## 5 Conclusions  
In this study, a novel BUSP-concrete composite bridge deck system was designed. To analyze the impact of size parameters on its mechanical performance, a Python-based ABAQUS parameterized modeling script was developed. Based on the presented results, the following conclusions can be drawn.  
* To achieve cast-in-place construction for the concrete structure of the bridge deck while maintaining the amount of steel used, thin steel plates were added to the original structure, and the crossbeam system was simplified. Finite element (FE) analysis demonstrated that the improved structure exhibited higher panel stiffness compared to the original design. Furthermore, the application of BUSP further increased the stiffness of the concrete overlay. Compared to the original design, it respectively reduced the maximum vertical displacement of the concrete overlay and the maximum tensile stress by 10.27% and 29.69%.
* When considering size parameters (\(h\), \(t\), and \(a\)) of a single U-rib of BUSP, it was observed that both the maximum tensile stress and maximum vertical displacement of the concrete overlay decrease with increasing \(t\) and \(a\). Additionally, for \(h\) values not exceeding 100 mm, stress and displacement also decrease with increasing \(h\). Compared to the original design, adjusting values of these three size parameters can reduce the maximum tensile stress of the concrete overlay by 15%. However, considering the quantities of steel and concrete used, adjusting the \(h\) value can be considered the most effective method for enhancing the mechanical performance of BUSP.
* By examining combinations of the three parameters (\(h\), \(t\), and \(a\)), their influence on the maximum tensile stress and maximum vertical displacement of the concrete overlay was compared. The research findings indicate that parameter \(a\) has the greatest impact on the stress of the concrete overlay, while parameter \(h\) has the greatest impact on vertical displacement.
* To investigate the combined effects of parameters \(h\), \(t\), and \(a\), the parameter \(A\), representing the area of the BUSP, was introduced. The results revealed that the minimum tensile stress of the concrete overlay is achieved when the value of \(A\) is approximately 11,000 mm\({}^{2}\).
* Reducing spacing parameters (\(e\) and \(w\)) can also enhance the mechanical performance of the BUSP. When only reducing the value of either \(e\) or \(w\) by half, the maximum vertical displacement and tensile stress of the concrete overlay can be reduced by approximately 10%. Furthermore, when simultaneously reducing the values of both \(e\) and \(w\), the reduction magnitude can reach 15% or more. However, this improvement comes at the expense of increased construction difficulty and material expenses, as it requires the addition of extra U-ribs in the transverse or longitudinal direction of the bridge.
* These findings contribute to a better understanding of the mechanical behavior of BUSP and offer insights for optimizing its design parameters to enhance its performance while considering construction feasibility and cost-effectiveness.  
Conceptualization, F.H.; Methodology, J.L. ([PERSON]) and J.L. ([PERSON]); Validation, D.W. and Y.G.; Formal analysis, J.L. ([PERSON]); Writing--original draft, J.L. ([PERSON]); Writing--review & editing, Y.G. and F.H.; Supervision, J.L. ([PERSON]); Project administration, D.W. and F.H.; Funding acquisition, D.W. and F.H. All authors have read and agreed to the published version of the manuscript.  
This work is supported by Guizhou Transportation Planning Survey & Design Academe (project no. ZLKY2023005).  
Not applicable.