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News Bits and Pieces -
November 01, 2005
Researchers analyzing damage from a 2003 earthquake in Turkey conclude in a recent report that the deaths of 168 people, many of them children, could have been prevented if minor design changes had been made to school buildings.
“Many lives could have been saved if a small number of reinforced-concrete structural walls had been in place in several of the buildings that collapsed during this event,” commented Julio Ramirez, a professor of civil engineering at Purdue University.
The report, recently prepared for the National Science Foundation (NSF), details how the quake caused extensive damage to 180 buildings, including 48 schools and four dormitories in the eastern Turkey city of Bingol.
Although Turkey has modern building codes in place, the report concludes: “However, there is a striking gap between the requirements of these codes and actual construction practice – both in the rural and the urban areas.”
Mete Sozen, Purdue’s Kettelhut Distinguished Professor of Structural Engineering, and Prof. Ramirez were the leaders of an NSF-sponsored U.S. team including researchers and engineers from Purdue, the University of Kansas and the structural engineering firm of Wiss, Janney, Elstner Associates Inc., headquartered in Northbrook, IL.
“What we observed was that the school buildings that failed had a fundamental and classic flaw,” Prof. Sozen said. “They had a feature called captive columns.
“This occurs when you build a reinforced-concrete column, which is nice and slender, and then you build a wall right next to the column but not as high as the column. That makes the unsupported portion of the column very rigid and brittle so that earthquake forces concentrate on the column, causing it to break.”
After one column breaks, the weight of the building is then concentrated on the remaining columns, causing them to break in series, resulting in the building’s collapse.
“It progresses like a zipper, with one column breaking after another,” said Prof. Sozen, an expert in reinforced-concrete structures.
The magnitude 6.4 Bingol earthquake struck on May 1, 2003, in a region of the world where the North and East Anatolian Faults converge. Buildings in earthquake-prone parts of the world should be constructed to endure the “lateral forces” exerted by the ground motion caused by the temblors, Prof. Ramirez said, and the likelihood of earthquakes makes this area a poor location for buildings with captive columns.
The report has been made available to Turkish officials in hopes that its findings will influence changes in construction practices there and in other parts of the world that are dangerously susceptible to earthquakes.
“The bottom line is that the schools are still out there, and what we saw in Turkey can happen in many parts of the world, certainly in the Caribbean and Latin America,” Prof. Ramirez said. “It’s important to note that it wouldn’t take very much to rehabilitate many of these existing buildings to make them more earthquake-resistant.”
The Virginia Engineer © IIr Associates 2005