Building on isolation bearings

Separate building sway from foundation travel and examine how an isolation bearing carries the resulting motion.

How does a building move on isolation bearings?

Monochrome sketch of a rubber isolation bearing between steel support plates beneath Pasadena City Hall
Reference sketch: an isolation bearing beneath Pasadena City Hall, adapted from a photograph.
Sketch from photo: Keithalanporter · CC BY-SA 4.0 · sketch adaptation

What you can model

A three-storey frame stands on a rigid foundation supported by one equivalent lead-rubber bearing. The diagram locates the bearing beneath the frame and shows the prescribed horizontal ground motion. The simulation connects foundation travel to structural sway, with displacements magnified ten times to make the motion visible.

Model diagram of the three-storey frame, equivalent bearing and prescribed ground motion.
Model diagram of the three-storey frame, equivalent bearing and prescribed ground motion.
Simulation of frame and foundation motion. Displacements are magnified ×10.

What you can explore

Compare roof motion relative to the foundation with foundation motion relative to the ground. Then read the bearing force–displacement loop to connect travel with the changing restoring force. These views bring structural deformation and isolation demand into the same study.

Structural sway, isolation travel and bearing hysteresis.
Structural sway, isolation travel and bearing hysteresis.

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