What are Dampers? Why do we use them in High Rise Buildings?

Tejas Jain

Premium Member
Sep 14, 2017
51
92
Mumbai
The dampers are huge concrete blocks or steel bodies mounted in skyscrapers or other structures, and moved in opposition to the resonance frequency oscillations of the structure by means of springs, fluid or pendulums.

Sources of vibration and resonance.They work by creating a flexible connection to the foundation and the ground. That allows the buildings inertia to prevent the building from shaking it's self apart. The energy is dissipated across the damper instead of the critical support structures that hold the building together.

Unwanted vibration may be caused by environmental forces acting on a structure, such as wind or earthquake, or by a seemingly innocuous vibration source causing resonance that may be destructive, unpleasant or simply inconvenient.
Dampers are classified based on their performance of friction, metal (flowing), viscous, viscoelastic; shape memory alloys (SMA) and mass dampers. Among the advantages of using dampers we can infer to high energy absorbance, easy to install and replace them as well as coordination to other structure members.

Earthquakes

The seismic waves caused by an earthquake will make buildings sway and oscillate in various ways depending on the frequency and direction of ground motion, and the height and construction of the building. Seismic activity can cause excessive oscillations of the building which may lead to structural failure. To enhance the building's seismic performance, a proper building design is performed engaging various seismic vibration control technologies. As mentioned above, damping devices had been used in the aeronautics and automobile industries long before they were standard in mitigating seismic damage to buildings. In fact, the first specialized damping devices for earthquakes were not developed until late in 1950.

Mechanical human sources

Dampers on the Millennium Bridge in London. The white disk is not part of the damper.
Masses of people walking up and down stairs at once, or great numbers of people stomping in unison, can cause serious problems in large structures like stadiums if those structures lack damping measures.

Wind

The force of wind against tall buildings can cause the top of skyscrapers to move more than a meter. This motion can be in the form of swaying or twisting, and can cause the upper floors of such buildings to move. Certain angles of wind and aerodynamic properties of a building can accentuate the movement and cause motion sickness in people. A TMD is usually tuned to a certain building's frequency to work efficiently. However, during their lifetimes, high-rise and slender buildings may experience natural frequency changes under wind speed, ambient temperatures and relative humidity variations, among other factors, which requires a robust TMD design.

1. One Wall Centre in Vancouver — employs tuned liquid column dampers, a unique form of tuned mass damper at the time of their installation.
2. ATC Tower Delhi Airport in New Delhi, India — a 50-ton tuned mass damper installed just beneath the ATC floor at 90m.
3. London Millennium Bridge — nicknamed 'The Wobbly Bridge' due to swaying under heavy foot traffic. Dampers were fitted in response.
4. Bloomberg Tower/731 Lexington in New York City, NY