# Development and Application of Digital Twin-BIM Technology for Bridge Management
## 4 Building Information Management
### Digital Twin of Comoro Bridge for Structural Performance Evaluation
#### 4.4.2 Structural Performance Evaluation Based on FE Analysis
Structural Evaluation for state conditions of Comoro Bridge  
When analyzing the Comoro Bridge model using an FE analysis, the obtained results can be compared to the theoretical values to evaluate the structural performance, as outlined below:  
* Displacement  
The displacement results from the dead load (DL + SDL) obtained from both the FE analysis and theoretical calculations are presented in Figure 20. The results indicated that the displacements obtained from both the FE analysis and theoretical calculations were quite similar in the internal spans. However, there was a slight variation in the displacements of the side spans due to the influence of the boundary. The results of the finite element analysis (FEA) can be utilized to assess the distribution of normal stress along the axis of the Comoro Bridge in comparison to the theoretical results. The normal stress distribution presented in this study was induced by the dead load (DL + SDL), as depicted in Figure 21. According to the Euler-Bernoulli theory, the normal stress is distributed according to the bending moment distribution along the bridge axis, resulting in peak values at the top of the piers. As observed in the figure, the normal stress distribution results obtained from both the FE analysis and theoretical calculations were consistent and nearly identical. However, the peak stress occurring at the top of the piers exhibited larger values than those predicted by the Euler-Bernoulli theory. The mechanisms underlying these differences are discussed later. \begin{table}
\begin{tabular}{c c} \hline
**Names** & **Types** \\ \hline Analysis & Linear static \\ \hline Dimension & Three dimensions \\ \hline Composed element & Solid \\ \hline Mesh order & Linear \\ \hline Mesh size & 0.25 m \\ \hline D.O. F & 6.6 million \\ \hline \end{tabular}
\end{table} 
Table 4: FE analysis types. Figure 20: Displacement due to the dead load (DL + SDL). Shear-Stress distribution  
Due to the uniform load action of the dead load (DL) and superimposed dead load (SDL), the shear stress exhibited a linear distribution with a downward slope, as illustrated in Figure 22a. Furthermore, the average shear stress, calculated using Equation (1), by dividing the theoretical value of the acting shear force by the equivalent cross-sectional area of the highlighted region in Figure 22b, demonstrated an excellent agreement with the results obtained from the structural analysis. This phenomenon is attributed to the uniform concentration of the shear stress on the web of the prestressed-concrete (PC) box girder, as illustrated in Figure 22c. The detailed FE analysis results obtained using the overall bridge model consistently aligned with the theoretically expected results, providing conclusive evidence of the significant value and usefulness of the digital twin in the bridge analysis. \[\mathbf{\tau^{\star}}=\frac{\textbf{Shear force}(\mathbf{Q})}{\textbf{Effective area}(\textbf{A}_{\textbf{eff}})} \tag{1}\]  
Figure 21: Normal stress distributions due to the dead load (DL + SDL). Figure 22: Shear-stress distribution along the bridge axis. (**a**) Shear-stress distribution due to the dead load (DL + SDL); (**b**) effective area; (**c**) contour map of the effective area. * Sectional force (Coefficient \(Z\) value)  
The finite element analysis enabled the evaluation of the sectional coefficient \(Z\) along the bridge axis, obtained using Equation (2), as depicted in Figure 23a. At certain locations, the coefficient \(Z\) was arbitrarily distributed; however, taking the average value results in a \(Z\) coefficient value of 6.059 m\({}^{3}\). This value closely aligned with the theoretical value of 6.195 m\({}^{3}\) based on the Euler-Bernoulli theory, as illustrated in Figure 23b. \[Z=\frac{\text{Inertia Moment}}{\text{neutal axis height}}=\frac{\text{I}}{ \text{y}} \tag{2}\]  
* Nonuniform normal stress (Shear-lag) distribution on box-girder section  
The phenomenon of the shear-lag effect can be evaluated in the box-girder section, as depicted in Figure 24a,b.