Ultra-high performance concrete (UHPC) has demonstrated significant application potential in beam components due to its excellent mechanical properties, durability, and environmental friendliness. However, the high material cost often leads to the misconception that UHPC structures offer low cost-effectiveness, which hinders their widespread engineering adoption. Existing studies mostly focus on optimizing the mechanical properties of UHPC components, but there is a notable lack of systematic evaluation regarding their flexural cost performance ratio. To address this gap, this paper established a comprehensive evaluation system for the flexural cost performance ratio of beam components, aiming to provide theoretical support for the rational design and engineering application of UHPC structures. Firstly, with “performance” and “cost” as the core considerations, an evaluation indicator for flexural cost performance ratio was constructed. Subsequently, the ultimate bending moment was selected to characterize the flexural performance of components, while the material cost per unit length of the pure bending segment was used to represent economic cost. Based on these, a quantifiable cost performance ratio indicator was established. Subsequently, the classic reference method was employed, taking conventional single-reinforcement rectangular beams with appropriate reinforcement as the reference benchmark. The cost performance ratio indicator was then rendered dimensionless throgh the range standardization method. On this basis, integreating probability theory and the K-means clustering algorithm, a grading system for flexural cost performance ratio was established, ensuring both scientific rigor and objectivity. Finally, the evaluation system was applied to comparatively analyze the differences in flexural cost performance ratio between conventional beam members and UHPC beam members. The research results show that the flexural cost performance ratio of reinforced concrete beams is independent of beam width but exhibits a positive correlation with both beam depth and material strength grade. In component design, priority should be given to combinations of higher-strength concrete and highe-strength steel reinforcement, and the substitution of tensile reinforcement with prestressed steel strands can also be considered. Furthermore, if UHPC is simplely used as a direct replacement for ordinary concrete in developing new components, it does not demonstrate an advantage in flexural cost performance ratio. Only through tailored designs that leverage the mechanical characteristics of UHPC and other construction materials can component forms with a high flexural cost performance ratio be achieved.

The steel structure has multiple advantages, including low carbon footprint, environmental friendliness, lightweight yet high strength, and excellent seismic performance. It has been widely used in high-rise buildings, large-span buildings and some civil buildings. However, its inherent problems such as buckling, corrosion and high cost hinder the further application of steel structures. The current anti-buckling and anti-corrosion measures for steel structures will greatly increase the cost of the structure and have a negative impact on the bearing capacity of the structure. Ultra-high performance concrete (UHPC) is a new type of fiber-reinforced cement-based composite material based on the maximum bulk density theory. It features high strength and excellent deformation capacity, along with outstanding durability properties, including superior resistance to water penetration, chloride ion infiltration, and freeze-thaw cycles. Nowadays, UHPC has been widely used in mechanical reinforcement and durability reinforcement of various structures. Recent research work shows that the combination of steel structure and UHPC can effectively realize the complementary advantages of the two. While giving full play to the excellent characteristics of light weight and high strength of steel structure, it greatly reduces the harm of fatigue, corrosion and instability to steel structure. This study focused on a newly developed thin-layer UHPC encased I-beam, which has been widely applied in practice. A sample database was established through finite element simulation analysis using Abaqus. At the same time, the comprehensive evaluation index of shear performance and shear cost performance of composite beams was proposed based on the radar chart method. The response surface-Monte Carlo method was employed to analyze the influence of four different response surfaces on the web size parameters of the composite beam. The analysis results show that there is a significant positive correlation between the shear performance of the composite beam and its cost performance. Moreover, as the thickness of the I-beam web increases, both shear performance and cost-effectiveness initially rise and then decline, reaching a peak at a specific thickness. This study provides valuable engineering insights for optimizing the design of I-beam encased UHPC composite beams.