“Where do I stack it?” A review of the heuristics for the block relocation problem in open yards

The management of inventory movements in open yard storage entails many aspects of both the type of unit loads handled (usually containers, swap bodies or large and heavy pallet) and the sequence of arrival and retrieval. In this highly dynamic scenario, the correct location of incoming load units in the yard is essential to ensure the effective use of resources (such as cranes and forklifts) and the timely shipment of the orders to the customers. In this respect, one of the main goals in managing open yard storage is to minimise handling operations. In particular, it is necessary to limit reshuffle operations, i.e. load units movement operations inside the yard to allow access to other units. In literature, a solution to this problem is represented by the research on the Block Relocation Problem (BRP), mainly developed in the seaport context. Both analytic and heuristics approaches have been formulated with different characteristics, levels of difficulty and effectiveness. Motivated by research activity in a company, in this paper, we develop a review of the main existing heuristics for solving BRPs, considering the importance they can play in yards management to optimise handling operations, reducing the number of movements.