Geometric optimization associated with the use of high-strength concrete in viaducts

Abstract In Brazil, there is a lack of infrastructure investment in roads, given that they facilitate the transportation of more than half the country’s cargo volume. One of the main variables in road infrastructure is overpass construction and maintenance. Concrete overpasses with post-tensioned I-section beams have been extensively used in Brazil. This study discusses the economic aspects of the use of high-strength concrete (HSC) associated with the geometrical optimization of decks of post-tensioned multi-girder overpasses. Twelve overpass decks were dimensioned and divided into two groups. In Group A the characteristic concrete strength varied, but not the geometrical characteristics of the deck. In Group B, the characteristic strength and the geometrical characteristics of the deck varied. These were the configurations that presented the best results for each group of characteristic concrete strength. It was determined that the use of HSC significantly decreases the reinforcement ratio-especially shear reinforcement. In addition, although the HSC has a higher cost per m3, it is still considered a viable option owing to the reduction in the reinforcement ratio. Lastly, in addition to providing the benefits that are widely commented on in literature, using HSC can also provide more economical overpass structures compared to conventional concrete.摘要 巴西道路基础设施投资存在缺口，原因在于公路承担了该国超半数的货运量。道路基础设施的核心影响因素之一包括立交桥的建设与养护。采用后张法工字形梁的混凝土立交桥在巴西已得到广泛应用。本研究探讨了将高强度混凝土（high-strength concrete, HSC）与后张法多梁式立交桥桥面几何优化相结合的经济可行性。本研究对12座立交桥桥面进行了尺寸设计，并将其分为两组：A组中混凝土的特征强度存在变化，但桥面几何参数保持一致；B组中混凝土特征强度与桥面几何参数均存在变化，且所选配置为对应特征强度组别下的最优方案。研究结果表明，采用高强度混凝土可显著降低配筋率，尤其是抗剪配筋率。此外，尽管高强度混凝土的单位立方米成本更高，但由于配筋率降低带来的成本节约，其仍被视为可行方案。最后，除了现有文献中广泛提及的各项优势外，相较于普通混凝土，采用高强度混凝土还可使立交桥结构更具经济性。