Highway 417 Bridge Replacements Reuse of Existing Piles Study

ABSTRACT: The Ministry of Transportation Ontario (MTO) continues to consider the reuse of existing piles to achieve traffic mobility, economic, sustainability and environmental advantages. Five structures at four sites along the Hwy 417 located in Ottawa Ontario have been selected for bridge replacement utilizing rapid bridge replacement (RBR) techniques. The plan is to rehabilitate the abutments and to salvage the existing deep foundation elements (where present). The bridges were constructed between 1960 and 1968 and have a similar 2-span configuration, supported on perched abutments and a central pier. The reinforced concrete abutments are founded on steel H piles at all sites. The piers are founded on spread footing shallow foundations at all sites with exception of the Richmond Road structures, where the northbound (NBL) and southbound (SBL) structures are supported on steel H piles. Corrosivity testing (including determination of soil resistivity, chloride content, and pH) was performed and reporting completed. A supplemental in situ investigation was conducted to expose the piles at two sites (Richmond Road and Woodroffe Avenue). Visual and ultrasonic testing of the exposed steel piles were carried out to determine the nominal thickness and damage to the piles over time due to corrosion. In addition to the testing of the piles, additional soil samples were retrieved for chemical analysis to determine the corrosivity of the soil at the site. This paper presents the results of the corrosion assessment and pile thickness loss. The paper also assesses the corrosion rate and predicted service life. The study is demonstrative of the MTO’s commitment to assess new technologies and applications that support Ministry initiatives, decarbonization, and operational needs and specifically to encourage the reuse of existing foundations.