worked closely with Kiewit and fabricators W&W/AFCO and G&G Steel to design the repair around readily available HPS70Wmaterial. During the completion of the work, an 18” section of the tie containing the fractured web and flange plates was removed for further forensic examination. Once the strengthening plates were installed and fully bolted, the post tensioning was removed, signifying successful repair of the damaged tie girder. Phase 3: Overall Tie Girder Repair While Phase 2 repairs were going on, extensive nondestructive test- ing (NDT) of all similar welds in the tie girders was completed and provided information leading to what became the Phase 3 repairs of the tie. NDT discovered indications ranging from very small to very large. The remedy for many of these smaller indications was to either core or grind them out, thereby removing the potential flaw. Larger indications were plated over to provide a redundant solution. The details used in Phase 2 were readily adaptable for Phase 3 and Kiewit worked with supplier AFCO/W&W Steel to obtain the necessary HPS70W plate. Tests were conducted on a portion of the damaged member that was removed as part of the Phase 2 repairs. The removed portion is cur- rently undergoing forensic examination at the labs of Wiss Janney Elstner Associates Inc. (WJE) in Northbrook, Illinois. The WJE team is conducting various tests on the material to document its properties, as well as microscopically examining the weld and the fractured surfaces to determine where and how the fracture began. By having the frac- tured component in their possession, the engineers at WJE were able to provide guidance for field-testing of other welds that were completed as part of the inspection in Phase 3. All Eyes on Memphis The emergency closure quickly gained attention across the country from the public, media outlets, and politicians alike. Tennessee Governor Bill Lee, Arkansas Governor Asa Hutchinson, and U.S. Secretary of Trans- portation Pete Buttigieg all visited the bridge in the days following the closure, with Secretary Buttigieg noting “We want to make sure that national attention and resources are available to help the state and local authorities who are resolving this and working toward a safe reopening of the bridge…Even for people outside this region, it is important that we restore this connection quickly because like so much about the Mem - phis region, it is an area of national logistical importance.” The impact of the shutdown of the Hernando de Soto Bridge on the economy was felt almost immediately. River traffic below the bridge had resumed by May 14, 2021, but all automobile traffic had to be diverted to the nearest crossing on Interstate 55 (I-55). The added traffic resulted in bottlenecks and delays, with the Arkansas Trucking Association estimat- ing that the additional travel time attributed to the closure was costing the trucking industry more than $2.4 million each day that the bridge was not in operation. This further reinforced that the timely, proper, and safe completion of the repairs was critically important. As the team moved through the initial find and into inspection, design and repair, it was of the utmost importance to maintain transparency and communication with the public impacted by the closure. A public awareness campaign was carried out in conjunction with the bridge’s repair activities. Project information and updates were shared via
UAS Inspection 3. Photo: Michael Baker International
media efforts (press releases and press conferences), as well as daily across the TDOT and ARDOT websites and social media channels. To support this, Michael Baker developed a 3D visualization of the repairs as they were being developed. Reopening the Hernando de Soto Bridge For several weeks, activities progressed 24-hours a day, supported by extended shifts. Initially, the eastbound and westbound lanes of I-40 crossing the bridge were initially scheduled to open on August 2 and August 6, 2021 respectively, but the eastbound lanes were opened ahead of this date on July 31, 2021, while the westbound lanes opened on August 2, 2021 – traffic was again flowing 83 days after the fracture was discovered. The project highlighted the importance of transparency, accountability and collaboration and exemplifies how two DOTs can work together to accomplish a common goal. All agencies and firms involved in the project brought a deep understanding of structural engineering to the work, and the commitment and partnership amongst them facilitated the analysis, design and construction needed to safely, effectively, and efficiently repair the fracture.
AARON STOVER, P.E., S.E. is Vice President and Great Lakes Regional Practice Lead – Bridge at Michael Baker International. TED KNIAZEWYCZ, P.E., S.E., is Structures Division Director at Tennessee Depart- ment of Transportation (TDOT). RICK ELLIS, P.E. is Division Head-Bridge Division at Arkansas Department of Transportation (ARDOT).
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csengineermag.com
october 2021
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