A Virginia Tech architecture professor has constructed the portable tuned mass damper (PTMD), a small, portable, inexpensive piece of equipment for reducing structural vibrations.
The device has potential uses in hospitals and labs, where sensitive equipment can too easily be negatively affected by environmental vibrations.
Crafted by the technicians at the college’s metal shop, the two-foot-high, 15-inch-wide box consists of plates, springs, and dampers that are tuned to the natural frequency of a structure.
It reduces vibrations by moving in the opposite direction of the structure, but at 10 to 20 times higher accelerations.
Mehdi Setareh, professor in the School of Architecture and Design, developed the PTMD with help from students.
The device has reduced vibrations by as much as 40–75% in the university's Vibration Testing Lab, as well as in campus buildings and a footbridge in the nearby Clifton Forge.
“With the increased use of modern, lightweight building materials to create elegant, flexible designs, we’ve seen an upsurge in the problem of structural vibrations,” said Setareh.
“While these vibrations are not necessarily dangerous, they can be disturbing to people and interfere with sensitive equipment and instrumentation.”
Tuned mass dampers are used worldwide to mitigate vibrations in structures like buildings and bridges, where excessive movement can be alarming or even sickening to occupants.
They are famously employed in landmarks like London’s Millennium Bridge, Trump World Tower in New York and Taiwan’s Taipei 101 skyscraper.
The dampers help minimise swaying from foot traffic and wind. The vast majority are multi-ton devices that occupy an average of 1,000sqft and are complex and costly to install, tune, and maintain.
Setareh’s PTMD presents an alternative; smaller than a nightstand and under 275 pounds, the device can be set up and adjusted by nontechnical personnel using a $5 iTunes application and Setareh’s instructions.
Mehdi Setareh, Virginia Tech professor, made the PTMD
The PTMD can also be integrated into the construction of a building or added as a post-construction corrective measure. Its small footprint means it can be put away in a cupboard or incorporated as a design feature.
“We are able to use them both as a fix or as part of the original design.”
“You can cut down on the cost of construction by using lighter steel beams and with devices like this, you can economically cut down the movement and vibration,” said Setareh.
Future development
Setareh has applied for a patent on the device and is working with students from the College of Architecture and Urban Studies and the College of Engineering to perfect it for commercial and industrial applications.
They are also working on new prototypes that can be integrated even more easily and effectively into building designs.
Setareh plans to package the device and place it on the market as a kit of parts. Each unit will include instructions on how to assemble, install, and tune it.
Though the units are mostly maintenance-free, the dampers may need adjustments every few years, depending on their level of use. These adjustments can be made by the consumer, following the re-tuning instructions included with each PTMD unit.
Mehdi Setareh
Mehdi Setareh is a professor in the School of Architecture and Design in Virginia Tech’s College of Architecture and Urban Studies. He is also founder/director of Virginia Tech’s Vibration Testing Lab.
Setareh is a nationally recognised expert on structural vibration. His 36-year career as an engineer has focused on using technology to study and enhance the interplay between structural design and vibrations.
He has earned national awards from the American Institute of Steel Construction for Innovative Design in Engineering and Architecture for his work on minimising vibration in a cantilevered corporate headquarters in Michigan and a monumental staircase at Michigan State University’s Broad Art Museum.
Setareh began working on the PTMD in 2014 as part of a National Science Foundation grant-funded project.
Virginia Tech
Virginia Tech’s Vibration Testing Lab is the only facility in the country dedicated solely to research on vibration serviceability issues.
Created in 2011 with major support from the NSF and industry partners, the lab houses a two-story, full-scale steel structure, embedded with sensors, dynamic signal analysers, force platforms and an assortment of sophisticated testing and measurement equipment.
Students use the lab in course-related work and serve as researchers and test subjects studying and solving structural vibration problems.
The students
Sriram Sankaranarayanan is a masters student in civil engineering.
“This research has been invaluable for me to apply in my future career,” he said. “Floor vibration is a serviceability issue in many structures.
“The work I’ve done here will help me as a structural engineer who is interested in seismic design and analysis.”
“Our work in the Vibration Testing Lab was eye-opening for me,” added Trey King, a third-year architecture student from Knoxville, Tennessee.
“It challenged me to think beyond aesthetics and building function and consider how my designs affect occupants in terms of vibration serviceability.”