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[pt] Além do seu importante papel metalúrgico, o coque representa mais da metade do custo de produção do ferro gusa e cerca de 20% do custo de fabricação do aço. Por isso, as siderúrgicas integradas buscam misturas de custo mínimo para produção de coque que atendam aos requisitos de qualidade. Para garantir essa qualidade, elas impõem aos seus fornecedores de carvão cláusulas contratuais relativas à umidade, cinzas, enxofre, fósforo, matéria volátil, fluidez, refletância e dilatação e, eventualmente, outras. Como nem sempre essas exigências são atendidas pelos fornecedores, penalidades contratuais são especificadas com o propósito de evitar que as siderúrgicas arquem com os custos causados por desvios de especificações. Entretanto, tais penalidades nem sempre refletem os custos realmente causados, pois estes decorrem não só da redução do material aproveitável, mas, também, dos reajustes necessários na mistura para que o coque se mantenha dentro da qualidade exigida. Essa dissertação propõe um sistema para determinação do ônus efetivamente causado por desvios nas especificações de um carvão contratado. Uma apresentação detalhada do problema, sua formulação como modelo de programação linear e um procedimento para a análise são propostos. Um sistema protótipo funcional foi desenvolvido e ilustrações numéricas das análises são discutidas. / [en] In addition to its important metallurgical role, the coke accounts for more than half of the total production cost of the pig iron and around 20% of the total cost of steel production. For this reason, the integrated steelmaking mills seek minimum cost coal blends for producing coke within the quality requirements. To guarantee this quality the steelmaking mills impose to their coal vendors some contractual clauses regarding humidity, ashes, sulfur, phosphor, volatile matter, fluidity, reflectance and dilatation, and sometimes, still others. Since these requirements are not always met by the vendors, contractual penalties are specified with the purpose of avoiding that the steelmakers end up with the burden of the costs caused by such specs deviations. Nonetheless, such penalties do not always reflect the actual costs they cause, because the latter derive not only from the reduction of the usable material, but also from the blend adjustments necessary to keep the coke within the required quality. This thesis proposes a system for determining the burden effectively caused by specs deviations. A detailed presentation of the problem, its formulation as a linear programming model and a procedure for analysis are proposed. A functional prototype system was developed and numerical illustrations of the analyses are discussed.

Quantity Flexibility contract is an arrangement where parties agree upon a scheme of forming ranges on volumes for their future transactions. The contract is based on setting upper and lower limits on replenishment orders as simple multiples of point estimates updated, published and committed by the buyers. We introduce a manufacturer with a limited capacity / also capable of subcontracting, for deliveries with a known lead time. He offers a Quantity Flexibility (QF) contract to a buyer while he has an active contract with another buyer serving a market with known demand forecast distributions. Using two-stage stochastic programming we study the effects of flexibility multiples and the environmental factors on the buyers&amp / #8217 / incentives and manufacturer&amp / #8217 / s capacity planning. Finally, the motivations of the Supply Chain actors to behave independently or to be involved into the integrated iv supply chain where information asymmetry is removed are investigated. Our experiments underline the critical roles played by the forecast accuracy and information sharing.