## 3 Monitoring Experiment Pertaining to Dynamic Bridge Deformation
### Microwave Interference Measurement Technology Monitoring the Dynamic Deformation of the Bridge  
When monitoring the dynamic deformation of the Fenghuangshan Road Bridge of Xiaoqing River, the micro-deformation monitoring system was placed on the sidewalk directly below the bridge, and a 5\({}^{\circ}\) angle was formed between the line of sight and the horizontal direction (Figure 5).  
Figure 4: Location diagram of Fenghuangshan Road Bridge.  
When a vehicle passes the bridge, the monitoring frequency of the instrument is set to 50 Hz and 100 Hz, and the dynamic deformation time series of the bridge is obtained.  
IBIS DATA VIEWER was utilized to process the monitored data, Rangebin Selection was selected, and multiple Rbin points were selected as the main monitoring points for bridge deformation according to the location of the distance monitoring instruments. The following were selected as deformation monitoring points for data processing: one mid-span position, two 1/4 span positions, two 1/8 span positions, and two bridge head positions. The processing results are detailed in Section 4.  
Monitoring Bridge Dynamic Deformation Based on the Isometric Virtual Plane Method That Incorporates the Digital Photography Technique  
To realize the goal of monitoring dynamic bridge deformation using close-range photogrammetry, fixed-frame camera equipment that is suitable for a total station was designed, and the camera equipment and telescope were matched in the line-of-sight direction; subsequently, bridge deformation was monitored at a distance from the bridge. The monitoring equipment and site are depicted in Figures 6 and 7. The specific monitoring process is as follows:  
Figure 5: Relative position of monitoring points on Fenghuangshan Road Bridge.  
Figure 6: Test site. (**a**) Layout of deformation point beacons; (**b**) overview of five warp point beacons.  
Figure 7: Remote monitoring of the close-range photogrammetry technical equipment and monitoring diagram. (**a**) Front view; (**b**) reverse view; (**c**) installation instruction; (**d**) field monitoring chart.  
1. Deformation monitoring points were arranged at the middle span, 1/4 spans, and 1/8 spans of the bridge, and the total station was placed on the sidewalk on the south bank of the Xiaoqing River. After centering, leveling, aiming, and focusing, the support and photography equipment were installed. Meanwhile, the close-range photogrammetry measuring device for remote monitoring was approximately 100 m away from the bridge.
2. During the red light period, multiple instances of remote monitoring with close-range photogrammetry measuring devices were utilized to simultaneously take multiple sets of photos of the corresponding monitoring position of the bridge at high speed, and the group of photos with the highest quality was selected as the reference photos (zero photos).
3. During the green light period, when large buses or heavy trucks passed by, multiple instances of remote monitoring with close-range photogrammetry measuring devices were utilized to monitor the bridge and to collect multiple sets of photos. The group of photos with the highest quality was selected as the corresponding position for follow-up photos, and a total of 208 follow-up photos were taken.