Image Credit: Lara Swimmer
Located in one of America’s highest seismic regions, the FBI Portland field office complex incorporates cutting-edge technologies to ensure unsurpassed multi-hazard protection. Designed by HGA Architects and developed by the Molasky Group of Companies to serve as the FBI’s Oregon headquarters, the crucial structural, seismic and blast-engineering design was provided by Weidlinger Associates.
FBI Portland comprises a four-storey office building, a one-storey annex, a 223-car post-tensioned concrete parking structure, and a small visitor screening facility bounded entirely by a state-of-the-art anti-ram fence. Along with its terracotta-hued facades and meticulously landscaped courtyard, the picturesque 142,604 square foot suburban campus features a covered walkway, a miniature waterfall, a garden, and even a basketball court.
The project features seismic-design strategies prevalently used on the west coast, where frames must support greater loads and resist swaying during seismic events.
The 135,000 square foot office building, a chevron-shaped structure with precast punched-window panels, houses the primary FBI offices. It features a dual seismic system that is more commonly used in taller buildings which consists of buckling restrained braced frames that absorb 75 to 90 per cent of the structure’s seismic load. Special frames help minimize seismic demand on the columns. Laminated box windows used throughout the building are designed so that, if the glass fails, it will remain in the frame and not become a hazard to occupants.
The 24,000 square foot annex serves primarily as a maintenance garage. Its entire perimeter was created using “tilt-up” construction, wherein concrete walls are poured onto a concrete slab and then “tilted up” into place after they cure. While concrete shear walls are intrinsically resistant to seismic forces, the walls of the complex have been designed to be heavier and thicker to simultaneously meet combined blast, seismic, bearing, and progressive-collapse specifications. The structure’s steel-joist roof was designed to be light and flexible to satisfy both seismic and blast-resistance criteria.
To overcome poor soils throughout the site, the engineering team specified the use of driven grout piles, a proprietary deep-foundation system capable of supporting loads greater than 100 tons.
“For FBI Portland, the challenge was to design an attractive campus with buildings of various construction types while meeting an extremely aggressive schedule and satisfying stringent, often-conflicting blast and seismic requirements. The office building, for instance, is aesthetically appealing, yet strong enough to function as a blast shelter,” said Weidlinger principal Peter DiMaggio.
Located a short distance from the airport and easily accessible from the freeway, the $65-million complex was among the largest Portland-area projects undertaken during the recession and currently houses more than 200 full-time employees. Proceeds from the sale of land rights to the site were used to support local economic development programs. The project was recently certified LEED Gold, surpassing the FBI’s requirement of LEED Silver certification.
The American Council of Engineering Companies of New York recently selected the project to receive an Engineering Excellence Gold Award, recognising that its construction required engineering achievements that demonstrate ingenuity and significant technical, economic, and social advancement.