This is very exciting engineering news: Buildings that can not only survive an earthquake, but return to “true and plumb” with damage confined to a few easily replaceable parts.
“What is unique about these frames is that, unlike conventional systems, they actually rock off their foundation under large earthquakes,” Deierlein said.
The rocking frames are steel braced-frames, the columns of which are free to rock up and down within steel “shoes” secured at their base. To control the rocking and return the frame to vertical when the shaking stops, steel tendons run down the center of the frame from top to bottom. These tendons are made of high-strength steel cable strands twisted together and designed to remain elastic during shaking. When shaking is over, they rebound to their normal length, pulling the building back into proper alignment.
At the bottom of the frame sit steel “fuses” designed keep the rest of the building from sustaining damage.