James Bypass Overflow Bridges on Manning Avenue

James Bypass was a multiple bridge project executed using the accelerated bridge construction method in order to keep Manning open to trucks and traffic for as much of the project duration as possible. The foundations for the two new bridges were constructed under the existing bridges, and the road was closed down for only 35 total days to demolish the old bridges, construct the new bridges, and pave the roadway. Since there was a very limited amount of space under the bridges to construct the foundations, the girders were designed with footings that would rest on the abutments and pier caps. Unfortunately, while pre-casting the foundations, it was discovered that alternative designs needed to be considered because the original girder design wouldn’t work. A design was chosen that raised the elevation of the pier caps and abutments utilizing a secondary concrete pour. While it added to the necessary road closure duration, this option was determined to maintain the best structural integrity of the options available.

Additionally, ensuring that the bridge maintained an even riding surface in spite of the camber of the girders and the minimum and maximum polyester concrete overlay thicknesses proved to be challenging due to the complex geometry of the bridge. The angles of the overall road slope, the crown of the pavement, and the skew of the bridge, combined with the uncertainty of the exact deflection of the girders due to the polyester concrete overlay, made it difficult to decide an appropriate elevation for the top of the bearing seats. With Cornerstone’s assistance, a height was determined that would provide sufficient cover for the rebar in the pier caps while still eliminating bumps in the surface, such that the completed bridge rides smoothly and drains well.

Funding for the project was provided by the federal Highway Bridge Program, with RMRA providing the local match. The original bid amount for the project was
$5,260,535, and the project was completed under budget at $5,036,122.
(See Supporting Documentation for additional info.)