## 2 Method
### Box Culvert Structural Analysis and Stress Visualization Method
#### 2.2.2 Visualization of Internal Forces in Box Culvert Model Based on BIM and Midas  
FEA effectively captures the values of internal forces within sections, and these values can provide an intuitive representation of the stress states in structural components, thereby facilitating the assessment of their safety conditions. In alignment with the objective of guiding construction, it is imperative that the computational results are presented to designers and construction personnel efficiently and intuitively [38; 39; 40]. The learning curve for finite element software operation is steep, creating a disconnect with practical application. To address this issue and enhance the information capacity and integration of BIM models, a method based on Dynamo was proposed to feed FEA results back into the BIM environment, thus realizing the visualization of internal forces in box culvert structures.  
Revit offers tools for an analytical visualization framework with the function of replacing traditional, redundant data visualization processes. It enables the direct display of computational analysis results within the Revit project environment, streamlining the analysis process and avoiding compatibility issues with data transfer between different software applications. Currently, the analytical visualization framework can be utilized to create colored surfaces, markers with text, diagrams with text, vectors with text, and deformed shapes.  
In this study, the visualization of internal forces in culvert structures is achieved through programming in Dynamo software. The specific steps are as follows:  
_Step 1: Creation of Analysis Display Style._ An analysis display style named \"Internal Force Visualization\" is established, as depicted in Figure 11. This style utilizes a gradient mode with no defined threshold. When new value-color pairs are added to the default maximum and minimum settings, the automatically assigned colors are interpolated between the colors above and below them (using a linear RGB interpolation). The precise numerical values corresponding to the \"automatic\" values vary in accordance with the analysis results.  
_Step 2: Acquisition of Visualization Space Analysis Manager._ The representation method for the analysis results is configured, and the Legend Setting node is used to set the related legend information, including display units, display names, text types, and legend dimensions, to elucidate the meaning of the internal force values represented by colors, as illustrated in Figure 12.  
Figure 10: Acquisition of materials.  
_Step 3: Creation of Analysis Result Data._ A colored-surface-based visualization mode is employed to exhibit the internal force analysis results. Initially, a specific surface, which acts as a visualization medium, is associated. The BoundingBoxUV of this surface is obtained and then segmented according to the arrangement of the internal force measurement points, as illustrated in Figure 13. Post-cutting, each segment is utilized to exhibit the analysis results of the corresponding internal force measurement points.  
_Step 4: Updating Spatial Analysis and Setting View Analysis Display Style._ The internal force calculation results from Midas Civil are exported to Excel. Dynamo is then utilized to acquire and organize the data in the table. These data are combined with the previously acquired coordinates of the associated surface UV domains. The Colored Surface Display Style node from the archi-lab package is used to update the spatial analysis results. In order to apply the analysis display style to the view, the current view's analysis display settings must be configured to the predefined analysis display style, as shown in Figure 14.  
Figure 11: Creation of analysis display style.  
Figure 12: Legend settings.  
Figure 14: Analysis display settings. (**a**) View properties. (**b**) Modification of the analysis display style.  
Figure 13: Segmentation of bounding box UV. (**a**) Setting of UV coordinate points. (**b**) Regional division of internal force measurement points.