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Long-spans amplify the collaborative
relationship between architects and engineers
By Sara Hart
The $50 million, 12,139-ton, retractable roof, manufactured
by Mitsubishi Heavy Industries of America, opens and closes
like a fan in about 10 minutes. Two fixed panels span across
the foul lines, forming the clerestory windows at the top.
Electric bogeys move the other five panels to each side, which
stack three on one side, two on the other.
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| Miller Park seats 42,500 spectators. A massive
retractable roof provides an open-air stadium (
top) on sunny days and a climate-controlled environment
on cold or rainy days. When the roof is closed (above),
a heating system keeps the seating bowl at 60 degrees
when the exterior temperature drops below 30 degrees.
No cooling is provided for the bowl, but the outfield
wall opens for ventilation. In order to minimize
the height of the dome while providing clearance
for fly balls within the stadium, the dome panels
hang from finlike trusses, creating a dramatic profile
(below). A cable truss underneath (bottom) provides
additional support. |
Photography: © Tim
Griffith |
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The roof’s unusual profile is the result of another
design and engineering innovation. The upturns, or finlike
trusses that support the panels, are on top of the roof. Typically,
they support the roof from underneath. Meis explains, “Because
the clearance must be 180 feet above second base [the maximum
height a ball presumably can be hit], roofs with trusses underneath
must be much taller than necessary to provide the required
clearance.” In this scenario, however, the structural
system is inverted, requiring only a cable truss on the interior.
This achieves a lighter, less bulky roof.
Of course, something has to hold up any roof, and here the
materials statistics for the whole park are rather staggering.
The 1,200,000-square-foot park includes 25 miles of deep piles,
70,000 cubic yards of structural concrete, 4,600 pieces of
precast concrete, and 9,000 tons of steel. The sum of these
materials is enough to build a 50-story building.
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