Container Handling and Layout Optimization in Empty Container Depots
Type of DegreePhD Dissertation
Industrial and Systems Engineering
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In this dissertation, we explore shipping container depot layout with particular emphasis on empty container depots with material handling provided by top-lifters. Top lifters are the most common handling equipment used in container depots and the port yards of many countries. We consider both rectangular and non-rectangular yard layouts and we estimate the relocation and cycle times of top-lifters as well as other common container handling equipment, the overhead crane, and the reach stacker. The first research topic, “Relocations in container depots for different handling equipment types: Markov models,” proposes a family of Markov models to analytically characterize the distribution of the number of relocations per retrieval in a container depot. In this study, we generalize the few models available in the literature by 1) relaxing the assumed material handling equipment type (we consider the three vehicles mentioned above) and 2) allowing for container arrivals during the retrieval process. The second research topic is “Retrieval and placement times estimation for top-lifters.” This addresses the estimation of retrieval and placement times using the Markov model of the first study. Along with the estimations of handling, we use regression models based on a time study directed in a real container depot in Chile. The third research topic is “An analytical model for the design of top-lifter operated container yard layouts” and this focuses on constructing alternative layouts for a container depot operated by top-lifters that have access to the top edge of a bay. In this study, we propose an analytical model that evaluates the expected cycle time of a top-lifter to find the optimal yard block design. We optimize the number of driving lanes, both vertical and horizontal, as well as block depth, height, and length of a bay design. We generalize the approach to be applicable for both rectangular and non-rectangular yard designs.