NSR OVER I-240 IN MEMPHIS, TN - A CASE STUDY IN CM/GC, ACCELERATED BRIDGE CONSTRUCTION AND SEISMIC DESIGN

摘要

Benesch led the design for the Tennessee Department of Transportation's (TDOT) I-240 widening project in Memphis, Tenn., commonly referred to as the MemFix4 project. This $55 million project involved the replacement of the existing 316-foot-long, double-track Norfolk Southern Railway (NSR) bridge that carries 40.8 MGT over I-240. By teaming Benesch with Kiewit, TDOT employed the Construction Manager/General Contractor (CM/GC) alternative delivery method to replace the structures along the congested I-240 corridor. This collaborative process resulted in plans that were accepted by both TDOT and NSR and included constructability and cost input from Kiewit. To accommodate NSR operating requirements, the replacement bridge was built using a temporary shoo-fly alignment supported on temporary substructure units. The shoo-fly alignment was highly constrained due to utilities, right-of-way and track alignment requirements. Accelerated Bridge Construction (ABC) methods were employed to facilitate the use of the new 338-foot-long, five-span, double-track, ballasted-deck superstructure in both the temporary and permanent alignment locations. The superstructure was designed and detailed as two separate, single-track bridges and then slid into place atop new permanent substructure units, one single-track "half" at a time during two multi-hour single track outages and full closures of I-240. Once in their final location, the two superstructure "halves" were connected to create a fully waterproofed, common ballast trough. A significant seismic design effort was required to develop final designs for the bridge due to the site's proximity to the New Madrid Fault.