Researchers analysing 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,” said Julio Ramirez, a professor of civil engineering at Purdue University.
The report, recently prepared for the US National Science Foundation, details how the quake caused extensive damage to 180 buildings, including 48 schools and four dormitories in the eastern Turkey city of Bingol. One of those dormitories collapsed, killing 87 people, said Mete Sozen, Purdue’s Kettelhut Distinguished Professor of Structural Engineering.
Although Turkey has modern building codes, the report concludes: “There is a striking gap between the requirements of these codes and actual construction practice, both in the rural and the urban areas.”
Sozen and Ramirez led an NSF-sponsored US team of researchers and engineers from Purdue, the University of Kansas and the structural engineering firm of Wiss, Janney, Elstner Associates, headquartered in Northbrook, Illinois.
“What we observed was that the school buildings that failed had a fundamental and classic flaw,” 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 Sozen, an expert in reinforced-concrete structures.
The magnitude 6.4 Bingol earthquake struck at 3:27 a.m. 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, Ramirez said, and the likelihood of earthquakes makes this area a poor location for buildings with captive columns.
“If those buildings had been constructed differently, there probably would have been no loss of life,” Ramirez said. “In many instances, it would have taken just the addition a few reinforced-concrete structural walls in specific areas to prevent collapse.”
The walls would have aided the columns in supporting the weight of the building and helped control the “lateral deformation” of the columns, he said.
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,” 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.”