## 5 Technical and Economic Analysis of the Test Design
### Material Usage Comparison  
The original design relies on Q370 qE steel and C50 concrete, while the test design relied on Q345 steel, C50 concrete for the deck, and RPC120 concrete for the infill of the chord members. A comparison of material usage between the test design and the original design is shown in Table 6. Compared to the original design, the test design used less steel and more concrete. Based on the material quantities, cost calculations were made, with steel priced at CNY 6000/t, C50 concrete at CNY 500/m\({}^{3}\), and UHPC at CNY 1500/m\({}^{3}\). A cost comparison between the original design and the test design is shown in Table 7. The total cost of the test design was approximately 82.71% of the original design, demonstrating better economic efficiency.  
The original design covers steel plates with thicknesses of 12 mm, 14 mm, 16 mm, 20 mm, 24 mm, 28 mm, and 32 mm, totaling seven types of steel. The test design only used steel plates with thicknesses of 16 mm, 20 mm, and 36 mm. In large-scale constructions, the test design could create higher economic value.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Material Usage**} & \multicolumn{2}{c}{**Steel**} & \multicolumn{2}{c}{**C50 Concrete**} & \multicolumn{2}{c}{**RPC120**} \\ \cline{2-6}  & **SUM (t)** & **t/m** & **SUM (m\({}^{3}\))** & **m\({}^{3}\)/m** & **SUM (m\({}^{3}\))** & **m\({}^{3}\)/m** \\ \hline Original plan & 1422.2 & 13.2 & 467.0 & 4.3 & 0 & 0 \\ Test design & 1115.2 & 10.1 & 415.2 & 3.8 & 345.8 & 3.2 \\ Rate of change & \(-23.5\%\) & & \(-11.6\%\) & & / \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of material usage in the trial design and in the original plan.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Plan**} & \multicolumn{2}{c}{**Compression**} & \multicolumn{2}{c}{**Tension**} & \multirow{2}{*}{**Compression Web Member**} & \multirow{2}{*}{**Tension Web Member**} \\  & **Upper Chord** & & & & & \\ \cline{2-6}  & **S2** & **X2** & **F1** & **F2** & **F1** & **F2** \\ \hline Original plan & 1.88 & 1.8 & 1.56 & 1.41 & 1.54 & 1.78 \\ Test design & 1.64 & 7.87 & 1.10 & 1.24 & 1.25 & 1.27 \\ Rate of change & \(-12.8\%\) & 337.2\% & \(-29.5\%\) & \(-12.1\%\) & \(-18.8\%\) & \(-28.7\%\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of strength safety factors in the trial design and original plan.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Material Usage**} & \multicolumn{2}{c}{**Steel**} & \multicolumn{2}{c}{**C50 Concrete**} & \multicolumn{2}{c}{**RPC120**} \\ \cline{2-6}  & **SUM (t)** & **t/m** & **SUM (m\({}^{3}\))** & **m\({}^{3}\)/m** & **SUM (m\({}^{3}\))** & **m\({}^{3}\)/m** \\ \hline Original plan & 1422.2 & 13.2 & 467.0 & 4.3 & 0 & 0 \\ Test design & 1115.2 & 10.1 & 415.2 & 3.8 & 345.8 & 3.2 \\ Rate of change & \(-23.5\%\) & & \(-11.6\%\) & & / \\ \hline \hline \end{tabular}
\end{table}
Table 7: Cost comparison between the trial design and the original plan.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Material Usage**} & \multicolumn{2}{c}{**Steel**} & \multicolumn{2}{c}{**C50 Concrete**} & \multicolumn{2}{c}{**RPC120**} \\ \cline{2-6}  & **SUM (t)** & **t/m** & **SUM (m\({}^{3}\))** & **m\({}^{3}\)/m** & **SUM (m\({}^{3}\))** & **m\({}^{3}\)/m** \\ \hline Original plan & 1422.2 & 13.2 & 467.0 & 4.3 & 0 & 0 \\ Test design & 1115.2 & 10.1 & 415.2 & 3.8 & 345.8 & 3.2 \\ Rate of change & \(-23.5\%\) & & \(-11.6\%\) & & / \\ \hline \hline \end{tabular}
\end{table}
Table 5: Comparison of the stiffness in the trial design and original plan.