The quake faker: GWU 'shake table' helps engineering students brace for nature's wrath
Trying to find the high-tech research building that houses George Washington University's driving simulator laboratory in Ashburn can be challenging. There is construction along Route 7, a new overpass and limited signage. MapQuest is behind the curve; directions have been rendered obsolete.
The temptation to pick up a cellphone and call the folks at the simulator lab -- "Where the h*** are you guys?" -- is severe.
Don't do it!
That's the advice of graduate students Johann Moreau, 26, and Simon Bonnevie, 26, who are studying transportation safety at GWU and can rattle off the statistics from memory: You are four times more likely to crash if using a hand-held device. You're 20 times more likely to crash if you're texting. But these engineering students also understand the danger in a more visceral way. A few months back, Bonnevie swerved into oncoming traffic while texting and almost killed two pedestrians crossing the road.
But then, this was on the university's driving simulator.
The blue Buick Regal, its engine removed and a slew of wires connecting it to a nearby bank of computers, sits in a warehouse-like laboratory. On the large screen in front of the car, images of a road winding through suburbia flicker by. Moreau and Bonnevie, along with their classmates, conducted a series of tests on each other last year to find out how texting, talking on a cell, encountering external distractions (such as construction) and internal distractions (such as chatty passengers passing maps) affect driving safety.
This is just one of the ways GWU is using high-tech simulators to conduct research that eventually will help save lives.
Down the hall from the Buick is the "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."
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.