Structural engineering for National Sept. 11 Memorial

The National September 11 Memorial & Museum, located at the World trade Center site in New York, commemorates the September 11 attacks of 2001 and the World Trade Center bombing of 1993.

Location

New York, USA

Client

National September 11 Memorial and Museum

Architect

David Brody Bond

Project Status

Completed in 2014

A Vast Invisible Structure to Support a Place of National Remembrance

The site is delineated by a landscaped Memorial Plaza containing two fountain pools, entitled ‘Reflecting Absence’. These 200ft x 200ft pools, which occupy the footprints of the original Twin Towers, are etched with the names of all those who died in the attacks. Beneath the park, descending as far as 70ft below the plaza level, is the museum, which contains hundreds of recovered artefacts. The museum is built up against the original slurry wall that held back the Hudson River on September 11 – this is now designated a federal landmark, and is one of the museum’s most dramatic exhibits.

Pool depth

30 ft 30 ft

Concrete shear wall thickness

4 ft 4 ft

Pool size (ft)

200 x 200 200 x 200

We provided structural engineering services to deliver the memorial and museum. The design and construction of this hugely significant and sensitive project was a very challenging task, considering the vast scale and complexity of both the plaza and the large space below. The 30ft-deep reflecting pools and waterfalls were designed to very strict standards and are an integral part of the overall structure. The plaza itself rests on heavy steel framing, which also forms the roof of the museum and chiller plant. This structure supports up to 6ft of landscaping soil, allowing the park to be lined with trees. The subterranean museum, meanwhile, required concrete shear walls up to 4ft thick, socketed up to 15ft into bedrock, to resist lateral pressure from the surrounding earth.