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

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The paper describes the design and construction of a new 133-ft, single-span integral-abutment bridge on realigned East Brighton Avenue over I-81 in Syracuse, New York. The alternative design shifted the roadway east and replaced a proposed two-span bridge with two single-span structures. This avoided staged construction on the existing alignment, reduced traffic disruption, eliminated temporary water-main relocations, and reduced bridge area and costs.<br /><br />Bridge 7S presented a major challenge: its abutments would exceed 42 ft in height, while NYSDOT standard integral-abutment designs cover heights only up to 15 ft. A taller abutment would require more concrete, create construction and quality-control risks, and require complex finite-element analysis. The solution was to build anchored soldier-pile and lagging retaining walls in front of the abutments, reducing their effective height.<br /><br />The constrained site required careful coordination of the bridge foundation and retaining-wall anchors. Bridge piles were changed from closely spaced HP14 piles to larger HP16 piles spaced farther apart, allowing tiebacks to pass between them. A 3D model helped identify and resolve conflicts, including crossing anchors around the abutments. The design also accounted for lateral loads on nearby retaining walls caused by thermal movement of the integral abutments.<br /><br />Retaining walls used grouted tiebacks in excavation areas and deadman anchors in embankment areas. Testing verified anchor capacities, while corrosion protection and structural checks addressed durability and strength. Because of shallow bedrock, possible karst voids, and the nearby existing bridge, piles were installed in augered holes to limit vibration. Field testing and construction observations led to adjustments in pile lengths and locations; variable rock conditions still caused installation difficulties.<br /><br />The project demonstrates how retaining walls, foundation redesign, 3D coordination, and detailed construction planning can make a tall integral-abutment bridge feasible within tight site constraints.

Keywords

integral-abutment bridge

single-span bridge

retaining walls

soldier-pile and lagging

bridge foundation redesign

tiebacks

HP16 piles

3D coordination

construction constraints

Syracuse New York