Buildings
Congested Site at Chicago's Millennium Park Calls for Delicate
Movement of Machinery
(enr.construction.com - 02/09/04 issue)
ByTudor
Hampton
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TANGLED Trades finishing music pavilion
fight for aerial real estate.
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A complex project without logistical
challenges is like a rock concert without dramatic flair.
Likewise, the story of Millennium Park’s amphitheater
in Chicago is a potent reminder of how contractors faced with
the daily problem of a congested and ever-changing urban site
must carefully select and plan equipment to make it work.
Communication among trades at Millennium
Park has been critical for safety at a site that has been
packed with machines. The 30,000 sq-ft apron area facing the
site’s Frank O. Gehry-designed music pavilion has during
construction hosted a cacophony of heavy equipment and materials
needed to erect the amphitheater. Scheduled to open in July,
its high-swooping, stainless-steel "ribbons" and
adjacent open-air trellis are the park’s centerpiece
(see p. 24).
"I had 19 aerial lifts and three
cranes on the job, all in the same [30,000-sq-ft] footprint,"
says Patrick R. Buck, project manager for Chicago-based Walsh
Construction, general contractor responsible for building
the music pavilion and surrounding 95,000-sq-ft seating area
that comprise about five acres of the 24.5-acre park near
Lake Michigan. He says that equipment utilization peaked last
August, after erection of the structural steel above the stage
was nearing completion.
In order to facilitate safe operations
last summer, "the subs would have a 10-minute talk session
every morning," says David J. Markovich, Walsh senior
superintendent. "If one of the dominoes fell apart, it
would wreak big havoc on the job," he adds. Site meetings
now are being held twice a week.
To complicate matters, ground loading
issues have restricted movement of equipment and materials.
The pavilion and trellis bear on a concrete raft slab covering
an active, 2,181-space, underground parking garage. "Site
logistics and utilization were very difficult," says
Wayne Anderson, Walsh’s senior project manager.
One innovative solution came from steel
erector Danny’s Construction Co. Inc., Gary, Ind., which
needed to position two crawler cranes without using added
shoring to support the slab. The firm designed a steel cribbing
system on which the two cranes could track from west to east
as erectors placed the pavilion’s elevated steel elements.
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REACH Steel erector’s 90-ton cribbing system bolsters
lift cranes.
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Built last February and struck
in mid-September, the 90-ton "grillage" included
five moveable "bays" of two, 29-ft-long girders
and two, 30-ft-long stringer beams. The unit was able to distribute
the weight of the two Manitowoc 999 275-ton lift cranes to
the garage columns and down through the caissons, according
to Dave Budzius, Danny’s project manager. "We’ve
done similar things in the past, but more to provide additional
bearing for the crane on less-than-desirable soil," he
says.
The project has had no major equipment
accidents to date. The team’s biggest challenge remains
orchestrating the movements of subcontractors installing the
pavilion’s stainless steel skin from 80 to 150-ft-tall
aerial lifts. "If we didn’t have open communication,
we would all be on top of each other," says Markovich.
(Photos courtesy of Walsh Construction)
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