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Streeterville Reawakening
New Vision for Partially Completed Project
by Sheila Bacon
Saddled with structural constraints left behind by the property's
previous developer, the Fairbanks at CityFront Plaza's project
team combined creativity with common sense to design and construct
a condominium tower that rises above the original vision.
The first phase of the three-phase, $700 million CityFront
Plaza development in Chicago's south Streeterville neighborhood--a
half-block east of Michigan Avenue's "Magnificent Mile"--will
feature an $87 million, 31-story tower with 350 condominium
units.
When the first occupants move in to phase one of the project--50
loft-style units--at the end of this month, it will signal
a milestone of sorts for the property, which for several years
had been home to a partially completed parking garage that
was part of the stalled beginnings of developer R.M. Chin
and Associates' failed mixed-use Grand Pier project.
The new owner, Chicago-based Centrum Properties, purchased
the partially developed property, which was originally configured
to feature an atrium hotel atop the parking garage, plus an
adjacent 75-story tower in December 2004, said Paul Ozaki,
Centrum's construction manager, and construction of the new
project began in November.
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Reinventing the Site
The design team had two distinct tasks: First, create a new
look for the existing eight-story parking structure that had
long served as a reminder to a rankled public of the initial
failed project; and, second, design a tower that matched the
new developer's vision while working within the structural constraints
of the existing parking structure.
Chicago architecture firm DeStefano + Partners designed a new
cladding system that redefined the garage and helped reintroduce
the new development to the neighborhood. A black terra-cotta-clad
rain-screen system replaced a multifaceted metal, glass and
perforated mesh panel facade.
The new masonry-inspired design responded better to the neighborhood's
residential character, said Scott Sarver, DeStefano + Partners
president.
The designers also transformed the south portion of the parking
structure and converted it to residential loft units, allowing
the developer to offer occupancy long before the tower is complete
and further enliven the long-dormant development.
A number of pre-existing conditions made the design of the tower
challenging, Sarver said. Because the garage featured post-tensioned
concrete floor slabs, new elevator and mechanical shafts to
serve the tower could not be cut, forcing the project team to
use only the structure's existing cores.
The under-way construction of a long-awaited Dominick's grocery
store at the base of the site also restricted the team from
cutting additional shafts in that area. Further complicating
the design was the capacity of the existing structure's caissons,
which would not support the weight of a concrete structure,
the typical building material used in residential high-rise
towers.
With few other options, the team decided to use steel for the
structure's frame. Such a system would not only be lightweight
enough to be supported by the existing caissons, but would allow
the developer to build 10 to 12 floors higher than the adjacent
building to the east.
Concrete shear walls instead of diagonal steel braces were added
for structural support at the outer edges along two sides of
the building where the existing caissons were stronger. Although
unusual to combine concrete and steel in a residential application,
the choice was the most economical because the strength of the
existing caissons in these areas provided sufficient support,
Sarver said.
The decision to use steel as the tower's main structural system
came with some caveats, however.
Use of a less expensive concrete structure would have likely
shaved an estimated $10 million off the cost of the structure,
said Centrum's Ozaki. And preliminary wind tunnel tests have
indicated that installation of a sophisticated damping system
may be required at the top floor once the steel erection is
complete in this month.
Those tests have shown that the light weight of the steel frame
will likely allow excessive movements and vibrations caused
by wind patterns, Ozaki said. Additional measurements will be
taken in September after the tower's topping out to determine
the need for the dampers.
The tower will feature a ceiling-to-floor window wall with painted
aluminum frames.
The light charcoal and silver color palate was chosen to set
the structure apart from its largely beige-painted concrete
neighbors, Sarver said. The windows will be low-emissivity glass
with a slight reflective quality to mitigate the appearance
of curtains and drapes.
Preparing the Podium
Preparing the already-built structure to receive a tower it
wasn't originally designed to carry required considerable arrangements,
said Bill Griffith, vice president of Linn-Mathes Inc., the
Chicago-based general contractor.
Crews poured a 6-ft.-deep, mildly reinforced concrete transfer
slab over the top of the parking garage and also incorporated
a 14-ft.-deep continuous concrete beam the length of the tower
to transfer the new structure's loads across the existing caissons
and parking structure.
With the onsite grocery store opening about the same time tower
construction was beginning, tower crane placement became an
issue, Griffith said. Typically located parallel to a structure,
this project's tower crane was located at the northwest corner
of the site, requiring longer struts and significant preplanning.
Ironically, the challenging site offered ample room for material
laydown and equipment staging, Griffith said. Although part
of a basement area built for the original development required
significant filling, it was able to eventually be used by the
construction team for storage, staging and hoists.
After occupancy of the initial 50 lofts this month, phased
move-ins to the tower are expected to start in August 2007.
Schematic designs are under way for phase two; the 41-story
condominium tower named the Saint Clair, which will offer
287 living units and is expected to break ground in spring
2007. Phase three, yet to be designed, will be the tallest
of the three towers, featuring 61 stories, approximately 300
condominiums and a premier hotel.
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