The Milton-Madison Bridge is the only crossing on a 72-mile stretch along the Ohio River, connecting Madison, Indiana and Milton, Kentucky. The narrow and deteriorating 83-year-old structure was not wide enough to accommodate modern day traffic and needed to be replaced.
To qualify for federal funding, the new bridge had to be built on the same alignment as the existing span. To meet this requirement, the project owners – the Indiana Department of Transportation (INDOT) and the Kentucky Transportation Cabinet (KYTC) – initially thought the bridge would need to be closed for one year while the structure was demolished and rebuilt. This would require a costly ferry service to maintain traffic.
The design/build team of Walsh Construction, Burgess & Niple and Buckland & Taylor proposed an innovative technique called truss sliding that would only require the bridge to be closed for a few weeks. The team was selected to design and construct the new bridge using this technique which eliminated the need for a year-long ferry service and lowered estimated project costs.
Engineering a Bridge Slide
Watch this animated model to see how truss sliding was used to reconstruct the Milton-Madison Bridge.
The new bridge is a steel truss structure that looks similar to the existing bridge. The bridge deck is 40 feet wide – double the width of the former bridge – with two lanes, shoulders, and sidewalks to accommodate pedestrians and bicyclists.
The new bridge truss superstructure was constructed downstream of the existing bridge on temporary piers. While the new bridge superstructure was being built, the existing bridge piers were encased in concrete, strengthened and modernized to current bridge standards. Once the piers were rehabilitated, the new truss superstructure was slid into place along steel rails and plates onto the existing piers.
At 2,428 feet-long, the Milton-Madison Bridge is one of the longest truss slides of its kind in North America.
Keep Traffic Moving
Using the truss sliding technique to construct the new bridge allowed traffic to be maintained across this important bi-state connection with minimal closures. Bridge closures were limited to a few weeks over the duration of the project – significantly less than the 365 days originally estimated.
Vehicles used the existing bridge while the new truss superstructure was built and placed on its temporary piers. After a brief closure, traffic was routed to the new truss via temporary approach ramps while the existing truss was removed and its piers were strengthened.
Next, the bridge was closed to traffic while the new truss was slid into place onto the rehabilitated piers. Once the slide was complete, traffic was routed across the bridge on newly constructed, wider approach ramps that were built concurrently with the new bridge.