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China Poly building’s stainless steel cable-net wall
By B.A. McKean
Nickel Magazine, December 2009 -- Few outside China are aware of China
Poly, a state-owned organization with diverse responsibilities in the defence trade, real estate, cultural
industries and, most recently, mineral exploration. The innovative architecture of its new Beijing
headquarters, however, is attracting international attention and awards, thanks in part to a combination of
the high strength and corrosion resistance of nickel-containing stainless steels.
In addition to the company’s headquarters, the 100,000-square-metre building houses office space, retail
shops, restaurants, and the Poly Museum. Designed by Skidmore Owings & Merrill (SOM) with a mandate to
establish a civic presence that would be reminiscent of Rockefeller Center in New York City, it’s a simple,
monolithic triangle with two distinct cablenet walls facing south (50 metres tall) and northeast (90 metres
tall). The north-eastern cablenet wall is one of the largest in the world.
Engineered safety
A conventional design using large trusses would have obstructed the view of the city. Instead, the wall is
supported by an innovative V-cable counter-weighted by a suspended museum space using a specially designed
pulley mechanism.
The relationship established between the wall and the floating museum is calculated to compensate for
movement during a seismic event, while the glass and stainless steel wall can withstand 100-year winds and
deflect up to ± 0.9 metres under maximum wind load.
Cables and castings
The cable-net walls are supported by 26- millimetre diameter vertical and 34-millimetre diameter horizontal
cables made of type 316 (S31600) stainless steel, while the cable net intersection points are connected with
high-strength clamp fittings made of duplex 2205 (S32205)
stainless. The rods between the main cable and the cable net are type 316 stainless steel. The support
armature is cast from the high-strength duplex alloy CD3MN (J92205
- the cast version of duplex 2205 stainless steel) with a glass-bead blast finish. The exterior plate of this
armature is slotted onto the interior plate and bolted through the glass-to-glass joint.
Stainless steel was selected because of its high strength and corrosion resistance. Beijing has a
corrosive environment with high levels of industrial pollution and there has been a significant rise in the
use of de-icing salt in the winter. Specification of corrosion-resistant stainless steels made it possible to
avoid high-maintenance coatings and the bare stainless steel is a sculptural,
structural design element.
Early design calculations indicated that large deflections would occur during high-wind loads due to the
movement of the cables and glass. SOM addressed this problem with a hinged stainless steel glass support
channel that allows free rotation of up to seven degrees without applying stress to the glass. The hinged
channel is connected back to the cable net and held off the diagonal bridge cables by high-strength duplex
2205 stainless steel rods, which are allowed to rotate in their assembly.
Enduring contributions
The new Poly Plaza is only one of many developments that are changing the face of Beijing. Nickel-containing
materials are found in all of them, making buildings safer, more efficient, and durable. Few of them will be
more visually impressive than Poly Plaza.
Photos: Nicole Kinsman, International Molybdenum Association
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