These photographs show an experiment carried out by the Vibration Engineering Section earlier this month to investigate the feasibility of monitoring the mid-span deflection of a suspension bridge using a camera-based monitoring system. Accurate displacement values are useful for bridge health monitoring; however, historically, displacement has been difficult to measure on bridges.
The bridge monitored was the Humber Suspension Bridge near Hull in the UK. Figure 1 shows a photo of the bridge. To monitor the displacement, we mounted a custom made target to the bridge parapet at mid-span, then we tracked the target using a camera, which was placed at the base of the tower as shown in Figure 2. Figure 3 shows a close in view of the equipment at the base of the tower. The camera was mounted on a tripod so, as the bridge deck moves, the ‘target’ moves in the image frame. Software was used to track this movement and quantify the displacement.
Figures 4, 5 and 6 show the movement of the bridge deck at mid-span as a truck passed.