## 3 Results & Discussion
### Results Analysis
#### 3.1.2 Distribution of Torsional Stress  
After the model beam section is converted into a full-steel section, the thickness of the top steel flange is 1.103 cm, the thickness of the flat steel web is 0.268 cm, and the torsional center of the section is calculated to be 9.110 cm below the center of the top steel flange. The generalized main sectional moment of inertia, \(I_{\overline{w}}=1.4682\times 10^{-6}\) m\({}^{6}\), the torsional moment of inertia, \(I_{\mathrm{d}}=7.7945\times 10^{-4}\) m\({}^{4}\), the polar moment of inertia, \(I_{\mathrm{p}}=8.5156\times 10^{-4}\) m\({}^{4}\), the generalized main sectorial coordinate, \(\overline{\omega}\), and the generalized sectorial static moment, \(\overline{\varepsilon}_{\overline{w}}\), of the full-steel section are shown in Figure 10.  
When an external torque, \(\widetilde{M}=4.25\) kN \(\cdot\) m, is applied, the restrained torsional normal stress, \(\sigma_{\overline{w}}\), free torsional shear stress, \(\tau_{\mathrm{s}}\), secondary shear stress, \(\tau_{\overline{w}}\), and total shear stress, \(\tau\), of Section A can be obtained according to the geometric characteristics of the section, as shown in Figure 11.  
It can be seen from Figure 11 that the torsional normal stress of the bottom steel flange of the box girder is significantly greater than that of the top concrete flange, and the torsional normal stress generated by the corrugated steel web is almost negligible. The free torsional shear stress exists only on the closed section, and it is uniformly distributed on each individual plate. The secondary shear stress generated by the corrugated steel web is large and basically consistent along the vertical direction. This is because the corrugated steel web has not only the secondary shear flow generated by balancing its own warping normal stress, but also the secondary shear flow generated by balancing the warping normal stress of the top concrete flange and bottom steel flange; therefore, the secondary shear stress on the corrugated steel web is large. The total shear stress of the box girder is mainly borne by the corrugated steel web on both sides and bottom steel flange, and less by the top concrete flange. The main reason is that the thickness of the corrugated steel web and bottom steel flange is thin, so that the shear flow shared by them per unit \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Section**} & **Torsional** & **Measuring** & \(T_{\mathbf{t}}\) & \(T_{\mathbf{h}}\) & \(T_{\mathbf{e}}\) & \((T_{\mathbf{h}}-T_{\mathbf{l}})/T_{\mathbf{h}}\) & \((T_{\mathbf{e}}-T_{\mathbf{l}})/T_{\mathbf{e}}\) \\  & **Stress** & **Point** & **(MPa)** & **(MPa)** & **(MPa)** & **(\%)** & **(\%)** \\ \hline \multirow{4}{*}{A} & \multirow{4}{*}{\(\sigma_{\overline{w}}\)} & S\({}_{1}\) & \(0.1351\) & \(0.1423\) & \(0.1396\) & \(5.06\) & \(3.22\) \\  & & S\({}_{2}\) & \(-0.0514\) & \(-0.0545\) & \(-0.0562\) & \(5.69\) & \(8.54\) \\  & & X\({}_{1}\) & \(-0.6736\) & \(-0.7124\) & \(-0.7042\) & \(5.45\) & \(4.35\) \\ \cline{2-8}  & & S\({}_{4}\) & \(0.0787\) & \(0.0827\) & \(0.0812\) & \(4.84\) & \(3.08\) \\  & & W\({}_{2}\) & \(1.6113\) & \(1.6537\) & \(1.7164\) & \(2.56\) & \(6.12\) \\  & & X\({}_{3}\) & \(1.8242\) & \(1.9182\) & \(1.8858\) & \(4.90\) & \(3.27\) \\ \hline \multirow{4}{*}{B} & \multirow{4}{*}{\(\sigma_{\overline{w}}\)} & S\({}_{1}\) & \(-0.0096\) & \(-0.0103\) & \(-0.0098\) & \(6.80\) & \(2.04\) \\  & & S\({}_{2}\) & \(0.0038\) & \(0.0040\) & \(0.0041\) & \(5.00\) & \(7.32\) \\ \cline{1-1}  & & X\({}_{1}\) & \(0.0502\) & \(0.0518\) & \(0.0513\) & \(3.09\) & \(2.14\) \\ \cline{1-1} \cline{2-8}  & & S\({}_{4}\) & \(0.1032\) & \(0.1083\) & \(0.1061\) & \(4.71\) & \(2.73\) \\ \cline{1-1}  & & W\({}_{2}\) & \(2.0874\) & \(2.1663\) & \(2.1979\) & \(3.64\) & \(5.03\) \\ \cline{1-1}  & & X\({}_{3}\) & \(1.2832\) & \(1.3674\) & \(1.3017\) & \(6.16\) & \(1.42\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Torsional stress comparison. thickness is large.