23 Skidoo! The “Flatiron”: a Failure or a Feat of Engineering?
“One vast horror, facing Madison Square, is distinctly responsible for a new form of hurricane, which meets unsuspecting pedestrians as they reach the corner, causing them extreme discomfort. I suppose the wind is in some way intercepted by the towering height of the building, and forced down with fury into an unaccustomed channel. When its effects first became noticeable, a little rude crowd of loafers … used to congregate upon the curb to jeer at and gloat over the distress of ladies whose skirts were blown into their eyes as they rounded the treacherous corner. Hanging about this particular spot soon became a recognised and punishable offence, and anyone loitering there more than a few moments is now promptly “moved on” by the police. A lawsuit is also at this moment pending against the owner of this building, brought by a neighbouring tradesman whose shop-window has twice been blown in by the newly created whirlwind.”
— Sir Phillip Burne-Jones, Dollars and Democracy, 1904
This is how Sir Phillip Burne-Jones characterized a unique manifestation of engineering ingenuity in his travelogue of the United States in the early 1900s. He was describing the Flatiron building, located on 23rd Street at the intersection of Fifth Avenue and Broadway, New York, forming an acute angle.
The building has become an icon of New York City. The initial public response, however, was somewhat mixed — what praise it received was mostly for the cleverness of the engineering involved in the design. The Municipal Art Society declared that it was “unfit to be in the Center of the City”. The New York Tribune described the new building as “A stingy piece of pie… the greatest inanimate troublemaker in New York”. The New York Times said it was a “monstrosity” [1].
New Yorkers took an immediate interest in the building, even placing bets on how far the debris would fly when the wind knocked it down.
This presumed susceptibility to damage was referred to as “Burnham’s Folly”, after the Chicago architect Daniel Burnham who was commissioned to design it. But thanks to the steel bracing designed by engineer Corydon Purdy, the building was able to accommodate four times the typical wind loads, and it still stands tall today.
Nevertheless, the wind is a major reason for the building’s popularity. Due to the geography of the location, the wind currents around the building were treacherous. The layout of the area, combined with the shape of the building, could create unpredictable gusts of wind, strong enough to lift women’s skirts.
This is said to have given rise to “23 skidoo”, an American slang phrase, generally referring to leaving quickly.
Perhaps the most widely known story of the origin of the expression is connected to what policemen would shout at men trying to catch glimpses of women’s skirts being blown up by the winds swirling around the building.
The construction of any building inevitably changes the microclimate in its vicinity, even more so when it comes to skyscrapers. The wind pushes against the surface of a skyscraper creating vortices and vortex shedding, which can cause the building to shake and vibrate, and create extreme discomfort for pedestrians. The aim of any skyscraper design is to break up these vortices. That includes rounded or notched facade corners, open slots to let wind pass through and more — all to help break up the wind.
“It’s interesting that the aerodynamics of a building are almost counter-intuitive. We don’t want smooth shapes, we want shapes that break up the air flow.”
— Baker DeSimone, Chief Executive of DeSimone Consulting Engineers
Over time, the techniques that engineers and architects employ in building design have become more and more sophisticated to account for wind. Early in the design process, different shapes for a proposed tower are tested using numerical simulation with Computational Fluid Dynamics (CFD).
You can find out more about the design of the Flatiron building (and its effect on the local micro climate) in our collaborative video with How to Architect below.
To learn more about building aerodynamics and the application of CFD tools to predict and assess it, watch this webinar on “CFD for Wind Comfort and Safety in Urban Areas”.
References
1. Treasures of New York City: The Flatiron Building (TV, 2014) WLIW. Accessed: April 3, 2014
