Optimal Scheduling For Container Terminal Loading And Unloading Operations With Heavy Tailed Operating Times

The loading to and unloading operations of a container vessel,as a key that impacts the supply chain efficiency,determines the profits of the container terminal itself and its upstream and downstream firms.The complexity of its scheduling decision features in the heavy tailed distributed operating times,the dynamic correlation of a container operating system,the flexibility of equipment assignment,and the multi-objective scheduling decision-making.However,the scheduling problem of loading and unloading operations in a container terminal is a semi-structured decision problem because of the heavy tailed distributed operating times,which makes this problem extremely hard to solve and imposes great challenges to the operation management of a container terminal.This research studies the scheduling problems for container terminal loading and unloading operations with heavy tailed operating times.It is under the context of quay crane double cycling and yard mixed storage strategy in container terminals.This study uses system analysis to study the wholeness,relevancy and hierarchy of the loading and unloading operating system.The optimal equipment assignment problem and sequence optimization problem are explored in succession to overcome the complexity from the heavy tailed operating times.The research includes the following aspects:(1)Problem statement and analysis for the scheduling of container terminal loading and unloading operations with heavy tailed operating times.This section studies the loading and unloading operating unit of a container terminal in the context of quay crane double cycling and yard mixed storage strategy.It provides the problem statement for the scheduling problem of container terminal loading and unloading operations with heavy tailed operating times.It analyses the main influencing factors for heavy tailed operating times,and how it effects the scheduling of loading and unloading operations.The decision process for the scheduling problem is decribed and analysed.(2)An optimal equipment assignment method with heavy tailed operating times.This section provides a problem statement for the optimal equipment assignment problem of container terminal loading and unloading operations.We consider an operating system to unload containers from and load containers to a bay of a container vessel,which consists of one quay crane serving as the key operating equipment,two yard cranes cooperating with each other as the service equipment,and N yard trucks as the accessory equipment.Firstly,a stochastic programming model is developed to determine the number of yard trucks and truck cycle times for quay crane double cycling.Secondly,a two-node closed queueing network is established to evaluate the performance of the quay crane in the programming model.This section also includes the development of a three-step method to solve the performance of the queueing network under heavy tailed service times.The performance problem with exponential distributed service times is solved in the first step using Markov chains.In the second step,a simulation model for the queueing process of the loading and unloading operations is developed.In step three,the results from the simulation model and from the Markov chains solved by queueing network are compared,and an empirical estimation for the performance of queueing network with heavy tailed service times is discussed.In the last part of this section,a heuristic algorithm to solve the complex integer programming model is developed.(3)A multi-objective optimization method for operation sequencing with heavy tailed operating times.A problem statement for the operation scheduling problem with heavy tailed operating times is first defined,which aims to minimize the makespan to finish all import and export containers in a bay of a vessel and to minimize the total time that no yard trucks show at the quayside or at the yard side.The unloading and loading sequences of quay crane at the quayside,stacking and retrieving sequence for yard cranes at the yard side,and container assignment for yard trucks are included in this problem.Then,a multi-objective mixed integer programming model is developed,and is used to analyze the optimization model.Finally,a PNSGA-II algorithm is designed to solve this NP-hard problem.Besides,illustrations for the key algorithm steps are provided.(4)Numerical experiment and case study.This section presents the numerical experiments results based on the real operation data from a container terminal in north China.First,the numerical experiments are performed with the parameters setting based on the real case data.Then,the performances of the proposed methods for the equipment assignment problem and the operation sequencing problem are evaluated,respectively.Third,the numerical experiments results are presented to show how the scheduling decisions for loading and unloading operations would be affected by different types of heavy tailed service times,yard truck scheduling strategies,and yard layouts.Finally,this section presents the managerial insights from these results.This study proposes a sequential decision making method for the optimal scheduling for container terminal loading and unloading operations with heavy tailed operating times under quay crane double cycling and yard mixed storage strategy.In this sequential decision making method,the equipment assignment decision and operation sequencing decision for loading and unloading operations are made successively.This decision making scheme offers a new solution for modeling and solving the operation scheduling problem with heavy tailed operating times.This study offers a Markov chain and simulation based method to evaluate the efficiency of quay crane under heavy tailed operating times.The new method also helps to solve the multi-objective mixed-integer programming problem with large solution space and dynamic parameters affected by decision variables through embedding a simulation based module into the algorithm.It will contribute to solving the NP-hard problem of sequence optimization in container terminals.This study is the extension of the collebrative scheduling theory,queueing theory,and multi-objective optimization problem.It provides solutions of scheduling for container terminal loading and unloading operations with heavy tailed operating times,which will provide decision support for improving the effectiveness and scientificalness of daily operating in container terminals.