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The 1989 Loma Prieta earthquake was a double blow for the museum; not only did the turn-of-the-19th century building require repairs, but the potential for major damage by subsequent earthquakes eventually cost the museum the federal insurance critical for mounting the rare, irreplaceable exhibits that had earned the institution its world-class reputation. So the museum's budget hemorrhaged millions before it closed in 2000.

Plot Twists

The new 293,000-square-foot (27,000-square-meter) building opened in October 2005. Project manager Nuno Lopes of Fong & Chan explains it can move up to three feet (91 centimeters) due to a unique system of ball-bearing sliding plates and viscous fluid dampers that absorb kinetic energy and convert it to heat.

"During a seismic event, that building essentially is going to shake itself loose from the ground," Lopes says. The building would shift within a concealed moat, pushing up loosely fixed pavers around the building. Typically, the moat would be a covered, podium-like device, but that seemed incompatible with the design imperative of harmony with the park setting.

"Obviously for us to create that illusion of the building sitting grounded into the landscape, the idea of putting the building up on this podium was not very exciting," Lopes said. "So we early on decided that we needed to bury this podium."

Also, the tower and the three-story main building represented different engineering problems. While the tower is not seismically isolated, it needed an extreme solution to counteract its roughly 40-degree torque as it rises to the observation deck.

The architects decided to apply an innovative use of vertical post-tensioning cables in the walls. Lopes explains: "The top of the wall of the ninth floor is sitting on a staggered wall, so there's nothing directly below it. During a seismic event there are pressures for it to keep rotating in that direction. So you need to have a post-tensioning cable that is constantly pulling back on the tower, so you don't over-rotate."

Towering View

The dramatic tower lookout is a gift to the public. Going up is free, independent of museum admission. But the original plans had called for a much different view.

The initial design called for cloaking the entire tower with perforated copper. However, Lopes says, "The more everyone thought about it... they quickly realized it was probably not going to be a breathtaking view anymore if you have copper in front of it."

Only after the tower was in construction and the panels were going up was the decision made to remove the perforated metal intended to veil the panorama windows for the ninth-floor deck and the narrower slit several floors below.

Even though the top of the tower was to have the largest perforations on the facade, it would have been frustrating to "start peeking through these little holes out to this vast landscape," Lopes says.

But because the decision was made during construction, the architects worried that too much exposed glass would require major changes in energy and HVAC systems. The tower had not been designed to counteract the combined heat gains from the active occupants, the ambient summer air temperature, and solar radiation through the glazing. "So we had to limit the amount of exposed glass," Lopes explains.   >>>

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SUBSCRIPTION SAMPLE The new de Young Museum, in Golden Gate Park, San Francisco, designed by architects Fong & Chan and Herzog & de Meuron. Photo: Mark Darley The twisting, copper-clad tower. Photo: Mark Darley Gallery of the new de Young Museum. Photo: Jorge Bachman Site plan. Image: Fong & Chan Lower level floor plan. Image: Fong & Chan Ground-level floor plan. Image: Fong & Chan Upper level floor plan. Image: Fong & Chan Section looking northwest. Image: Fong & Chan   Click on thumbnail images to view full-size pictures.