One Project, but Many Seismic Solutions
In order to submerge the moat cover without trapping it, the design team devised a 6-foot-6-inch-wide "pop-up zone" of loosely set pavers and planted material placed over a layer of filter fabric. During a major temblor, the cover will move back and forth and press on this zone, resulting in a small pile of debris. Although the museum and its contents should sustain no serious damage, "the impression will be that the [earthquake] took a heavy toll," says Lopes.
Early in the design of the de Young, engineers decided to use the crawl space around the bearings to house many of the building's services and use the adjacent moat area for exhaust. The arrangement keeps the lower structure's copper-clad roof, which Herzog & de Meuron refer to as the museum's "fifth facade," free of the clutter of mechanical equipment and reduces space devoted to ductwork above gallery ceilings.
This double use of the crawl space required careful coordination between the mechanical and structural teams. To avoid crushing equipment during a seismic event, engineers used the maximum displacement of each bearing and damper to identify a "no-go" space around each element, says San Francisco−based Ray Keane, an associate with Arup, the project's mechanical, electrical, plumbing, and lighting consultant.
The need for access to these areas for maintenance and service also raised security issues. A building lifted off its foundations and surrounded by an open zone could be vulnerable to intruders, points out David Fong, principal of Fong & Chan. An exhaust grille that can be opened only from the interior was just one of the myriad of details requiring careful scrutiny to safeguard the museum and its artifacts.