Bridge Complexity and Site
Beyond the bridge structure, it is important to consider its complexity, size, and setting. Is there a benefit to sending a drone on a 50-ft single-span concrete frame, adding time and complexity to what is otherwise a routine, efficient procedure? Perhaps not. But on larger structures, drone inspections may be accomplished in a fraction of the time, and with fewer inspectors needed on the ground.
For example, a recent inspection of the concrete-steel Mike O’Callaghan–Pat Tillman Memorial Bridge on the border of Nevada and Arizona, utilized drones and created a significant cost savings for the client. By deploying drones, the inspection team completed views of bridge components that would have otherwise required additional time for manual rope access and experienced bridge inspection engineers.
The inspection team now utilizes drones on alternating inspection cycles for this bridge to reduce staff costs while facilitating an alternative view of the structure. Drone use also provides inspectors key points of interest and concern to focus on using conventional techniques. Such points of interest and concern were encountered on a steel girder structure in North Dakota, where the bearing pad was not easily accessible using conventional methods. The drone was able to easily capture key areas of interest and identify a bearing which may require closer inspection. This allowed the inspection team to focus time and resources on the specific area in question, rather than squandering that time on other, less important aspects.
From a site perspective, it is important to consider whether there is a launch point for the drone that is free of vehicles and pedestrians. Will the drone provide safer access to the bridge element to be evaluated than sending a bridge inspector?
Traffic is a common site obstacle to drone inspections. Current regulations and safety procedures prohibit or place restrictions on flying drones over live traffic, taking away access points to highway and interchange structures.
On the flip side, drones offer a safer alternative to sending an inspector in snow and icy weather, or areas with harsh terrain, steep slopes, loose riprap, and so forth. Rain and heavy winds may, of course, keep drones grounded, however.
Data and Technology
Finally, it is important to consider the digital output that will result from drone inspections.
Still photos from the drone are useful, but by stitching them together into a usable model, the digital twin of the bridge can be shared with clients and allows for inspectors to view any angle of the structure or bridge element in virtual or augmented reality.
Above all, developing a data governance framework and roadmap is an important fundamental approach, and should be integrated during early project planning activities to ensure data is properly organized, managed, described, integrated, and communicated. Early identification of risks, such as data gaps and inconsistencies, will help to apply mitigation measures and monitor potential risk exposure. It also encourages collaboration around digital innovation at all levels of the project.
The fact is, data is often managed ad-hoc or in duplicate, using personal computers, network file sharing, removable storage media, or cloud environments. Without a plan for managing the location and metadata for each file taken, the time savings offered by drone inspections may quickly be eclipsed by post-inspection administrative work.
