Buildings in California share a fatal flaw with those in the Turkey earthquake

As seismic engineers study earthquakes in Turkey and Syria that have killed more than 20,000 people this week, it is becoming clear that an important cause of the devastation involved building design common in California and other parts of the United States.

Faults in ductile concrete construction are found throughout the Golden State, with many buildings not being appraised or modified and at risk of collapsing in a serious earthquake.

It may be tempting for Californians to assume that their structures are inherently better than those of Turkey. But the state has not been tested by a magnitude 7.8 earthquake in more than a century. And this event – the Great Earthquake of 1906 – devastated much of San Francisco.

It will take time for structural engineers to prepare a comprehensive report on damaged and destroyed buildings in Turkey and Syria. But several experts, who looked at photos and videos of the splayed structures, said the underlying flaw was already clear: They were ductile concrete buildings, which have an improper configuration of steel reinforcing bars that allow the concrete to become brittle and snap out of the structure’s columns when shaken. .

“Most of the residential buildings in the area are made of fragile concrete and are highly vulnerable to earthquake-induced vibrations,” structural engineering firm Miyamoto International said in a statement.

Concrete frame buildings were popular after World War II and line many of Los Angeles’ most famous streets. But its fatal flaws were made internationally evident during the 1971 Sylmar earthquake, which occurred 52 years ago on Thursday.

In that earthquake, the officials were stunned to find that the newly built Olive View Medical Center was severely damaged. The five-story hospital was swaying sideways when some of its first-floor columns were blown off. Three concrete stairs fell. A two-story psychiatric building collapsed. Three people died.

Workers crowd the ruins of a Veterans Administration hospital in Sylmar, which collapsed in a 1971 earthquake.

(Bruce Cox/Los Angeles Times)

USGS simulations said it is plausible that a 7.8-magnitude earthquake in Southern California could cause 50 non-ductile concrete buildings to collapse in whole or in part, with up to 7,500 lives lost.

“We have several thousand of them all over California, and tens of thousands of Californians live and work in these buildings,” said James Dolan, professor of geosciences at the University of Southern California, an expert on fault systems in California and Turkey. “We know they won’t do well in earthquakes. It’s not a knowledge gap. We understand what happens to them when they get shaken in big earthquakes.”

These buildings have shown earthquake vulnerabilities around the world for half a century, including in Mexico and New Zealand.

The flaw was so severe that officials quickly banned construction of the non-ductile concrete design after the Sylmar earthquake and updated minimum building requirements to ensure that future concrete structures constructed in the 1980s and later would be ductile — or resilient — when vibrating. But for decades, governments around the world did not require that older buildings be updated.

Many local governments have not required concrete buildings to be evaluated or retrofitted, including some of California’s most populous cities, such as San Jose, San Francisco, and Long Beach. Three cities — Los Angeles, Santa Monica and West Hollywood — have ordered retrofits. But the Los Angeles deadline is decades later, scheduled for the 1940s.

Structural engineers have applauded mandatory retrofit orders, which were enacted after a 2013 Times investigation highlighted a failure of city officials to act. They were very concerned that other cities had not taken the same steps.

The USGS said in 2008 that non-ductile concrete structures are one of two types of buildings “most likely to kill people during an earthquake.” Unreinforced construction, including older brick buildings, is the other type. Many cities in California have ordered that unsupported masonry buildings be modified or demolished, although some—particularly in the Inland Empire—do not have such a requirement.

Miyamoto International’s CEO, Structural Engineer Kit Miyamoto, warned in an interview that failure to order retrofits for non-ductile concrete buildings will ultimately cost lives in California. Deadline LA was a long way away, he said, “but at least they have something there. At least the public awareness is there.”

If other cities don’t act, “this political weakness will kill people,” said Miyamoto, who is also California’s earthquake safety commissioner, and added that his comments were not on behalf of the commission. “They need to be retrofitted. Otherwise, you will see some consequences.”

Cyclists roll past the remains of a collapsed Kaiser Permanente clinic and office building in the San Fernando Valley after the 1994 Northridge earthquake.

(Jonathan Alcorn / Los Angeles Times)

Non-ductile concrete buildings in Los Angeles suffered catastrophic collapses in the 1971 Sylmar earthquake – with a magnitude of 6.6 – and the 1994 Northridge earthquake, with a magnitude of 6.7. When the Veterans Administration hospital in Sylmar fell during the 1971 earthquake, 49 people were killed. In the Northridge earthquake, Kaiser Permanente’s office and clinic and Bullock’s store partially collapsed.

“If your columns explode outward, your floors will turn into pancake,” Dolan said. “It’s the same thing over and over in earthquakes all over the world, where this type of building is very common. We know they will fail in the same way.”

Another reason buildings are vulnerable to collapse, Dolan said, is a lack of proper connections between vertical columns and horizontal floors, which break when shaken.

Other factors—including corruption in safety inspections and negligence and incompetence in design practices—contributed to collapses elsewhere. Government investigators investigating the collapse of the CTV building in Christchurch, New Zealand, during the 2011 earthquake found that the person dealing with structural design in the 1980s “was operating outside their purview”. The collapse of the structure killed 115 people.

The collapse of the Pyne Gould Corp building in the Christchurch earthquake killed an additional 18 people. In this case, investigators determined that the structure, which was built in the early 1960s to the standards in force at the time, could not have been legally built in 2011. Investigators also uncovered documents from 1997 showing that structural engineers hired by the building’s owner They warned of the possibility of collapse in an earthquake but also noted that “damage limitation measures are optional”.

Rescue workers surround the Pyne Gould Corp. building in Christchurch, New Zealand, on February 23, 2011, after a 6.3-magnitude earthquake.

(Hannah Johnston/Getty Images)

Some California cities say they are exploring retrofits for a different kind of flawed structure: soft-story apartment buildings—also called dingbats—that have often flimsy floor stories to accommodate cars or garages. The collapse of one of these complexes in the 1994 Northridge earthquake killed 16 people.

“At this time, we do not deal with non-strengthened concrete buildings,” Lisa Joyner, deputy director of the San Jose Department of Buildings, said in a statement. However, San Jose—Northern California’s most populous city—has requested an inventory of soft-floor apartments and is debating ordinances requiring modifications. Long Beach, the second largest city in Los Angeles County, does the same.

A decade ago, San Francisco became one of the first cities to require retrofits for thin-floor apartments. Of the nearly 5,000 buildings covered by city ordinance, 90% are now modified. But San Francisco is still not required to retrofit the non-ductile concrete buildings, of which there are 2,000 to 3,000 in the city.

“We’ve made steady progress toward developing a code,” Brian Strong, San Francisco’s chief resilience officer and director, said in an email.

Los Angeles, Santa Monica, and West Hollywood have laws that cover retrofitting of both non-stressed concrete buildings as well as soft-storey residential buildings.

But Dolan urged other California cities to work faster to address these fatal building defects.

“This is a really big threat to life and limb that needs to be taken very seriously,” he said.

More coverage of the earthquake hazards of concrete buildings

Times investigation: Buildings across Los Angeles conceal risk of collapse in earthquake

Why are concrete towers potentially unsafe?

Map: Where are the concrete buildings in Los Angeles? Search our database

UC’s list of applicable buildings

Los Angeles requires retrofitting of concrete buildings

Where LA stands with retrofits

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