Overpass gets an upgrade

By: Big R Bridge

When Kansas City Southern, a Class I railroad, needed to upgrade its line speeds and prepare clearances for a future second line through downtown Edwards, Miss., it ran into an obstacle with a famous but extremely deficient timber overpass bridge.

The timber bridge was filmed during the final scenes of the 2000 movie “O Brother Where Art Thou,” which starred George Clooney. Town officials were proud of the bridge and its movie appearance, so while the railroad wanted to upgrade its line speeds and clearances, the town wanted to maintain a visual centerpiece.

Town and railroad officials came to an agreement that the best solution was the turnkey design and supply of a 58-ft span by 25-ft rise Super·Cor Arch and precast MSE wall system with adobe brick form liner from Big R Bridge .

Aside from the aesthetic challenges, the downtown area also presented a difficult obstacle for a traditional bridge arrangement. The arch was the only solution that would avoid impacting nearby historical downtown houses and a business district roadway entrance, while maintaining a tight budget and time schedule.

The existing timber bridge offered just enough clearance for train traffic and the existing driveways. The new bridge had to minimize approaches and maximize clearances.

The arch was designed for HS20-44 highway loads. It also needed to have minimum vertical rise for the required train clearances with only 3 ft of backfill material over the crown, resulting in no impacts to the downtown structures. Because the rail line was the lowest point in town, the cross section required a drainage ditch on both sides of the line, and the structure could easily accommodate the largest available sizes for a soil-metal structure.

Given the tight conditions, a vertical MSE wall provided the best solution for the arch head and wing walls. Big R Bridge supplied the precast panels and steel-reinforcing mats that made up the wall system.

The backfill material for the wall and arch were in the same zone, so the MSE wall offered the most economical solution. The MSE wall gave the appearance the town officials wanted, with an adobe brick form liner and paint finish.