A Mathematical Formulation and a Heuristic for the Spatial Scheduling of Mega-Blocks in Shipbuilding Industry

Abstract

In shipbuilding industry, to reduce the staying time of the ship in a dock, floating crane and floating dock are used to handle the mega-blocks, thus it increased the turnover of the dock. Therefore, spatial scheduling for mega-block in an assembly yard becomes important in shipbuilding industry. However, spatial scheduling of mega-blocks has some unique characteristics compared with the well-known classic bin-packing problem, and not many studies can be found on this issue. This research proposes an enhanced mathematical formulation and a heuristic algorithm for spatial scheduling of mega-block arrangement problem. The formulation provides tight bound compared with the existing formulation, and the proposed heuristic can obtain good quality of the solution in a reasonable amount of time even when the size of the instance became large. Shipbuilding industry involves constructing ships and other floating vessels. Block is a base element of the shipbuilding process, and the blocks are assembled and welded in the block assembly shop, and finally erected to a ship in a dry dock. A size of a block is around 15~30 meters with a weight of around 30~300 tons (Zheng et al. 2011), and a large ship consists of around 150 blocks (Koh et al. 2011b). Some blocks are outsourced and timely delivery and quality of blocks have an absolute impact on the ship’s quality. Also, it is possible to shorten the dock duration by receiving blocks from several companies at the same time.