A Column Generation Algorithm for Slab Stack Shuffling Problem

As a kind of warehousing operations management problem, the slab stack shuffling (SSS) problem plays a key role between continuous casting and hot rolling in the steel industry. If a slab in the yard that stacks in a middle tier of the stack is chosen for hot rolling, other slabs above it should be moved away first before the target one can be retrieved, then shuffle occurs. SSS is to choose appropriate slabs for hot-rolling schedule, from their respective candidate slab sets aiming at minimizing the resulting shuffle number. Proper selection of slabs can reduce shuffles during the retrieval process, improve working efficiency of cranes in the slab yard and decrease the time spent on feed preparation of hot-rolling and also logistics costs. Since slabs are piled one upon another in a stack, the number of shuffles for retrieving the chosen slabs not only depends on the slabs about to be taken out, but also the slabs previously taken out from the stack. SSS is formulated as a nonlinear model. Because of its complexity, several intelligent algorithms have been applied to SSS but few optimization algorithms have been introduced to solve it according to previous literature. In this paper, the concept of a stack-scheme is proposed to synthetically consider the decision situation in a stack. The net shuffle number in a stack is independent with the situation in other stacks and thus the needed shuffle number associated within a stack-scheme can be individually calculated. Based on the above, the original problem can be reformulated as a linear master problem and a set of sub-problems by Danzig-Wolf decomposition. Column generation (CG) is then applied to solve it and a branch-and-bound method is proposed to get the optimal solution. The performance of the proposed algorithm is verified by numerical experiments.


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: pp 142-148
  • Monograph Title: Proceedings of the International Forum on Shipping, Ports and Airports (IFSPA) 2012: Transport Logistics for Sustainable Growth at a New Level

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Filing Info

  • Accession Number: 01483812
  • Record Type: Publication
  • ISBN: 9789623677578
  • Files: TRIS
  • Created Date: Jun 5 2013 6:13PM