by Thousands of buildings in California are at fault with the buildings that collapsed in Turkey and Syria in early February, but experts say it’s unlikely a similar crisis could take place in the United States.
On February 6, two earthquakes measuring 7.8 and 7.5 magnitude hit Turkey and Syria, with further aftershocks only adding to the chaos. Millions were displaced and tens of thousands died while rescue workers worked around the clock to extricate survivors from the rubble. One of the main reasons that the buildings collapsed like “pancakes”. is the widespread use of non-ductile concrete, a building material that does not have much steel reinforcement and has poor resistance to seismic conditions. Ductile concrete is more heavily reinforced and can be subjected to more severe conditions before failure.
Terrence Paret, a senior engineer who has studied the seismic retrofit and conducted seismic risk assessments in Turkey, said that the presence of so much non-ductile concrete is why Turkey experiences “seismic tragedies about every decade.” gives. While the thousands of non-ductile concrete buildings in California are alarming, they aren’t nearly as prevalent as in Turkey, largely because such buildings stopped being constructed in the United States after a 1971 earthquake in San Fernando, California.
Still, thousands of buildings in California built before 1976, when new building codes made more stringent requirements, are made of the same material. It’s difficult to pinpoint an exact number of buildings, several experts told CBS News, but estimates range from a few seven thousand to as many as seventeen thousand buildings in the highest-risk counties. Most are residential, but some are schools and government buildings.
While these buildings share the same flaws as the Turkish and Syrian structures – they are fragile and are located in a part of the country prone to earthquakes and other seismic events – several “aggravating factors” mean such a crisis is unlikely Larger scale could occur on the west coast.
One key difference is attitudes toward such construction: California cities are actively working to retrofit buildings made of non-ductile concrete. The first such ordinance was introduced in Los Angeles in 2015, and other cities including Beverly Hills, Burbank and Santa Monica have enacted similar ordinances. Retrofits are slow, however: Los Angeles’ plan spans 25 years, and Karin Liljegren, an architect who founded Omgivning, a company focused on revitalizing downtown Los Angeles, and a white paper on non-ductile concrete retrofits, said she thinks that goal is unlikely to be met, despite “really positive movement” to see changes.
Another big difference is construction in the United States. Turkish buildings tend to have what is called “soft” or “weak” history on the ground floor, meaning that floor is more flexible or weak because a door, window, or other open feature is where a load-bearing wall would be and the lack of stability that would protect against an earthquake. This is less common in the United States due to building codes. Buildings with these floors in the US have also been retrofitted.
“What has collapsed in Turkey is almost entirely non-ductile concrete structure,” said Paret, who spent time in the country after a similarly devastating earthquake in 1999. “The buildings that have collapsed in this part of Turkey are endemic. . which is why so much in Turkey is at such high risk. We don’t have hundreds or thousands or millions of them, so initially the scale of the problem here is much smaller than there.”
Although the scale of the problem is much smaller in California than in Turkey, a major barrier to retrofitting is cost. Liljegren said this could quickly become a multi-million dollar lawsuit for many.
“Everybody wants to retrofit their building, but nobody has four million dollars,” said architect Liljegren.
Robert Kraus, a structural engineer, said early cost estimates in Los Angeles estimated it would cost about $150 to $200 per square foot renovated. Another issue is the invasiveness of the renovations: To retrofit non-ductile concrete requires “placing new, stiff members” around the older members to limit their movement in earthquakes and strengthen them, Kraus said.
“These naturally extend over most of the construction area,” said Kraus. “It’s not like you can stick it in a closet or smuggle it into too many places. Those are pretty big elements.”
