Ever wonder how a 16-story building can float?
Yes, you read that correctly, and it’s the latest and most advanced technique for seismic building safety. It’s called "base isolation".
Think of a big, rectangular box. The area inside the box represents the hole in the ground where the hospital’s foundation will sit. Now picture this: the building itself will be smaller than the space allows.
Why? To allow the ground to move under the building in the event of a massive earthquake. This allows the structure to safely absorb the force of the quaking by moving laterally inside the security of the box — up to 40 inches in any direction — rather than crumbling because it had nowhere to go.
The box, in the case of the future Adult and Children’s Hospital towers which are part of Vision 2020, is a hole of the following dimensions:
Depth: 50 feet, three inches
Width side to side: 260 feet
Width front to back: 410 feet
In this hole, the foundation — four feet of concrete reinforced with rebar — will support steel pedestals.
These pedestals, currently under construction in Arizona, will be installed by the end of 2017, on top of which will be placed the base isolators — the moving parts that will control the building’s motion during a quake. The primary steel structure of the building will sit atop the isolators.
If you’re ever a patient in this new hospital complex during an earthquake some movement may occur.
Rest assured, it’s a good thing.