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Analyzing project size for fabric structure budgets

Exteriors, Features | January 1, 2010 | By:

Small projects

Not everyone gets a bird’s-eye view of his or her handiwork. But that is exactly what Sollertia Inc., Montreal, Canada, founder and president Claude Le Bel did when he leapt from an airplane above Parachutisme Nouvel-Air. Soaring above the fields and meadows, La Bel liked what he saw—a graceful, highly visible, tensile fabric canopy that easily identified the school’s rural location for parachutists. “I can testify firsthand that you can see the structure very well from the sky,” says Le Bel. “It does what it is supposed to do—tell the parachutist where is his home.” For Nouvel-Air, Canada’s leading skydiving school located in Farnham some 40 minutes drive from Montreal, Sollertia’s team of architects, designers and engineers was a perfect match.

Nouvel-Air’s owner, Michel Lamay, long on enthusiasm and short on cash, wanted the tensile structure to span a new bilevel, wood terrace with four goals in mind: create maximum shading for jumpers and visitors; provide maximum views to the sky; create a visual discourse between the canopy and the school’s architecture; and be “cheap.” The first three functional and aesthetic requirements were achieved easily enough through the design of three sail-like forms made from a micro-perforated PVC fabric (Naizil SunControl 410 white). Supported by galvanized metal masts installed in concrete footings at the terrace’s edge, these membranes all connect to the tallest mast that punctures the terrace at an angle, creating a visual path to the building’s entrance. The three sails work collectively to provide needed shade, a luminous degree of transparency and open vistas to the sky. Like a distant cousin, the project’s lyrical design makes a visual connection to the airborne parachutes.

Budget was another matter. “We needed to make the project as cost effective as possible and still have a great look,” states Le Bel. The answer? Use galvanized “off the shelf” metal poles instead of stainless steel for the masts. Nouvel-Air provided another notable cost-saver. From Sollertia’s drawings, Lamay and staff cut and fabricated the three sails themselves. “At first we were skeptical,” says Le Bel. “But the owner, being in the business of fabricating and repairing parachutes, knew what he was doing and it worked beautifully.” With this in-house labor perk, the project, which was begun in 2006 and installed in 2007, was completed for an enviable $50 per square foot.

Although galvanized poles were substituted for stainless due to cost, the PVC fabric was chosen because of its meshlike quality and that it would be sustainable for a much longer time than a less expensive fabric. Le Bel estimates the average percentages of total budget for the small custom Nouvel-Air project, as the following. Design and engineering 20%, fabric 23%, structure and hardware 30%, foundations 15% and installation 12%. Thus, the cost for the project design, foundations and the fabric was approximately 60% of the total Parachutisme Nouvel-Air project budget.

By the way, Sollertia is a Latin word meaning “ingenuity.”

Medium projects

SkySong, the signature design element in the Arizona State University (ASU) Scottsdale Center for New Technology and Innovation, embodies its name. In this new, partially completed mixed-use 17-hectare development, SkySong is an enormous custom tensile fabric structure whose swooping form suggests some futuristic amusement park ride. When the project is completed, SkySong will straddle the intersection of two connecting roads and connect four separate buildings, designed by Pei Cobb Freed. Two of the buildings are now occupied. In conjunction with Higgins Development Partners of Chicago, FTL Design Engineering Studio, New York City, designed the dramatic white structure and FabriTec Structures, Costa Mesa, Ca., supplied the fabric and constructed it. Tenants will have access to ASU resources.

According to Nic Goldsmith, FAIA, senior principal of FTL, the goal was to create a new urban icon for the ASU Scottsdale campus that would also be a shaded gathering space for students, faculty and workers. Visually and structurally complex, Skysong’s 4500m2 of Teflon®-coated (PTFE) fiberglass fabric (Sheerfil® I by Saint-Gobain) covers eight integrated conical-shaped structures, each of which is supported by a steel “leg”® measuring 34m in length and weighing 10,800kg. When completed, the undulating structure will be illuminated by white lights (Bega metal halide fixtures) and colored LED (Martin) fixtures that will allow it to change color for a specific need or event.

“In spite of its size, the interior space is surprisingly intimate,” comments Goldsmith. He likens SkySong’s rhythmic form to the configuration of the dancers in Matisse’s famous painting “The Dance” (1910), who move in rotational symmetry. “When you stand under it you have the sense that the forms are moving around you in rotational symmetry—it is not static at all,” explains Goldsmith.

A few budgetary concessions were made from the original concept. The steel column bases were initially to be conical in shape but are now cylinders. Also to reduce cost, the details and fittings below 6m are stainless steel and above are galvanized. “Above 6m these details are less noticeable,” says Goldsmith.

In Scottsdale’s intense solar climate, choosing the optimum fabric was critical. Although more expensive, the PTFE fabric has a shelf life of about 30 years. The benefit of replacing the fabric less frequently outweighed concerns of cost. Also, the LEED silver project is a passive solar structure that reflects light and heat. Of the approximate $230 million total project budget the infrastructure and tensile structure cost approximately $4-5 million. “It’s gotten tremendous response,” adds Goldsmith. “The mayor even likes it.”

Large projects

For the new 45,000-seat Nelson Mandela Bay Stadium in Port Elizabeth, South Africa, the critical environmental issue was not the sun, but wind. Known as the Windy City, Port Elizabeth is perched on the ocean’s edge and the new open-air stadium, built to host the 2010 World Cup matches, needed to shield soccer and rugby fans from the unrelenting winds. Completed in April 2009, its materials also had to withstand the Windy City’s corrosive port environment. Equally important was that the Nelson Mandela stadium have a post-World Cup life, one that would benefit Port Elizabeth. No white elephants here. The sustainable structure also had to have an aesthetic presence that would contribute to the city’s architectural environment.

The solution is a strikingly beautiful design whose unique, almost corrugated form effortlessly wraps over the pedestrian concourse circling the stadium and the seating within. Elegant but straightforward, the design was based on the principles of a suspension bridge and an arch bridge and was a joint effort between GMP Architekt, Berlin, engineers Schlaich Bergermann und Partner, Stuggart, and subcontractor BirdAir Inc., Amherst, NY. The sophisticated structural design eliminated the need for secondary girders that often block sightlines. The tensile roof system features two alternating cladding materials: perforated aluminum and a white PTFE-coated Fiberglas® membrane. Uniquely, the aluminum covers the primary truss system on the interior. “The design does not showcase the structural elements as in many stadia,” states Knut Göppert, the lead engineer. “The design showcases the open space, the area in between the structural elements.”

According to Göppert, the PTFE membrane was the logical fabric of choice. “It has a long life span and needed to be essentially maintenance free. And it needed to have solar capabilities,” says Göppert. “The benefits of the membrane outweighed any cost considerations.”

From the exterior, the alternating aluminum and membrane creates a rhythm of light reflection and absorption and also one of surface texture. The opaque perforated aluminum reflects the sunlight and the translucent PTFE membrane allows daylight to illuminate the interior concourse. “It is an interesting and unique visual play of materials,” adds Göppert. About 22,000m2 of membrane was used in the cladding system and constituted approximately 10% of the overall roof material. The membrane constituted approximately 20% of the roof budget and roughly 4% of the total project budget of roughly 22 million euros.

Göppert describes the design as elegant and economical. “We optimized the design. It looks quite complicated but the design is really very simple without looking simple,” he says. “And the sports fans will be protected from the wind.”

Mason Riddle is a contributing editor for Fabric Architecture.

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