## 4 Lab Experiment  
### Experiment Set-Up  
In this section, we conducted a laboratory experiment on a full-scale steel continuous beam bridge to substantiate the efficacy of our proposed damage localization algorithm. The bridge boasts a total span of 22 m, segmented into lengths of 6 m, 10 m, and another 6 m, as shown in Figure 7. The southwestern end of the bridge is anchored with a fixed bearing, while the other supports feature sliding bearings. Steel platforms, as depicted in Figure 8, have been mounted at both extremities of the bridge to act as the vehicle's starting and ending points. The cross-sectional specifications of the bridge are detailed in Figure 9.  
Figure 7: Three-span steel continuous beam model (Unit: m).  
\begin{table}
\begin{tabular}{c c c c c c} \hline Damage extent & 10\% & 20\% & 30\% & 40\% & 50\% \\ \hline Reconstruction (E-3 m) & 0.401 & 0.403 & 0.405 & 0.408 & 4.12 \\ \hline Simulation (E-3 m) & 1.959 & 1.980 & 2.008 & 2.045 & 2.096 \\ \hline Difference (\%) & 388.4 & 391.7 & 396.04 & 401.54 & 409.12 \\ \hline \end{tabular}
\end{table}
Table 5: Comparison in difference between scenarios with different damage extents.  
For the purpose of this experiment, an electric vehicle, as shown in Figure 10a, was utilized to impose a dynamic load on the bridge. The vehicle's geometric specifications are outlined in Figure 10b. Weighted mass blocks, depicted in Figure 10c, were secured to the vehicle to simulate the varying traffic loading conditions. The front axle load varied between 93 kg and 187 kg, while the rear axle load ranged from 92 kg to 395 kg. The vehicle was programmed to travel across the bridge at a steady velocity of 0.51 m/s. Over the course of several runs, the vehicle's traversal path was diversified, adopting stochastic patterns that included traversing the right lane, the central lane, and the left lane, as well as executing an \"S\" shaped route across the bridge. This approach was also designed to simulate various traffic scenarios and to assess the algorithm's performance under different loading conditions.  
Artificial damage was introduced to the middle span of the bridge, as illustrated in Figure 11. A section of the bottom flange was removed to emulate a reduction in structural  
Figure 8: Steel platform and steel bridge [39].  
Figure 10: Electric vehicle [40]. ((**a**) Vehicle; (**b**) Geometric specifications; (**c**) Weighted mass blocks).  
Figure 9: Cross-section of the steel bridge (unit: mm) [40].  
stiffness. The damaged section measures 10 cm in length, with its central point located at a coordinate of \(-2.1\) m. As indicated in Figure 12a, the inflicted damage is positioned near the quarter-point of the middle span, providing a controlled scenario to test the damage localization algorithm's accuracy and responsiveness.  
As for monitoring system, five mid-span cross-sections of the bridge have been equipped with inclinometers at the coordinates of \(\pm 2.4\) m and \(\pm 4.4\) m. The layout of these sensors is presented in Figure 12a, marked by triangular indicators. These sensors function at a sampling frequency of 20 Hz to ensure accurate data capture. Figure 12b offers a close-up view of the sensor placements on each cross-section. The inclinometers, signified by the triangular markers in Figure 12b, are installed on the inner side of the bridge's left floor plate.