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Top1. Introduction
Container terminals play a crucial role in transporting goods in global supply chains. Deep-sea container terminals handle millions of containers annually transported by mega containerships. Container terminals have undergone a variety of developments in order to transport and handle containers efficiently (Gharehgozli et al., 2016 and 2020; Duru et al., 2020; Li et al., 2020; Ma et al., 2019). Substantial investments, especially in new technologies, have been made to improve efficiency and security in infrastructure and operations. According to United Nations Conference on Trade and Development (UNCTAD) (2017), ports have invested around $68.8 billion in port infrastructure and superstructures between 2000 and 2016 (also see Gharehgozli et al., 2014c).
How to efficiently stack containers has a great impact on the terminal operation efficeincy. Container stacks (also known as container blocks) are arrayed in multiple tiers, rows and bays by automated rail mounted gantry (RMG) cranes or rubber tired gantry (RTG) cranes (Thoresen, 2003; Vis and De Koster, 2003; Vis, 2006). In transshipment terminals (common in Asia), RTG cranes stack containers parallel to the quay, to move containers efficiently from one ship to another. Detailed discussions on the the impact of parallel layouts on terminal performance can be found in works such as Lee et al. (2018); Alessandri et al. (2008); Petering and Murty (2009); Petering (2009, 2011, 2010); Woo and Kim (2011); Lee and Kim (2013, 2010b,a); Alcalde et al. (2015); Woo et al. (2016); Liu et al. (2004); Jiang et al. (2013); Zhen et al. (2016); Zhen (2016, 2014); Kim et al. (2008); Wiese et al. (2010); Zwerpour et al. (2019). In export and import terminals (common in Europe), containers are stacked perpendicular to the quay by RMG cranes, also known as automated stacking cranes (ASCs) (Gharehgozli et al., 2014b and 2017b; Gharehgozli and Zaerpour, 2018). This helps decouple the landside and waterside operations. Commonly used ASC configurations are as follows.
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Single ASC (see, Figure 1a): It is the most common configuration. A single ASC moves containers between the transfer zones and assigned locations. Example of implementation: Europe Container Terminals (ECT) Delta Terminal in Rotterdam, the Netherlands (Gharehgozli et al., 2014a and 2021).
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Double ASCs (see, Figure 1b): In this setting, two different size ASCs stack and retrieve containers at the same time. The larger ASC can cross over the smaller one. Example of implementation: Container Terminal Altenwerder (CTA) in Hamburg, Germany (Vis and Carlo, 2010).
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Twin ASCs (see, Figure 1c): Similar to the double ASCS, except that twin ASCs are of the same size and cannot pass each other. Example of implementation: Euromax Terminal in Rotterdam, the Netherlands (Gharehgozli et al., 2015 and 2017a).
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Triple ASCs (see, Figure 1d): Triple ASCs consist of three cranes, with two smaller equal sizes and one larger size. The larger crane can cross over the two smaller ones. Example of implementation: Container Terminal Burchardkai (CTB) in Hamburg, Germany (Dorndorf and Schneider, 2010).