Structures can be earthquake resistant and sustainable.

Several studies indicate that constructing safe structures in earthquake-prone areas can be achieved using sustainable materials ranging from massive timber to recycled tires.

Written by Alice Turner, Simpson Strong Tie Foundation Writing Fellow (@SeismoAlice)

Citation: Turner, R., 2024, Structures can be earthquake-resistant and sustainable, Temblor, http://doi.org/10.32858/temblor.346

The construction industry is one of the most energy-intensive sectors, accounting for 40% of global CO2 emissions. Steel and cement manufacturing are two of the main culprits. As of 2020, steel manufacturing alone was responsible for between 7% and 9% of global CO2 emissions from human activities, according to the World Steel Association. The manufacture of cement, the main ingredient of concrete, is responsible for a similar amount of these emissions. Furthermore, reinforced concrete—a super-strong material that resists collapse and often protects buildings from earthquakes in seismically active areas—is a combination of concrete and steel. Thus, its manufacturing process also contains the CO2-emitting power of both of its main components. But are there more sustainable alternatives? Ongoing research offers interesting options that could have significant potential.

The construction industry is one of the most energy-intensive sectors, accounting for 40% of global CO2 emissions. Image credit: Carbon Cure, Image: https://www.carboncure.com/wp-content/uploads/2021/11/Build-A-Low-Embodied-Carbon-Future-Infographic-01.png

Mitigating the effects of logging

Around the world, massive timber has become a popular alternative to concrete and steel. Massive timber products consist of layers of wood bonded together to form strong panels or beams. “Basically, [you] “We take smaller-dimensional timber, glue it together in layers and compress it together to make large timber sections,” says Eric McDonnell, a structural engineer at Holmes Engineering. Using timber instead of concrete and steel reduces the carbon footprint of construction, as the carbon that trees remove from the atmosphere during their lifetime continues to be stored in timber buildings.

“[Timber] “Wood is the only material we use in our buildings that can grow in sun and water,” says McDonnell. “I think there’s something wonderful and special about that.” Thanks to sustainable forestry practices, new trees are planted to replace those used in the building, mitigating some of the environmental impact of cutting down those trees.

The skyscraper on Lake Mjøsa in Brumunddal, Norway, is built from cross-laminated timber, a type of massive timber. Image credit: NinaRundsveen, CC BY-SA 4.0 via Wikimedia Commons

Unlike regular timber, massive timber panels and beams can be used to build multi-story buildings that are resistant to collapse in earthquakes. Large-scale shake table tests of timber buildings, such as the TallWood project, show that even massive 10-story timber buildings can withstand relatively large ground movements.

There are clear advantages to timber buildings in earthquake-prone areas. “A lot of earthquake damage is directly proportional to mass,” says McDonnell. Timber buildings tend to be lighter than concrete and steel alternatives. As a result, components designed to prevent collapse—such as reinforced frames and sheer walls—receive less lateral force, he explains. That means the building can sustain less damage.

Smart design features also play a role in the earthquake resistance of the 10-story building tested in the TallWood project. McDonnell says that four of the TallWood’s strong timber panels feature a “shake wall” design that allows the panels to move with an earthquake, and a metal beam pulls the walls back into place (or to a completely vertical position) when the shaking stops. The earthquake-resistant design also prevents the structures from being irreparably damaged, thereby reducing construction waste.

Recycled tires may protect buildings from impacts

According to the American Tire Manufacturers Association, American motorists throw away about 274 million tires each year. To save these tires from landfills, they are often recycled into shock-absorbing rubber flooring for children’s playgrounds. This led researchers at Edinburgh Napier University in the United Kingdom to ask: What are the physical properties of recycled tires, and what other uses are there for these recycled tires?

When testing recycled rubber, Juan Bernal Sanchez, a geotechnical engineer at Edinburgh Napier University in Scotland, found that the material was able to absorb a significant amount of energy. This observation led him to explore a potential application—protecting buildings from earthquakes.

Laboratory experiments show that by placing tiny particles of recycled rubber tires under or around a building—for example, in trenches—the rubber can act as mini airbags, says Bernal-Sánchez. In the event of an earthquake, the tiny rubber particles dissipate energy, protecting the building, he explains. But that’s not all. The rubber-filled trenches could also bounce some of the seismic energy back in the direction it came from, he says.

However, placing rubber in soil can also have unintended consequences, particularly on water flow and aquatic organisms. Recent studies have found that in most cases, these potential effects should be minimal. If that is the case, the researchers are exploring how encasing the rubber in recycled bags could mitigate such problems, says Bernal-Sanchez. Their goal is to prevent the rubber from interacting with the soil, while still maintaining the air cushion effect.

So far, Bernal-Sanchez and his colleagues have only tested the recycled rubber in the lab. But the project has just received funding to scale up—the recycled tires will be used to test the protection of a building in Thessaloniki, Greece, where real ground will be subjected to vibrations generated by a machine that simulates earthquakes.

Tires are one of the most problematic sources of waste. Advances in recycling have dramatically reduced the number of tires going to landfill. Copyright: ŠJů, Wikimedia Commons, CC BY-SA 3.0, via Wikimedia Commons

Concrete and cement

“Concrete is the most widely used human product in the world,” says Megan Stringer, a structural engineer at Holmes. Buildings made of reinforced concrete are tough, strong, ductile and remarkably earthquake-resistant. Reinforced concrete structures are also inexpensive.

Traditionally made concrete—a mixture of sand, gravel, water, and cement (made from limestone and clay)—may be responsible for up to 3.3 gigatons of carbon dioxide emissions annually. Since concrete will remain an important building material for the future, the concrete industry is working to address the problem, Stringer says. And since “cement alone accounts for about 90 percent of concrete’s environmental impact,” it makes sense to start there.

Look at this image showing the concrete manufacturing process and its contribution to greenhouse gas emissions.

Replacing some cement with materials such as fly ash, a byproduct of coal burning, or slag, a byproduct of iron and steel manufacturing, would reduce the overall carbon footprint. However, these potential substitutes come from energy-intensive processes, so moving toward a more sustainable future could reduce the availability of these byproducts.

Another possible option is to use less cement in the concrete, resulting in a mixture that has a higher proportion of other concrete ingredients. This could be a simpler way to achieve the same goal, provided the material properties of the concrete mix remain the same. Stringer says that a 10 percent reduction in emissions is possible based on just using less cement in the concrete mix. Mixes with less cement have been approved for use across the United States, including in seismically active states like California.

Sustainable Building Exhibition

Located in the greater San Francisco Bay Area, Marin County, California, is at risk for devastating earthquakes in the future. It is also the first county in the United States to pass a low-carbon concrete ordinance, making it a major testing ground for low-carbon concrete. There, all construction projects must comply with the ordinance by replacing or reducing the amount of cement used in concrete.

Massive timber is also being showcased in cities across the United States. For example, the Carbon12 apartment building in Portland, Oregon, is an 85-foot-tall timber building that also has a reinforced frame system, making it earthquake-resistant.

Future steps to decarbonize

These three examples—massive timber, recycled rubber, and low-carbon concrete—aren’t the only ways the construction industry can directly address decarbonization. Other new technologies are under development. “I’m excited about new bio-based materials made from fibers,” says McDonnell. For example, bamboo and grasses could be used in prefabricated building components.

Moreover, the future of sustainability is not limited to new buildings. The most sustainable building is the one that has already been built. The environmental impact of rebuilding or repairing after an earthquake can be significant. Following the 2011 Great Tohoku Earthquake and Tsunami in Japan, construction activities generated 26.3 million tons of carbon dioxide. While retrofitting an existing building has environmental impacts, research shows that the benefits of preventing collapse far outweigh the mitigation effects. Retrofitting an existing building also provides cost benefits, which can be calculated using CARE, the Carbon Leadership Forum’s retrofit estimation tool.

As societies move toward a greener future, the path to sustainability lies in innovative materials. “There are a lot of really exciting new technologies out there,” says Stringer.

But sustainability also requires thoughtful preservation to increase the resilience of the buildings we already have.

“Sustainability goes hand in hand with resilience,” says McDonnell.

References

Amirkhanian, A., and Skelton, E. (2021). 18- Applications of tire-derived concrete blocks in civil engineering. In T. M. Letcher, V. L. Schulman, and S. Amirkhanian (eds.), Waste tires and recycling (pp. 565–578). Academic Press. https://doi.org/10.1016/B978-0-12-820685-0.00016-8 Bernal-Sanchez, J. (2020). Cyclic performance of rubber-soil mixtures for enhanced seismic protection. https://doi.org/10.17869/enu.2020.2683555 Nehdi, M. L., Marani, A., and Zhang, L. (2024). Is net zero possible: A systematic review of technologies for decarbonizing cement and concrete. Renewable and Sustainable Energy Reviews, 191, 114169. https://doi.org/10.1016/j.rser.2023.114169Pan, C., Wang, H., Huang, S., & Zhang, H. (2014). The Great East Japan Earthquake and Tsunami Aftermath: Preliminary Assessment of Carbon Footprint of Housing Reconstruction. In Y. A. Kontar, V. Santiago-Fandiño, & T. Takahashi (Eds.), Tsunami Events and Lessons Learned: Environmental and Societal Significance (pp. 435–450). Springer Netherlands. https://doi.org/10.1007/978-94-007-7269-4_25Vratsikidis, A., & Pitilakis, D. (2023). Field testing of gravel-rubber mixture as geotechnical seismic isolation. Bulletin of Earthquake Engineering, 21(8), 3905-3922. https://doi.org/10.1007/s10518-022-01541-6Wei, H.-H., Shohet, I.M., Skibniewski, M.J., Shapira, S., & Yao, X. (2016). Life-cycle sustainability cost-benefit assessment of earthquake mitigation designs for buildings. Journal of Architectural Engineering, 22(1), 04015011. https://doi.org/10.1061/(ASCE)AE.1943-5568.0000188

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