FORMULATIONS AND SOLUTION APPROACHES FOR THE INTEGRATED LOT-SIZING AND CUTTING STOCK PROBLEM APPLIED TO LATTICE JOIST PRODUCTION

Abstract

ABSTRACT In the construction industry, lattice joists (final items) are precast structures that combine a steel truss and a concrete base. Their production is based on a client’s order that specifies the quantity, length, and deadline for delivery. A process manager uses this information to create a weekly production plan that determines the number and type of final items to produce in each period. The primary concerns of the factory include minimizing the waste of steel bars (objects) and optimizing setups and inventory costs. In this paper, decisions regarding purchasing steel bars and managing stocks in different sizes are considered extending the literature by adding an extra level of decision. We propose two alternative mathematical formulations for this integrated lot-sizing and cutting stock problem. Further, heuristic solution strategies are proposed to address the resulting mixed-integer programming formulations. Computational tests are conducted to evaluate the effectiveness of the proposed solution approaches.