How Cras Now Support the Statue of Liberty

Architecture How CRAs now support the Statue of Liberty

Built in 1886, the copper-clad Statue of Liberty has required quite some maintenance and renovation to keep it in pristine condition. In 1986, for example, engineers decided to replace rusty iron components with advanced materials such as Ferralium and 316L.

By David Sear Image: Wikimedia Commons

A gift of friendship from the people of designed the internal framework that At the heart of the Statue of Liberty became a national cause in the USA France to the United States, "The Statue keeps the Statue of Liberty standing. Eiffel therefore placed a sturdy iron and also France, with many companies of Liberty Enlightening the World" is As visitors to the Statue of Liberty will tower, comprising four legs. This tower donating both materials and services to recognized the world over as a uni- testify, it is in fact nothing more than a is surrounded by a secondary array of the project. versal symbol of freedom and democ- hollow shell, formed by 310 skillfully con- supporting iron beams and bars. These Engineers tasked with working out racy. Since its dedication in 1886 it has toured copper plates riveted together at connect the central tower to so-called how best to repair the Statue of Liberty become an iconic structure instantly rec- the edges. Eifel realised that this copper ribs, fl at strips of iron which have been decided that the ‘puddled iron’ in the ognised by people from all continents. shell, weighing more than 80 tonnes, bent into shape to follow the exact cur- internal superstructure needed replac- When fi rst built the Statue of Liberty would be unable to support its own vature of each and every copper plate. ing. For the rigid fl at bars they chose was the world’s tallest structure (some weight, much less withstand the buffet- Finally, the ribs are connected to the Ferralium® 255, which at the time was 46 metres high) and naturally made ing winds of New York! plates by saddles – U-shaped copper being made by Cabot Haynes. Investiga- use of the most modern materials and Eifel therefore developed a new profi les which were connected to the tion had shown that this alloy, when used construction techniques available at the construction method which would both plates using rivets. for the fl at bar structure and associated time. Moreover, one of the architects support the copper plates and facili- bolting, exhibited minimal reaction with behind the Statue of Liberty was none tate movement, allowing the metal to Galvanic corrosion the copper cladding. It offered thermal other than Alexandre-Gustav Eiffel, expand and contract during the hot As Eiffel was aware, combining dis- expansion and elasticity similar to that of the French bridge engineer famed for summers and cold winters. This tech- similar metals in such a fashion can the wrought iron, but was far stronger. building the Eiffel Tower in Paris, France. nique would later become known as the lead to galvanic corrosion. He therefore However, at the time it was deemed He is widely acknowledged as having ‘curtain-wall’ technique. specifi ed that asbestos cloth coated with that Ferralium® 255 would have been shellac be used to isolate the copper too diffi cult to form into more complex saddles from the iron bars. This method parts needed elsewhere, so Alloy 316L was initially successful yet over time the stainless steel was selected for shaped shellac dried out, allowing the asbestos elements such as the ribs. 316L was said to become dry and porous causing it to to exhibit minimal reactivity with the absorb moisture. So the cloth which was copper, and have a modulus of elasticity designed to prevent corrosion actually similar to the wrought iron. promoted it! As the iron bars corroded The refurbishment was successfully they swelled and distorted, in some completed in time for the grand reopen- cases to such an extent that the copper ing of the Statue of Liberty, timed to rivets pulled though the copper sheets. mark its centenary in 1986. Ten years This problem had already been rec- later, an inspection report indicated ognised by the early twentieth century, that the corrosion problems had been and indeed during the course of the corrected and that the installation had years various coatings were applied to remained corrosion-resistant. try and stop corrosion whilst iron bars which became more severely corroded References were replaced. However, by the late • Copper Development Association 1970s a decision was taken to give Inc. the Statue of Liberty a more extensive • Wikipedia restoration. Indeed, the condition and • The New York Times subsequent refurbishment of the statue • The Washington Post

Insider Tip: SSWN extends our thanks to Rodney Rice for bringing this unusual yet telling application of stainless steels to our attention. Would you like to share your Image: Wikimedia Commons favourite case history? Then simply contact David on [email protected], or Standing 46 metres high, the Statue of Liberty was the world’s tallest structure when ﬁ rst built +31 575 585 528.

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