|Title:||Yard allocation problem with time dimension at seaport terminal|
|Advisors:||Xu, Zhou (LMS)|
|Subject:||Harbors -- Management|
Freight and freightage
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Logistics and Maritime Studies|
|Pages:||xii, 118 pages : color illustrations|
|Abstract:||Seaports constitute the most important cargo distribution terminal in modern logistics. According to statistics released by the United Nations in 2020, the annual container throughput of Port of Singapore had reached nearly 38 million TEUs in 2019, and the number keeps increasing year by year. Large Asian ports have limited land and yet, they play key roles as international maritime hubs. How to balance various facilities to store a growing number of containers within the limited yard space? This is a challenge for port managers. This thesis considers the yard space allocation problem with a time dimension. The time dimension is mainly reflected in two aspects. First, visits to ports of different vessels have different patterns in terms of time periods, which adds complex constraints when allocating storage spaces at different periods. Second, containers transported by the same vessel always arrive at the yard during a time interval. A consignment strategy can help avoid overlapping of storage space allocations. The storage space should also be non-decreasing with time. In essence, the second yard space allocation problem with time dimension is a three-dimensional packing problem with irregular shapes. This makes it challenging to obtain a high-quality space allocation schedule with existing algorithms. Besides, the complexity caused by the time dimension and the scheduling of yard trucks are closely related to space allocation. Unreasonable space allocation can lead to traffic congestion in yard lanes and lead to inefficient container handling due to uneven workload distribution, affecting the port operations on the berth side. Therefore, yard space allocation plays a critical role in the overall seaport schedule.|
This thesis addresses the yard space allocation problem with the time dimension at container terminals. We build mathematical models and design efficient algorithms by considering traffic congestion in the yard and low space utilization in a yard block. This thesis addresses two optimization problems relevant to the yard space allocation problem: allocation of containers to blocks at the yard level and optimization of flexible storage spaces allocation to different requests at the block level. The main contributions of this thesis are summarized as follows. (1) Yard-level space optimization. Considering vessels with multiple periods, we take the sub-block as the primary storage space allocation unit in this study. Both the sub-block location decision and the loading and unloading time decisions are considered. To avoid traffic congestion in the yard, we minimize the operating cost of yard trucks and the total time deviation between the actual operating time and the expected handling time of all vessels. We propose a three-stage heuristic algorithm based on a critical element, which can efficiently obtain an allocation schedule that minimizes the transportation cost and time deviations. As a result, containers from each vessel are allocated to different blocks. Each block is assigned with containers from different vessels. (2) Block-level space optimization. Following the assignation of containers to a block at the yard-level optimization, we aim to obtain a space-saving allocation schedule for this block. We remove the boundaries between the fixed subblocks and consider a rectangular storage space with flexible shapes and positions. Such flexible rectangular spaces are allocated to containers at each time. In this study, a new dynamic shape adjustment and placement algorithm is proposed, which can efficiently obtain a solution with high space utilization in each block. The decision of this optimization problem refines the space allocation and saves available storage space for a block. In summary, the algorithms proposed in this thesis can coordinate yard space allocation and scheduling of yard trucks, so that the yard can avoid traffic congestion and optimize the space usage in each block. Our research provides an effective yard allocation solution for port managers and can help them make competitive decisions which accommodate more container storage requests in limited yard area.
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