Composite-based bridge nears completion in Florida
David Wagman | October 25, 2019Work is moving ahead on a $7.6 million, 57-foot-wide Florida bridge made of rust resistant materials intended to protect the structure against damaging weather.
Once completed this autumn, the bridge will include a 12-foot travel lane in each direction, eight-foot shoulders and five-foot sidewalks. Including approaches, it will be roughly .33 miles in length.
Deck pour in May 2019. Credit: FDOTThe Florida Department of Transportation (FDOT) said that corrosion is a constant concern, including high humidity, high temperatures, high water tables and high exposure to salt water. It said that a study of 54 bridge projects in one part of the state showed that corrosion was responsible for three quarters of maintenance costs on average.
FDOT said that construction costs for the new Halls River Bridge are about 30% higher than traditional concrete-and-steel construction. It said these additional initial costs are expected to be paid back in savings on maintenance and extended service life, which is expected to exceed the 75-year service life that FDOT requires for all new bridges.
Performance monitoring
The new Halls River Bridge in Homasassa Springs is testing a variety of new technologies that may address maintenance and longevity issues. The FAMU-FSU College of Engineering and the University of Miami College of Engineering will help to monitor the project, including fabrication, construction and installation of experimental technologies.
The current structure was built in 1954, and due to significant deterioration, is being replaced. FDOT made it part of an initiative that focuses on developing structural applications for fiber-reinforced polymers (FRP), a class of corrosion-free materials that earlier had been tested in an FDOT research program.
The concrete piles that support the bridge are prestressed with carbon fiber composite cables (CFCC). The hybrid composite beams (HCB) to support the bridge deck have been used in other bridges nationally, but these will be the first in Florida. Glass-fiber-reinforced polymer (GFRP) will be used in the guard rails, the pier caps, the bridge deck and as reinforcement in the CFCC-prestressed sheet piles that serve as retaining walls.
Stay-in-place form installation, May 2018. Credit: FDOTConcrete products
The bridge will also use several concrete products in combination with noncorrosive reinforcement. The bulkhead caps will be cast with Seacrete, which FDOT said has identical mixture properties to conventional concrete but uses seawater rather than fresh water and includes a retarder to offset high chloride content. Seacrete shows higher early age strength than conventional concrete mixtures, FDOT said.
In addition, a Green-RAP and a Green-RCA concrete mix will be used in bridge components. In Green-RAP concrete, recycled asphalt pavement partially replaces the aggregate; Green-RCA concretes use recycled concrete aggregate. Test blocks in varying combinations of Seacrete, Green-RAP and Green-RCA concretes will be cast to monitor the performance of different concrete mixtures in real-world conditions.
In addition to the engineering school monitoring, the bridge will be equipped with sensors, which will allow researchers to monitor performance of the bridge’s components.
The Key term here is "rust resistant" not Rust Proof.
Due to legal restrictions.