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Staten Island September 11th Memorial

Structural and site/civil engineering for "Postcards" memorial and park. Unprecedented use of high-strength composite laminate (FRP). Fast track.

Masayuki Sono's "Postcards" memorial honors Staten Islanders who lost their lives in the September 11, 2001, terrorist attacks. It consists of two mirror-image 38.5-foot-high walls that tilt nine degrees away from each other and bend at the corners, framing the view where the Twin Towers once stood. High-strength composite of fiberglass, foam core, and vinyl ester resin (FRP), commonly used to construct racing boats but never for a structure of this form or size, proved more economical than concrete. No codes governed FRP's use or its interaction with steel and concrete. In a successful operation with no margin for error, the walls were prefabricated off site, then barged to the site and placed on the foundation in a single day. The deadline was absolute (September 11, 2004) and the budget fixed ($2.3 million).

The thin arcing walls cantilever beyond the retaining walls and expansion joint of the windy waterfront site. Each wall contains rows of individual plaques with silhouettes of the deceased and identifying text. The vertical slots in the walls complicated the walls' structural behavior by weakening them in the middle and diverting the forces to the ends. Weidlinger designed steel brackets to transfer the forces to 72 anchor bolts embedded in the concrete mat foundation. Templates of the anchor bolt locations were used to fabricate and attach the steel brackets to the walls. The bolt holes had to line up with the anchor bolts. When the walls were hoisted from the barge and placed on the foundation, the brackets fit perfectly and the installation was a success.

The bottom elevation of the foundation trench box was below mean sea level, raising the possibility that sea water might flow in during high tide and that stormwater and surface runoff trapped inside the trench box might not be discharged into the sea. Because steel bolts and anchorage plates could rust under such conditions, undermining structural stability, a check valve was installed to control water flow.

Photographs, sketches, and computer graphics were used to develop the likenesses of the deceased. Recessed light shafts highlight the silhouettes, creating depth. The memorial is almost dark inside, day and night, intensifying the light on the faces.

Completion Date: 2004
Location: Staten Island, New York
Owner or Client: NYC Economic Development Corporation
Prime Consultant(s): WAI Prime; Masayuki Sono Architect

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