Seven Mile Bridge Repair/Rehabilitation

Seven Mile Bridge Repair/Rehab

Client: FDOT D6

Location: Monroe County, FL

Contract Delivery:  Design-Bid-Build

Services Provided:

  • Bridge Design
  • Bridge Inspection

The SR 5/US-1 Overseas Hwy at Seven Mile Bridge 90010 Rehabilitation is a substructure rehabilitation of the longest segmental bridge in Florida. The Seven Mile Bridge is a segmental box girder bridge, 6.8 miles long, 39′ wide carrying two lanes of traffic (one each way), which has 266 spans with 236 low level piers (3’-dia. columns connected by precast struts) and 29 high level piers (vertically post-tensioned box columns).

BPA’s inspection team performed a visual hands-on inspection of the bridge’s substructure above water focused on the pier columns to identify and measure delaminations, spall and cracks. A written report showing deficiency description, dimensions, location and state conditions was submitted, and later used to prioritize necessary repairs based on available budget and structural adequacy of the affected members. The following repairs were preformed to the bridge based on the proposed deficiencies outlined in the inspection report:

  1. Typical spall and delamination repairs
  2. Critical spall/delamination and crack repairs at top of columns
  3. Bearing replacement at 16 piers, which required jacking the superstructure using a TSS
  4. Installation of a sacrificial cathodic protection system to drilled shafts, struts and pier columns
  5. Application of a concrete deck sealer (Methacrylate) to prevent concrete deck deterioration
  6. Replacement for the existing fender system due to extensive damage to concrete piles

BPA participated in the preparation of the rehabilitation plans for the bridge’s substructure under a subconsultant agreement providing construction contract documents for the substructure rehabilitation, deck scaling, and bridge fender system replacement. The substructure piers consist of two drilled shafts each supporting a reinforced concrete column braced with a concrete strut. The substructure for the raised section of the bridge consists of vertically post-tensioned concrete boxes supported on pile caps. The rehabilitation included repairs of cracked, spalled and delaminated concrete at the drilled shafts, struts, columns and shear keys, and the replacement of 16 column tops severely damaged. The project also required a unique temporary support system with stringent jacking provisions as traffic was maintained during repairs.

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