Staten Island 9/11 Memorial produced with vinyl ester resin
(Published on June-July 2005 – JEC Magazine #18)
Designed by architect Masayuki Sono, the 11.2-m tall monument, entitled “Postcards,” includes two, 3.65-m cantilevered, composite wings which rise in honour of the 9/11 victims from Staten Island. The 12.2-m long rectangular main boxbeams, consisting of 40-mm girders, were contoured to follow the shape of the sculpture’s “wings.”
Sono’s twin “postcards” makes a metaphoric reference to the site of the twin towers, and features touchable “commemorative stamps” that bear the name and profile of each victim. The wings frame a view of lower Manhattan featuring the former site of the WTC.
The monument was built by New England Boatworks (NEB) of Portsmouth, Rhode Island (USA). The challenge they faced with the memorial’s softly curving design was how to build it. They knew that postreinforced concrete would be unable to withstand the loads that high winds would impose on the design’s cantilevered wings.
After conducting a structural analysis, the engineers in charge of the project specified a composite laminate of E-glass, foam core, and vinyl ester resin. Once testing was conducted, Reichhold, Inc.’s Hydrex® 100-HF, low-styrene, 100% vinyl ester resin was selected, and NEB began building the structure using a vacuum infusion technique. The resin is designed specifically for the vacuum infusion process.
|Less expensive, much lighter with composites|
|By choosing composites instead of concrete, cost savings of 30% were realized. Composites decreased the weight of the piece by 90%. Building the Staten Island 9/11 Memorial gave New England Boatworks’ Composites team an opportunity to perfect the vacuum infusion process. To obtain the strength that the structure will need to withstand repeated flexing in high winds meant pulling resin through as many as 38 layers of heavy fibreglass. Small channels scored into the foam core allowed the Hydrex 100-HF resin to migrate.|
The vacuum infusion process uses vacuum pressure to drive resin into a laminate. Materials are laid dry into the mould and the vacuum is applied before resin is introduced. Once a complete vacuum is achieved, resin is “pulled” into the laminate via carefully placed tubing.
“Composite construction can withstand high loads and repeated flex without cracking,” noted David MacBain, a partner at NEB. “By applying composite technology to buildings and sculptures, we are able to find elegant solutions to structural problems.”