Optimizing the woodpulp stowage using Lagrangean relaxation with clusters

Abstract

The cargo stowage process in ships consists in arranging items into holds. This paper approaches the problem of finding the maximum number of stowed units of woodpulp into holds of dedicated maritime international ships. This problem, essentially three-dimensional can be reduced for the two-dimensional case due to constraints provided by the transport, and becomes similar to the manufacturer's pallet loading problem. We present in this paper a formulation to the woodpulp stowage solved by a lagrangean relaxation with clusters (LagClus) that considers the conflict graph generated by overlaps of woodpulp units.Computational tests are performed and compared with the real results obtained in Brazilian ports. The results obtained by LagClus were better than the real results, and consequently, it can provide savings if we look at the shipping logistics costs.

Column generation approach for the point-feature cartographic label placement problem

“…Besides, the authors proposed a column generation for that problem using the cluster relaxation idea. Another interesting application was performed on woodpulp stowage context (Ribeiro and Lorena, 2005). This problem consists of arranging items into holds of i.…”

An effective recursive partitioning approach for the packing of identical rectangles in a rectangle

“…Moreover, if compared to the method in Alvarez-Valdes et al (2005a), the combined approach improves the solutions of 116 instances of problem set Cover III, whose 98 016 instances involve packings from 100 up to 150 boxes. Requiring moderate computational resources, the combined approach also improves the solutions of practical examples of the woodpulp stowage problem, when compared to the method presented in Ribeiro and Lorena (2008). These are large examples involving packings of hundreds of woodpulp units by hold (ie, boxes by pallet).…”

“…It is assumed that there are no constraints related to cargo weight, density, fragility, etc. This problem also appears in other logistics settings, for example, in the problem of finding the maximum number of stowed units of woodpulp into holds of maritime ships, referred to as the woodpulp stowage problem (Ribeiro and Lorena, 2008). Apparently easy to be optimally solved, the problem is claimed to be NP-hard although it has not been proven (Dowsland, 1987a;Nelißen, 1995;Letchford and Amaral, 2001).…”

Estivagem de unidades de celulose via modelo de corte e empacotamento.

“…Em três dos quatro casos os resultados das abordagens aqui propostas se mostraram melhores que os planos reais. LORENA, 2008) pode ser definido como um problema que busca alocar a máxima quantidade de unidades de celulose ao porão de cargas de um dado navio, respeitando as restrições físicas de dimensões, de posicionamento, de não-sobreposição das unidades e de capacidade máxima do porão do navio.…”

“…Esse tipo de problema, que a rigor é um problema tridimensional, pode ser reduzido a um equivalente bidimensional (MORALES; MORABITO; WIDMER, 1997;RIBEIRO;LORENA, 2008). Essa redução é possível devido às restrições físicas e operacionais de estivagem das unidades de celulose, que determinam que as camadas de unidades de celulose estivadas em um mesmo porão podem possuir configurações idênticas.…”