From motoring to construction, from power lines to wind generators. The Mass damper, Also known as dynamic absorber, is a device that is mounted on different types of structures in order to mitigate the negative effects deriving from vibrations.
On what concept is the mass damper based?
The purpose of the mass damper is to transfer the energy introduced by a force field into a vibrating system, deliberately sending a part into resonance to ensure that the remaining portion of the system is kept at rest. Buildings, including high-rise buildings with a high rise, are easily affected by fluctuations due to gusts of wind or earthquake shocks.
Il Mass damper can be of two types: passive, as in the case of Tuned Mass Damper (TMD), or active, Active Mass Damper (AMD).
The TMD (is an oscillating mass capable of discharging forces onto the structural elements on which it is anchored via a spring-damping connection. It allows the energy of movement of the structure to be "captured" around its resonance frequency.
- Active Mass Damper (AMD), the active and most advanced version of the passive device Tuned Mass Damper, consist of an auxiliary oscillating mass, operated by an actuator, which exerts a force on the mass, causing it to vibrate. The control force exerted on the structure is given by the inertia force of the mass thanks to the principle of action and reaction.
Who invented mass dampers?
The mass damping technique was first invented by Herman Frahm in 1901. Later, in 1909, the concept of Tuned Mass Damper (TMD) was developed when Frahm invented a vibration control device called a dynamic vibration absorber.
Il mass dumper was later applied to seismic da bill robinson, in the early 70s, who developed the seismic shock absorber, built using lead and high-density rubber to absorb the force of earthquakes.
Bill Robinson, earthquake engineer from New Zealand
From Asia to Europe – The Evolution of the Mass Damper
Mass dampers are systems adopted above all in Asia, where for decades they have been common anti-seismic solutions, capable of counteracting any type of vibration, even that of the wind, and for this reason used on very tall buildings, such as skyscrapers.
Certainly the most famous example of existing TMD concerns the skyscraper Taipei101 in Taiwan, where a 660-ton pendulum was installed, equipped with a total of eight enormous hydraulic dampers.
Diagram of the Taipei 101 building, Taiwan
The first implementation of a active control device on a building was with the adoption, in the 1989, of an AMD system in Tokyo within the Kyobashi Seiwa.
This 11-storey structure mounts inside two active masses of 5 tons in total (the weight of the building is approximately 400 tons) to counteract both the transverse motion of the building and the torsional motion from the actions of the wind.
Diagram of the Kyobashi Seiwa building, Tokyo
Active Mass Damper in Europe and Italy: the ISAAC cases
ISAAC has patented the first AMD-type active control system in Europe capable of significantly improving the global behavior of a structure subjected to a seismic event.
The system involves the installation of actuators on the roof of the building to be protected and of accelerometer sensors positioned in strategic points of the structure. A central computer coordinates and controls the entire system. The purpose of the latter is to counteract the motion of the building during the earthquake, going to reduce the oscillation amplitudes of the construction and consequently making the forces acting on the resistant structural elements less intense. This process takes place through the generation of forces by the machines, determined by the control algorithm implemented inside the central computer. The latter measures the accelerations of the building at the points where the sensors are positioned and, consequently, calculates the forces that the machines must generate.
The adoption of active control systems within civil structures allows to obtain improvements in the dynamic behavior of the building in the event of an earthquake comparable to those obtainable with the adoption of passive systems, but exploiting the advantage of less invasiveness during installation. A system of this type, in fact, makes it possible to intervene on the buildings without disturbing the inhabitants and allows the accessory preparatory work for installing the system to be reduced to a minimum.
The future of seismic protection is today. Find out more about ISAAC active protection systems.
