Acrobat Nik Wallenda performed two tightrope walks in Chicago, for which Thornton Tomasetti was the structural consultant. Photo by Adam Panek.
On Nov. 2, thousands watched renowned acrobat Nik Wallenda – without a net or harness – walk a tightrope across the Chicago River and between the Marina City towers. But our eyes were on the structures supporting Wallenda’s tightropes.
A team of our engineers and forensic architects worked with the owners of four buildings to verify that the structures would not be damaged by the unusual loads imposed by this once-in-a-lifetime event.
Team members, from left: Ken Maschke, Lance Parker, Matt Thomas, Nick Aitken and Bill Bast. Apparel provided by Marmot (jackets and gloves) and Icebreaker (hats and base layer). Photo by Adam Panek.
We reviewed the loads imposed by the tightropes as well as the camera and lighting equipment installations. We even laid out load placement diagrams for helicoptered equipment lifts. And when 70-mph winds shook the Loop just two days before the event, our engineers canvased each impacted rooftop to review the stability of the installations.
The longer tightrope (left) was attached to a steel plate using existing anchor bolts at the Marina City west tower. Adjacent to it is the platform from which Nik Wallenda began his walk. The shorter tightrope (right) was anchored to each of the Marina City tower’s concrete cores by long cable slings. Photos by Bill Bast.
Wallenda began his walk over the river at Marina City, where his tightrope was attached to existing anchor bolts that once held the bracing of an antenna for TV Station KBKB. Across the river at the Leo Burnett building, the other end of the tightrope was attached to a steel cooling tower beam and supported by two custom-designed A-frames. Wallenda’s blindfolded walk between the two Marina City towers required the tightrope to be secured via guy wires anchored to the building’s trademark semi-circular concrete balconies. Our engineers reviewed drawings from the early 1960s construction, oversaw field testing of existing conditions using ground-penetrating radar, and performed analyses on the loads imposed. We even measured the building sway and estimated the resulting additional load imposed in the tightropes.
Our team is proud to have had the opportunity of supporting our clients in hosting Team Wallenda and to be a part of the success of this spectacular feat.
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