aon center  Amoco Hysteresis
[1,2]

Location: Chicago, Illinois
Year: 1989
Type: Façade Failure due to Thermal Hysteresis

The failure of the Amoco Building in Chicago serves as arguably the most infamous example of thermal hysteresis. Constructed as the headquarters for Standard Oil of Indiana in 1974, the building changed names along with the company in 1985 to become the Amoco Building. It was then later sold and renamed in 1999 and is now called the Aon Center, seen in Figure 1 above.[a] At the time it was completed, the tower’s height of 1,136 feet made it the tallest building in Chicago and the fourth tallest building in the world.[b]

For the façade, the architect Edward Durell Stone recommended to his client that they use thin marble slabs, stating that they would be “longlasting and outstanding.”[b] The claim had some merit; Italian Carrara marble had been used by Michelangelo to sculpt his masterpiece David in the early 1500s and was selected by Alvar Aalto in his construction of the Finlandia Concert Hall in Helsinki – a building which eventually suffered the same fate as the Amoco Building.[c] Stone convinced Standard Oil that a Carrara marble skin would convey a sense of prestige befitting fifth largest energy company in the world.[b]  Following his recommendation, Standard oil imported almost 6,000 tons of the stone, which were then cut into 45 inch by 50 inch slabs 1 1/4 inches thick. Requiring 43,000 of these panels, the marble façade helped propel the project’s total cost up to $120 million.[b]

However, the panels lasted less than 15 years.[b] After years of exposure to Chicago’s large temperature swings, much of the façade began to deteriorate to dangerous levels. Known as thermal hysteresis, years of extreme thermal cycling caused the thin marble slabs to permanently bow outward, as seen in Figure 2 above. While marble is a brittle material, it exhibits some plastic behavior over long periods of exposure, resulting in permanent deformation and a substantial loss in flexural strength.[d]

Eventually every one of the 43,000 marble panels had to be taken down and replaced with granite from North Carolina, a repair which took 3 years to complete and cost $80 million.[e] “To recoup its costs, Amoco sued all parties involved: Edward Durell Stone & Associates as well as Perkins & Will, the tower’s architects; Turner Construction of New York, the general contractor; Peter Bratti Associates Inc., a New York firm that installed the marble; and Alberto Bufalini Successori, the Italian marble supplier.”[b] The parties ended up settling out of court, with the results kept confidential.[f] Still, the building serves as a cautionary tale for those who might attempt to use marble for their building facades.

[c] Siegesmund, S; Ruedrich, J; Koch, A. “Marble Bowing: Comparative Studies of Three Different Public Building Facades.” Environmental Geology 56, no. 3 (December 2008): 473-494.

[d] Newlin, J; Jimenez, G. A; Hester, D; McIntosh Blank, L. “Thin Marble Facades: History, Evaluation, and Maintenance.” Structures Congress, 2010 ASCE: 1051-1062.

[f] Hook, G. “Look Out Below! The Amoco Building Cladding Failure.” Progressive Architecture, 75, no. 2 (1994): 58-61.

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