Logistics Operations Scheduling in Port Terminals

Abstract

As international trade has grown tremendously during the last couple of decades, ports have played the major role in this area as they represent the focal point in goods exchange between countries and continents. Sea ports are one of the most important types of ports as they represent the interface between different transportation modes. Nowadays, 60% of the world trade in transported by sea. Therefore, ports compete with each other in terms of the quality of service provided to shipping lines. Thus, ports exert a huge effort to reduce vessels turn-around time to improve their customer satisfaction together with minimizing ports overall costs and efficiently utilizing available resources. Since scheduling problems in ports have very complex nature, research tackling such problems has started many years ago to aid decision makers to achieve improved port performance and minimizing costs to enhance competitiveness. Researchers have classified decision making problems in ports according the area in the port and the resources used. Port areas can be classified into a quay area and a land or yard area, each area contains different types of material handling equipment. Research tackling the quay area included berth allocation problem, quay crane assignment problem and quay crane scheduling problem. Berth allocation problem is considered one of the most important problems in ports scheduling due to the huge investment needed to construct a berth. Thus, berthing space is considered as a scarce resource in port terminals. Berth allocation decision is concerned with assigning berthing time and location to incoming vessels. Also, problems related to quay cranes scheduling attracted the attention of researchers. Quay crane assigning problem is concerned with assigning available quay cranes to berthed vessels, while quay crane scheduling problems is concerned with determining a detailed schedule for each quay crane according to vessels stowage plans. Since both berth allocation decisions and quay crane assignment decisions are dependent, integrated models for berth allocation quay crane assignment decisions were introduced by researchers. Most of the existing literature is concerned with developing solution techniques using metaheuristics to obtain optimal or near optimal scheduling decisions. The objective of this thesis is to study different parameters affecting port scheduling performance. Different performance measures such as mean flow time; make span and berth utilization are considered to study port scheduling performance. In order to perform this study, a model for berth allocation problem is developed. The model aimed to obtain a berthing schedule for incoming vessels with static or dynamic vessel arrival in a continuous berth port. An analogy between berth allocation problem and parallel machines scheduling problems is introduced where it was shown that berth allocation problem is a special case of parallel machines scheduling problem. The developed model is the extended to perform the quay crane assignment, thus; the model is capable to solve the integrated berth allocation quay crane assignment problem. An analogy is performed to compare berth allocation quay crane assignment problem with parallel machines scheduling problems. The analogy shows that berth allocation quay crane assignment problem is a special case of parallel machines scheduling problem with additional resources. Since the problem under study is known to be NP hard in a very strong sense, a genetic algorithm model is proposed to solve berth allocation problem. Also, a heuristic is proposed to perform quay crane assignment for berthed vessels based on the berthing sequence and positions obtained by the genetic algorithm. The developed genetic algorithm is applied to berth allocation problems where the results are compared with that obtained using exact solution methods. The proposed genetic algorithm is found to be capable to obtain the same objective value for small size problems in much less computational time. Also, the developed heuristic is applied to solve integrated berth allocation quay crane assignment problems. The obtained results are compared with that obtained using exact solvers where a gap ranging between 1.5% to 4% exists in the objective value. The proposed genetic algorithm and crane assignment heuristic is applied to analyse different parameter and their effect on port scheduling performance. The effect of incoming vessels configurations is studied where problems with different vessels configurations are solved for minimum mean flow time and maximum berth utilization. The difference between berthing schedules which satisfy different objectives is studied. It is concluded that minimum make span and maximum berth utilization are achieved through the same berthing schedule. While minimum mean flow time together with minimum vessels waiting time are achieved through a different schedule.