One WTC Will Feature Intelligent Elevators

An insight into the project’s elevator features, particularly the Destination Dispatch system.

Reprinted from ThyssenKrupp’s yearbookINGENIEURKUNST

Buildings like One World Trade Center (WTC) in New York City (NYC) would not be possible without modern elevator systems. A visit to the construction site in Lower Manhattan reveals just how much engineering has gone into the elevators for the tallest building in the U.S.

Mike Hoeler and his colleagues usually spend their lunch break on the 103rd floor. They roll up the construction plans, close their laptops and eat the sandwiches they’ve brought with them. On some days, the top of One WTC is surrounded by clouds, but on a clear day, the view from the 417-m-tall building is spectacular: the whole of Manhattan, the Brooklyn Bridge and as far as Queens. Taxis on the streets are just yellow dots, and the Statue of Liberty looks on from Liberty Island. But that’s not why the men stay where they are to eat: the trip from the roof to the ground floor takes almost as long as their lunch break.

At least, it does at the moment. But, the construction elevators will soon be replaced by the fastest and most advanced elevator system in the world. Hoeler and his team work for ThyssenKrupp Elevator, the company awarded an exclusive contract to install 73 elevators and 11 escalators in NYC‘s newest landmark. In the future, visitors will be able to reach the observation deck on the 100th floor in just 1 ­min. The five express elevators travel at over 10 mps – close to record-breaking speed.

When the window panes were still missing from the uppermost floors of the skyscraper, the sounds of the city could be heard only faintly through the blue safety netting that stretched across the windows. Through a large square hole in the roof that opened onto the sky, a crane inserted the SF-1000 motors for the high-speed elevators. There are a total of eight, each weighing around 53,000 lb. “We expect more than five million visitors a year to the observation deck alone,” said Joe Braman, regional vice president of ThyssenKrupp in NYC responsible for the project. “That’s 14,000 people a day. And there’ll be more than 10,000 people working on the office floors below every day.”

Braman continued:

“We had to come up with intelligent solutions to manage these passenger numbers, because a building like this just wouldn’t be possible if we couldn’t transport people and materials smoothly. The higher the building, the higher the demands on us engineers.”

While motors were being installed on the roof, a team of engineers on the 37th floor was setting up elevators for the lower stories. Ben Wells stood in the machine room with his laptop computer and checked whether the central computer was transmitting signals from ground level to the right motors. He typed in a numerical code, and the coils on one of the ten DAB-530 motors started moving. Wells entered more commands. “Now we’ll try out the emergency brake,” he said, and hit the “enter” key. The motor stopped abruptly. Shortly afterward, Wells‘ colleagues, Mike Siegler and Scott Lahmers, reported by radio from the shaft: “3.27 m braking distance.” Wells smiled. “That was good; test passed!” he said.

Elevators are Building‘s Vital Arteries

These elevators are the building’s vital arteries. That fact is also reflected in the architecture. A quick glance at the tower‘s floor plan shows a small square inside a big square. “The new building has a strong core,” said Braman, as he knocked on the almost-1-m-thick concrete wall surrounding the elevator shaft. The old Twin Towers had an exoskeleton. When terrorists crashed planes into the towers on September 11, 2001, the outer skin was destroyed, and the buildings became unstable. That cannot happen any more.

Safety is a key aspect, and the elevators also play an important role in this. “In the past, if there were a fire, the emergency elevator stopped just below the floor affected, and the firefighters had to take the stairs to get to the source of the blaze,” said Braman. In the future, the shaft of the emergency elevator will be pressurized to prevent smoke from entering. The cab has a second door. In emergencies, it can be opened onto a separate corridor, from which the firefighters can assess the situation. “We’re all proud to be involved in this project. And we’re doing our best to ensure that the tallest building in the Western world gets the best elevators,” Braman said.

New Elevators Are Fast, Efficient, Intelligent

Only 10 elevators will travel directly from the ground floor to the roof. Five service elevators can stop at every floor, while elevators to the observation deck speed to the top without stopping. People working higher than the 64th floor will first take an express shuttle to the sky lobby and, from there, take one of the elevators serving the highest office levels.

That saves space, and, above all, time, for New Yorkers are in a hurry. A survey showed that 28 s. is the longest they are prepared to wait for an elevator; after that, they start to get restless. An intelligent control system will help distribute passengers efficiently. All the elevators are connected via an intranet. People heading for the same destination are grouped together and share an elevator.

The compulsory building passes contain not only information about the holder, but also about where they work. When visitors go through the security gate, these data are passed on to the elevator. Almost immediately, the digital display lights up with the number of the waiting elevator. Visitors authorized to access several floors can change their destination on a touch screen outside the elevator.

“The fact that our elevators are fast, quiet and smooth and have virtually no buttons is something passengers will experience for themselves every day,” Braman said. “But the technology behind them, the numerous solutions big and small that we came up with, will remain hidden.” Take the rail clips, for example – at first glance they look like perfectly normal bolts joining the elevator rails to the building. “But a great deal of engineering has gone into them,” Braman pointed out. The rail clips hold the rails in position, but at the same time, allow the material a certain amount of play. “That’s enormously important to avoid fractures, because when the concrete dries, it contracts. Also, in high winds, the building will sway back and forth. So, our designs need to be flexible.”

Building‘s Movements Helped Guide Elevator Engineering

One WTC, shaped like an obelisk with chamfered corners, is a megatall tower. Its movements played an important part in the engineering of the elevators. “That won’t happen any more. Our mathematicians simulated the movements of the building, then we developed a system of rollers that weighs the cables down and minimizes the effect. From a certain speed, air drag in the elevator shaft also becomes an issue. It’s something we know from the subway – when the train pulls into the station, it pushes a wall of air in front of it. We have attached wedge shapes to the top and bottom of the cabs to make them more aerodynamic when they speed up and down the shafts,” explained Braman. Acoustics specialists also helped in the cab design to reduce noise during travel. These technologies were then tested in ­ThyssenKrupp Elevator’s test towers.

Elevators, Escalators Represent Global Effort

The elevators and escalators are the result of global collaboration. ThyssenKrupp Brazil manufactured the special rollers that guide the cabs along the rails, while the German operations were responsible for the motors and drive systems. Colleagues in the U.S. provided the Destination Dispatch system. A 25-story test tower was used in South Korea. “Everyone contributes their expertise, and everything dovetails together,” said Braman. He takes off his hard hat and shows the “Stars and Stripes” stickers on it. “We’re all proud to be involved in this project. And we’re doing our best to ensure that the tallest building in the Western world gets the best elevators.”