## 4 Numerical Simulation
### Parametric Sensitivity Analysis
#### 4.3.3 Sensitivity Analysis of Temperature  
(1) The effect of overall heating on structural deformation  
Taking an overall temperature rise of 10 \({}^{\circ}\)C and an overall temperature drop of \(-10\)\({}^{\circ}\)C, the longitudinal deformation of the structure under the overall temperature difference is shown in Figure 17. The fixed support is located at 0 m, and the structural deflection remains virtually unchanged under the overall temperature difference.  
(2) The influence of local temperature difference on structural deformation  
The effect of local temperature difference on structural deformation of steel box beams is set according to the height of the section. For example, a temperature gradient of +10 \({}^{\circ}\)C is set, with a linear distribution along the beam height of 10 \({}^{\circ}\)C for the top plate and 0 \({}^{\circ}\)C for the bottom plate. The deflection changes during the lifting condition of 1# and the completion condition is calculated. Under the action of a 10 \({}^{\circ}\)C temperature difference, taking a positive temperature difference as an example, the  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Construction Conditions**} & \multirow{2}{*}{
\begin{tabular}{c} **Lifting the 1\# Span** \\ **Mid-Span of 1\#** \\ \end{tabular} } & \multicolumn{4}{c}{**Completed**} \\  & & **Mid-Span of 1\#** & **Mid-Span of 2\#** & **Mid-Span of 3\#** & **Mid-Span of 4\#** \\ \hline Original deflection (mm) & \(-196.2\) & \(-170.0\) & \(-120.1\) & \(-103.4\) & \(-162.1\) \\ Deflection (mm) & \(-186.9\) & \(-162.9\) & \(-114.6\) & \(-98.6\) & \(-154.5\) \\ Rate of change (\%) & \(-4.7\%\) & \(-4.1\%\) & \(-4.6\%\) & \(-4.6\%\) & \(-4.7\%\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: The influence of changes in elastic modulus on the mid-span deflection value.  
Figure 15: Vertical deflection variation of the first span steel box girder caused by elastic modulus.  
Figure 19: Deflection error caused by temperature difference between top and bottom plates at 10 \({}^{\circ}\)C under bridge completion condition.  
Figure 20: Structural stress under the effect of +10 \({}^{\circ}\)C temperature difference under bridge completion conditions.  
As the construction progresses, the numerical simulation will provide valuable guidance for construction monitoring. Starting from the prefabrication of steel box girders at the factory to the final closure of the entire bridge, the construction monitoring platform will rely on the numerical simulation results throughout the whole construction process. All field-measured stress and displacement data must be compared and analyzed against the results of FEM on the platform, to ensure that the structural safety during construction and the stress and displacement of the bridge after closure are within the design requirements. In particular, the construction monitoring platform will provide real-time construction instructions and guide the installation process, especially for monitoring the stress on the corbel connections, which are the main load-bearing components before the completion of welding.