How to Earthquake-Proof a Building
How do you earthquake-proof a building? Apparently it involves allowing the building to shake in a controlled fashion. Clay Dillow explains one new use of this approach:
A research team led by Stanford and the University of Illinois successfully tested a structural system that holds a building together through a magnitude-seven earthquake, and even pulls it back upright on its foundation when the quaking stops. The key: embracing the shaking, by limiting the damage to a few flexible, replaceable areas within the building’s frame.
When a quake strikes, the new system dissipates energy through steel frames in the building’s core and exterior. These frames are free to rock up and down within fittings fixed at their bases. Steel tendons made from twisted steel cables run the length of each frame, keeping the frames from moving so much that the building could shear. When the quake stops, these tensile tendons pull the frames back down into the “shoes” at their bases, returning the building to its plumb, upright position.
So where does all that energy go? At the base of each frame is a flexible steel “fuse” that takes the brunt of the force, keeping the frame and constituent tendons from shouldering the entire load. The fuses are easily replaceable when they blow — just like an electrical fuse — so after a quake, the building can be refitted with fresh fuses for its next bout with Earth’s occasional tectonic fits.