Engineering experts from FIU and Lehigh University are using an innovative part-physical, part-computational testing method known as real-time cyber-physical modeling to get a full picture of how powerful winds affect tall buildings. This information is critical for building better, safer and more resilient high-rises.
The team’s test links a building model at FIU’s Wall of Wind, part of the Extreme Events Institute, with a model on a computer to create realistic simulations of how skyscrapers face powerful winds. The physical and digital buildings adjust to each other’s movements at 260 actions per second to remain in sync, creating an ultra-realistic simulation.
“If we only simulate a building in a computer, we are not getting realistic wind actions, and if we only simulate it in the laboratory, we are not mimicking a building’s exact changing position in the wind. These two models complement each other, allowing us to find new ways to make buildings resilient to natural hazards,” said Amal Elawady, an assistant professor of civil and environmental engineering at FIU’s College of Engineering and Computing and co-principal investigator of research at FIU’s Natural Hazards Engineering Research Infrastructure Wall of Wind Experimental Facility.
The research comes as major hurricanes are more common and high-rise buildings and offices are steadily developed. Tall buildings, like skyscrapers, are designed to sway in the wind without compromising the building’s structural integrity or occupants. Too much drift, however, can damage windows. Wind-driven rain can then leak into a skyscraper, creating structural problems, interior damage and human health issues. The swaying can be unsettling to residents or office workers and can cause nausea.
Cyber-physical testing is not new. It has been used for decades in earthquake studies, where natural disasters would be replicated and studied in slowed-down cyber-physical simulations. The Lehigh Real-Time Multi-Directional Hybrid Simulation Experimental Facility has developed cyber-physical testing for real-time applications where structural systems are subjected to extreme natural hazard events. Its application to wind has rarely been made before.
The video below illustrates how data is captured both at the Wall of Wind and in the computer simulation in real time.
“This is going to revolutionize wind tunnel testing,” said James Ricles, the Bruce G. Johnston Professor of Structural Engineering at Lehigh University, principal investigator of research at Lehigh’s Real-Time Multi-Directional Hybrid Simulation of Wind Experimental Facility and an expert in cyber-physical simulation of civil infrastructural systems subjected to natural hazards. “It’s impossible to bring a skyscraper into the laboratory, so we are linking a model in a computer with a physical model in the laboratory to obtain the most accurate results possible.”
In the cyber-physical test, a building model about the height of a mailbox records wind surface pressures, which are difficult to replicate in a purely cyber experiment. Then, the wind pressures are exerted onto the cyber model, representing a full-fledged building, and communicated back to the model in the laboratory about how the building should be expected to sway. Actuators attached to the building model at the Wall of Wind adjust the building’s position accordingly.
The pressure on one side of the building can affect how the whole structure sways, making these adjustments essential to understand how these buildings behave in real life. The wind speed, like the size of the building, is also scaled in the simulation. In the Wall of Wind, the wind speed increases up to 21.5 miles per hour, equaling a scaled-up wind speed in the simulation of 230 miles per hour.
While studying skyscrapers, the researchers are exploring how dampers, which are typically used for reducing vibrations in buildings, can best mitigate the negative effect of swaying.
After validating the testing method and completing recommendations for improving skyscrapers, the research team plans to study how hurricane-force winds affect other large civil infrastructural systems, such as transmission lines, wind turbines and long-span bridges.
Contributors to the research include Elawady, Ricles, Lehigh research scientists Liang Cao and Thomas Marullo, FIU Ph.D. candidate researcher Haitham Mohamed and Wall of Wind research scientist James Erwin.