Improving occupant comfort by enhancing a structure’s dynamic response to externally induced motion
When a structure is subjected to external forces—wind, pedestrian movement or seismic activity, for example—it vibrates or sways. In tall buildings and on large bridges, such movement can make people uncomfortable. In other structures, it can hasten material fatigue or other failures.
There are ways to reduce this motion. For example, designers can add stiffness, add mass or change the shape of the structure. Unfortunately, such methods of reducing vibration are costly and may not work as well as needed.
An alternative method is to install a Tuned Mass Damper (TMD). This device adds mass, as in a traditional solution—but here the mass moves. This movement is passive, requiring no electricity or computer system to control it. The device simply responds to the structure’s movement according to basic physical principles and helps reduce it. Thus the moving mass supplements the damping already inherent in the structure.
A properly designed damping system can easily double or triple the inherent damping capacity of a traditionally designed structure. The result is far superior response.
Supplemental damping is usually less expensive and less restrictive than other solutions. Sometimes this strategy even makes an otherwise impossible structure possible.
We work in partnership with the entire project team—from lead architect to structural engineer to general contractor to crane operator—to provide practical, functional and reliable control of structural motion. The architect defines the shape; the structural engineer determines how to make that shape stable; we enhance the structure’s ability to dissipate the energy absorbed from the external conditions it will experience; the general contractor makes it real.
This approach has a lot in common with designing an engineered suspension for automobiles. Our goal is to smooth out the bumps without changing the look.
Our solution will be unique to your design, local conditions, budget and construction schedule. We understand the priorities and pressures of every stage in the process, and we have consistently met them for more than 20 years.
We combine three evaluations—external energy source, building response and damper dynamics—into one coherent (though complex) analysis. These analyses draw on our decades of experience worldwide with weather data and wind forces, seismic forces or pedestrian-induced loads, as the application requires. We use the resulting computational models to demonstrate structural performance both with and without various damping systems.
There are many options to consider. We have an in-house design for placing a large damping mass in a small space, especially in very tall, thin buildings. But if that solution isn’t right for your project, we’ll use another strategy. And our design process ensures that the device will fit in the designated space without incident. For every project there is an ideal solution that meets all requirements; we find it.
Before fabrication starts, we demonstrate how the device will perform, in detail. And we participate in its fabrication, installation, testing and commissioning, so you can be assured that the final system will perform as specified.
We have designed 59 mass damping systems that are installed or in progress in 15 countries. They are found in towers, bridges, air traffic control towers, architectural features and other tall structures, including bridge supports, an oil rig, a pinnacle and a spire.