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Innovations Case Study

SR 115 Over Red Bay
Branch Repair Project

FBT has very specialized experience working directly for contractors and material vendors as a Specialty Engineer. This unique experience allows us to be very innovative in our solutions. FBT was recently honored by the FDOT when they included this project on the FDOT website - Invitation to Innovation, in the structures design category - Transportation Innovation: Ultra-High Performance Concrete (UHPC).

Slab Unit Connection detail using UHPC

FBT developed an innovative approach to retrofitting old bridges which were constructed using transversely posttensioned Sonovoid bridge deck panels.  As these bridges age, the side-to-side connection between bridge deck panels deteriorates and the deck panels no longer distribute live load to adjacent panels. 


That results in the need to post the bridges with weight limit restrictions.  Many repair methods have been unsuccessfully attempted by other firms in the past.  However, the approach using UHPC was refined by FBT and included a custom design method with tie bars to retrofit the connection between adjacent deck panels, thus improving the bridge’s load rating capacity.  Special bracing systems are needed when the existing bridge has raised sidewalks because the exterior bridge deck panels are not stable with the eccentric load of the sidewalk once the existing transverse post-tensioning bars are cut or snapped due to extensive corrosion.  


FBT worked with FDOT to develop Special Provisions and Project Pay Items in the contract documents for Hydro demolition and Developmental Specifications for UHPC (among other elements). This project was unique because it was the largest project to date to use UHPC for existing Sonovoid PSB joint repairs in Florida, consisting of 29-spans with 8 joints each totaling approximately 7,000 LF.


A key issue that arose as part of FBT’s project was that the funding source does not have to come from the New Bridge funding pool. Since all work is self-contained on or above the bridge deck (and no work occurs under the bridge), it was determined that 3R and Maintenance Funding sources are allowable for use to perform the retrofit.  This is a significant development considering the large number of Sonovoid bridges that have been in existence since the 1960s to the 1980’s bridge projects.

Innovative structural engineering methods using Ultra High Performance Concrete
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