Otimização de vigas protendidas de concreto de altíssimo desempenho com foco na redução das emissões de CO₂

Abstract

Ultra-high-performance fiber-reinforced concrete (UHPFRC) is a cementitious composite that exhibits high mechanical strength and durability, enabling the design of more slender and lighter structural elements when compared to conventional concrete. These characteristics give UHPFRC the potential to reduce material consumption and mitigate carbon dioxide (CO₂) emissions associated with structures, provided that its application is combined with appropriate structural design strategies. In this context, this study aimed to investigate the potential use of UHPFRC in prestressed concrete beams with a focus on reducing CO₂ emissions while maintaining, at a minimum, the originally required load-carrying capacity. The adopted methodology was based on finite element numerical modeling of a reference prestressed beam. UHPFRC was employed as an alternative material to conventional concrete, considering two steel fiber volume fractions, equal to 1% and 2%. The dematerialization of the cross-sections was performed through structural optimization based on genetic algorithms, with the objective function defined as the minimization of CO₂ emissions associated with the product stage of the life cycle (A1–A3), with the analysis concentrated on substage A1, related to raw material supply. The results indicated that the proposed approach enables reductions of approximately 23,3% and 17,6% in CO₂ emissions for fiber contents of 1% and 2%, respectively, compared to the conventional concrete beam. A significant reduction in self-weight was also observed, on the order of 49,8% and 50,2%, highlighting the direct effect of the dematerialization achieved through structural optimization. It is concluded that the use of UHPFRC in prestressed beams represents a promising solution for reducing CO₂ emissions when combined with structural optimization, reinforcing the importance of integrating mechanical performance and environmental sustainability at the structural design stage.