Long-Term Durability Study: Long-Span Structures

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Long-Term Durability Study: Long-Span Structures

Hensley, Scott I. / Perry, Phil

Well over 2,000 long-span structural plate structures have been constructed in the United States over the past 25 years, both as grade-separation structures and culverts. Long-span structural plate structures are short-span bridges defined in the AASHTO Standard Specifications for Highway Bridges, Section 12, as structural plate structures (pipe, pipe-arch, and arch) that exceed the maximum sizes imposed by Article 12.6 on flexibility factor limits. Both applications have the potential to subject the long-span structure to corrosive action from runoff and deicing chemicals and also to abrasion from an abrasive bedload. In an effort to ensure that current design methods incorporate proper protection, if required, 21 long-span structures were inspected and rated in terms of condition with regard to the effects of corrosion and abrasion. Core samples were extracted from each structure and analyzed for metal loss. Samples of runoff and backfill were also taken and analyzed for pH, resistivity, and chloride content. Given this information, structure performance was compared with accepted methods of projecting metal loss in corrugated steel drainage structures.