From The University of Washington (US) Civil & Environmental Engineering: “A new wave of research – Working to understand the chaotic nature of tsunami debris”

From The University of Washington (US) Civil & Environmental Engineering

In

The University of Washington College of Engineering

At


The University of Washington(US)

1.11.22

By: Brooke Fisher
Photos: Dennis Wise and Dana Brooks / University of Washington
Video: Kiyomi Taguchi / University of Washington

Making sense of chaos isn’t an easy task, but a team of CEE researchers is up for the challenge. With an elevated risk of a tsunami event in the Pacific Northwest, the researchers are working to better understand how debris collectively causes tsunami-induced damage in coastal communities.

1
A side view of the test specimen while it is struck by debris in the wave flume.

2
Associate Professor Mike Motley diagrams the test parameters being studied through the experiments.

“The idea we came up with was to really embrace the chaos of the event and the fact that debris is rarely a single shipping container. It’s usually a house that has separated into its individual components or a parking lot full of cars,” says CEE Associate Professor Mike Motley. “We are looking for ways to quantify something that is random and amorphous.”

The research is timely, with a major subduction zone earthquake predicted for the Pacific Northwest, which could trigger a tsunami along the Washington coast, extending up into British Columbia and down into California. The Cascadia Subduction Zone, which last ruptured in A.D. 1700, is active roughly every 300-600 years.

Cascadia subduction zone

“It’s a very urgent concern. There have been tsunamis in Chile, American Samoa, Indonesia and Japan. We are the one area that hasn’t been directly impacted in the past 20 years,” Motley says. “The interesting thing here is we get one shot — once the subduction zone event occurs, it resets and we wouldn’t expect to see another event for several hundred years.”

To ensure that structures are designed to withstand a tsunami event, the researchers’ goal is to inform the tsunami building codes used in the United States. Now in its second year, the three-year National Science Foundation-funded project is led by Motley in collaboration with CEE Professors Pedro Arduino and Marc Eberhard. Also involved are graduate students Nikki Lewis, Dakota Mascarenas, Justin Bonus and undergraduate students Abbey Serrone and Haley Herberg.


UW researchers look at how tsunami debris impacts buildings.

Debris damage

Joining forces with waves and water, debris can cause major damage during a tsunami. While existing research details how a single piece of debris impacts the built environment during a tsunami, there is a gap in understanding how different types of debris, called a debris field, interact with structures simultaneously.

“If you look at any tsunami event, the flow itself isn’t comprised of only water, but everything the tsunami picks up when it goes through an area. Debris can include trees, collapsed buildings, vehicles and fixtures,” says Ph.D. student Nikki Lewis. “Anything that can be swept away in a flow and transported to a different location can cause damage to another structure.”

To learn how different types of debris act together to cause damage during a tsunami, the researchers are investigating the collective forces in a debris field. They are also exploring a phenomenon called damming, which occurs when debris collects in an open space, such as between two columns on a bridge. This creates a dam that causes additional debris and fluid to accumulate, which may cause the structure to give way — and potentially join the debris field.

2
3
4
Top:Ph.D. student Nikki Lewis watches video from an overhead webcam in the wave flume that offers a better view of the lateral movement of debris. Middle: A field of debris of various shapes impacts the test specimen and accumulates, creating a damming force. Bottom: Undergraduate student Haley Herberg organizes debris for future tests. To study the effect of geometry and mass when the debris strikes the specimen, the debris was cut into various thicknesses and lengths.

Early experiments

By conducting repetitious experiments with slight variations, the researchers hope to identify patterns that emerge. During the course of 10 weeks, more than 400 trials were conducted in a wave flume that simulated tsunami-like waves at The Oregon State University (US)’s O.H. Hinsdale Wave Laboratory in spring 2021.

5
Tests conducted at Oregon State University entailed releasing debris into a wave flume, which tsunami-like waves transported to an orange instrumented box that measured the impact.

“If you take one piece of debris, it is easy to quantify the ways it impacts something, but there are a lot of ways numerous pieces of debris can orient themselves,” Motley says. “So, we tried to do as many realizations as we could, to look at how much randomness we would get and the disparity of results for tests that are to some extent the same.”

During the experiments, which ran continuously in 15-minute increments, rectangular debris blocks were lowered into a wave tank. Once released, a tsunami-like wave carried the debris toward an instrumented box equipped with sensors and other technology to measure the impact of the debris. The researchers used debris of varying sizes and quantity and arranged them in different configurations, from random to organized. The velocity of the waves also varied.

“If you envision a house that collapsed during a tsunami event, what remains could affect other structures in a random assortment of impacts. And so we tested configurations with various parameters, including how tightly packed the debris field was,” says master’s student Dakota Mascarenas, who led the experiments.

Subsequent experiments were conducted at the UW’s Harris Hydraulics Lab this autumn, as the researchers evaluated the facility’s capabilities in preparation for additional trials in the coming year.

“The idea moving forward is to have thousands of pieces of debris that can be introduced into the flume and will be representative of a tsunami-like event,” Motley says. “We hope to model the actual physical tsunami a little better on a smaller scale.”

Looking for patterns

Identifying trends and patterns in the preliminary data will enable the researchers to begin building computer models capable of predicting how a debris field will interact with structures during a tsunami.

6
Ph.D. student Nikki Lewis takes notes as an array of high density polyurethane blocks, which serve as debris, is deployed into the flume.

“We are already starting to see some trends shake out, such as trends based on the amount of debris that we put in the flume and the orientation of the debris field,” Motley says.

Considering the complex nature of a debris field, the researchers will combine multiple modeling methods: high fidelity fluid models that explore how water flows around rigid shapes and material point models that evaluate how objects interact in a fluid flow. The modeling work will be undertaken in collaboration with the Natural Hazards Engineering Research Infrastructure SimCenter at The University of California-Berkeley (US). In addition to predicting tsunami damage, the models will also help answer pressing questions, such as pinpointing what caused the ultimate failure of a structure — the tsunami or the earthquake.

“We are on a quest for understanding,” Lewis says. “We want to ensure that design guidelines are suitable for future tsunamis, which are so chaotic and unpredictable that it’s hard to intuitively say what will happen.”

See the full article here .


five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

The University of Washington (US) Civil & Environmental Engineering

Take a moment to look around you. Buildings, bridges, running water and transit systems are the work of civil and environmental engineers.
2
Civil and environmental engineers design, construct and manage the essential facilities, systems and structures around us. Their work plays a crucial role in enabling livable, sustainable cities, healthy environments and strong economies.

At the University of Washington, Civil & Environmental Engineering students and faculty are taking on the challenges presented by our aging national infrastructure, while developing new approaches to address the needs of urban systems and communities around the globe. UW CEE is dedicated to providing students with leading-edge technical skill development and opportunities for hands-on practice to enable them to tackle complex engineering problems in response to changing technological and societal needs.

Housed in an outstanding university, UW CEE offers one of the world’s premier programs in the field. The UW College of Engineering undergraduate program is ranked #18 and CEE’s graduate programs are ranked #16 for civil engineering and #27 for environmental engineering for 2020, according to U.S. News & World Report.

The University of Washington College of Engineering

Mission, Facts, and Stats

Our mission is to develop outstanding engineers and ideas that change the world.

Faculty:
275 faculty (25.2% women)

Achievements:

128 NSF Young Investigator/Early Career Awards since 1984
32 Sloan Foundation Research Awards
2 MacArthur Foundation Fellows (2007 and 2011)

A national leader in educating engineers, each year the College turns out new discoveries, inventions and top-flight graduates, all contributing to the strength of our economy and the vitality of our community.

Engineering innovation

Engineers drive the innovation economy and are vital to solving society’s most challenging problems. The College of Engineering is a key part of a world-class research university in a thriving hub of aerospace, biotechnology, global health and information technology innovation. Over 50% of UW startups in FY18 came from the College of Engineering.

Commitment to diversity and access

The College of Engineering is committed to developing and supporting a diverse student body and faculty that reflect and elevate the populations we serve. We are a national leader in women in engineering; 25.5% of our faculty are women compared to 17.4% nationally. We offer a robust set of diversity programs for students and faculty.

Research and commercialization

The University of Washington is an engine of economic growth, today ranked third in the nation for the number of startups launched each year, with 65 companies having been started in the last five years alone by UW students and faculty, or with technology developed here. The College of Engineering is a key contributor to these innovations, and engineering faculty, students or technology are behind half of all UW startups. In FY19, UW received $1.58 billion in total research awards from federal and nonfederal sources.

u-washington-campus

The University of Washington is one of the world’s preeminent public universities. Our impact on individuals, on our region, and on the world is profound — whether we are launching young people into a boundless future or confronting the grand challenges of our time through undaunted research and scholarship. Ranked number 10 in the world in Shanghai Jiao Tong University rankings and educating more than 54,000 students annually, our students and faculty work together to turn ideas into impact and in the process transform lives and our world. For more about our impact on the world, every day.
So what defines us —the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.