Sand Could Be Key to Safer, Stronger Structures
OXFORD, Miss. – According to a University of Mississippi press release, engineers have been working to protect buildings, bridges, and other structures from severe weather and natural hazards damage for centuries, but one of the best methods may begin with sand, according to a new study published.
Many high-rise buildings, bridges, and other structures use dampers to mitigate vibrations and absorb vibration energy, reducing the amount of stress placed on the structure’s beams and columns. These devices help increase the building’s life span, but traditional, liquid-based dampers are costly and difficult to replace.
The new study, published in the ASCE Journal of Structural Engineering, shows that pressurized sand dampers perform better under extreme temperatures and provide a cheaper, more environmentally friendly option for construction.
“The damper is an energy dissipation device that you use every day,” said Liang Cao, incoming University of Mississippi assistant professor of civil engineering. “Every vehicle you drive has dampers to try to reduce vibrations. As civil engineers, we took that concept and applied it to modern structures, but typical dampers are oil-based or really complex mechanisms, and that makes it expensive to build.
“That’s where the sand damper comes in. Sand is inexpensive, easy to maintain, and environmentally friendly.”
Builders have long used dampers as energy absorbers to reduce damage from high winds, earthquakes, and other events. Traditional dampers are filled with oil or other viscous liquids, meaning if they fail, they can damage the surrounding environment and be expensive to replace, said Kostas Kalfas, assistant professor of structural engineering at Texas State University.
“When viscous dampers are subjected to continuous loading, this can increase the temperature inside the damper housing, resulting in the viscous heating effect that can in turn damage the end seals that protect the oil from leaking out,” he said.
“We cannot just go and add more silicon oil because viscous dampers are complicated mechanisms. It needs to be removed completely from the structure and sent back to the manufacturer for them to replace or repair it.”
While the dampers are damaged or are in the process of being replaced, the building is more susceptible to vibrations. While severe weather events could cause damage during this time, even normal wind and other weather can affect the building’s inhabitants, Cao said.
“In high rise buildings, even if the structure is fine, too much vibration means people may get motion sickness and can no longer work in that building,” he said. “So even if the building is structurally sound, you have an economic loss.”
Swaying skyscrapers have also been associated with tiredness, low mood and difficulty concentrating.
In comparison, pressurized sand dampers can be replaced or repaired within a few hours of being damaged, Kalfas said.
“The sand damper is very easy to build,” he said. “This is something that a lay person or a machinist can repair with human strength alone, so you don’t have to send it back to the manufacturer.”
Cao, Kalfas, James Ricles, professor of civil engineering at Lehigh University, and Usama El Shamy and Nicos Makris, professors of civil and environmental engineering at Southern Methodist University, tested sand dampers at internal temperatures of up to 140 degrees and as low as 42 degrees to ensure they could withstand extreme conditions.
The researchers also analyzed whether wet sand changed the damper’s ability to perform and found it did not.
“That means even if the humidity causes moisture to form in the damper, it’s still functional,” Cao said.
In the next phase, the researchers plan to test the sand dampers designed at Southern Methodist University both through simulations and in real-world situations using a large-scale structure.
“We have already shown that the damper is stable in different temperatures, different conditions, and now we need to do optimization tests for the dampers in dynamic conditions,” Cao said. “We want to show the effectiveness and test how it works in a full-scale structural system.”
This material is based on work supported by the National Science Foundation grant nos. CMMI-2036131 at Southern Methodist University and CMMI-2037771 at Lehigh University.
This material is based upon work supported by the Lehigh Natural Hazards Engineering Research Infrastructure Experimental Facility, which is funded by the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
