Isolators Move Up To Allow Bigger Addition to Building
Structural engineers at Simpson Gumpertz & Heger have taken performance-based seismic design to new levels by placing compliant isolators, typically used under structures, on the 825 x 100-ft roof of an existing three-story building in San Francisco. The location a first in the U.S. according to SGH allowed the addition of 150,000 sq ft in two levels above the roof, instead of 50,000 sq ft planned when the concrete building was constructed.
The strategy allowed the $44-million project to proceed with minimal disruption to the mid-1980s building’s 400 occupants. Like a mother hen nesting, the 770 x 100-ft addition has become a giant untuned mass damper, reducing earthquake forces and displacement demand on the old building.