Grand Canyon Skywalk To Become Highest Structure
📅 Thu December 28, 2006 - Midwest Edition
Brenda Ruggiero - CEG CORRESPONDENT
The highest man-made structure in the world is rapidly taking shape high above the Colorado River at the edge of the Grand Canyon.
Initial construction of the Grand Canyon Skywalk began in mid-2006, and completion is nearing. March 28, 2007, was recently set for the official public opening date. The dollar amount for the project exceeds $30 million, which is privately funded.
The Skywalk is part of Grand Canyon West, which is owned by the Hualapai Tribe. Consisting of approximately 2,000 members, the tribe currently owns nearly 1 million acres of land throughout the Grand Canyon’s western rim.
The horseshoe-shaped Skywalk will be suspended 4,000 ft. (1319.2 m) above the Colorado River and extended 70 ft. (21.3 m) from the cliff edge of the Grand Canyon at the western rim. The height spans twice the altitude of the world’s tallest skyscraper, and it has been calculated that a freefall from the edge to the canyon floor would take 15 seconds.
The floor and sidewalls of the Skywalk are made of glass, and the structure also contains 1 million lbs. (453,592 kg) of steel. It was designed to withstand an 8 magnitude earthquake 50 mi. away.
Colin Daviau of Preferred Public Relations reported that in order to secure the structure, engineers cantilevered it to the cliff using 94 steel rods that bore 46 ft. (14 m) into the limestone. It is estimated to withstand 70 tons (63.5 t) of weight, but operators have limited the maximum occupancy to 120 people.
“If the four footings for the Skywalk bridge could all be loaded uniformly in tension at ultimate load for the threadbar rock anchors, the footings would hold 75 Boeing 747’s, assuming the weight of a 747 is 910,000 pounds,” Bill Karren of Lochsa Engineering explained.
The structure’s steel anchors were flux-core welded, and the steel sections were each 2 in. (5 cm) thick, 8 ft. (243.8 cm) long, 2.5 ft. (76.2 cm) wide, and 4.5 ft. (137.1 cm) deep. Joined to form 46-ft. (14 m) anchors, they are now weighted in cement to secure the structure.
The main horseshoe was formed by welding two box girders of A572 grade 50 carbon steel. The girder sections are 2 in. (5 cm) thick, 6 ft. (1.83 m) long, and 2.5 ft. (76.2 cm) wide. They were shipped in 40-ft. (12.2 m) sections and assembled onsite. A 100-ton (90.7 t) crane was used to unload the pieces.
According to Daviau, the “historical rollout” of the Skywalk structure, with the glass in place, is scheduled for Feb. 27 to March 2.
“The initial part of the rollout process involves jacking the structure up off of the supports and then subjecting the structure to several days of thorough tests that replicate the conditions of final placement,” he said. “After the final testing is complete, the multi-million pound steel enforced structure will be rolled out across the canyon’s edge, which takes multiple days. Immediately after the structure is in position, it will be seated and attached to the foundation.”
Mark Johnson, architect for the project, noted that the process will not involve a crane, since it would be impossible to use in that particular area. Instead, the move-out will involve two-ton trucks with winches to move the structure forward and backward very slowly — at a rate of one in. (2.54 cm) per minute. The process will also involve I-beam rails, 1-in. solid steel rods, and counterweights.
“It’s really pretty simple,” he said. “It’s kind of like when they built the pyramids, except they used logs instead of steel bars.”
Daviau noted that the Grand Canyon is obviously an inhospitable place for a bridge-like structure. On a typical day, vertical winds can reach 90 mph. If these conditions occur once the Skywalk is open to the public, it will be shut down for the comfort of the visitors, even though the walkway can easily handle such conditions.
“The Skywalk, although an amazing feat, uses tried and true construction methods,” he explained. “The weather is usually moderate…similar to Las Vegas most of the year. There have not been any high winds while they are working on getting the walkway into position. Since it has not yet been moved from its initial position, winds have not yet become a factor. The statistics on wind conditions are theoretical — the walkway can withstand winds 100 miles per hour from eight different directions. Wind is an engineering factor that has been accounted for, not a construction challenge. If there are excessive winds at the canyon during rollout, they will not be working.”
The Skywalk facility will also include a 6,000 sq.-ft. (557.4 sq m) visitor’s center on three levels, a museum, a movie theater, a VIP lounge, a gift shop, and several restaurants, including The Skywalk Café, a high-end establishment offering outdoor seating on the edge of the canyon. The visitor’s center will also offer private indoor and outdoor facilities for meetings, special events, and weddings.
The concept for the structure came from Las Vegas-based entrepreneur David Jin.
“Just like an eagle can fly into the Grand Canyon, my vision was to enable visitors to walk the path of the eagle, and become surrounded by the Grand Canyon while standing at the edge of the Glass Bridge,” he said. “The bridge gives us a chance to share the wonder of the canyon that the Hualapai Tribe has graciously offered. My dream was to find a balance between form, function, and nature. Once a dream…now a reality.”
The Skywalk was designed by Las Vegas-based MRJ Architects, and is being structurally engineered by Lochsa Engineering, LLC. The glass was manufactured in Germany and Austria by Saint Gobian , a European company which specializes in designing structural glass for unique building projects. The steel was manufactured by Mark Steel in Utah.
Once the structure is completed, access will be offered to the Skywalk from dawn to dusk at a cost $25 per person (in addition to the cost of a Grand Canyon West entrance package). It is hoped that the attraction will increase the number of visitors to Grand Canyon West by more than 250 percent, to 500,000 per year. CEG