The parallel stack loading problem considering multiple batches of storage plates

This paper considers a parallel stack loading problem with multiple batches of storage plates, a problem that occurs in the plate logistics of shipbuilding. The objective of this problem is to store batches of plates in a yard simultaneously so that the number of relocations during the retrieval stage is minimal. Instead of choosing the plates’ location in the yard alone, the storage order should also be decided, and the storage priority between plates in a batch should be maintained. Such a problem can be regarded as a variant of the capacitated vehicle routing problem. This paper analyzes the influence of stack number, stack capacity, and batch number on the relocation number; optimal conditions and upper bounds under different parameter ranges are provided. Four mathematical models and an ALNS-based algorithm are designed to solve the small-sized and large-sized instances separately, and the experiments on benchmarks are conducted to demonstrate the performance of the proposed methods. Finally, some management suggestions are provided based on the analysis of the problem and experiment results.