Remaining Strength of Deteriorated Corrugated Steel Culverts

Currently, corroded corrugated steel culverts are typically assessed based on the results of visual inspections that provide qualitative data about corrosion levels. However, there is a lack of experimental data relating the extent of corrosion to the capacity of the culvert that would allow engineers to assess the remaining capacity and also the end-of-service-life condition for deteriorated culverts (answering the question, how much deterioration is too much?). To address this need, a series of experiments were conducted on culverts with varying levels of corrosion and two levels of soil cover (0.45 and 0.9 m) subjected to simulated vehicle loading. The results of the experiments indicate that backfill compaction plays a more significant role in the behavior of deteriorated pipes than corrosion for most levels of deterioration. For example, the control pipe (with no corrosion) was not the stiffest pipe and developed significant bending moments under service loading rather than carrying the loads in thrust, which was believed to be the result of poor backfill. The most deteriorated specimen that was tested to failure, with 34% remaining wall thickness at the water line, failed because of local buckling of the remaining strips of steel between perforations in the wall in the corroded region. However, a specimen with 47% remaining wall thickness failed because of the formation of plastic hinges in the top half of the culvert, suggesting that the failure was unrelated to the corrosion. These preliminary results suggest that there is a critical level of corrosion that causes a reduction in capacity but that the condition of the surrounding soil has a significant influence on the ultimate capacity and that the two cannot be assessed independently.