The Brilliant Idea: A replaceable, building-wide system to help hospitals, apartment buildings and office towers survive severe seismic shaking.
Innovators: Gregory Deierlein, Stanford University; Jerome F. Hajjar, Northeastern University
“Elastic high-strength steel cables run down the center of the system’s frame. The cables control the rocking of the building and, when the earthquake is over, pull it back into proper alignment.”
“A steel frame situated around a building’s core or along exterior walls offers structural support. The frame’s columns, however, are free to rock up and down within steel shoes secured at the base.”
“Steel fuses (in blue) at the frame’s center twist and contort to absorb seismic energy. Like electrical fuses, when they “blow out” they can be replaced, restoring the structural system to pre-earthquake conditions.”
For decades, the goal of seismic engineers has seemed straightforward: Prevent building collapse. And so they add steel braces to a skyscraper’s skeleton or beefier rebar to concrete shear walls. After absorbing the brunt of seismic shaking, however, the compromised structures often must be demolished. “The building, in a sense, sacrifices itself to save the occupants,” says Gregory Deierlein, a Stanford University civil and environmental engineer. A team Deierlein led with Jerry Hajjar, a Northeastern University engineer, hopes to change that, designing a system that protects both people and the structures they live and work in.
Last fall, the engineers successfully tested a 26-foot-tall, three-story, steel-frame building outfitted with the new system, built atop the E-Defense shake table—the world’s largest earthquake simulator—in Miki City, Japan. Steel “fuses,” not structural elements, absorbed the shock of an earthquake greater than magnitude 7, and cables pulled the building back into plumb once the shaking stopped. After an earthquake of that scale, the deformed fuses could be replaced in about four days—while the building remained occupied. Jim Malley of the San