Happy July 4, everybody! In the United States, this is a day to celebrate our nation’s independence, and give thanks for the centuries of freedom that we have enjoyed since our founding on July 4, 1776. There is no greater symbol of that freedom, than the Statue of Liberty (official title: “Liberty Enlightening the World”) – the glorious structure that since 1886 has welcomed millions of immigrants, many of whom were fleeing repression in their native lands.
Growing up in New Jersey, I saw the Statue of Liberty often. Catching that first glimpse of it while driving down the New Jersey Turnpike or while heading into New York to witness yet another Mets’ baseball loss was always an exciting moment, and today when I fly into New York it still is. To me (and many others) the statue is both beautiful art and one of the greatest symbols of all that is right with this country. But as a structural engineer I have another reason to get a lump in my throat when I see it — did you know that the Statue of Liberty may well have been the world’s first skyscraper?
Many people are familiar with the story behind the statue. In 1869, the French sculptor Frédéric Bartholdi and abolitionist Édouard de Laboulaye promoted the idea of the statue as a colossal gift to the United States, on behalf of France, to celebrate both the nation’s centennial of independence and the end of slavery following the end of the civil war. Bartholdi enthusiastically embraced nearly all of the responsibilities for the project – lobbying President Ulysses S. Grant for support, scouting the ultimate location on Bedloe’s (later, Liberty) Island, designing the statue, managing its construction, and even pitching in with the fund raising. But Bartholdi was not qualified to do it all alone, so in certain areas he recruited help: his mother served as the model for Miss Liberty’s face, and Eugène Viollet-le-Duc was signed on as the project’s Chief Engineer.
Viollet-le-Duc’s proposal for Miss Liberty’s structural support was consistent with the times – anchoring the statue’s copper skin to internal brick piers. The use of masonry was common for buildings of the time as well as large sculptures such as the Sancarlone near Arona, Italy and the Hermannsdenkmal (Arminius statue) in Ostwestfalen-Lippe, Germany. In fact, another prominent symbol of this nation was at that moment nearing completion, using masonry technology. The Washington Monument in Washington, DC, when finished in 1884, became the world’s tallest structure (today it remains the world’s tallest masonry structure).
Engineering history may have been different if Violett-le-Duc had not died in 1879, before the project had progressed very far. At this point Bartholdi replaced him in the Chief Engineer position with the man probably most associated with the Statue of Liberty — Gustave Eiffel. Eiffel, who of course gained later fame with his eponymous tower, probably rightly deserves this credit due to his use of the most innovative structural engineering techniques of his time to not only realize Bartholdi’s dream, but to likewise – perhaps unwittingly — usher our cities into the modern era.
Eiffel realized that the project presented unique challenges. The unprecedented size of the sculpture and the environment in which it was located (60+ mile-per-hour winds) would require that the structure resist large loads. The use of copper, and its differential rate of thermal expansion, would cause tearing if anchored to a rigid base. The fact that the statue would have to be transported across the sea (the intent was to build the statue in France and then ship it to New York) called for an absolute minimization of its weight. (In fact, the statue ended up being fully assembled in France, then divided into 350 pieces for its trip across the Atlantic, with final reassembly — like a giant 3D puzzle — being done on site.)
In a bold move, Eiffel decided to replace the traditional masonry pier design with a puddled iron truss tower (a design which Eiffel later duplicated on the Eiffel Tower). Eiffel attached the inner iron armature to a mesh of flat iron bars that in turn were loosely connected to the structure’s copper skin. The flexible interior allowed the metal to expand on hot days and let the statue move slightly with the harbor’s winds, features which allowed it to maintain its external appearance and structural integrity. In the final design the walls were non-load bearing, instead relying on the interior framework for support. By creating one of the earliest examples of curtain-wall design, Eiffel managed to complete a structure that when dedicated by President Grover Cleveland on October 28, 1886 became the tallest man-made object in New York City. And more interesting, from an engineer’s point of view: at 151 feet tall, the total weight of the Statue of Liberty was an efficient 225 tons (1.5 tons of structure per foot of height), whereas a traditional structure such as the Washington Monument, at 555 feet tall, weighed in at 100,000 tons (180 tons of structure per foot of height).
Architectural historians have a word to describe tall buildings in which the load bearing is resisted by internal iron or steel skeleton frames – “skyscraper”. So it would not be a stretch to call the Statue of Liberty the world’s first skyscraper, even if nothing had followed. If nothing had followed, the impact of Eiffel’s accomplishment would have been impressive, but limited – the New York City skyline would have been dominated by this beautiful, innovative symbol of liberty and freedom…but the world would not have changed significantly.
But somebody was watching Eiffel’s progress as he assembled the statue in Paris starting in 1881. William Le Baron Jenney, a civil war veteran, Chicago engineer/architect, and coincidentally, a classmate of Eiffel’s at Paris’ École Centrale des Arts et Manufactures (where both had learned engineering), decided to take a similar approach – curtain wall design, with all loads supported by an internal iron and steel structure — on an office building that he was designing. And thus in 1884 was born Chicago’s Home Insurance Building, a 10-story building traditionally considered to be the world’s first skyscraper.
The Home Insurance Building was revolutionary for its time. Weighing only one third as much as an equivalent masonry structure, city officials were skeptical enough about the new design to temporarily halt construction while they assured themselves that the radical structure was truly safe. Engineers immediately recognized the significance of this new method – in fact, one engineer, Minneapolis-based Leroy Buffington actually went so far as to patent the skyscraper in 1888, claiming he had dreamt up the idea seven years earlier. From that point on the sky was truly the limit.
So the success of the Statue of Liberty’s design and its subsequent application to the Home Insurance Building brought in the era of the skyscraper with a bang, changing the world’s urban landscape forever. A mere three years after the Statue of Liberty was completed, the iron frame of the Eiffel Tower soared to a height of 985 feet, holding the record for tallest structure on earth until 1930 — when it was finally topped by New York City’s Chrysler Building (and then the Empire State Building one year later). Today, Dubai’s Burj Khalifa, using basically the same technology as that pioneered by Eiffel, at 2700 feet is nearly 18 times as tall as its ancestor, the Statue of Liberty.
So this Fourth of July, join me in celebrating not only this nation’s independence and the liberty that it offered to so many of this nation’s immigrants, but also an innovative engineering masterpiece as well – the world’s first skyscraper.
Building a symbol of liberty, or simply the world’s tallest skyscraper? Why not use CloudCalc, the scalable, collaborative, cloud-based engineering software. www.cloudcalc.com – Structural Analysis in the Cloud.
By Tom Van Laan
Copyright © CloudCalc, Inc. 2015