The de Young Museum Revisited
THE HIDDEN STRUCTURE
Photographs of the interstitial level between the the ceiling of the upper level galleries and the roof bring to mind the areas above theater stages where the complicated mechanisms of staging are located. Here, in the museum’s attic, the light boxes designed to meet the lighting standards for the artworks therein rise above the ceiling. Catwalks surrounding them allow access to the boxes for maintenance.
There are two types of boxes. One has a stretched flexible PVC membrane flush with the ceiling and a secondary layer of clear PVC above it to catch dirt and bugs. The other type is recessed and has glass sides and drywall top. Daylight filtered through the rooftop skylights is mixed with artificial light.
To reduce the shadow effect caused by elements of other building systems such as sprinkler pipes, ceiling supports, and ducts related to the mechanical systems that snake their way around the catwalks, a translucent fabric was draped vertically between the light source and the outer surface of the light box. A tiny slit around the base of the box allows air to circulate.
Copyright: 2004 Rutherford and Chekene
Also invisible along the floor below are the full-story steel trusses that frame the structure allowing greater spans between columns and make ground floor columns unnecessary. Remarkably, only one free-standing column is visible on the main floor; it stands near the counter in front of the fern court.
On the upper floor most interior structural columns are concealed in the side sections of the floor-to-ceiling vitrines in the Pacific islands and Africa ethnic arts galleries. The columns extend below the floor and above the ceiling to the roof. Eliminating columns reduced the expense of the base isolators required for their support.
The exterior cuts that open up spaces for the entry and interior garden courts are framed in steel trusses with post-tensioned concrete perimeter girders. The areas most vulnerable to seismic damage–the 20-foot-wide passage between the pointed ends of the interior garden courts, the pointed end of the entry court, and the triangular cut for the education entrance–are reinforced with steel plates recessed in the concrete deck. (The steel plates are buried under the concrete floor and roof diaphragms to help transfer shear forces between the north and central wings of the main building. The system of plates will insure that these transfer areas remain elastic during very large earthquake events.)
Overall these strategies, along with the base isolation system, exemplify the kind of architectural and structural sleight-of-hand so important to the success of public buildings like the de Young Museum. It is regrettable that their magic is so rarely explained.
