Reuse of Existing Piles Study

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The study assessed whether existing steel H-piles at Highway 417 bridges in Ottawa could be reused during rapid bridge replacements, avoiding unnecessary foundation work. Detailed investigations focused on the Woodroffe Avenue and Richmond Road bridges, including historical records, boreholes, soil and groundwater testing, geophysical testing at Richmond Road, and exposure and ultrasonic inspection of three piles at each site.<br /><br />The exposed piles showed pitting corrosion and localized flange thinning. Although soil tests indicated moderately to very corrosive conditions, analysis of observed section loss produced average site corrosion rates of 0.015 mm/year at Woodroffe and 0.007 mm/year at Richmond. Current estimated cross-sectional area loss averaged about 15% at Woodroffe and 7% at Richmond. The study treated 0.015 mm/year as a conservative design rate; corrosion may slow over time, making a constant-rate assumption conservative for future performance.<br /><br />Structural evaluations at Woodroffe found that pile capacity could support the proposed bridge and a further 75-year service life when assessed using the selected corrosion rate. Geotechnical capacity was generally adequate, though Richmond Road pile lengths and bearing conditions were less certain. Structural evaluations for Richmond Road had not yet been completed.<br /><br />The supplementary corrosion assessment cost approximately $400,000. By supporting reuse of the existing abutments and deep foundations, it was estimated to avoid about $1.65 million in construction costs, as well as reduce construction duration, public impacts, and carbon emissions. The findings also informed expectations for the Maitland and Pinecrest sites, where piles were not exposed but conditions were considered similar.<br /><br />Overall, the study demonstrates that site-specific corrosion testing can validate foundation reuse and guide cost-effective bridge replacement decisions.
Keywords
steel H-piles
bridge replacement
foundation reuse
corrosion assessment
Highway 417
Ottawa bridges
Woodroffe Avenue
Richmond Road
ultrasonic inspection
geotechnical capacity