To build a building that can handle violent ‘quakes, all you need to do is make sure it shakes from its foundation.
Yes, you read that correctly.
A team led by researchers at Stanford and the University of Illinois has successfully tested a structural system that helps a multi-story building hold itself together through a magnitude-seven earthquake.
Even better? After the ‘quake is over, the system will return the building to standing straight and true on its foundation.
Somewhat like a car’s crumple zone, the system confines damage to a few easily replaceable parts. The secret to the system? Embrace the earthquake’s sudden shaking.
The system dissipates energy through steel frames in the building’s core and exterior. The frames are allowed to rock up and down within fittings fixed at their bases, anchored by steel cable “tendons” that run the length of each frame and prevent them from moving enough to shear the building.
The same tendons pull the frames back down into “shoes” at their bases, returning the building to an upright position.
So what about those “easily replaceable” parts? The system is designed to funnel dissipated energy through the frames and “tendons” to a flexible steel “fuse” (pictured, right) at the base of each frame, which “blow” — yep, like the electrical fuses in your house – when a quake occurs. Sacrificing themselves for the building, the fuses can be replaced after the damage is over.
The question, of course, is whether the fuses can handle aftershocks that can be almost as devastating as a real ‘quake.
The team tested the system at Japan’s Hyogo Earthquake Engineering Research Center by constructing a three-quarters-size model of a three-story office building. During testing on a massive shake table, the system survived simulated earthquakes in excess of magnitude 7, more severe than the 1994 Northridge earthquake near Los Angeles, Calif. or the 1989 Loma Prieta earthquake near San Francisco, Calif.
Best of all, the system can be retrofitted to existing buildings using readily available materials.
Stanford professor Greg Deierlein explains how the system works: