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Case study: bridge installation

April 1st, 2012 / By: / Anchoring, Feature, Project Briefs

Installing tents for the dedication of the University of Virginia’s South Lawn pedestrian bridge was no walk in the park.

When the University of Virginia (UVA) asked Skyline Tent Co. of Charlottesville, Va., to install a tent on a new 100-foot-wide pedestrian bridge to accommodate 340 people for a sit-down dinner, Skyline proposed using a crane to lift concrete anchors onto the bridge. “But the project engineers would not allow that much weight on the bridge,” says John Hingeley, Skyline’s president and owner. “And we found out after the third planning meeting that the sidewalks on the left and right side of the structure had delicate piping running underneath them to melt snow and ice. We were not allowed to use any type of forklift or pallet jack due to concerns that a forklift would crack the thin sidewalk slab installed over the pipes.

“Because engineering and UVA facilities took so long to review the original plans before rejecting them, we had to come up with a new anchoring system with only a few weeks remaining before the event.”

A place to anchor

The event on Oct. 22, 2010, included a dedication ceremony with Gov. Bob McDonnell, dinner and dancing to celebrate completion of a 10-year expansion of the school’s South Lawn, which included the terrace crossing, the pedestrian bridge over Jefferson Park Avenue. One can imagine the enthusiasm university officials would have for Skyline’s anchoring alternative: drilling holes in the concrete bridge that was part of a $105 million expansion project that included the South Lawn and 109,000 square feet of new buildings.

“At first, UVA wouldn’t allow any concrete anchors to be drilled anywhere on the Terrace Crossing,” Hingeley recalls. “We finally came up with a plan that the UVA would accept: to dig into the planting beds running along each side of the bridge and install 14 anchors in the rebar-reinforced concrete wall that formed the edge of the planting beds. An engineer was required to spec the correct anchor sizes and produce drawings of the system. We ended up having to fabricate 1-inch-thick, stainless steel angle iron for each anchoring point and excavate below grade in the planting beds.” Each angle iron was fastened to the concrete using stainless hardware set in epoxy. A stainless steel eyebolt was bolted to the angle iron to attach to the tent straps.

Because the tent guys would extend across the sidewalks to the anchors in the bridge piers, Skyline had to create scaled drawings to show the university’s building and fire inspectors that the straps would not interfere with emergency egress from the tent. (A 6-foot person would have a 6-foot-wide pathway.)

The system also included water-cube weights on each of the 20 tent legs, secured with 2-inch webbing straps.

Roof swap

In addition to the 50-by-120-foot, gable-end Navi-Trac® tent for the dinner, the job included a 50-by-50-foot Navi-Trac tent with a dance floor and stage for the band, a 16-by-32-foot frame tent for the kitchen, and a 12-by-42-foot food preparation tent. The challenge with the dance tent—set on a circular plaza at one end of the bridge—was that the top had to be changed mid-event. The university wanted a white top “so there was no glare on the governor” during the dedication, Hingeley explains, and then a clear top for dancing under the stars. The changeover, which took an hour, had to be accomplished as quickly and quietly as possible (while guests were inside a building enjoying cocktails) to avoid impacting the celebratory ambiance.

Smooth transitions

Skyline’s crew of 16 worked an 18-hour shift on the entire installation. They had one day to install the tents and plywood flooring because the following day was reserved for other vendors to set up decorations and catering equipment. Skyline also had one day for disassembly. “And we had to keep a pathway clear for students,” Hingeley notes, since the grass-covered bridge connected academic buildings.

“We covered the anchors back up with dirt and left all of the anchoring hardware in place,” Hingeley says. “If they ever want to tent that location again, we’ll be ready.”

Janice Kleinschmidt is a freelance writer based in Palm Springs, Calif.

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