Tornado Alley (PROG)

[blackhawks]

Because O'Donnell needed to build tall (and thus profitably), 150's north and south flanks look as thin as a reed. Their aspect ratio — the building's height relative to the width of its core — is a jaw-dropping 20-1. Imagine a reed blowing in the wind. Now imagine that that reed is an office building with people inside who get as queasy as passengers on a storm-tossed ship.

http://www.chicagotribune.com/entertainment/ct-150-north-riverside-review-ae-0423-20170419-story.html

To prevent that, the engineers inserted two enclosed concrete vaults near the building's top. The water in the vaults, which are called "tuned liquid dampers," is not for swimming. When the wind pushes the high-rise one way, the water sloshes the other way, damping wind-induced sway and eliminating the threat of rattling chandeliers and whitecaps in the toilets.


https://en.wikipedia.org/wiki/Park_Tower_(Chicago)

Park Tower is a skyscraper located at 800 North Michigan Avenue in Chicago, Illinois. Completed in 2000 and standing at 844 feet (257 meters) tall with 70 floors — 67 floors for practical use, it is the twelfth-tallest building in Chicago, the 43rd-tallest building in the United States, and the 83rd-tallest in the world by architectural detail. It is one of the world's tallest buildings to be clad with architectural precast concrete (the Transamerica Pyramid Building in San Francisco is taller).

It is one of the tallest non-steel framed structures in the world—it is a cast-in-place concrete framed structure. This building was originally intended to be 650 ft (200 m) tall. But later, the ceiling heights were increased allowing it to reach 844 ft (257 m).

The building occupies a footprint of 28,000 square feet (2,600 square meters). Because of the small footprint and the fact that it is a non-steel-framed concrete building, this is the first building in the US to be designed with a tuned mass damper from the outset.

While other skyscrapers in America have anti-sway systems, they were always added later. A tuned mass damper counteracts wind effects on the structure. (The 300-ton damper is a massive steel pendulum hung from four cables inside a square cage.) Because of its massive weight, the damper has inertia that helps stabilize the building from swaying in the wind.