After landing in Taipei at 6am local time, we felt surprisingly energetic. Resisting the urge to lay down on our hostel bed for “just 10 minutes”, we went exploring and found ourselves at Taipei 101, a skyscraper that was the tallest building in the world from 2004 to 2010. Tickets to the observatory area on the 89th floor give you access to excellent 360 degree views of the city, but that’s not the only attraction. Geeks like me also come to see the tuned mass damper. The damper is even a cultural phenomenon of sorts — it has it’s own mascot, the damper baby!
As the name suggests, Taipei 101 (1671 ft, 509 m) has 101 floors (above ground). I would describe the architectural style most succinctly as “postmodern pagoda”, though there’s much more to it. The website of the architect, C.Y. Lee & Partners, has more background on the inspiration for the building and role of feng shui, which is actually very interesting. Check out this link if you want to learn more.
The tuned mass damper
Taipei experiences typhoons and earthquakes on a regular basis. Taipei 101’s tuned mass damper (TMD) was designed primarily to reduce movement of the building in wind events, but it also helps out in seismic events. To give you an idea of its effectiveness, the TMD is estimated to reduce movement of the building in wind events by around 40%! The concept behind the tuned mass damper can be described with various degrees of complexity, so choose-your-own-adventure below based on your interest level.
- Simple explanation: The tuned mass damper reduces how much the building sways during typhoons and earthquakes.
- Slightly-more-complicated explanation: The tuned mass damper acts as a pendulum to help dissipate vibrations in the building induced by typhoons and earthquakes.
- Complicated version: The tuned mass damper is a pendulum with a frequency “tuned” to match Taipei 101’s resonant frequency. When the building experiences vibrations due to a typhoon or earthquake, the movement of the TMD’s mass block (1, below) counters the movement of the rest of the building. The kinetic energy of the TMD’s mass block is absorbed by viscous dampers through compression/tension, reducing the amplitude of the vibrations more quickly than if the building were left on its own to damp out the vibrations. Taipei 101’s TMD is less effective for earthquakes because, as a very tall building, excitation of other building modes (i.e. less dominant building frequencies to which the TMD is not “tuned”) can have a significant effect on how much the building moves.
Taipei 101’s TMD is the largest and heaviest in the world. The 18-foot (5.5 m) diameter sphere, made of 5 inch (125 mm) thick plates welded together, is suspended from the 92nd floor and it runs all the way down to the 87th floor. All together, it weighs 727 tons (660 metric tonnes). It’s quite impressive to see!
Significant movement of the damper has been observed in several past events. The largest displacement of the damper was 39 inches (100 cm) during a typhoon in 2015. Check out the video below to see the damper in action during that event. The damper is designed to displace up to 60 inches (150 cm).
Earlier in 2015, there was a magnitude 6.6 earthquake off the east coast of Taiwan. The video below shows the TMD moving in that event, along with a crowd of blissfully unaware tourists taking photos in front of it. The shaking starts around 0:38 into the video.
Taipei 101’s tuned mass damper is a surprisingly beloved piece of engineering, and it’s popularity earned it a Sanrio mascot. There are several different damper babies, each with different personalities. Damper baby memorabilia of all kinds is widely available.
It’s not often that engineering and pop culture intersect, and it’s pretty amazing to see so many people get excited about structural engineering technology.
Stay tuned for next geeky engineering post about the 921 Earthquake Museum in Taichung!