Westpark Corporate Center, a venture of Northwestern Mutual Life Insurance Company and the National Automobile Dealer Association, is the first of two nine-story office towers to be located in McLean, Virginia. The project also contains five levels of below grade parking. A long-span reinforced concrete floor system was specified to satisfy the numerous requirements of the tenants.

Structural System
buildings_westpark2Typical bay dimensions for the office tower are 30-by-42-feet, with end bays spanning 47 feet. A banded beam system was utilized for the floor framing. Beams spanning in the long direction are 72-inches wide by 16-inches deep. A 9-inch thick post tensioned slab frames between the 72-inch 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 five-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 inches 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.

Westpark Corporate Center L.L.C.

The Mark Winkler Company, Alexandria, Virginia 

Leo A. Daly, Omaha, Nebraska

Structural Engineer:
Fernandez and Associates, Falls Church, Virginia 

General Contractor:
Bovis Land Lease

Concrete Contractor:
Miller & Long, Bethesda, Maryland