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Column: Vista Tower tour reveals the engineering secrets that hold up Chicago’s latest skyline standout

Available for your viewing, from a distance, this Thur. evening as the cameras scan north from Soldier Field for the kickoff game of the 100th season of the NFL.

Also loving views will surely be had of the newly unveiled statues of NFL founder G.S., and W. Payton.

The attention to detail that has gone into the design and construction of this particular building is mind boggling.

I started copying and pasting this before I finished reading the entire story. Damned post is nearly as long as the building is tall.

By Blair Kamin

Chicago Tribune |

Sep 03, 2019 | 5:00 AM



A view to the northwest from the open 83rd-story blow-through floor of Vista Tower on Aug. 27, 2019. (Brian Cassella / Chicago Tribune)

As real estate agents like to say, the view from the 83rd floor of Chicago’s under-construction Vista Tower is to die for. The vast blue-green expanse of Lake Michigan spreads to the east, north and south. Downtown skyscrapers look like toys.

But this raw concrete space, roughly 25 feet high, is never going to become some billionaire’s penthouse.

Instead, it’s going to remain empty even though a unit here would likely sell for well over $10 million. The floor will be covered by a screenlike perimeter wall that lets Chicago’s famous winds whip right through the space. This so-called blow-through floor, the first of its kind in Chicago, is expected to dramatically cut wind-induced sway.

Chandeliers in the condominiums above and below won’t rattle. Whitecaps won’t appear in the toilets. Residents won’t reach for motion sickness pills, as they’ve done in other supertall buildings plagued by high winds.

Neither will Dogs and cats, living together or not, howl and meow in terror.

Welcome to the Vista Tower, which will be Chicago’s third-tallest building when it opens next year. Designed by Chicago star architect Jeanne Gang, it’s also going to be the world’s tallest building designed by a woman.

On Tuesday, Tribune photographer Brian Cassella and I took a tour of the 101-story, 1,191-foot skyscraper to see firsthand the engineering features that undergird its striking curvilinear shape. Few of these elements are visible to passersby, but they’re essential to making the tower stand up — and make a profit for its developers.

We saw other unusual things besides the quirky blow-through floor. Vista’s perimeter columns step outward or inward instead of going straight up.

We also viewed the outside of one of six tanks tucked in the tower’s top. The tanks will hold more than 400,000 gallons of water.

When the wind pushes the tower one way, the water will slosh in the opposite direction, joining with the blow-through floor to counteract sway.


Monroe Harbor is seen from the 64th floor of Vista Tower on Aug. 27, 2019. (Brian Cassella / Chicago Tribune)

These things are not frills. A skyscraper’s structure, including foundations and the aboveground assembly of columns and beams, can account for up to 30% of its construction cost, according to Dave Eckmann, who runs the Chicago office of Magnusson Klemencic Associates, a Seattle-based structural engineering firm with a branch office in Chicago.

Eckmann, who attended the University of Illinois at Urbana-Champaign’s architecture school at the same time as Gang, was our tour guide. From the outset, he and other members of the firm teamed with the architect on the Vista Tower design.

“I like to work with engineers early on in any project,” said Gang, whose father was a civil engineer in Boone County, which encompasses her hometown of Belvidere. “It gives you more insight: What are the main forces (of wind and gravity) that you’re going to have to resist, that you’re having to put money into? Knowing that up front is important."

Backed by a joint venture of Chicago Magellan Development Group and China’s Wanda Group, the Vista Tower occupies a complex multilevel site at 363 E. Upper Wacker Drive. The first 11 floors above East Wacker will contain a hotel.

There will be 396 condos on floors 13 to 93. Additional levels, including mechanical floors at the tower’s top and parking underneath, bring the overall height to 101 stories.



Vista Tower, which is still under construction, as viewed from Navy Pier on Aug. 27, 2019. (Brian Cassella / Chicago Tribune)

Combine that jumbo size with a prime riverfront site and eye-catching geometry — stacks of tapering, truncated pyramids that alternate between right-side-up and upside-down — and you have a tower that has redrawn Chicago’s skyline.

Vista’s snaking curves stand out in a city where the right angle has long been king. So does its sleekness, which contrasts with the muscular X-bracing of the former John Hancock Center and other high-rises that boldly express the hidden heavy lifting. The tower is further distinguished by its ultraskinny top, which is nearly six times as thin as the highest floor of the adjoining Aon Center.

“It’s definitely a different aesthetic,” said Daniel Safarik, who edits the journal of the Chicago-based Council on Tall Buildings and Urban Habitat, which monitors skyscrapers worldwide. “For lack of a better word, luxury is communicated by smoothness or sleekness as opposed to musculature.”

Beginning with the internal frames of steel that made skyscrapers possible in the 1880s, Chicago has long been a center of innovative structural design. But the developers cranking out formulaic apartment high-rises in the current building boom have shown scant interest in breaking out of the box.

As a result, many of the city’s top architects have been exporting their best ideas to fast-growing parts of the world, like China, that are more receptive to new ideas. Now, ironically, Chinese money — in the form of the Wanda Group’s investment in the Vista Tower— is bringing leading-edge concepts back to Chicago.

Engineering the Vista Tower

The three stalks of the Vista Tower reach up to 1,191 feet tall, which will make it Chicago's third tallest building. At the top of the tower, the footprint is smaller than other super tall structures in Chicago. Here are some of the key innovations used by engineers to create the structure.

Buttressed core and ‘spine’ wall

The core structure of the Vista Tower has two key features.

‘Spine’ wall: A concrete wall in the tower’s midsection links the two outer cores. This helps the two towers act as one unit. The wall is perforated so doors and hallways go through.

Buttressed core: The core structures in the two outer stalks are built out to the outer edge of the building. The outer walls are also perforated, leaving openings for windows.

Walking columns

The inward and outward curves (zigzag shape) of the towers are supported by columns that shift in or out between floors.

Columns move in or out 5 inches per floor

Floor plate

The columns on floors where the inner and outer angles intersect, where the building shape is most narrow, do not shift.

Tuned liquid sloshing dampers

Six pools of water, containing more than 400,000 gallons of water, are positioned in the top floors of the tower to reduce the effect of wind.



Blow-through floor

A double-height floor at level 83 is left vacant without windows allowing the wind to blow straight through. Special, perforated covers will allow air to flow through.

Those are sort of being reexported and we’re adapting them to the American market,” Safarik said.

As we waited for the construction elevator that would take us up the tower’s south side, Eckmann took out a pen and drew a diagram of the Vista Tower’s unusual floor plan.

These days, a typical skyscraper is shaped like a square or rectangle, with an elevator core encased in concrete set in the middle. Like a silo, the core helps brace the high-rise against the overturning force of the wind. Vista is different.

Its three high-rise tiers, which wags have compared to a cellphone’s signal bars, are offset. That gives the building eight corners instead of the usual four.

More important, the tower’s midsection has two elevator cores (one on the east, the other to the west) linked by a concrete wall that runs between them. Other walls, also perforated to make way for doors, extend the core to the building’s perimeter, further strengthening it against the wind. The engineers call the arrangement a “buttressed core.”

David Fields, a Magnusson Klemencic senior principal who worked on Vista Tower with the firm’s CEO, Ron Klemencic, compares the design to a skier who spreads his stance to create stability.

A tree offers another useful metaphor. “Its shape perfectly demonstrates what’s needed," Fields said in a telephone interview. "It gets thinner at the top. When the wind blows, it’s not going to fall over.”


A view of Buckingham Fountain and the Museum Campus from Vista Tower on Aug. 27, 2019. (Brian Cassella / Chicago Tribune)

How does Vista Tower compare?

http://www.chicagotribune.com/columns/blair-kamin/ct-biz-vista-tower-structure-kamin-20190903-duclxwejdbfktkfwatd3judnim-story.html

John Hancock Center Vista Tower Willis Tower Trump Tower Aon Center

Completed: 1974 2009 2020 1973 1969

1,451 ft 1,389 ft 1,191 ft 1,136 ft 1,128 ft



The arrangement also has an urban design benefit: It means that the middle tier doesn’t have a core that needs to anchored in the earth. That leaves the ground free for a pathway that will link a park in the middle of the Lake Shore East development, of which Vista is a part, with the vibrant downtown riverwalk.

After the hoist elevator took us upward, Cassella and I got a taste of the high life that one of the building’s occupants will enjoy. The roof of Vista’s middle tier doubles as an 8,000-square-foot outdoor deck for a 71st floor penthouse in the building’s top tier. The deck will be outfitted with an elevated infinity pool — a nice spot to sip a pina colada after a tough day at the office.

Yeah, anyone who can afford a unit? Their 'tough days at the office' were over long ago. The nut was made, pour another pina colada; thank you very much.

Climbing 12 flights of stairs (an elevator wasn’t available), the tour group reached the blow-through floor on 83. The prevailing winds, which come from the southwest, were howling. That’s typical at high elevations, Eckmann explained. There’s nothing to get in the wind’s way.

According to the engineers, the blow-through floor is expected to cut wind-induced sway by nearly 25%. But it can’t single-handedly stabilize the tower’s uppermost floors.

Call in the aforementioned water tanks, which go by the name of “tuned liquid sloshing dampers.”

Eckmann pointed his smartphone’s flashlight at a concrete wall that encloses two of the dampers, which are tucked inside the 83rd floor’s elevator core. Four smaller pools will be hidden in mechanical levels at the top.

Other superthin Chicago high-rises, like 150 North Riverside, use dampers to counteract sway. But none has an exterior as complex as Vista’s.

To accommodate the building’s curves without sacrificing usable floor space, the engineers worked with Gang to make Vista’s perimeter columns step inward and outward instead of going straight up. Each column projects about 5 inches outward or inward from the one beneath it.

The arrangement, which the engineers call “walking columns,” was visible as Cassella and I looked through the windows on the 64th floor. Viewed from afar, the stepping pattern creates the illusion of Vista’s curves.

It’s also functional. Had the perimeter columns been set on a diagonal, about 5 feet of interior space would have been unusable because of the gap between the column and the exterior walls, Eckmann said. Such a tight fit was equally important in Vista’s hotel rooms, which are considerably smaller than the condos.

“Every inch counts,” Gang said.


A view of Lakeshore East from Vista Tower on Aug. 27, 2019. (Brian Cassella / Chicago Tribune)

With construction workers still putting interior stud walls and the rest of the tower’s glass into place, it remains to be seen whether form truly follows function at the Vista Tower.

When I posted pictures of the skyscraper and Gang’s famously curvaceous Aqua Tower on Twitter last week, the architecture critic Witold Rybczynski derisively labeled them “architecture as product design.”

But when I interviewed Gang, she said the tower’s design is functional, saying it accommodates a variety of uses, from the hotel to large and small condos.

Other elements of the design, which might seem purely aesthetic, also have a purpose.

Consider the tapering frustums, which are sheathed in greenish glass that shifts from dark to light. The darker glass is meant to prevent the narrower sections of the frustums from overheating. The lighter glass opens the wider sections, which are less prone to solar gain, to daylight. The glass itself is not highly reflective, Gang said, which should reduce the chance of bird collisions.

Sometimes skyscrapers are as fascinating in this in-between construction stage as when they’re finished. That’s certainly the case at the Vista Tower, which is sure to be a topic of conversation and debate at the upcoming Chicago Architecture Biennial, the big design exhibition that opens Sept. 19, and the Council on Tall Building and Urban Habitat’s 10th world congress, which starts here Oct. 28.

The engineers may be overlooked in the publicity brochures for Vista, but without their expertise, the tower would be impossible.

“We don’t get involved in projects (where the clients say) ‘Here it is — go engineer it up,’ ” Eckmann said. “That not where we can bring value.”

Blair Kamin is a Tribune critic.