“It’s one of those once in a lifetime jobs,” said Shaw Construction’s project superintendent Tim White.
Indeed, White’s current project is unique. While other major contractors are busy erecting steel beam buildings, pouring yards of concrete or laying miles of asphalt, White’s company is building a tent.
A tent? Well not just a tent per say, but a one-of-a-kind 2,100-seat music tent. The structure is being built for the Aspen Music Festival and School and will serve as a venue for musical and theatrical performances and other various functions.
Work on the $12-million Benedict Music Tent began in August 1999. The structure was designed by Harry Teague Architects of Aspen who stated, “The tent building is a statement of elegant modern design and awareness to the architectural style of the neighboring buildings and the alpine surroundings.”
The facility was modeled after the Jeppesen Terminal at the Denver International Airport which was designed by Fentress Bradburn Architects of Denver. The terminal features a 180,000-square-meter (2 million sq. ft.) structurally tensile-membrane roof, the largest such roof in the world. The roof membranes are comprised of Sheerfil fabric and each membrane weighs less than two pounds per square foot, or approximately 400 tons.
The multi-peaked white roof, which was inspired by the snow-capped Rocky Mountains, reaches heights of 45.5 meters (150 ft.) from the terminal floor to its highest peaks. The catenary cable system support system is similar to that of the Brooklyn Bridge and utilizes 34 masts and 10 miles of steel cable.
According to Fentress Bradburn, this unique roof system relies on the design curvature and equalization of the fabric’s internal stress fields provide the roof with the stability and strength to support wind and heavy snow loads.
Installed by Birdair Inc. of Amherst, NY, the roof fabric is comprised of two layers, with a Teflon-coated waterproof outer shell and an uncoated inner shell. Both layers are made of woven fiberglass and are about as thick as a credit card. Together the inner and outer roof membranes of the Jeppesen terminal comprise 15 acres of material.
The roof of Aspen’s Benedict Music Tent is comprised of the same Sheerfil membrane fabric and was also installed by Birdair. This unique Teflon-coated outer layer is said to provide easy wash-down maintenance, while the white fabric allows only 10 percent of the outside light to pass through for day-lighting. In addition, the fiberglass has little mass so it doesn’t conduct heat or store it.
The tent’s structural framework, according to White, consists of a three-dimensional, 31.8-meter (105 ft.) diameter, 3-meter (10 ft.) thick structural steel disk. The disk sits on top of four 15-meter (50 ft.) steel pipe columns. Eighty radial and eleven catenary cables support the disk.
The cables are held in place by five wickets and are ultimately secured to eight anchors. The foundation for the anchors required pouring more than 1,064 cubic meters (1400 cu. yds.) of concrete.
“Because this structure is cable supported, layout has been critical,” White explained. “We tried to keep all of the anchor placements to within a one-sixteenth of an inch.”
To do this, White said, crews used a Total Station, an electronic device that uses satellites to help pinpoint the overall layout and plotting points.
The wickets, which resemble giant versions of the wickets used for playing croquet, are made of 25.4-centimeter (10 in.) diameter 2.54-centimeter (1 in.) thick steel pipe and measure 3-meters (10 ft.) high and 9 meters (30 ft.) wide. Three of the wickets provide structural entrances to the tent, while the other two act as station piers.
White explained that an adjustable vertical louver system encloses the perimeter of the tent between each wicket, allowing music to drift outside. Each entrance can also be closed in cold or rainy weather. The 2,100 theatre seats within the tent are set below grade.
Also included in the project is a new Back of House building that will house the dressing rooms, restrooms, instrument tuning rooms, a recording studio, choral balcony, instrument storage, offices and the mechanical and electrical rooms.
In addition a sub-grade concrete and steel tunnel connects the Benedict Music Tent to a newly installed elevator landing in the adjacent Harris Concert Hall. With this performers can conveniently access both buildings.
“Before this project, we hadn’t heard of canting cables or wickets before,” said White. “Building this world-class acoustic facility has been a once-in-a-lifetime opportunity because of its uniqueness and complexity. But this has been a 100-percent safe job with no lost days due to injuries and is on schedule to be complete in time for the Summer 2000 Music Festival.”
The tent is set for completion by the first concert date in June 2000.
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