Unlike TMDs, AMDs require power and internet connectivity for operation and maintenance access. However, the current draw is very low (equivalent to a laptop), and a great amount of research has gone into developing a robust design that is essentially maintenance free. A key feature is these devices are plug-and-play, with very little tuning required. Being light and compact, the devices can be easily installed to the web of a beam or anchored directly to the floor (top or bottom).
Example time traces from the AMD installation are shown in Figure 3 for both the “AMD off” and “AMD on” conditions. The top plot is the acceleration versus time trace, and the bottom plot is the response factor, which is defined as the multiple of the ISO base curve (i.e. R=4 indicates levels four times the ISO base curve level). A fourfold reduction in response factors is observed with the AMD on, going from R=8 (ISO–workshop) to R=2 (ISO–residential night).
The choice between TMD and AMD is generally project specific. By proper design, both technologies effectively reduce vibrations and therefore, higher performance objectives can be attained. Response maps can be used in conjunction with TMD or AMD models to provide an understanding of where higher performance can be achieved. This can be very beneficial for adaptive reuse projects where combined structural-TMD/AMD solutions can be developed to optimize cost and performance.
Specifying vibration controls
When required, supplementary damping devices can be included in Division 10 – Specialties on building projects. These specifications will typically be developed by the vibration engineer as they require specialized knowledge and information. While some solutions are offered “off the shelf,” more often, they must be customized for the project. As a minimum, a well-written specification should include the following information:
- Number and locations of TMDs/AMDs.
- Total weight and anchorage forces for installation points,
for each device. - Access requirements for power, ethernet, maintenance,
as appropriate. - A list of qualified suppliers.
- Commissioning and performance verification test methodology and reporting requirements (factory and field, as appropriate).
- Requirements for submittals, such as shop drawings and performance verification test reports.
