1. How is the box girder structure inspected?
Box girder structures are divided into exterior and interior zones: exterior areas such as the girder soffit and outer web faces are inspected by a drone equipped with the under-bridge autonomous navigation module, which flies stably even without GPS signals; the interior of the box girder (the box cavity) is enclosed and signal-blocked, unsuitable for drone operations, so a crawler robot enters the interior to perform the inspection.
2. Why is a drone not used inside?
The box girder interior is narrow, GPS-denied and structurally obstructed. Flying a drone in an enclosed space carries high safety risk and low operational efficiency; a crawler robot can travel along the walls and shoot at close range, making it better suited for defect inspection in enclosed parts such as the box cavity.
3. Application scenarios for inside-and-outside combination
| Area | Inspection method |
|---|---|
| Girder soffit, outer web faces | Drone + under-bridge navigation module |
| Box girder interior cavity | Crawler robot |
| Critical parts such as bearings | Drone targeted re-capture |
4. Applicable conditions and scenarios
- Exterior structures such as the girder soffit are covered by the drone
- The box girder interior cavity is inspected by a crawler robot entering inside
- Restricted areas such as railways or navigable waters require permits from the competent authority
5. Notes
Interior box girder operations require evaluation of robot dimensions, power supply and access passages; the specific inspection method and equipment configuration are subject to the project plan.