Mills Peninsula Hospital
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| From Engineering Details |
Built to Rock and Roll…
Situated a mere 1.67 miles from the San Andreas fault, Mills Peninsula Hospital is located within seismic zone #4. To combat the threat of a massive quake, Mills Peninsula Health Services decided to install “Friction Pendulum” Seismic Isolation bearings made by Earthquake Protection Systems, an engineering firm and bearing manufacturer out of Vallejo, California, that designs and manufactures bearings for use in critical seismic applications all over the world. In conjunction with the 176 isolators, Mills has 32 linear viscous dampeners (shock absorbers) that inhibit lateral movement. This page will give you an understanding of how this award winning seismic system works here at Mills.
To begin, the foundation is constructed with concrete pedestals that the isolators sit atop.
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| From Construction |
The pedestals are cast on top of a spread footing foundation.
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| From Construction |
Once cast, the tops of the pedestals are roughened to a 1/4″ amplitude and shim packs are set in place to insure the bearings are set at the correct elevation.
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| From Engineering Details |
The bearings are then flown into place and set atop the pedestals.
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Before being pried off again to ensure there are no air gaps in the grout underneath the bearings.
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Once the bearings have been grouted in place, column bases are then bolted to the top of the bearing.
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And structural steel follows close behind.
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The mechanics of a seismic isolator…
The inside of Triple Friction Pendulum Seismic bearing is a concave surface with a large steel puck inside.
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| From Engineering Details |
And inside that steel puck, there is another puck.
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Put simply, the bearings literally isolate the structure from the moving ground below by permitting the building to move up to 30″ horizontally and 2″ vertically in an earthquake.
Click Here to see an animation of how the isolators work
To prevent the building from moving more than 30″ horizontally and literally falling off its foundation, large shock absorbers or viscous dampeners are connected to the structure and to embeds set within the foundation.
Here is a shot that shows the viscous dampener reaction blocks in relationship to the isolators.
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| From Engineering Details |
Up close, the dampener reaction block embeds look like this:
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| From Engineering Details |
Once the foundation is complete, the viscous dampeners are connected to the structure on one end and the dampener reaction block embed on the other.
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| From Engineering Details |
A pivot connection where the dampener connects to the reaction block allows for 30 degrees of movement.
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| From Engineering Details |
A completed portion of the base isolated building.
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| From Engineering Details |
Mills Peninsula Hospital 
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