The high-rise mixed-use tower at 181 Fremont in downtown San Francisco houses Facebook’s new headquarters and residents of 55 multi-million-dollar condominiums, as well as a top floor $42 million penthouse.
What is instantly recognizable about the tower is its encasement of large ivory-colored beams zig zagged along its exterior before tapering on one side into a skyward spire. The aluminum exoskeleton serves as a giant shock absorber, improving the chances of the building’s survival in case of high winds and seismic events. As a result, the tower has come to be lauded as being invincible to earthquakes.
But risk and resilience engineer Ibrahim Almufti at Arup, the company that designed the tower, told Business Insider that’s not entirely true.
“Every time I read [earthquake-proof] I cringe,” Almufti said, a sentiment he said is echoed by most engineers.
Still, the high-rise might just be the tallest most resilient residential building in a seismic zone.
Here’s how it works:
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The mixed-use tower is divided into two sections around the middle: above the V-shaped zone are the 55 condos, priced at or north of $4 million each. Below is occupied by the tower’s sole commercial tenant, Facebook.
The ivory-colored exoskeleton hugging the tower is architectural and purely for aesthetic purposes. Behind the facade is where the heavy-duty, earthquake-fighting hardware is.
Tucked away inside those zig-zagged beams are sets of three parallel steel braces that run diagonally up the building’s sides.
The braces make up the secret sauce to the building’s resilience against seismic activity. Within the outside braces of the sets of three are viscous dampers, which in this case are devices used to cushion the blow of a seismic event.
They act as giant shock absorbers to combat the impact of a rumbling earthquake and allow the tower some room to sway. They’re not unlike ones you would find on your car, except that they’re stories tall.
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Source:: Business Insider