The World is Our Laboratory A glimpse at CEE’s ground-breaking research

THE WORLD LABORATORY IS OUR

Over the past year, faculty from the School of Civil and Environmental Engineering have conducted research that helps us to better understand the world around us—from tiny microbes to massive ocean waves. Read on for a look at some of the interesting research produced by our CEE faculty.

Rolling Back Energy Regulations Loosening restrictions threaten progress against harmful ozone

Pollutants from coal-fired power plants help make ground-level ozone, and a warming world exacerbates that. Rollbacks of U.S. energy regulations may speed climate change, keep pollutants coming, and thus slow the fight against harmful ozone.

Currently, 30 percent of the U.S. population lives with ozone levels that exceed government health standards. Though past environmental regulations have vastly helped clean the air and put the U.S. on a positive trajectory to reduce pollutants — including ozone — policy rollbacks could slow the progress and even reverse it, according to a study led by Armistead G. Russell, Regents Professor and Howard T. Tellepsen Chair in the School of Civil and Environmental Engineering. Continuing progress against ozone would pay off in better health and finances: The more ozone in the air, the more cases of respiratory illness and the higher the cost of meeting ozone level targets.

“Additional ozone is tough to control technologically. The costs would be very high — tens of billions of dollars,” said Russell, a principal investigator on the study. “In the meantime, more people would die than otherwise would have.”

The researchers published their results in One Earth, a Cell Press journal, in October 2019. The research was funded by the U.S. Environmental Protection Agency and by the National Science Foundation.

The study focuses on ground-level ozone people breathe to the detriment of their health, which should not be confused with the stratospheric ozone that protects us from the sun’s harmful radiation.

In the last three years, various energy policies have been loosened, which should result in raised carbon dioxide emissions and continued emissions of ozone precursors in years to come, the study’s authors said.

“Incentives are being retired like production and investment tax credits, which have been very influential in solar and wind,” said Marilyn Brown, a Regents Professor in Georgia Tech’s School of Public Policy and a principal investigator on the study. “The Investment Tax Credit gives a 30 percent tax reduction for investments in solar or wind farms or the purchase of solar rooftop panels by homeowners. The Production Tax Credit for utilities reduces tax liabilities by 23 cents for each kilowatt-hour of electricity generated by solar, wind or other renewable energy sources.” —Ben Brumfield

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The Power of the Hypar

Researchers study the stuctural properties of origami

While perhaps not as iconic as the paper crane, the hypar origami with its sweeping opposing arcs and saddle shape has long been popular for artists working in the paper folding tradition.

Now researchers at the Georgia Institute of Technology and the University of Tokyo are looking at the shape with an eye toward leveraging its structural properties, hoping to find ways to harness its bistability to build multifunctional devices or metamaterials.

For a study reported in September 2019 in the journal Nature Communications and supported by the National Science Foundation, the researchers examined first whether the popular origami pattern that resembles the geometric hyperbolic paraboloid – or hypar – had the same physical characteristics as its geometric counterpart and tried to understand how its folds contribute to the formation of the pattern.

“The hyperbolic paraboloid is a striking pattern that has been used in architectural designs the world over,” said Glaucio Paulino, the Raymond Allen Jones Chair in the School of Civil and Environmental Engineering. “As an origami pattern, it has structural bistability which could be harnessed for metamaterials used in energy trapping or other microelectronic devices.”

Structural bistability refers to the origami

Professor Glaucio Paulino holds hypar origami

pattern’s ability to find a resting equilibrium in two different states – when the saddle shape reverses on itself. That capability could enable devices based on the origami’s structure to reconfigure to point the arcs in opposite directions on the fly.

Like any other origami, the pattern starts with a flat sheet of paper, which is then folded along concentric squares. Those folds combine to pull the tips of the paper in opposite directions, forming the opposing arcs of a hyperbolic paraboloid.

To understand more about the mechanisms that creates the saddle shapes, the researchers created a theoretical model that could serve to predict the behavior of the origami, and their analysis reinforced the idea that the structure exhibited the same characteristics of its geometric counterpart.

“One of the really interesting things we found was that the folds of concentric squares did not have to be uniform in their offsets in order to form the hypar origami,” said Ke Liu, a former graduate student at Georgia Tech and now a postdoctoral fellow at the California Institute of Technology. “So some squares could be quite close together and others farther apart and still the overall shape would be a hyperbolic paraboloid.” —Josh Brown

Withstanding Waves

Research on large waves could lessen impact

When cyclones or other massive oceanic storms make landfall, their giant waves batter coastlines and sometimes cause widespread damage.

Now, an international team of researchers has analyzed months of data of large nearshore waves to provide new insights that could help improve the designs of a variety of coastal structures from seaports to seawalls to better withstand destructive waves.

In the study published in October 2019 in the journal Scientific Reports, the researchers report combining a mathematical model to describe the formation of large waves with real-world measurements taken in shallow waters just off of the coast of Ireland, where waves have been reported to hit the shore with enough force to move 100-ton rocks.

“In this work we have analyzed real data in order to show that, over the course of several months measuring different storm events, we find that the extreme waves that we have observed in the coastal data tend on average to be smaller than the rogue waves we have observed in deep water, but they have similar characteristics,” said Francesco Fedele, an associate professor in the Georgia Tech School of Civil and Environmental Engineering.

“These large nearshore waves are still caused by constructive interference – the effect of waves coming in all different directions and basically meeting at one point and piling up to form a large wave, and by second order nonlinearities that distort the sinusoidal shape of waves to have sharper crests and shallower troughs,” Fedele said.

The research team also included M. Aziz Tayfun, professor emeritus from Kuwait University, Frederic Dias, a professor at the University College Dublin, and James Herterich, a postdoctoral associate at the University College Dublin.

In the study, which was sponsored by Science Foundation Ireland, the researchers analyzed measurements captured by an acoustic doppler current profiler (ADCP) device that was deployed for several months on the ocean floor off Killard Point during Spring 2015 and off the Aran Islands during Spring 2017.

—Josh Brown

Read more faculty research at: ce.gatech.edu

Sub-surface Soil Exploration

Advanced robot will improve sensing technology

An interdisciplinary research group from Georgia Tech has received a grant from the National Science Foundation to design an advanced selfpropelled robot to explore the subsurface and record a range of signals as it advances.

The project is led by principal investigator Chloé Arson, an associate professor in the School of Civil and Environmental Engineering. The research team includes faculty from across the Institute, including fellow Civil and Environmental Engineering Professor David Frost, Associate Professor Polo Chau from the School of Computational Science and Engineering, Professor Daniel Goldman from the School of Physics and Assistant Professor Frank Hammond from the George W. Woodruff School of Mechanical Engineering.

The Georgia Tech researchers will collaborate with four professors at Imperial College London for the three-year project. The grant, which is co-funded by the NSF and UK Research and Innovation, has a total budget of $1,765,477, including $800,000 for Georgia Tech. The joint project formally began on Jan. 1, 2020 at both Georgia Tech and Imperial College London.

The project aims to develop a multi-functional modular sensing system known as the Burrowing Robot with Integrated Sensing System (BRISS).

Most current geotechnical probes enter the soil vertically and record signals from one of several sensors that typically measure resistance force, fluid

A rendering of the research group's proposed multi-functional modular sensing system known as the Burrowing Robot with Integrated Sensing System (BRISS)

Photo by Miguel Vera

pressure or shear wave velocity. The result is a set of measurements that provide information from just the localized region around the probe.

In contrast, the proposed BRISS would incorporate a novel multi-sensor system and have the ability to advance in any direction vertically or horizontally, propel itself through the subsurface, and incorporate machine learning algorithms to instantaneously analyze data and implement investigation changes while soundings are in progress.

Researchers hope that the minimally-tethered robot will pave the way toward fully autonomous, wireless and multi-directional subsurface sensing technology that would ultimately revolutionize fields such as deep sediment characterization and extra-terrestrial exploration.

“This grant will support the development of a smart suite of tools to explore, characterize and model the subsurface with more accuracy and reliability than ever before,” Arson said. “We have the opportunity to push the boundaries of current knowledge in tribology, computational geomechanics, soft robotics, control systems, signal processing and machine learning to achieve our ambitious objectives. This collaboration between three colleges at Georgia Tech and three departments at Imperial College London provides a fantastic foundation to rethink subsurface characterization.”

Rising Tundra Temperatures

Effect on microbes could exacerbate climate change

Rising temperatures in the tundra of the Earth’s northern latitudes could affect microbial communities in ways likely to increase their production of greenhouse gases methane and carbon dioxide, a new study of experimentally warmed Alaskan soil suggests.

About half of the world’s total underground carbon is stored in the soils of these frigid, northern latitudes. That is more than twice the amount of carbon currently found in the atmosphere as carbon dioxide, but until now most of it has been locked up in the very cold soil. The new study, which relied on metagenomics to analyze changes in the microbial communities being experimentally warmed, could heighten concerns about how the release of this carbon may exacerbate climate change.

“We saw that microbial communities respond quite rapidly – within four or five years – to even modest levels of warming,” said Kostas T. Konstantinidis, the paper’s corresponding author and the Richard C. Tucker Professer in the School of Civil and Environmental Engineering. “Microbial species and their genes involved in carbon dioxide and methane release increased their abundance in response to the warming treatment. We were surprised to see such a response to even mild warming.”

The study was supported by the U.S. Department of Energy and the National Science Foundation and reported July 2019 in the early edition of the journal Proceedings of the National Academy of Sciences. Researchers from the University of Oklahoma, Michigan State University and Northern Arizona University collaborated with Georgia Tech on the study.

The study provides quantitative information about how rapidly microbial communities responded to the warming at critical depths and highlights the dominant microbial metabolisms and groups of organisms that are responding to warming in the tundra. The work underscores the importance of accurately representing the role of soil microbes in climate models.

The research began in September 2008 at a moist, acidic tundra area in the interior of Alaska near Denali National Park. Six experimental blocks were created, and in each block, two snow fences were constructed about five meters apart in the winter to control snow cover. Thicker snow cover in the winter served as an insulator, creating slightly elevated temperatures — about 1.1 degrees Celsius (2 degrees Fahrenheit) in the experimental plots.

Other than the temperature difference, the soil conditions were similar in the experimental and control plots. Soil cores were taken from the experimental and control plots at two different depths at two different times: 1.5 years after the experiment began, and 4.5 years after the start. Microbial DNA was extracted from the cores and sequenced using the Genomics Core at Georgia Tech.

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ce.gatech.edu —John Toon

Renewable Natural Gas

At scale, RNG systems could be climate intensive

Renewable natural gas is envisioned by some policy makers and energy strategists as a climate-friendly energy source that could be a substitute for fossil fuels to reduce our carbon footprint.

But research from Assistant Professor Emily Grubert finds that renewable natural gas (RNG) may not be a good climate solution in the long run. In a paper published in Environmental Research Letters, Grubert says that while promising, RNG has significant drawbacks, which include leaking methane into the atmosphere and competing with other lower-emissions resources.

RNG is essentially pure methane, usually derived from biogenic or captured carbon dioxide. What differentiates it from fossil natural gas (FNG) is that it utilizes greenhouse gases that would otherwise escape into the atmosphere—such as methane released from waste decomposition in a landfill.

But RNG is only carbon negative if in fact the methane is truly captured. Grubert says the amount of capturable waste methane available is very limited, and wouldn’t be able meet our current energy demands and serve as a replacement for FNG.

Some policy makers have proposed investments in reconfiguring the natural gas infrastructure to accommodate RNG, which could be supplemented with additional methane from other sources. Grubert’s research shows that even small leaks from the existing natural gas infrastructure would be significant because methane is such a potent greenhouse gas.

While RNG is less climate intensive than FNG, Grubert argues that it’s not the energy solution we should be focusing on.

A decade ago, the climate community talked about natural gas as a bridge fuel that would serve as a cleaner, albeit imperfect, alternative to coal. While renewable natural gas is an even cleaner alternative, it’s not zero carbon and shouldn’t be where we focus our time and resources.

“If this is something we could do temporarily that didn’t cost that much, that’s exciting,” Grubert said. “But much like we talk about FNG as a bridge fuel away from coal, there has to be an end date on RNG to get to a zero-carbon fuel system.”

Read more faculty research at: ce.gatech.edu