After many hours and multiple classes of reviewing and discussing which was the more efficient method for making an earthquake-resistant building, I concluded that my group and I were going to make an earthquake-resistant structure by using the Tuned Mass Damper method. The Tuned Mass Damper system, which is also commonly associated with the name Harmonic Absorber, is a device installed in buildings to decrease the structure’s amplitude of mechanical vibrations. Their application can prevent discomfort, damage, or outright structural failure to a high rise building. They are also frequently used in power transmission and automobiles.
Safety comes at a hefty price and standing by that statement, a tower’s tuned mass damper cost around US$4 million to build. A tuned mass damper (TMD) consists of three parts, a mass (m), a spring (k), and a damping device (c). When an external force is applied to a system, such as the ground shaking underneath a skyscraper, there has to be an acceleration. Consequently, the people in the tower would feel this acceleration. To make the occupants of the building feel more comfortable, tuned mass dampers are placed in structures where the horizontal deflections from the earthquake’s force are handled the greatest, effectively making the building stand relatively still.
Ideally, the frequencies and amplitudes of the Tuned Mass Damper and the structure should nearly match so that when the construction begins to oscillate or sway, the Tuned Mass Damper starts to take effect by creating an equal and opposite push on the building, and when the building is forced right, the Tuned Mass Damper simultaneously forces it to the left keeping its horizontal displacement at or near zero. However, if their frequencies were significantly different, the Tuned Mass Damper would create pushes that were out of sync with the forces from the earthquake amplitude, and the building’s motion would still be uncomfortable for the people inside, and the building would again experience too much action. The effectiveness of a Tuned Mass Damper is dependent on the mass ratio (of the Tuned Mass Damper to the structure itself), the ratio of the frequency of the Tuned Mass Damper to the rate of the formation, and the damping ratio of the Tuned Mass Damper (how well the damping device dissipates energy). Despite not having the material to make a real-life Tuned Mass Damper, we worked with the items that we had in the classroom. We concentrated on the fundamental features of the method, such as a mass that hangs from the ceiling which is the core of this techniques and springs attaching our weight to the roof. We made our centre out of 3 marbles wrapped up in aluminium and then attached four elastic bands around our counterweight. We then suck the elastic bands onto the top layer using hot glue.
It was a necessity to not have the mass be too dense because we decided as a group that if the mass was too large it’ll not swing and counteract the direction as well as it would’ve if the weight were not as heavy because the pressure will not be equal and could potentially bring the model to a particular side instead of creating a horizontal displacement near to zero. Our elastic bands attaching the mass and the top level of our model was vital to making the mass swing and generating a horizontal movement near to zero. We made sure that our elastic band was coated in hot glue to make sure it’s secure and would not break while in a shaking motion.Taipei 101, previously named as the Taipei World Financial Centre – is a well-known high rise structure located in Taipei, Taiwan. The judicious formation is one of the most commonly associated high rises using the Tuned Mass Damper system.
The Tuned Mass Damper is a ball of stacked steel plates measuring 18 feet in diameter and weighing 728 tons, suspended above Floor 87 by cables anchored at Floor 92. This system allows for withstanding typhoons and earthquakes, and it’s said to cut down on the swaying of the building by almost 40%. Acting like a giant pendulum, the massive steel ball sways to counteract the building’s movement caused by strong gusts of wind. Eight steel wires develop a sling to sustain the iron ball, while eight dampers function like shock absorbers when the orb changes. I believe that my group’s model demonstrates my chosen earthquake resistant building technique well. My team and I were able to create a model that was stable and a secure environment for the mass that we hand-made. Our model was made up of five double layers of cardboard which formed four firm levels.
By having a firm structure, this made our model’s structural integrity strong and was able to withstand a dominant side to side motion from the shake table. We decided to make our counterweight from scratch because we believed that we would have more control over the adjustability and we would be confident that the weight of the damper was not too heavy for just a cardboard model. Our model, however, did not have anything that we could attach it to the shake table other than connecting tape to the bottom cardboard level, this is the primary cause of damage and structural failure to our high rise cardboard model. Our model was able to withstand six seconds of intense shaking before the tape unattached, and our model fell to it’s right. After looking through our video of our model on the shake table, I concluded that our attachment to the model was done poorly. It was the cause of the fall, and our model was deeply affected by it either, which goes to show how strong our model was.
All things aside, our most thought out feature of our model was that it would be strong and would not be damaged after a harsh encounter, hence why we double layered most of our materials. I believe that we were able to do this successfully and even though our model fell over, it stayed in-tact. I also can see that our model was able to remain stable for so long because of the Tuned Mass Damper system that kept its horizontal displacement near to zero. Every time the model was thrust in a direction the counterweight would swing in the opposite which balanced out the sudden movements. Buildings, power transmission and automobiles that use the Tuned Mass Damper technique seem to have shown significant effect, improvement and progress from their previous state. For example, it’s been heard that Taipei 101 has cut down on the swaying of the building by almost 40%, which is fantastic progress.
Once looking over all of my research and data that my group and I had gathered regarding this project, I believe that my model was a well-done representation of a real-life building that used the same method. Despite not having the material to make a real-life appearing structure, I do think that we were able to show how the movement of the model and the mass counteract which creates a horizontal displacement near to zero.