Researchers at the School of Engineering and Applied Science are really shaking things up.
The Robert A. W. Carleton Strength of Materials Laboratory in the department of civil engineering and engineering mechanics has been using its custom-designed shake table to relentlessly rattle a 10-foot-high, two-and-a-half-ton stone pylon to simulate earthquakes.
The pylon is a one-to-one model of the pinnacles that sit atop the National Cathedral in Washington, D.C., and the shaking is equivalent to an earthquake with a 5.8 magnitude tremor, like the one that rattled D.C. in August 2011 and cause millions of dollars in damages to the cathedral alone.
The Carleton Lab was contracted by the cathedral to design and test a new, more earthquake-resistant pinnacle to replace the one damaged by the quake. Cathedral stonemasons created the pinnacle model that was then trucked, piece by enormous piece, from Washington to New York, where it was assembled and tested in February.
George Deodatis, chair of the civil engineering and engineering mechanics department, said that the tests proved successful.
“The pinnacle sustained zero damage,” Deodatis said. “We looked very closely for any damage but it was impossible to detect even the smallest crack.”
Deodatis worked with Robert Mark, professor emeritus of architecture and civil engineering at Princeton, to design the new pinnacle.
“There's always a lot of excitement when you're testing something you have designed,” Deodatis said.
The new design included a metal rod to support its core—the original model was supported only with small bronze dowels.
“There is always some level of excitement, you always feel some pressure ... you don't want your model to sustain any damage,” Deodatis said. “Thankfully, the design proved to be an excellent one, but there is always a lot of excitement at the moment when the earthquake starts.”
The cathedral is working to adopt the lab's model for its pinnacles.
The cathedral tests are not the first time that Carleton has worked on the infrastructure of iconic buildings and bridges.
“The Carleton Lab frequently performs specialized testing in the lab or even field experiments involving the monitoring of infrastructure in New York City and elsewhere,” Andrew Smyth, the lab's research director, said.
Carleton often collaborates with federal, state, and municipal agencies as well as engineering consulting firms to perform diagnostic tests on critical infrastructure including bridges, Deodatis and Smyth said.
Recently, the lab undertook an extensive vibration monitoring project at the Metropolitan Museum of Art that Smyth said required the placement of specially developed automatic alert systems within the galleries to prevent damage to priceless, fragile artifacts by construction near the museum's Egyptian wing.
“This area of infrastructure monitoring is one of the department's core strengths: turning sensor data into valuable information for design decisions and infrastructure performance assessment and management,” Smyth said.
Civil engineering professor Maria Feng, who helped with the sensor instrumentation for the cathedral tests, said she took advantage of the opportunity to try out a new kind of sensor that the Carleton Lab is developing. These sensors use video cameras to track the movements of a structure's surface using certain points, which means the sensors themselves don't have to be installed on the surface.
According to Feng, the results from the new sensors “matched very well” with the standard sensors. Feng and her team recently applied for patents through Columbia, and “they have the potential to be commercialized,” she added.
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