Problem statement
During the casting of a new bridge on the Alaska Highway, complications arose and a large number of casting cracks were noted on the underside of the bridge deck. There was uncertainty as to whether the gouges were only superficial or whether they were also deeper in the structure. A Canadian firm performed non-destructive testing on the bridge, but the client doubted the results, so Invator was contacted to perform an independent inspection.
Outcome
A careful survey of the bridge revealed that the damage was limited to the concrete cover layer on the underside of the bridge deck, and that all damage was visible to the naked eye. We could not find any hidden damage in the structure. Our report helped the client make a decision to repair the bridge instead of demolishing it and building a new one.
Solution
First of all, a lot of time was spent reviewing drawings to create an inspection plan, which was necessary to plan the equipment to be packed for Canada and to ensure that no unforeseen events could affect the inspection. Once on site, the bridge deck was marked out in the necessary sections to allow the data to be processed at all. The bridge was 51 meters long and 14 meters wide, and the entire surface of the bridge deck was scanned using ultrasound. Once the scan was complete, the data was analyzed and some suspicious areas were selected for a more thorough inspection using impact echo.
Based on these results, we selected a few areas to core drill and verify our findings.
Equipment
- GPR – to locate beams and reinforcement
- Ultrasound (Mira and ELOP) – to scan over larger areas and locate cavities in the bridge deck.
- Impact echo – to further investigate the areas that had suspected voids.
- Core drilling equipment was used to verify the results.
