Researchers at Oregon State University have demonstrated that model buildings can play a significant role in providing valuable design information for low-lying areas that are vulnerable to storm surges and large waves. The researchers subjected two scale model structures to simulated storm conditions in the lab. The models responded the same way real wood-frame houses did during recent hurricanes.

"We wanted to establish a way to build scaled wood-frame specimens that would behave, and ultimately fail, under wave loading like their full-scale counterparts have been observed to," said Sean Duncan, who led the study as a graduate research assistant with the Oregon State College of Engineering. "And we also set out to develop an equation that could predict the distribution of the uplift pressure on elevated structures. We were able to accomplish both of those goals."

One model was built with the living areas off the ground and one was built on the ground, or “on grade.” The on-grade model was unable to withstand water levels as high as the elevated structure. This is what the researchers expected. Both structures sustained damage that was consistent with homes impacted by Hurricane Ike in 2008 and Hurricane Sandy in 2012.

The models were tested on a simulated coastline in the Directional Wave Basin at the O.H. Hinsdale Wave Research Laboratory. The basin is 48.8 m long, 26.5 m wide and just over 2 m deep. Multiple instruments measured the hydrodynamic loads. The waves and water depths replicated conditions during Hurricane Sandy.

The models were built to one-sixth scale and constructed with strength and stiffness that matched real residences in Ortley Beach, New Jersey, hit by Hurricane Sandy and those on Bolivar Peninsula in Texas that were hit by Hurricane Ike.

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Vertical forces on the elevated structure correlated with wave height, air gap and water depth, Duncan said, with the forces peaking in the deepest water at maximum submergence. Air gap refers to the elevation of the bottom of the lowest horizontal member, or LHM, of an elevated structure relative to the still water level.

"Uplift pressure is also affected by how and where the waves break," he said. "Waves that broke right on the specimens generally caused bigger vertical forces. And the predictive equation we developed, based on wave height and air gap, is valid for a range of structure length to wavelength ratios, wave heights, air gaps and water depths."

The extensive damage caused by these storms focused attention on the vulnerability of coastal communities to waves and storm surges, prompting more learning on designing and constructing storm-resistant homes, said Duncan.

The researchers also demonstrated the use of lidar (a remote sensing method) to track the progression of damage to the models during the simulated waves and storm surges increased in intensity.

"Populations in those types of communities are rising, and so are sea levels," said Duncan, now a ports and marine engineer with WSP U.S. in Federal Way, Washington. "That means risk associated with hurricanes is rising too, especially because research indicates hurricanes are increasing in intensity and will continue to do so. That's why it's so important to understand the forces these storms generate and how coastal structures respond, so planners and the construction industry can work together to mitigate the potential damage from these very likely, very potent storms."

Findings were published in Coastal Engineering (2021), and the research was supported by the Department of Homeland Security and the National Science Foundation

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