The Aluminum rods of British Pavilion in Shanghai are void or soild?

Wednesday, September 22, 2010

Beekman Tower

Apartment buildings line the sidewalks of New York City’s streets. High or low, old or new, brick or glass, they define Manhattan neighborhoods. Before the real estate bubble burst and demand for luxury apartments could not be sated, savvy developers enlisted world-renowned architects to make their buildings stand out from the rest. Now, three such buildings featuring highly innovative facades are completing construction, from the Financial District to Greenwich Village to Chelsea.

Forest City Ratner hired none other than Frank Gehry to put his signature on what will be the tallest residential building in Gotham. The unprecedented stainless-steel folds that now drape all but the top few floors of the over-850-foot-tall Beekman Tower have already created a new landmark on Lower Manhattan’s skyline beside Cass Gilbert’s Woolworth Building and the Brooklyn Bridge. “I designed this building for New York,” says Gehry, FAIA. “I’m a deeply rooted contextualist regardless of what anybody says. I stair-stepped the building like a New York skyscraper. It fits in without pandering to, or copying, its neighbors.”

To produce the tower’s distinctive, wavy skin in a cost-efficient and easily constructible process, Gehry Partners (GP) developed a concept for a flat, unitized curtain wall with a back-ventilated rain-screen cladding attached to its front. The firm solicited technical proposals and cost estimates from three curtain-wall contractors early in design development. Permasteelisa, with whom GP had worked previously on such projects as the Guggenheim Museum Bilbao and the Walt Disney Concert Hall in Los Angeles, was selected to procure and engineer the wall through the construction-documents phase of the project in a highly collaborative effort that also included Gehry Technologies (GT).

Computer models of the T-shaped tower were created by scanning physical models, a process that produced point clouds of scalable data. Designers used Rhino software to do preliminary surfacing of the building, but once those forms were refined, the team switched to Digital Project, an offshoot of Catia, Dassault Systèmes’ aerospace and automotive design program, which GT developed to be a more user-friendly platform for the architecture and engineering community. “No other platform out there could have made Beekman Tower,” says Terry Bell, GP’s project partner. “It is the only one that has the ability to analyze surfaces in a sophisticated way that can be tied to parametrics and script writing.”

This was especially crucial as the tower’s design began to go through several iterations. Since work on the project began in 2003, the shifting economy caused dramatic changes in program, and even threatened to cut the building in half. “That was devastating for a while to contemplate,” Gehry recalls.

The switch from condominiums to a building composed entirely of rental units caused significant disruption to the facade because of adjusted floor-to-floor heights and smaller room sizes. “Whenever a unit changes, everything shifts on the surface,” explains GT’s Dennis Shelden. “The flow of the metal is different.”

The digitized physical surface allowed the designers the flexibility to tweak the facade yet still remain within established parameters. For instance, the rain-screen panels can curve out as much as 6 feet; the minimum projection is 6 inches. Throughout the process, Permasteelisa used the revised dimensions and geometries of the 10,300 curtain-wall units to update pricing and automate production.

“We developed a naming convention with Permasteelisa for the different units,” says Bell. “All the various component sizes, angles, and extrusion types could be tracked to a particular unit. They were also tied to the manufacturing process with CNC data through to fabrication and installation.”

While the facade is complex, the building’s concrete structure is straightforward. But because of the surface’s waves, each tower floor plate is unique (a rectangular, brick-clad structure forms the building’s base). Pouring the concrete slab became complicated at the slab edges, where 4-inch-deep aluminum embeds, to which the curtain-wall units are fit, needed to be precisely located. Three separate surveyors were used to verify the coordinates of the embeds

The 16-gauge stainless-steel face sheets of the rain screen were produced in Permasteelisa’s factory in Grand Rapids, Michigan, while the flat curtain-wall units were fabricated in its Miami facility. Despite the complicated geometry of the facade, the shop-fabricated wall assemblies of the unitized system made installation easy and economical.

The design team says there was no cost premium for the curving facade. The tower’s southern wall, by contrast, is completely flat. “That was a design choice,” says Gehry. “I wanted it to slice. When you see the building in profile from the east and west it looks like someone took a rock and cut it.”

1 comment:

Commercial Roofing said...

Rain screen cladding has become an integral part of the whole construction process.