Merchants Bridge Replacement

Our team provided design and environmental services for the replacement of the Merchants Bridge main span over the Mississippi River, including foundation repairs.

The bridge, built in 1889, carries five Class I railroads. The double-track structure has three main truss spans of 520 feet each that were replaced. In addition, the unreinforced masonry piers had been significantly scoured and did not provide AREMA-level seismic resistance.

During the 30% design phase, the project team studied several scenarios: open deck and ballasted deck options, E80 and E90 live loading, various truss panel configurations, truss float-in scenarios, seismic resistance of existing foundations, seismic retrofit schemes, seismic isolation bearings, and barge vessel collision analysis.

Final design of the three new 520-foot truss spans included strengthening of the existing masonry foundations to withstand seismic and barge collision events, as well as a combination of float-in, lifting spans with strand-jacks, and lateral slide-into-place.