## 3 Case Study
### BIM-Midas-Based Verification of Box Culvert Structure  
Structural calculation is one of the key processes in box culvert design. Utilizing finite element simulation analysis generates theoretical values for the structural stress and deformation of a box culvert. These calculated values not only assure structural safety during the design phase but also serve as a guide for maintaining quality and safety measures during construction. _Step 1: Conversion to Box Culvert Finite Element Model_  
On the basis of the model established in the previous section, we continued to run the Dynamo node program according to the method described in Section 2.2.1 to enable the BIM model to generate the Midas finite element model in one click with the assistance of information flow by converting to an.mct file. Taking the second section of the box culvert as an example, the conversion result in Midas Civil is illustrated in Figure 17.  
_Step 2: Internal Force Analysis of Box Culvert Finite Element Model_  
The box culvert was simulated using beam elements with the properties of C35 concrete material. In the model, except for the position of the intersection between the middle web and the bottom plate, which was considered a consolidation, the other bottom plate units were simulated as elastic connections connected with the foundation. The main loads considered in the calculation and analysis of the box culvert were self-weight, vertical overburden pressure, lateral earth pressure, vehicle load (excluding impact force), and additional earth pressure caused by vehicle load. After establishing boundary conditions and implementing loads, the software was executed to carry out an FEA on the box culvert. Figure 18 depicts internal force diagrams representing the bending moments of the box culvert under various working conditions. In particular, the bending moment envelope under the load-bearing capacity limit state of  
Figure 16: Box culvert BIM model in Revit. Figure 17: Finite element model of the box culvert in Midas Civil. the box culvert is illustrated in Figure 19. A summary of the maximum bending moment values of the corresponding control sections is presented in Table 2.  
Figure 18: _Cont._  
Figure 19: Bending moment envelope of the box culvert under ultimate limit states: result in Midas Civil. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Location** & **Left End** & \begin{tabular}{c} **Mid-Span of Left** \\ **Chamber** \\ \end{tabular} & \begin{tabular}{c} **Central Partition** \\ **Wall** \\ \end{tabular} & \
\begin{tabular}{c} **Mid-Span of Right** \\ **Chamber** \\ \end{tabular} &
\begin{tabular}{c} **Right End** \\ **Right End** \\ \end{tabular} \\ \hline Top slab & \(-\)4242.59 kN-m & 4813.96 kN-m & \(-\)10,265.23 kN-m & 4813.96 kN-m & \(-\)4242.59 kN-m \\ Bottom slab & 4332.13 kN-m & \(-\)3996.91 kN-m & 8694.87 kN-m & \(-\)3996.91 kN-m & 4332.13 kN-m \\ \hline  & **Upper end** & **Mid-span** & **Lower end** & & \\ \hline Left side wall & 4242.59 kN-m & 2035.08 kN-m & 4330.97 kN-m & & \\ Right side wall & \(-\)4242.59 kN-m & \(-\)2035.08 kN-m & \(-\)4330.97 kN-m & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Maximum bending moment of the box culvert under ultimate limit states. Figure 18: The bending moment envelope under the load-bearing capacity limit state of the box culvert: results in Midas Civil. (**a**) Self-weight. (**b**) Vertical overburden pressure. (**c**) Lateral earth pressure. (**d**) Additional earth pressure caused by vehicle load (left). (**e**) Additional earth pressure caused by vehicle load (right). (**f**) Vehicle load. was 4813.96 kN\(\cdot\)m. For the bottom slab, the maximum negative bending moment was \(-\)8694.87 kN\(\cdot\)m, and the maximum positive bending moment was 3996.91 kN\(\cdot\)m. Given the symmetry of the double-chambered box culvert structure and the boundary conditions, the bending moment distribution was also symmetrical under symmetrical loads. In accordance with the principles of structural mechanics, these results align with the actual scenarios.