In the last two decades, many of Georgia’s bridges have been widened to meet increasing capacity demands. Originally, these bridges were often designed for the H15 truck loading, and 15 psf of future wearing surface. If the sufficiency rating is high enough, the H15 section of the bridge is retained and incorporated into the new bridge width. New sections of a widened bridge are designed for the current live loading. In the past, no attempt has been made to upgrade the original H15 sections to meet the higher loads because traditional strengthening methods such as external post-tensioning or externally bonding steel plates to the members were cost-prohibitive. Recognizing the need for a solution, GDOT’s Office of Bridge Maintenance decided to find a cost-effective solution to the “sandwich” problem: utilizing fiber-reinforced polymers (FRP).

Built in 1962, S.R. 92 over Noon Day Creek in Cherokee County, was a 26 ft wide by 160 ft long bridge composed of five 32-ft long reinforced concrete T-beam spans. The original section of the bridge would require a 30% increase in both flexure and shear capacity. The method of FRP shear strengthening used for this project was unique. Drawing from recent research on carbon fiber shear strengthening, special L-shaped brackets were used.

The carbon fiber installation was completed in only 50 days using daytime single-lane closures. A total of 1000 square ft of carbon fiber laminate was installed on the beams and slab, upgrading roughly 3900 square ft of bridge.

Owner
Georgia Department of Transportation
Atlanta, Georgia

Project Engineer/Designer
J.B. Trimble & Associates
Atlanta, Georgia

Repair Contractor
Engineered Restoration Company
Lawrenceville, Georgia

Material Suppliers
B.G International LLC
Riverwood, Maryland

Structural Composites, Inc.
Houston, Texas