GWU earthquake simulator helps engineering prepare for the real thing

George Washington University’s laboratory in Ashburn features a “shake table,” as students call the earthquake simulator. The table — a $1 million, 10-by-10-foot metal structure that moves in six directions — replicates earthquakes and allows engineering students to test construction materials to see how they hold up under tremors of varying strength. Last year, students built a 90 percent scale model of a bridge’s concrete columns to test how earthquakes affect such highway overpass supports.

“If I say, ‘the concrete is crushed and the column deformed,’ these are just words,” explains Pedro Silva, an associate professor in GWU’s Civil and Environmental Engineering department. “But if they can watch it fall apart, and if the bar fractures, they can witness it and feel it and then explain it mathematically.”

Karen Houppert writes that at the moment, Silva is gearing up for his next project with graduate students: building a scale model of a Haitian home using material and construction techniques employed by builders there. Using the shake table to create powerful tremors, Silva will watch how the Haitian house falls. The table moves as much as 8 inches in any direction and is built on 170 tons of concrete that dip 25 feet to 30 feet below to help keep the table’s vibrations from shaking the building itself.

“We will study the rubble and how the house collapses so that fire or search-and-rescue teams can see what area a person is mostly to survive in,” he says. “That way, if they have only a few minutes to go in, they will know where they should look first.” After this first experiment, Silva and his students will rebuild the house, retrofitting it with materials that will make it more structurally sound and efficient. “Not stronger,” Silva cautions, explaining that this term can be misconstrued. “With earthquakes, you want to build so that the house is more flexible.” They will then reactivate the shake table to test how well the altered structure withstands a quake.

For Silva, what makes this project so challenging — and interesting — is that neither he nor his students can work in isolation but have to think within the social and economic context of Haiti. In other words, it will not do any good for Silva’s research simply to identify the best material for reinforcing houses in Haiti; if it is costly or hard to come by, the upgrades will not happen.

Houppert writes that to that end, Silva also is partnering with other GWU departments and universities in the Caribbean to identify realistic options. At GWU, students in the engineering management department will analyze trash from Haitian landfills to see what salvageable materials might be recycled and cheaply redeployed to reinforce existing structures. They are casting a wide net. An abundance of plastics, metals, fruits and similar things might prove useful. Silva is feeling optimistic about mangoes. A factory to weave the discarded fibrous tissue might put out useful reinforcing material, he speculates, or maybe it could be baled into bricks?