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Arthur T Knackerbracket has found the following story:

Given the choice between safer and cheaper construction, many housing design companies in earthquake-prone developing countries see themselves forced to save on expensive construction materials and opt for the latter. EPFL structural engineers have gathered new data on how these structures respond to earthquakes, and in which circumstances they may fail.

Earthquakes almost never kill people by themselves. Instead, the high toll they take can be explained by a lack of resilient buildings and infrastructure. In Chile in 2010, many thin-walled reinforced concrete buildings were damaged in one of the strongest earthquakes ever recorded. Yet today, more and more structures with even thinner walls are being built in some Latin American countries. Recently, engineers from EPFL evaluated the stability of thin reinforced concrete walls to understand how they fail. Their findings are published in the journal Bulletin of Earthquake Engineering.

To find out how very thin-walled structures behave in an earthquake, João Almeida and Angelica Rosso, two of the study's authors, tested two 80-millimeter-thick, 2-by-2.7-meter wall segments, similar to those used in low-income housing projects in some South American countries. By clamping the wall segments to the floor of the laboratory and loading them with five actuators strong enough to slowly bend the walls back and forth in different directions, they simulated the impact of an earthquake on the structure. By slowing down the process the researchers had time to watch the damage spread and to find out how cracks propagate across the wall, ultimately destabilizing it.

"The data we gathered in our experiment is unique," says Katrin Beyer, the principal investigator of the study. "It is the first to contain detailed measurements of a so-called out-of-plane wall failure, which means that the wall structure was irreversibly deformed perpendicularly to its surface." According to Beyer, it was also the first time that displacements greater than the wall thickness itself had been observed under these conditions. By the end of the test, the wall's reinforcement bars had bent, with the concrete crumbling in one corner of the structure. Thanks to an array of sensors, cameras, and strain gauges, the researchers were able to capture and analyze every motion leading up to the collapse of the wall.

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