April 23, 2019 – NASHVILLE, TN – As the Music City prepares to host the NFL Draft for the first time, one of its most iconic structures is poised to take center stage.
The 1,758-foot John Siegenthaler Pedestrian Bridge is a popular tourist attraction and downtown pedestrian gateway. For this national event, the historic bridge’s 318-foot steel truss main span will bear the load of a 4,000-pound three-dimensional sign, perfectly positioned to be in view from the Draft’s mainstage on Broadway.
Local structural engineers from Alfred Benesch & Company were on hand during the planning phase of the event to ensure the sign could be safely lifted into—and stay in—place. Several factors such as an unusual load requirement and atypical vehicular use required innovative modeling techniques to ensure the structural integrity of the 111-year-old bridge. In addition to the signature sign, an LED Team Pillar for each of the 32 NFL teams will be on display on the bridge. Each pillar weighs over 4,000 pounds, resulting in a total addition of about 140,000 pounds spread over the three steel truss spans.
Benesch’s familiarity with the John Siegenthaler Pedestrian Bridge goes back to 2017, when we completed our finite element modeling analysis of the structure’s main steel trusses. Equipped with this prior knowledge and through an on-call contract with lead firm Civic Engineering & IT, Inc., Benesch was able to model the unique loads upon the structure resulting from the sign lift and installation, including the addition of a potential 11,400-pound horizontal wind load reaction at the center support. In total, the analysis accounted for all phases of construction (lifting, mounting and dismounting) of the sign and its final mounting position—creating a variety of vertical member load scenarios to consider.
Following the successful completion of the structural review, the sign was brought in by barge on the Cumberland River and lifted into place utilizing temporary beams and cable hoists mounted atop the bridge, and the team pillars were set up on the bridge deck.
The sign was successfully installed on the morning of April 23 and will remain in place until the Draft’s completion on April 27.