BNSF RAILWAY BRIDGE 482.1 WEST MEMPHIS APPROACH
Kraemer reconstructed the west approach spans that cross the Mississippi River between West Memphis, Arkansas, and Memphis, Tennessee. Opened in 1892, the existing west approach structure is 2676-feet long and consists of 52 spans. The new west approach structure is 2712-feet long with 27 spans. Construction began with building the substructure including caissons, columns, and caps under the existing bridge while the track above remained in service. The new bridge is founded on 8-foot and 10-foot diameter caissons with 120-foot micropiles incorporated into the caissons. Round 8-ft. and 10-ft.-dia. concrete columns support rectangular concrete pier caps. Next, the superstructure including bearings, steel girder spans, and track panels were installed during four switchouts. Kraemer removed and replaced eight spans at a time on the first three switchouts and four spans on the fourth.
The demolition method developed for the final phase of this single-track railroad bridge replacement for BNSF demonstrates Kraemer’s high level of innovation, expertise, and attention to detail. Although many challenges were overcome while replacing the existing 52-span bridge, removal of the 340-foot-long deck truss span for the new 27-span bridge on the same alignment was the biggest challenge and success. Deck truss removal was challenging because construction was ongoing underneath while removal occurred and blasting was not allowed. A new pier constructed inside of the truss at mid-span and two 200-foot long spans would be staged on either side of the deck truss for a roll-in following the deck truss removal. The truss demolition occurred in a 24-hour period as part of a 55-hour track outage. To hoist the truss, the team evaluated a gantry system using large cranes. Other options revolved around temporary falsework support to allow the truss to be dismantled into more manageable pieces. Due to the time constraint and a need for a compact system to allow work to continue along the truss, a strand jack system founded onshore towers was used.