Bridging Challenges: Creative Solutions for the I-81 Bridge Foundation Design-PPT Presentation

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The I-81/I-690 reconstruction in Syracuse includes a replacement East Brighton Avenue bridge. NYSDOT generally requires integral abutments, which avoid expansion joints and reduce maintenance, but site conditions and construction constraints demanded an alternative approach.<br /><br />The original bridge concept involved a two-span structure at the existing location. The team developed an alternate design with two single-span bridges shifted east. This maintained traffic, avoided relocating two active watermains, reduced the bridge footprint and construction staging complexity, and lowered anticipated maintenance and construction costs.<br /><br />For Bridge 7S, the single-span design had a 42-foot-tall integral abutment—well above NYSDOT’s standard 15-foot limit—and required complex finite-element analysis. Subsurface conditions included a thick, variable layer of weathered rock and possible localized karst, though geophysical surveys found no major voids below the pile tips. Retaining walls placed in front of the abutments reduced their height, enabled standard NYSDOT design methods, and cut concrete volumes.<br /><br />The walls required extensive anchoring near the bridge piles, creating tight clearances and potential anchor conflicts. The team revised the abutment pile layout, used larger, more widely spaced piles, and applied 3D modeling to coordinate anchors and resolve crossing conflicts. Augered holes helped limit vibration during pile installation.<br /><br />Construction presented additional challenges: some piles extended nearly 14 feet deeper than planned, some deviated from their intended locations, and pile-tip damage occurred. PDA testing was used to verify installed pile capacity.<br /><br />Key lessons included the value of adapting bridge alignment and foundation systems to site constraints, using detailed geotechnical investigation and geophysical surveys, and applying 3D coordination to improve constructability. These measures supported a durable design with lower long-term maintenance costs.

Keywords

I-81

I-690

Syracuse

East Brighton Avenue bridge

integral abutments

single-span bridges

geotechnical investigation

retaining walls

pile foundation

3D coordination