Pedestrian Bridge Structural Inspection Survey
Southport, Gold Coast QLD · Client: State Infrastructure Authority
Area Scanned
2,400 sqm (deck and soffit)
Time on Site
1 day
Sector
Civil & Infrastructure
Deliverables
4 formats
Overview
A 120-metre concrete pedestrian bridge over a tidal canal required a condition survey to assess spalling on the underside of the deck. Traditional rope-access inspection was planned, but the client wanted a permanent 3D record that could be re-examined remotely by multiple engineers. We scanned the bridge from both abutments, the mid-span pier, and from a boat positioned beneath the deck to capture soffit geometry. Thermal imaging was overlaid onto the point cloud to identify areas of delamination not visible to the naked eye. The resulting dataset allowed engineers to measure crack widths, spalling depths, and deflection profiles directly from the 3D model. Remediation quantities were extracted without returning to site, and the scan data became the baseline for future comparative surveys.
01 Challenge
Scanning from a boat introduced motion that degraded scan quality. Tidal windows limited underside access to four hours per day. The bridge remained open to pedestrians throughout the survey.
02 Solution
We stabilised the scanner on a levelling plate bolted to the boat deck and timed each scan to slack tide. Pedestrian traffic was managed with spotters at each end of the bridge to pause foot traffic during the 90-second scan exposures from the deck surface.
03 Outcome
The engineer identified 14 areas of soffit delamination from the thermal overlay that were not visible in the RGB point cloud alone. Remediation scope was finalised without a second site visit, saving approximately $12,000 in rope-access mobilisation costs.
Equipment Used
- Trimble X7
- FLIR T640 Thermal Camera
- Trimble RealWorks
- CloudCompare
Deliverables
- E57 Point Cloud
- Thermal Overlay Report
- Defect Map (CAD)
- Cross-Section Profiles
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