Investigation of the Failure Mechanisms of Intact and Deteriorated Culverts

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Regier, Caleb
Cuvlert , Deteriorated
The goals of this research are to better understand the impact of wall section loss due to corrosion as well as the influence of different failure mechanisms on corrugated steel culverts. An accelerated corrosion technique was first developed to degrade multiple pipe specimens to different degrees of deterioration. A total of six deteriorated pipe specimens were created. Two dimensional maps of the remaining wall thickness of each specimen were then developed using an ultrasonic thickness gauge, showing that the average remaining wall thicknesses for the samples ranged from 18% to 47%. Seven corrugated steel pipes specimens (six accelerated corroded samples and one intact pipe) were then buried in the test pit at Queen’s University and examined under single wheel loading at both 0.9 m and 0.45 m of cover. The test results show that the surrounding soil compaction has a greater impact on the overall behaviour of corrugated metal culverts than the level of deterioration. However, the results suggest that a potential for a critical level of corrosion may exist which dictates the controlling failure mechanism. Current design procedures may consider the wrong failure mode in some instances, as the capacity of the intact pipe tested in this study was controlled by local bending in the top half of the pipe rather than thrust at the springlines. Lastly a full scale test was conducted on an intact horizontal ellipse culvert to understand the behaviour of these structures during backfilling and live loading. The horizontal ellipse culvert was tested at two different burial depths (0.9 m and 0.45 m) using tandem axle loading. The results suggest that the ellipse behaves similar to a circular culvert during backfilling, although the vertical stiffness of the ellipse was less than the horizontal stiffness. The live loading of the culvert suggests that the load carrying mechanism changes from thrust at 0.9 m of cover to bending at 0.45 m of cover. The structure ultimately failed due to the formation of a three-hinge plastic collapse mechanism across one shoulder.
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