Published: Dec. 20, 2018 By

San Fransisco skyline

San Francisco has many “non-ductile concrete” buildings.

While California and other seismically active parts of the U.S. haven’t had a major earthquake in over two decades, the next one could be particularly devastating. That’s because thousands of concrete buildings in high population areas are “non-ductile” – meaning they lack the extra reinforcing steel and seismic detailing needed to survive a massive quake.

It’s a problem that can be found up and down the coast from Los Angeles to Anchorage and it means that major cities in that area could see loss, not only to life and property, but to their local economies and housing supply. But addressing the issue isn’t cheap and owners face little motivation to update their buildings, which creates a pressing engineering and policy problem.

CU Boulder Associate Professor Abbie Liel has studied the issue through a CAREER Award from the National Science Foundation. Her work uses simulation to quantify how valuable retrofitting buildings would be for building owners and communities and how much work is actually needed to prevent some of the worst-case scenarios. So far, the work has shown that retrofitting these buildings is particularly effective at preventing loss of life and is a great aid to public safety.

“We think some of these buildings could be devastatingly deadly in the next earthquake – but don’t have good tools for understanding which are most vulnerable,” she said. “The work looks to fix that and define what you can accomplish with a retrofit because we know that we can solve these problems. So, if you retrofit all of these buildings in your city, what can you accomplish in terms of seismic performance? Logic says you can learn something by individual analysis, but you have to scale that to understand implications at the community level to make a case for retrofit.”

Abbie Liel portrait on blue background

Abbie B. Liel

The NSF Faculty Early Career Development, or CAREER, Award recognizes talented young faculty members with grants to support outstanding research projects and to encourage the integration of teaching and research. It is one of the most prestigious grants a faculty member can receive. Liel’s is set to finish this spring. She said the award was a chance for her to integrate various pieces of her work to provide context and address what the engineering community thinks is one of the biggest seismic safety concern right now.

Testing for these kinds of questions isn’t easy because every building is, essentially, built differently. You can’t test a building in one city and come up with an answer to those questions for every other building along the coast for example. Some buildings need reinforced walls or other large-scale work, while others may be fine with something smaller.

“One of the challenges for structural and civil engineering is that everything we build is totally different. We don’t build 100,000 widgets where we can test one of them a thousand times and know the other 99,999 are good,” said Liel who is based in the Civil, Environmental and Architectural Department. “All buildings are special children in their own way and figuring out how to understand, characterize and asses a building has its own challenges.”

With long-term research, there are always slight changes in direction and this project has been no different. Los Angeles recently announced plans to mandate retrofit of these non-ductile concrete buildings over the next 30 years and Liel said she has now found her work heading away from the question of “why should we” to the question of “how best” when it comes to retrofitting. The difference being a policy perspective and one she was eager to explore. 

“Where LA goes, often the other communities in southern California go too and San Francisco appears to be headed the same direction as well. So, it’s no longer about convincing the biggest city they need to do this,” she said. “Now we are saying ‘you could do it better this way,’ or how ‘how do you prioritize this in the face of other problems in a state like California where there are big wildfires for example.”

The NSF award has a required teaching and education component to it, which Liel worked into her probability and statistics class. During the semester, she took students to a Habitat for Humanity building project to get their hands a little dirty on a construction site. She said the combination of experience building structures and the end community benefit made for a fun project incorporating ideas about risk and uncertainty.

Liel said she is unsure where the work will go from here but is eager to continue working on the policy aspect. She said this kind of project was why she got into engineering in the first place.

“I wouldn’t be engineer if I couldn’t do something where I could see and have an influence on people. My motivation for the details comes from a desire to help protect people and communities. Those are the kinds of problems I have to work on to be happy in my career,” she said.