TOP 10 BRIDGES: Safe at home (No. 3)

Ohio River bridge to be slid into place

Bridges Article November 04, 2011
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Historic preservation was an important factor in replacing the Milton-Madison Bridge. Madison, Ind., is home to the largest National Historic Landmark District in the state.
Through an environmental assessment process, the Indiana Department of Transportation and the Kentucky Transportation Cabinet decided the most cost-effective plan for replacing the structurally deficient bridge was to place a new truss superstructure on the rehabilitated existing piers.
The existing piers consisted of under-reinforced pier stems above unreinforced caissons sunk about 5 ft into bedrock. To rehabilitate them to meet modern wind and barge load standards, the contractor needs to bore holes up to 70 ft into the caissons, insert bundles of reinforcing steel and grout the reinforcement in place. The pier above the caisson is then encased in at least 2 ft of reinforced high-performance concrete, designed for high strength and low permeability. Finally, the pier caps will be widened to accommodate the wider superstructure.
To protect the piers from scour, riprap is being placed to a 60-ft radius around the piers.
The new superstructure will be 40 ft wide, including two 12-ft-wide lanes and 8-ft-wide shoulders, with a 5-ft-wide sidewalk cantilevered onto the downstream side of the truss.
The state owners arranged for a ferry to shuttle passengers across the Ohio River between the towns of Milton and Madison for up to 365 days. That was the limit the states put on the bridge closure. Bidders were allowed to include no more than 365 days of bridge closure, with each day of closure valued at $25,000. There is no other river crossing within 25 miles of the bridge, which many area residents rely on for their daily commute as well as trips for shopping and other purposes.
Walsh Construction won the contract with a bid that included only 10 days of closure. The new superstructure will be constructed along the river shoreline before it is lifted in sections onto temporary piers parallel to the existing bridge. The grand finale will be when Walsh slides the new truss over a lubricated PTFE surface onto its permanent, strengthened piers.

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