considered. Instead, it was included in the travel time of the jobs. To
prevent congestion and accidents in the terminal, the speed of each truck was
restricted to 15 km/hr. Assigning higher speeds could have led to decrease in the
makespan. The capacity of each truck has been assumed to be one container although
some trucks could carry two number of TEU containers. Further, due to space
limitations each train could carry a maximum 90 TEU containers.
7.3 Recommendations for further research
To conclude the thesis, the following recommendations are made for further research
which could lead to further improvement in efficiency and productivity in container
terminals.
In practice, one important issue is how to determine a storage location for each
unloading container. In the models described here, the storage location is not
considered as a decision variable. Considering storage location as a decision variable
is likely to improve the efficiency of terminals but it makes the problem highly
161
complex. Another aspect that could be considered in future work is to identify routes
for each truck with the objective to minimize the makespan and at the same time
avoid congestion in the terminal. This would lead to decrease in the cost of
operations. In this work, the time taken by the yard crane to load and unload the
containers was assumed to be included in the travel time. In future work, the time
taken by the yard for loading and unloading may be considered separately.
162
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Appendix A
Glossary of container terminal terms used in this thesis
Adaptability: capacity of CT operators to implement solutions, i.e., changes to
shipping line schedules and fulfil other customer requirements.
Automated Guided Vehicle (AGV): is a mobile robot used highly in industrial
applications, such as container terminal to move containers from point to point.
Berth: location in which ship is docked alongside a Quay to be loaded o unloaded at
a Container Terminal.
Berth Assignment or Berth Assignment Plan: a document describing which Berth
and machines are to be assigned to a specific Ship. This decision is based on Ship
line schedule (Ship Data), Bay plan (no. of Containers to be loaded/unloaded),
Contracts, Berth Availability and Resource Availability.
Bulk Cargo: is homogeneous unpacked cargo such as grain, coal or sugar.
Chassis: A frame with wheels and container locking devices to secure the container
for movement.
Container Capacity: is used to determine the number of containers that can be
handled with the current resources for the year (for a Port or Terminal).
Container freight station (CFS) A dedicated port or container terminal area, usually
consisting of one or more sheds or warehouses and uncovered storage areas where
cargo is loaded (“stuffed”) into or unloaded(“stripped”) from containers and may be
temporarily stored in the sheds or warehouses.
Containerisation International (CI) magazine: is the premier source of high-level
industry intelligence for the container industry.
Customhouse: A government office where duties are paid, documents filed, and so
forth, on foreign shipments.
Demurrage: A penalty charge against shippers or consignees for delaying the
carrier’s equipment beyond the allowed free time.
180
Dispatching: A method of generating scheduling in job shops whereby the decision
about which job to progress next is made using simple priority rules whenever the
workstation becomes available for further processing
Dry Port: a facility located in the hinterland or away from a body of water and
operates many of the activities associated with a traditional port or terminal, such as:
stripping and stuffing containers; receiving and dispatching goods and containers,
temporary storage for an arriving ship, etc.
Dwell Time: time that a container waits in a terminal to be loaded or unloaded onto
another mode of transport.
Gantry crane :A crane fixed on a frame or structure spanning an intervening space
typically designed to traverse fixed structures such as cargo (container) storage areas
or quays and which is used to hoist containers or other cargo in and out of vessels
and place or lift from a vessel, barge, trucks, chassis, or train.
Heavy lift charge: A charge typically imposed when special lifting gear is required
to handle a given piece of cargo, which may be of either heavy weight or of large
dimensions (often referred to as “out of gauge” when dealing with container vessels).
Inland Container Depot is an organisation offering a total package of activities to
handle and control container and general cargo flows between road, rail and
waterways, and vice versa, resulting in maximum service for inland transportation at
minimum costs.
Inland Container Depots: are interfaces between connecting modes of
transportation.
Intermodal container terminal is a terminal where containers enter and leave by
multiple means of transport, as trucks, trains, air cargoes and vessels (I/O transport
means).
Operating Cost: Cost per time period for operating a piece of equipment, such as a
Quay Crane, a ship, Straddle Carrier, Yard Crane, etc.
181
Pallet :A flat tray, generally made of wood, but occasionally steel or other materials,
on which goods can be stacked. There are two principal sizes: the ISO pallet, which
measures 1 x 1.2 meters, and the euro pallet at 0.8 x 1.2 meters.
Priority sequencing rules: the rules that specify the job processing sequence when
several jobs are waiting in line at workstation
Rail-mounted gantry (RMG): Rail-mounted gantry crane used for container
acceptance, delivery, and stacking operations in a container yard.
Service Time: time that ship is served may include down (time that is non productive
stop time for lunch, maintenance, etc.
Spreader: A piece of equipment designed to lift containers by their corner castings.
Stack: physical arrangement of containers assigned according to yard layout.
Stevedoring charges: Fees for loading and stowing or unloading a ship.
Stowage: The method of placing cargo into a single hold or compartment of a ship to
prevent damage, shifting, etc
Straddle carrier: Type of equipment that picks up and transports containers between
its legs for movement within a container terminal.
Terminal handling charge (THC): A charge made for a service performed in a
terminal area typically referring to handling associated with receipt, delivery, or
inspection of cargo via land-based operations.
Terminal productivity : deals with the efficient use of labour, equipment and land. A
means of quantifying the efficiency of the use of these resources. Limits on the
productivity of a container terminal may be imposed by either physical or
institutional factors or a combination of both.
Twenty-foot Equivalent Unit (TEU) container size standard of twenty feet. Two
twenty-foot containers (TEUs) equals one FEU. Container capacity is often measured
based on TEU as well as container port or terminal throughput capacity.
Tired mounted gantry (RTG) :Gantry crane on rubber tires typically used for
acceptance, delivery, and container stacking at a container yard.
182
Turnaround time: the time it takes between the arrival of the vessel or train and its
departure.
Yard Location: a cell in a container stack according to Container Characteristics.
There are several types of Stacks, for example a hazardous stack or reefer stack, etc.
Note: Compiled from various sources: UNCTAD, Interviews, Webster’s Dictionary,
Chapman’s Seaman’s dictionary, various trade and industry brochures and
http://en.wikipedia.org.
183
Appendix B
Table B1 - Technical information of TMGC used in CONCOR
Project No :K100-K103
1-General Crane Specifications
- Rated load40 tonnes- Width(mm) 7+1 containers (27000 mm)- Height (mm) 4+1 Containers (15240 mm)- Container Range 20’ & 40’ retractable flipper
2-Speed
- Main Hoist 20 m/min (40 Ton)40 m/min (empty spreader)
- Trolley 75 m/min- Gantry 90 m/min
3-Electrical Equipment
- Control Voltage 220 VAC- Main Voltage 415 VAC, 50 Hz
Table B2 - Technical Information of RMGC used at CONCOR
Project NO: K 063 FELS
1-Lifting capacity
- Rated load under spreader 40 tonnes- Lift height 9.5 m- Span 22.5 m- Outreach from Rails (both sides) 7
2-Speed
- Main Hoist 20 m/min (40 Ton)40 m/min (empty spreader)
- Trolley 75 m/min- Gantry 90 m/min with empty spreader
25 m/min with rated load3-Electrical Equipment
- Control Voltage 230 VAC- Main Voltage 480 VAC, 50 Hz
Board Particulars of Bogie Container Flat Wagon
184
1. The design of the wagon has been optimised to achieve lower tare weight, thereby having a higher payload.
2. The wagon has been designed for transportation of 2896mm(9’-6”) high series I ISD containers at operating speed of 100 kmph.
3. The wagon is provided with single pipe gradable release Airbrake System with two stage automatic load sensing advice and wheel type hand brake.
4. The wagon loaded with 2896mm (9’-6”) high ISO Containers when standing on straight and level track is within the maximum moving dimensions of standard class locomotives.
Table B3 - Examples of CT operating systems and land used per annum
Operating Systems m2 per 1000 TEU p.a. Examples of operating
system
Wheeled operation 50000 Norfolk, Baltimore, New
York/New Jersey
SC 20000 Norfolk, Antwerp,
Zeebrugge,Gothenburg
TMGC 12000 Antwerp, Rotterdam
RMGC 8000 Kaoshiung
AGV/ASC 2500 ECT in the Netherlands
(withautomated stacking
cranes, ASC)
185
Table B4 - Comparison of yard equipment OHBC, RMGC, and TMGC.
Item TMGC RMGC OHBC
Possibility of application
at conventional terminal Very easy Easy Very difficult
Precision of job Low High Very high
Initial Investment Low High Very high
Technical problem
Engineering
facilities are
necessary to prevent
settlement of
ground
Engineering facilities
are necessary to
prevent settlement of
ground
-Engineering facilities
are necessary to
prevent settlement of
ground –
manufacturing steel
boom with high
intensity
Terminal retaining the
equipment
CONCOR-TKD
New Delhi
ECT/DSL,
Thames port
HHLA
Singapore (PPT)
186
Appendix C
Code for Mathematical Model using AMPL software
param m;
param n;
param k;
set I={1..n};
set J={1..m};
set M={1..k};
param K=10000;
param d{1..n};
param s{1..n};
var ta{I}>=0;
var td{I}>=0;
var y{I,M} binary;
var x{I,J,M} binary;
minimize T: max{i in I}ta[i];
subject to
onetruck {i in I}: sum {j in M} y[i,j]=1;
jobafteri {i in I,p in M}: sum {j in J:j<>i} x[i,j,p]<=y[i,p];
jobbeforei {j in J,p in M }: sum {i in I:i<>j} x[i,j,p]<=y[j,p];
precedence {i in I, j in J,p in M:j<>i}: x[i,j,p]+x[j,i,p]>=y[i,p]+y[j,p]-1;
#precedence1 {i in I, j in J,p in M:j<>i}: x[i,j,p]+x[j,i,p]<=1;
mix {i in I, j in J,p in M:j<>i}: ta[i]<=K*(1-x[i,j,p])+ta[j];
comp {i in I}: td[i]+2*d[i]=ta[i];
depart {i in M}:td[i]=if i=1 then s[1] else sum{a in 1..i} s[a];
depart2{i in k+1..n}:td[i]=min{a in i-k..i-1}ta[a]+abs (min{a in i-k..i-1}ta[a]- max {a
in i-k..i-1}td[a])+s[i];
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Appendix D
Code for Greedy Algorithm Based Model
/***************************************************************/
/* Final Code for Greedy Algorithm as on May 2007*/
#include <stdio.h>#include <stdlib.h>#include <math.h>#include <string.h>#include <iostream.h>include <CONIO.h>#include "rvector.cpp"
void moment(float data[], int n, float *ave, float *adev, float *sdev, float *var, float *skew, float *curt) ;
void piksr2(int n, float arr[], int brr[]);void sortdescending(int n, float arr[]);int RandomInteger(int, int );
float findavg(float [], int );float findstddev(float [], int);float findmax(float vals[],int num_els) ;float findmin(float vals[],int num_els) ;
void get_f(char name[]) ;
/* routine to find average of values */float findavg(float *vals,int num_els){float average, summation=0.0F;
for (int i=1;i<=num_els; i++) {summation=summation+vals[i];
}average = summation/num_els;return average;
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}/**********************************************//******This function returns standard deviation of n flaot values ****/float findstddev(float *vals,int num_els) /* no semi colon here */{
float avg,stddev,square_sum;float sum = 0.0F;float sum_square = 0.0F;
for (int i = 1; i <= num_els; i++) {sum += vals[i];sum_square += vals[i] * vals[i];
}
avg = sum/num_els;square_sum = avg * avg * num_els;stddev = sqrt((sum_square - square_sum)/(num_els - 1));if(stddev==0) stddev=1;return stddev;
}/**************************************************************************/ /**************************************************************************/ /* routine to find the maximum value for a given array starts here */float findmax(float vals[],int num_els) /* no semi colon here */{float max=vals[1];int i;
for (i=1;i<= num_els; i++)if (vals[i]>=max) max=vals[i];
return max;}/**************************************************************************/ /* routine to find the mimimum value for a given array starts here */float findmin(float vals[],int num_els) /* no semi colon here */{
int i;float min=vals[1];
for (i=1;i<=num_els; i++)if (vals[i]<=min) min=vals[i];
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return min;}/**************************************************************************//*************************************************************************/void sortascending(int n, float arr[]) {int i,j;float a;
for (j=2; j<=n; j++) {a=arr[j];i=j-1;while(i>0 && arr[i]>a) {
arr[i+1]=arr[i];i--;
}arr[i+1]=a;}
}/********ROUTINE TO SORT num_els number of values ************************//*************************************************************************/void piksr2(int n, float arr[], int brr[]) {/* arranges arr values and ascending but keeps the linkbetween index and values intact */int i,j;float a;int b;
for (j=2; j<=n; j++) {a=arr[j];b=brr[j];i=j-1;while(i>0 && arr[i]>a) {
arr[i+1]=arr[i];brr[i+1]=brr[i];i--;
}arr[i+1]=a;brr[i+1]=b;}
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}/***********************************************************/void moment(float data[], int n, float *ave, float *adev, float *sdev, float *var,
float *skew, float *curt){
int j;float ep=0.0, s,p;if (n<=1) nrerror (" n should be atleast 2");s=0.0;for(j = 1; j <= n; j++) s+=data[j];*ave = s/n;*adev=(*var)=(*skew)=(*curt)=0.0;for(j = 1; j <= n; j++) {
*adev+=fabs(s=data[j]-(*ave));ep+=s;*var+= (p=s*s);*skew+= (p *=s);*curt+= (p*=s);
}
*adev /=n;*var=(*var-ep*ep/n)/(n-1);if (*var==0.0) *var=0.01F;*sdev=sqrt(*var);if (*var) {
*skew/=(n*(*var)*(*sdev));*curt=(*curt)/(n*(*var)*(*var))-3.0;
}else nrerror ("No skew/kurtosis when variance is zero ");
}/*****************************************************************//*************************************************************************/void sortdescending(int n, float arr[]) {int i,j;float a;
for (j=2; j<=n; j++) {a=arr[j];i=j-1;while(i>0 && arr[i]<a) {
arr[i+1]=arr[i];i--;
}arr[i+1]=a;}
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}/*****************************************************************/main(){ char title[80];//char stationfile[ARRAY_SIZE][STR_SIZE] ;int ii, jj, tt, Njobs, Ntrucks;int *y, *truckAvail;float W, CurMin, PreMin, makespan;float *s, *d, *x;float **Tarr, **Tdep;float waiting=0.0;
FILE *f1,*f2;
/* Open the main List file */if(!(f1 = fopen("results.txt", "w"))) {
printf(" Can't open GreedyAlgorithm.lst on f1/n") ;exit(1) ;
}if(!(f2 = fopen("input1.dat", "r"))) {
printf(" Can't open GreedyAlgorithm.lst on f2/n") ; exit(1) ; }
fscanf(f2,"%d ",&Njobs); fscanf(f2,"%d ",&Ntrucks);
fprintf(f1,"Number of jobs=%d\n",Njobs); fprintf(f1,"Number of trucks=%d\n",Ntrucks); //fgets(title, 80, f1); //puts(title);
printf("Njobs = %4d & ", Njobs);printf("Ntrucks = %4d\n", Ntrucks);printf("press a key to continue\n");
s = vector (1, Njobs);d= vector (1, Njobs);x= vector (1, Ntrucks);y= ivector (1, Ntrucks);
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truckAvail= ivector (1, Njobs);fprintf(f1,"Job_Number Processing_Time Travel_Time \n");fprintf(f1,"==========================================\
n");for(ii = 1; ii <= Njobs; ii++) {
fscanf(f2,"%f %f" ,&s[ii],&d[ii] );
fprintf(f1,"%2d\t %2.2f\t %2.2f \n",ii,s[ii],2.0*d[ii]);}
printf("data read successfully; press a key to continue\n");
(void)fclose(f2) ;
Tarr = matrix(1, Njobs,1,Ntrucks);Tdep = matrix(1, Njobs,1,Ntrucks);
W = 0.0;PreMin = -100.0;
ii =1;jj=1;for(tt = 1; tt <= Ntrucks; tt++) {
truckAvail[tt] = tt;Tdep[jj][tt] = jj*s[jj];Tarr[jj][tt] = Tdep[jj][tt] + 2.0*d[jj];x[ii] = Tarr[jj][tt];
// printf("x[%d]=%3.2f\t",ii,x[ii]);ii = ii +1;jj=jj+1;
}
for(ii = 1; ii <= Ntrucks; ii++) {y[ii]=ii;
}
piksr2(Ntrucks, x, y);fprintf(f1,"\n");float z=0.0;float c=0.0;float total=0.0;float ww=0;
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fprintf(f1,"Job_Number Depart_Time Arrival_Time Waiting_Time Travel_Time Truck_No Cost(Rs)\n");
fprintf(f1,"===============================================================================================\n");
for(ii = 1; ii <= Ntrucks; ii++) {printf("x[%d]=%3.2f , ",ii, x[ii]);printf("y[%d]=%d\n",ii, y[ii]);
z=z+s[ii];
fprintf(f1,"%3d\t %5.2f\t %5.2f\t %3.2f\t %5.2f\t %d\t %6.2f \n",ii,z,z+2.0*d[ii],ww,2.0*d[ii],ii,c=(2.0*d[ii]*4.0)+(z*2.0));
total+=c; ww=z; waiting+=ww;
}
// stage loop starts here
for(jj = (Ntrucks + 1); jj <= Njobs; jj++) {CurMin=x[1];//previous minimum arrival time
CurMin = x[1];truckAvail[jj] = y[1];
PreMin=0;//previous maximum departure time
for(int kk=1 ;kk<jj;kk++){//printf("\ntruck[%d]=%d \
n",kk,truckAvail[kk]); if (PreMin<Tdep[kk][truckAvail[kk]]) PreMin=Tdep[kk]
[truckAvail[kk]];}
W = PreMin-CurMin;if (W<0) W=W*(-1.0);
printf("jj=%4d\t",jj);printf("PreMin=%3.2f\t", PreMin);printf("CurMin=%3.2f\t", CurMin);printf("truckAvai[%d] =%d\t",jj, truckAvail[jj]);
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printf("W =%3.2f\n", W);
//if (W>=s[jj]) W = 0.0;//printf("W after correction =%3.2f\n", W);
//PreMin = CurMin;
Tdep[jj][truckAvail[jj]] = CurMin+s[jj] + W;Tarr[jj][truckAvail[jj]] = Tdep[jj][truckAvail[jj]] + 2.0*d[jj];
printf("Tarr[%d][%d]=%3.2f\n",jj,truckAvail[jj], Tarr[jj][truckAvail[jj]]);c=4.0*(Tarr[jj][truckAvail[jj]]-Tdep[jj][truckAvail[jj]])+0.5*W+s[jj];fprintf(f1,"%3d\t %5.2f\t %5.2f\t %2.2f\t %5.2f\t %d\t
%6.2f \n",jj,Tdep[jj][truckAvail[jj]],Tarr[jj][truckAvail[jj]],W,Tarr[jj][truckAvail[jj]]-Tdep[jj][truckAvail[jj]],truckAvail[jj],c);
total+= c ;waiting+=W;x[1] = Tarr[jj][truckAvail[jj]];y[1] = truckAvail[jj];piksr2(Ntrucks, x, y);
}makespan = Tarr[Njobs][truckAvail[Njobs]];printf("makespan=%3.2f\n", makespan);fprintf(f1,"\n\nMakespan=%3.2f\n",makespan);
fprintf(f1,"Total Cost=%3.2f\n",total);fprintf(f1,"Total waiting=%3.2f",waiting);
//print the resultsprintf("Job No. Truck Assigned\n");for(jj = 1; jj <= Njobs; jj++) {
printf( " %4d % 4d\n", jj, truckAvail[jj]);} fclose(f1);return 0;
} /* end of main */
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Code for Reverse Greedy Algorithm Based Model
/***************************************************************//* Final Code for Greedy Algorithm as on 15 June 2007*/#include <stdio.h>#include <stdlib.h>#include <math.h>#include <string.h>#include <iostream.h>
#include "rvector.cpp"
const unsigned STR_SIZE = 25; //no. of characters in filenamesconst unsigned ARRAY_SIZE = 10; //depends upon number of files
void moment(float data[], int n, float *ave, float *adev, float *sdev, float *var, float *skew, float *curt) ;
void piksr2(int n, float arr[], int brr[]);void sortdescending(int n, float arr[]);int RandomInteger(int, int );
float findavg(float [], int );float findstddev(float [], int);float findmax(float vals[],int num_els) ;float findmin(float vals[],int num_els) ;
void get_f(char name[]) ;
/* routine to find average of values */float findavg(float *vals,int num_els){float average, summation=0.0F;
for (int i=1;i<=num_els; i++) { summation=summation+vals[i];
}average = summation/num_els;return average;
}/**********************************************//******This function returns standard deviation of n flaot values ****/float findstddev(float *vals,int num_els) /* no semi colon here */{
float avg,stddev,square_sum;
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float sum = 0.0F;float sum_square = 0.0F;
for (int i = 1; i <= num_els; i++) {sum += vals[i];sum_square += vals[i] * vals[i];
}
avg = sum/num_els;square_sum = avg * avg * num_els;stddev = sqrt((sum_square - square_sum)/(num_els - 1));if(stddev==0) stddev=1;return stddev;
}/**************************************************************************/ /**************************************************************************/ /* routine to find the maximum value for a given array starts here */float findmax(float vals[],int num_els) /* no semi colon here */{float max=vals[1];int i;
for (i=1;i<= num_els; i++)if (vals[i]>=max) max=vals[i];
return max;}/**************************************************************************/ /* routine to find the mimimum value for a given array starts here */float findmin(float vals[],int num_els) /* no semi colon here */ {
int i;float min=vals[1];
for (i=1;i<=num_els; i++)if (vals[i]<=min) min=vals[i];
return min;}/**************************************************************************/
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/*************************************************************************/void sortascending(int n, float arr[]) {int i,j;float a;
for (j=2; j<=n; j++) {a=arr[j];i=j-1;while(i>0 && arr[i]>a) {
arr[i+1]=arr[i];i--;
}arr[i+1]=a;}
}/********ROUTINE TO SORT num_els number of values ************************//*************************************************************************/void piksr2(int n, float arr[], int brr[]) {/* arranges arr values and ascending but keeps the link between index and values intact */int i,j;float a;int b;
for (j=2; j<=n; j++) {a=arr[j];b=brr[j];i=j-1;while(i>0 && arr[i]>a) {
arr[i+1]=arr[i];brr[i+1]=brr[i];i--;
}arr[i+1]=a;brr[i+1]=b;}
}/***********************************************************/void moment(float data[], int n, float *ave, float *adev, float *sdev, float *var,
float *skew, float *curt) {
198
int j; float ep=0.0, s,p;if (n<=1) nrerror (" n should be atleast 2");s=0.0;for(j = 1; j <= n; j++) s+=data[j];*ave = s/n;*adev=(*var)=(*skew)=(*curt)=0.0;for(j = 1; j <= n; j++) {
*adev+=fabs(s=data[j]-(*ave));ep+=s;*var+= (p=s*s);*skew+= (p *=s);*curt+= (p*=s);
}
*adev /=n;*var=(*var-ep*ep/n)/(n-1);if (*var==0.0) *var=0.01F;*sdev=sqrt(*var);if (*var) {
*skew/=(n*(*var)*(*sdev));*curt=(*curt)/(n*(*var)*(*var))-3.0;
}else nrerror ("No skew/kurtosis when variance is zero ");
}/*****************************************************************//*************************************************************************/void sortdescending(int n, float arr[]) {int i,j;float a;
for (j=2; j<=n; j++) {a=arr[j];i=j-1;while(i>0 && arr[i]<a) {
arr[i+1]=arr[i];i--;
}arr[i+1]=a;}
}/***************************************************************/main(){char title[80],temptitle[80];
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char datafile[ARRAY_SIZE][STR_SIZE] ;int ii, mm, jj, tt, kk, Njobs, Ntrucks, Nfiles;int *y, *z, *jobseq, *truckAvail, *Ntrips, *revindex, *x;int **jobByTruck;float W, CurMin, PreMin, makespan, netCost;float *s, *d, *rd, *xarr, *xdep, *diff, *TD, *TA,*cost;float **Tarr, **Tdep;
float shipCost = 10;float truckCost1 = 5; //per minute costfloat truckCost2 = 4; //per truck costfloat waitSum=0.0;FILE *f1, *f2;/*Nfiles = 1;if(!(f1 = fopen("ReverseGreedyAlgorithm.lst", "r"))) { printf(" Can't open GreedyAlgorithm.lst on f1/n") ; exit(1) ; }
fgets(temptitle, 80, f1);puts(temptitle);printf("Names of files as read from Main File\n");for (mm=1; mm<=Nfiles; mm++) {
fgets(datafile[mm],STR_SIZE, f1);printf("%3d %s\n", mm, datafile[mm]);
}
for (mm=1; mm<=Nfiles; mm++) {for (ii=1; ii<=STR_SIZE; ii++) {
if (datafile[mm][ii] =='\n') datafile[mm][ii]='\0';}
}(void)fclose(f1);
/*****************************************//* open the actual data file */
/* for(mm = 1; mm <= Nfiles; mm++) { if(!(f2 = fopen(datafile[mm], "r"))) {
printf(" Can't open datafile on f2\n") ; exit(1) ;
}fgets(title, 80, f2) ;
}*/// puts(title);if(!(f1=fopen("Results2.txt","w"))) printf("Can not create file ");if(!(f2=fopen("input2.dat","r"))) printf("Can not open file ");
200
fscanf(f2,"%d ",&Njobs);fscanf(f2,"%d ",&Ntrucks);
printf("Njobs = %4d\t", Njobs);printf("Ntrucks = %4d\n", Ntrucks);fprintf(f1,"Number of Jobs=%d\n",Njobs);fprintf(f1,"Number of Trucks=%d\n",Ntrucks);printf("press a key to continue\n");
s = vector (1, Njobs);d= vector (1, Njobs);rd= vector (1, Njobs);xarr= vector (1, Ntrucks);xdep= vector (1, Ntrucks);diff= vector (1, Ntrucks);TD = vector (1, Njobs);TA = vector (1, Njobs);
y= ivector (1, Ntrucks);z= ivector (1, Ntrucks);revindex = ivector (1, Njobs);Ntrips = ivector (1, Ntrucks);
truckAvail= ivector (1, Njobs);jobseq= ivector (1, Njobs);fprintf(f1,"Job_Number Processing_Time Half_Travel_Time\n ");fprintf(f1,"==============================================\
n");for(ii = 1; ii <= Njobs; ii++) {
fscanf(f2,"%f %f" ,&s[ii],&d[ii] );
fprintf(f1,"%2d\t %3.2f\t %3.2f\t\n" ,ii,s[ii],d[ii] );}
printf("data read successfully\n");(void)fclose(f2) ;
//reverse the job orderjj=0;float ww=0.0;float waiting=0.0;
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fprintf(f1,"Job_Number Depart_Time Arrival_Time Waiting_Time Travel_Time Truck_Number Cost\n ");
fprintf(f1,"=======================================================================================\n");
for(ii = Njobs; ii >= 1; ii--) {jj=jj+1;rd[ii]= d[jj];
}printf("order reversed\n");
Tarr = matrix(1, Njobs,1,Ntrucks);Tdep = matrix(1, Njobs,1,Ntrucks);cost= vector(1,Njobs);
W = 0.0;PreMin = -100.0;float a=0;
float total=0.0;ii =1;jj=1;
makespan=0.0F;for(tt = 1; tt <= Ntrucks; tt++) {
a+=s[jj];truckAvail[tt] = tt;Tdep[jj][tt] = a;Tarr[jj][tt] = Tdep[jj][tt] + 2.0*rd[jj];if (Tarr[jj][tt]>makespan) makespan = Tarr[jj][tt];xarr[ii] = Tarr[jj][tt];xdep[ii] = Tdep[jj][tt];
cost[tt]=4.0*(Tarr[jj][truckAvail[jj]]-Tdep[jj][truckAvail[jj]])+2.0*a;
printf("xarr[ii]=%3.2f\n", xarr[ii]);printf("xdep[ii]=%3.2f\n", xdep[ii]);fprintf(f1,"%2d\t %5.2f\t \t%5.2f\t \t %3.2f\t \t %5.2f\t %5d\t \t %5.2f\t\
n",jj,Tdep[jj][tt],Tarr[jj][tt],ww,Tarr[jj][tt]-Tdep[jj][tt],tt,cost[tt] );total+=cost[tt];ww=a;waiting+=ww;ii = ii +1;jj=jj+1;
}
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for(ii = 1; ii <= Ntrucks; ii++) {y[ii]=ii; z[ii]=ii;
}
piksr2(Ntrucks, xarr, y);
piksr2(Ntrucks, xdep, z);printf("Arrival times in ascending order\n");for(ii = 1; ii <= Ntrucks; ii++) {
printf("xarr[ii]=%3.2f\n", xarr[ii]);}
for(ii = 1; ii <= Ntrucks; ii++) {printf("y[ii]=%d\n", y[ii]);
}
printf("Departure times in ascending order\n");for(ii = 1; ii <= Ntrucks; ii++) {
printf("xdep[ii]=%3.2f\n", xdep[ii]);}
for(ii = 1; ii <= Ntrucks; ii++) {printf("z[ii]=%d\n", z[ii]);
}
// stage loop starts here for(jj = (Ntrucks + 1); jj <= Njobs; jj++) {
W = xdep[Ntrucks] - xarr[1];if (W <0.0) W =0.0F;waitSum=waitSum+W;printf("W=%3.2f WaitSum = %3.2f\n",W, waitSum);CurMin = xarr[1];truckAvail[jj] = y[1];
printf("jj=%4d\n",jj);printf("PreMin=%3.2f\n", PreMin);printf("CurMin=%3.2f\n", CurMin);printf("truckAvai[jj] =%d\n", truckAvail[jj]);printf("W =%3.2f\n", W);
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PreMin = CurMin;
Tdep[jj][truckAvail[jj]] = CurMin+s[jj] + W;Tarr[jj][truckAvail[jj]] = Tdep[jj][truckAvail[jj]] + (float)2.0*rd[jj];if (Tarr[jj][truckAvail[jj]]>makespan) makespan = Tarr[jj][truckAvail[jj]];printf("Tdep[jj][truck[jj]]=%3.2f\n", Tdep[jj][truckAvail[jj]]);printf("Tarr[jj][truck[jj]]=%3.2f\n", Tarr[jj][truckAvail[jj]]);xarr[1] = Tarr[jj][truckAvail[jj]];xdep[Ntrucks] = Tdep[jj][truckAvail[jj]];y[1] = truckAvail[jj];piksr2(Ntrucks, xarr, y);cost[jj]= 2.5*(Tarr[jj][truckAvail[jj]]-Tdep[jj][truckAvail[jj]])+0.5*W+s[jj];
fprintf(f1,"%2d\t %5.2f\t\t%5.2f\t \t %5.2f\t \t %5.2f\t %5d\t \t %5.2f\t\n",jj,Tdep[jj][truckAvail[jj]],Tarr[jj][truckAvail[jj]],W,Tarr[jj][truckAvail[jj]]-Tdep[jj][truckAvail[jj]],truckAvail[jj] ,cost[jj]);
total+=cost[jj];waiting+=W;}printf("makespan=%3.2f\n", makespan);netCost = makespan*(shipCost - truckCost1)-Ntrucks*truckCost2;printf("netCost=%3.2f\n", netCost);printf("waitSum=%3.2f\n", waitSum);
// REVERSE THE indexii=Njobs+1;for(jj = 1; jj <= Njobs; jj++) {
ii=ii-1;revindex[ii]=jj;
}printf("After reversing \n");
printf("jobs truck available Arrival time Departure time\n");for(ii = 1; ii <= Njobs; ii++) {
kk = revindex[ii];
}
// calculate number of trips for each truckjobByTruck = imatrix(1, Ntrucks, 1, Njobs);
for(jj = 1; jj <= Ntrucks; jj++) {for(ii = 1; ii <= Njobs; ii++) {
jobByTruck[jj][ii]=0;
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}}
for(jj = 1; jj <= Ntrucks; jj++) {Ntrips[jj] =0; kk =0;for(ii = 1; ii <= Njobs; ii++) {
if (truckAvail[revindex[ii]] == jj) {kk=kk+1;Ntrips[jj] = Ntrips[jj]+1;jobByTruck[jj][kk] = ii;
}}
}
for(jj = 1; jj <= Ntrucks; jj++) {printf( " %4d % 4d\n", jj, Ntrips[jj]);
}
printf( " Jobs by each truck\n");
for(jj = 1; jj <= Ntrucks; jj++) {printf(" Truck No = %4d\n", jj);for(ii = 1; ii <= Ntrips[jj]; ii++) {
printf("%4d\n", jobByTruck[jj][ii]);}
}
printf("truck job Arrival time\n");for(jj = 1; jj <= Ntrucks; jj++) {
ii = jobByTruck[jj][1];kk = revindex[ii];y[jj]=ii; xarr[jj] = Tarr[kk][truckAvail[kk]];
// printf( " %4d % 4d\n", jj,jobByTruck[jj][1]);printf( " %4d %4d %3.2f\n", jj,ii,Tarr[kk][truckAvail[kk]]);
}
//sortthe last Ntrucks arrival times
piksr2(Ntrucks, xarr, y);
printf("Arrival times in ascending order\n");for(jj = 1; jj <= Ntrucks; jj++) {
printf("xarr[jj]=%3.2f y[jj]=%d\n", xarr[jj], y[jj]);}
for(jj = 1; jj <= Ntrucks; jj++) {
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ii = jobByTruck[jj][1];kk = revindex[ii];diff[jj]= xarr[Ntrucks] - Tarr[kk][truckAvail[kk]];printf("diff[jj]=%3.2f \n", diff[jj]);
}
// re run the algorithmtt=0; ii=0;while (tt< Njobs) {
ii=ii+1;for(kk =1; kk <= Ntrucks; kk++) {
tt = tt+1;jobseq[tt] = jobByTruck[kk][ii];if (tt==Njobs) break;}
}printf("makespan=%3.2f\n", makespan);for(ii = 1; ii <= Njobs; ii++) {
printf("jobseq[ii]=%4d\n", jobseq[ii]);}printf("Job ArrTime DepTime\n");for(ii = 1; ii <= Njobs; ii++) {
kk = revindex[ii];// printf( " %4d % 4d %3.2f %3.2f\n", ii, truckAvail[kk], Tarr[kk]
[truckAvail[kk]], Tdep[kk][truckAvail[kk]]);TA[kk]= makespan-Tdep[kk][truckAvail[kk]] ;TD[kk] = TA[kk] +s[kk];printf("%4d %4.2f %4.2f\n", ii, TA[kk], TD[kk]);
}fprintf(f1,"\n\nMakespan=%6.2f\n",makespan);fprintf(f1,"Total Cost=%6.2f\n",total); fprintf(f1,"Total waiting=%6.2f\n",waiting); fclose(f1);
return 0;
} /* end of main */
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Start
Input Njobs, Ntrucks, si ,di
Assign job i to available truck ii<=Ntrucks
i=1
Ouput results
Calculate Tdi,Tai, Wii=Ntrucks+1
i<=Njobs
k<=i
Assign job i to available truckavial
Calculate Tdi,Tai, Wi
End
Calculate truckavial
Complexity of greedy algorithm
Greedy Algorithm: first loop (i=1 to Ntrucks) complexity=Ntrucks
Second loop (i= Ntrucks+1 to Njobs) inside loop (k=1 to i)
Complexity= (Njobs-Ntrucks-1)*Njobs
Total complexity =O ((Njobs)2)where O(n) is big O function
Complexity is the same for reverse greedy
207
k=1
Appendix E
List of publications
1. Dayoub M, Suhaib S and Khan R. A, Shipport’s handling Equipment-A Review ,
Proceedings of National Conference on emerging Trends in Manufacturing Systems
(ETMS-2005), Seth Jai Parkash Mukand Lal Insititute of Engineering & Technology
(JMIT) Radaur (Yamuna Nagar) ISO 9001: 2000 Certified , March 15-16, 2005
2. Dayoub M, Suhaib S and Khan R. A, Material handling Equipment-A Review ,
Proceedings of National Conference on Recent Trends in Design and Manufacturing
Technologies (RTDMT-2005), Kumaraguru College of Technology, Coimbatore
(Tamil Naidu), March 17-18, 2005.
3. Dayoub M, Suhaib S and Khan R. A, Technologies for containers movement in
container terminal – a survey , Proceedings of International Conference on Advances
in Materials, Product Design and Manufacturing Systems (ICMPM 2005), Bannari
Amman Institute of Technology, Sathyamangalalam (Tamil Nadu), December’ 2005.
4. Dayoub M. Suhaib M. and Khan R.A., Loading and Unloading Containers
Operations at Container terminal and application of greedy algorithm , Proceedings
of Advances in Mechanical Engineering (AIME 2006), Faculty of Engineering and
Technology Jamila Millia Islamia, New Delhi, January 20-21, 2006.
5. Dayoub M. Sharif M, .Rakesh N, and Khan R.A.,Selection of Material Handling
Equipments Using Expert System , Proceedings of International Conference on
Advances in Manufacturing Engineering,(ICAME-2007), Department of Mechanical
and manufacturing Engineering ,MIT, Manipal.October 24-26 -2007.
208