- Arthur Ashe Stadium is 25 years old, but the addition of a retractable roof in 2016 required special engineering to keep the venue unloaded.
- Engineers learned from Ash and added a second retractable roof to the brand new Louis Armstrong Stadium in 2018.
- One control room, located at Ashe’s broadcast level, will operate both roofs at the US Open, which begins Monday, August 29.
During the annual two-week U.S. Open tennis event, engineer Mark Sharamitaro often watches the world’s best tennis matches in the master control room at Arthur Ashe Stadium. There he can relax…until he can’t.
The Billie Jean King National Tennis Center in Flushing, New York hosts the US Open each year. Thanks to upgrades in 2016 and his 2018, the site now boasts retractable roofs over both Arthur Ashe Stadium and Louis He Armstrong Stadium, which were completed in 2018. Sharamitaro was instrumental in the design of both systems and has been the primary operator of these roofs ever since their construction. online.
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If all goes well, he can push a button in the master control room and watch each of the steel railed roofs with polytetrafluoroethylene (PTFE) fabric move at 25 feet per minute. increase. But when things go wrong, he’s responsible.
“I worry about unexpected storms with the wind,” he says. popular mechanic. “It’s not because of the wind or the structure, it’s because the wind pushes water where it doesn’t need it,” said Sharamitaro, president of Sharamitaro Industrial Solutions, based in Clayton, North Carolina.
Ash, which celebrated its 25th anniversary with the August 29th-September 11th event, required careful engineering when added in 2016 just to attach a retractable roof on top. The ash roof not only needed to avoid stressing the existing structure, it also had to be completely waterproof.
Sande Friesen, partner at Rosetti Architects, based in Detroit, Michigan, said: popular mechanics“That is absolutely unacceptable in our hospital. [United States Tennis Association]The seam is in the middle of the coat, [water] A complete deal breaker. Leakage tolerance is zero. ” Rosetti is the company responsible for the design of the stadium. New York City-based Hardesty & Hanover designed Ashe’s mechanized system.
How to build movable roofs over 6,000 tons
Ash and Armstrong roofs have many similarities. According to Friesen, this is partly for ease of maintenance. The most obvious difference, however, is that Ash’s roof is sloping, about 60 feet higher in the center than at the ends, while Armstrong’s is flat.
The Ashe, the world’s largest tennis stadium, has 23,500 seats and should manage a more generous opening. A 250 ft x 250 ft roof opening requires four major roof trusses spanning the octagonal stadium. The roof is made of a total of 6,500 tons of steel and is covered with a lightweight and durable Teflon-coated fiberglass membrane fabric (PTFE). To minimize seams, the roof he consists of two panels. Each moveable panel weighs about 1 million pounds.
The Armstrong also has a two-piece roof, but with a seating capacity of only 14,000, the openings are small and the 0.03-inch-thick PTFE and steel system weighs 284,000 pounds per panel.
Then comes the winch. According to Sharamitaro, the winch functions are essentially the same on his two roofs, but Ash has four winches and Armstrong has only one. Ash has a north and south winch on each panel, driven by 10 electromechanical motors. All in all, there are five 40 hp motors per winch, and he has two winches on each side. Total horsepower: 800.
“It’s like pulling a wagon up a hill with two ropes, one on each side, trying to keep it centered and not skewed,” Shalamitaro says. “You don’t want one crawling up a hill faster than the other.” Because each winch has independent controls, the system adjusts and centers the panels exactly at the same time to create a smooth visual effect.
In Armstrong, on the other hand, a single winch 40 hp motor (160 hp total) drives four ropes, each attached to one end of each panel. Steel ropes cannot stretch and keep each roof in exactly the same configuration when opening and closing.
“At Armstrong, we monitor skew, but we can’t control it. Armstrong has a built-in cable adjustment system, he added.
smooth movement
Both roofs slide on railway-style rails, so rail clamps must be used to hold the roof in place. Rail systems are not unique to tennis centers, but the use of winches is not common. Many football venues incorporate motors that drive wheels that generate torque. By powering the winch with a motor, he has one large gear on the drum and a small pinion gear around the winch. All torque is transferred to the drum and 2 inch diameter rope.
“We don’t have to worry about the wheels slipping,” Shalamitaro says. With the tennis center having to close the roof suddenly and possibly inclement weather approaching, removing the threat of wheel slippage was paramount. In large stadiums, decisions about roof closures are often made several days before the event.
“USTA’s philosophy is that it is an outdoor event as long as it can be done,” says Sharamitaro. “We are put in the control room waiting for the storm to come. Close it just in time and open it again when the rain stops. ”
Of course, everyone thinks that about 6 minutes is enough to close the roof on the Ash and about 7 minutes and 30 seconds to close the Armstrong. (Ash moves at a maximum speed of 25 feet per minute, while Armstrong moves at 17 feet per minute.)
Since roof sensors monitor everything from tilt to winch power, the only time the rail clamps are not set is when the roof is moving, so care must be taken not to manipulate the roof in high winds. I have. If the gust exceeds 50 mph, stop and set the rail clamps. If you go over 45 mph for 3 consecutive seconds, it will stop. “The roof is like the wing of an airplane, so in theory it can change position with the wind,” he says. “We never had to stop for wind during an event, but we did have to stop for commissioning and maintenance.”
A more modern marvel
The controls are different for Ash and Armstrong as the roof slides on an arc with a radius of 780 feet. At Ash, the winch pulls the panel up the slope, but gravity can be used to pull the panel back up in a controlled descent, says Friesen. At Armstrong, the winch does all the work of opening and closing. must be done.
The Ash requires more horsepower to tilt the heavy panels than the lighter panels of the Armstrong’s flat roof, but the Armstrong requires a more complex system. “There’s a lot of cabling,” Friesen says. One winch he feeds 4 threads. “Armstrong’s rope his diagram is much more complicated because he’s pulling in two directions at once,” he says.
Sign a contract
After closing, the seal is of utmost importance. “Indeed, it’s definitely art and science combined,” says Friesen. “It’s a very complicated piece.”
While very simple in concept, Friesen says the reality of making a waterproof roof work is more complicated, especially since in the world of retractable roofs you don’t usually need a 100% waterproof solution. So they got creative. In both stadiums, one panel overlaps the other. A set of bristle brushes several feet long cover the overlap to help keep the wind and rain out. This can only be done after the roof is stuck. A gutter behind the bladder catches escaping water and drains it off the court.
“It’s a belt and suspenders and a little bit of duct tape that makes it work,” Friesen says.
Ash allows shutters to be pulled down from the sides of the roof structure and placed over the existing stadium threshold. This is the only point of gentle contact between the two entities. This highly engineered umbrella can turn Ash into a climate-controlled indoor venue. Armstrong uses 13.5 miles of terracotta louvers to naturally ventilate the venue.
With the roof opening and closing during the U.S. Open, and at least every night of the event, Taro Sharami and his team have a lot to keep an eye on. But sometimes all you have to do is press a button and watch the winch work.
