Center Fixed and South Fixed Bridge Replacements
The Center Fixed and South Fixed Bridge replacement project was a $16 million bridge replacement project located in Charlotte County, Florida. Both bridges were nearing the end of their service life and considered to be “functionally obsolete” and “scour critical.” The “scour critical” designation indicates that these bridges were susceptible to scour related collapse under certain storm induced flows. The Gasparilla Island Bridge Authority (GIBA) wanted to replace the bridges with attractive, safe bridges of minimal height and width which maintained the alignment to the greatest extent possible.
This project included the design of the replacement bridges for GIBA’s Center Fixed Bridge and South Fixed Bridge. Both bridges are located on the GIBA’s 2.5-mile long privately owned Boca Grande Causeway. GIBA’s two fixed bridges are critical to the transportation needs of the public as they are the only land link between Placida in Cape Haze and Gasparilla Island.
DRMP led the structural design effort from the concept stage through final design for all structural elements on this project, which included the replacement of the two bridges, bulkhead wall to protect the abutments and a retaining wall. The bridge designs included consideration of significant anticipated scour, vessel impact and wave impact forces. Sufficient right-of-way was available at the approaches to raise the Center Bridge above the storm surge but constrictions at the South Bridge approaches allowed for limited modifications to the profile. At this location, a flat slab was selected because of its ability to resist wave impact and buoyancy forces. Cast in place closures within the continuous precast flat slab system were mechanically connected to the substructure using stainless steel dowels to prevent the superstructure from being dislodged during a storm event.
The replacement bridges were designed to be simple and aesthetically pleasing, minimally impede water views for both drivers crossing over the bridges and the residents on Gasparilla Island and to provide a minimum 75-year, low maintenance design life - all while minimizing cost. An additional criterion met was that the bridges remain serviceable immediately after passage of the design storm event since they provide the only land link to the island and must be used by emergency, security and life safety vehicles. This project was designed on an aggressive schedule so that construction could coincide with periods of reduced seasonal traffic volumes. In addition, the island residents were actively involved during the design and construction. The public involvement process was extensive as consensus was built and maintained for the duration of the project.
