Union City, CA
Bay Area Rapid Transit (BART), East Station Plaza, Danseurs (Dancing Ladies)
Union City sought to develop a civic plaza with a featured centerpiece and commissioned a terraced fountain with three bronze Danseurs on platforms positioned within the fountain. With the fountain located only 0.6 mi northeast from the Hayward fault line, SGH suggested mounting the 16 ft tall, 1800 kg statues on base-isolated platforms to limit damage during a design earthquake.
SGH provided structural engineering services for the fountain and the support structure for the sculptures. We proposed base-isolated platforms because base isolation would serve to protect the sculptures, but would be less obtrusive than an exterior bracing scheme.
For the design of the base-isolated platforms, SGH applied a concept similar to that used in base-isolated buildings, which are constructed on a suspension with springs and shocks to reduce the lateral forces. The isolation system for the sculptures utilizes cross-linear bearings and a bidirectional spring unit that acts as the energy dissipation element and the spring. To analyze the sculptures’ performance on the platform, SGH modeled the sculptures and steel platform as linear elastic elements and the spring unit as non-linear elements that followed the force-deformation response. In evaluating the seismic performance of the sculptures, we looked at the accelerations that the sculpture would experience and the stresses that would develop in the very narrow ankles of the sculptures.
Through the use of isolated platforms we were able to provide the architect and City an elegant solution to protecting their civic sculptures from earthquake damage.