Westpark Corporate Center
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Westpark
Corporate Center, a venture of Northwestern Mutual Life Insurance
Company and the National Automobile Dealer Association, is the first
of two 9-story office towers to be located in McLean, VA. The project
also contains 5 levels of below grade parking. A long-span reinforced
concrete floor system was specified to satisfy the numerous requirements
of the tenants.
Structural
System
Typical
bay dimensions for the office tower are 30 ft by 42 ft, with end
bays spanning 47 ft. A banded-beam system was utilized for the floor
framing. Beams spanning in the long direction are 72 in. wide by
16 in. deep. A 9-in. thick post-tensioned slab frames between the
72-in. wide beams.
Concrete with
a compressive strength of 5,000 psi is used for the slab and beams,
while columns in the lower floors utilize a 10,000-psi mix. Concrete
was produced from an on-site batch plant, which resulted in high
quality control: cylinders for the slab concrete easily reached
3,000 psi in 30 hours. This helped contribute to the 5-day floor
cycles.
Concrete
versus Steel Framing
Structural
steel was never really a viable option for this project for a variety
of reasons. Due to height restrictions, the floor-to-floor heights
needed to be kept to a minimum. By utilizing the banded-beam system,
the floor heights could be reduced by about 8 in. per floor, compared
to a structural steel floor system. This also resulted in a substantial
cost savings. Column transfers and the curvilinear profile of the
building were other reasons why structural steel was not used.
Credits
Owner:
Westpark Corporate Center L.L.C.
Developer: The Mark Winkler Company
Architect: Leo A. Daly
Structural Engineer: Fernandez and Associates
General Contractor: Bovis Land Lease
Concrete Contractor: Miller & Long
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