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Chicago’s New Type 316 Skyline

By Catherine Houska, TMR Stainless (Consultants to IMOA)

Stainless steel’s growing popularity as a construction material is changing skylines in major US cities. Many of the newly completed or planned, high profile, North American building projects in trend-setting Chicago and New York are using 2% molybdenum Type 316 stainless steel.

Chicago is currently leading the stainless steel building race. Chicago’s new Millennium Park (www.millenniumpark.org), which opened in July 2004, is the city’s new architectural crown jewel. This internationally acclaimed park’s most visible construction material is Type 316/316L stainless steel. It was used for the exterior of US architect Frank Gehry’s Jay Pritzker Pavilion and BP bridge, British sculptor Anish Kapoor’s bean shaped Cloud Gate, and the structural supports for Spanish artist Jaume Plensa’s Crown Fountain. The April 2005 issue of Condé Nast Traveler included the Millennium Park’s BP Bridge and the Cloud Gate in its list of seven new "wonders of the world" making this Type 316 park an important tourist attraction.

One of the smaller structures in the park, the 20 m (66 ft) long and 10 m (33 ft) tall Cloud Gate was fabricated from 100 tonnes of 19 mm (0.75 inch) thick mirror polished plate (Figure 1).

The underside of the bean is not accessible because some seams are still being welded and polished. Figure 2 shows the Chicago skyline reflected on the Cloud Gate’s curved surface. IMOA member Outokumpu supplied the plate for this project.

Figure 1:
Anish Kapoor’s Cloud Gate sculpture is
also known as the “bean”. The underside
will remain wrapped until welding and
polishing is completed.

Figure 2:
Chicago’s skyline, Pritzker Pavilion,
and the photographer reflected in the
Cloud Gate’s seamless mirror polished
surface.

Figure 4:
Both ends of the BP Bridge have a
serpentine shape. The entire structure
is clad in Type 316 stainless steel. The
bottom floors of the Blue Cross Building,
which is directly behind the bridge, are
clad in Type 316 to prevent deicing salt
corrosion.

Figure 3:
The sweeping Type 316 exterior walls of the Jay Pritzker Pavilion band shell and the structural supports for the sound system spanning over the concert lawn.

Figure 5:
The faces of 1,000 Chicago citizens are
projected on the glass block faces of the
Crown Fountain. The structural supports
for the fountain are Type 316 stainless
steel.

The glass block is held in place by Type 316 structural supports. The Type 316 tonnage used for the pavilion, bridge and fountain is not known but it is assumed to be significant.

Chicago’s recent high-profile use of Type 316 does not stop at the borders of Millennium Park. In 2005, two new adjoining Outokumpu Type 316L clad buildings were completed on South Wacker Drive. 111 South Wacker Drive was designed by Lohan Caprile Goettsch (Chicago) and Hyatt Center (Figure 6) was designed by Pei Cobb Freed & Partners (New York). These buildings are clad in about 400 tonnes of Type 316L stainless steel. The highly publicized, new Trump Tower, which is under construction, was designed by Skidmore Owings & Merrill (Chicago) and will use about 170 tonnes of Type 316 on the exterior.

Several important Type 316 buildings exteriors were recently bid in New York. Goldman Sachs’ new Pei Cobb Freed designed world headquarters will use about 430 tonnes of Type 316L, and Sir Norman Foster’s 610 Lexington Avenue design will use about 300 tonnes of Type 316L. 7 World Trade Center, which used both Type 316 austenitic and 2205 duplex stainless steel, is nearing completion. Freedom Tower (Skidmore Owings & Merrill, New York office), which will replace the World Trade Center towers, is expected to be clad in Type 316.

Although the tonnage of stainless steel that has been or will be used for most of Millennium Park, 7 World Trade Center, and Freedom Tower is not known, about 1,400 tonnes of Type 316/316L or 28 tonnes of molybdenum have been or will be used for the other projects mentioned in this article. It is important to note that only very high profile buildings were included in this article. Many Type 316 railings, storefronts, canopies, and similar applications are specified daily in these cities.

Photo credits:
All of the images were taken by or for IMOA.

Because New York and Chicago have the largest concentrations of architects in North America, IMOA has made them primary focus areas for market education and development efforts. In a 2005 IMOA sponsored market study, contractors and architects indicated that the first tier architecture firms in these cities are now consistently specifying Type 316 for exterior applications. The use of stainless steel in exterior applications has increased significantly in these cities in the past five years. IMOA workshops and literature were cited by respondents of the survey as the reason for increased specification of Type 316 by architects.