Sustainability-Oriented Pre-Selection of Reinforced NSC, HSC, and UHPC Flexural Members Under Ultimate and Serviceability Limit States

Early decisions concerning material class and member dimensions substantially influence the embodied environmental impact of reinforced concrete structures. However, preliminary sizing rarely integrates structural performance and environmental assessment within a common framework. This study presents a mechanics-based method for sustainability-oriented pre-selection of reinforced rectangular beams made of normal-strength concrete (NSC), high-strength concrete (HSC), and ultra-high-performance concrete (UHPC). For prescribed bending demands and design assumptions, combinations of material class and section height that satisfy equivalent ULS and SLS performance requirements are screened against selected ultimate-limit-state flexural and serviceability-limit-state deflection criteria. The global warming potential (GWP) is evaluated using user-defined environmental coefficients for cradle-to-gate modules A1–A3. The results show that increasing material strength generally reduces the required section depth but does not necessarily reduce GWP, as the geometric savings may be offset by the higher impact intensity of the material. In addition, including the deflection criterion shifts solutions towards greater section depths and thus higher GWP. The proposed framework provides a preliminary-design tool for identifying the minimum-GWP admissible sectional design candidate within a prescribed design space and represents a step towards integrating sustainability considerations into the structural design of concrete members.