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US engineers study Chile earthquake to bolster California building codes

Since the Chile earthquake, dozens of US engineers have visited Santiago and other affected cities to study the failures and successes of building codes here. They say it provides valuable insights for California.

By Aaron NelsenCorrespondent / April 2, 2010

A view through a window of La Poza Quartier in Constitucion city, south of Santiago March 10. The February 27 Chile earthquake destroyed hundreds of thousands of homes, wrecked bridges and roads and cracked modern buildings in the capital of Santiago.

David Mercado/Reuters

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Santiago, Chile

In the Santiago district of Maipu, passersby kept a safe distance from a broken four-story apartment complex. But Mehmet Celebi, a research engineers, wanted inside.

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Mr. Celebi had come here from the office of the US Geological Survey in Menlo Park, Calif., to study concrete structures damaged by the massive 8.8-magnitude earthquake that rattled Chile on Feb. 27. Reluctantly, and a bit incredulous, a guard lifted a band of yellow tape to allow Celebi to pass. The building, as it leaned precariously, had become one of the now-iconic images of havoc caused by the quake.

Celebi pored over the building, looking for the design failures that caused walls at the base of the building to crumble.

"This is what you call 'soft story,' " Celebi said, using the term to describe buildings that are weaker at the lower level than up top. When the quake hit, the largest load came down on the weakest part of the structure and the walls buckled.

IN PICTURES: Images from the magnitude-8.8 earthquake in Chile

"I think we have observed this is crushing," Celebi concluded, pointing to twisted rebar spilling out from the wall's interior. "This is a prize from an engineering point of view."

In the wake of the fifth-largest earthquake ever registered, dozens of scientists such as Celebi are flocking to Chile to better understand how structures perform when pushed to the limit. The Earthquake Engineering Research Institute in Oakland, Calif., sent more than 30 researchers to record data from Chile's homes, hospitals, bridges, and apartment buildings.

A unique opportunity in Chile

Structural engineers typically work as consultants to the architect. The architect designs the look, function, and spaces in the building, while the structural engineer designs the skeleton that ensures the building will withstand wind, earthquakes, and other forces. This is done according to codes often based on computer simulations. But when an earthquake occurs, it provides a unique opportunity to study a 'living laboratory.'

"It's fascinating to see the kinds of things that we do calculations on every day do occasionally get put to their ultimate test," says Joe Maffei, a structural engineer and principal with Rutherford & Chekene in San Francisco, who made a recent trip to Chile to study the behavior of concrete structures in Santiago, two coastal cities, and ConcepciĆ³n, the city nearest the epicenter. "This is an opportunity to see if we are applying the science right in building codes."

Chile is of particular interest to American engineers. It employs similar building codes to those in California and also has widespread use of reinforced concrete.

One of Chile's more successful earthquake-resistant designs was a "base-isolated" building. The building is placed on rubber or sliding supports designed to dissipate energy the earthquake imposes. The disruption to these buildings was markedly less than for non-isolated buildings. Despite widespread damage, a remarkably small number of large structures collapsed.

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