How can damping be used to control vibration in structures?

Passive damping is achieved by adding damping devices or materials to the structure. These devices can include dampers, viscoelastic materials, or frictional elements. They absorb and dissipate the energy generated by the vibrations, reducing their magnitude. Passive damping systems are often effective in reducing resonant vibrations and can be applied to various structural components. Tuned mass dampers (TMD): TMDs are commonly used to control vibrations in tall buildings, bridges, or other structures. They consist of a mass-spring-damper system attached to the vibrating structure. The TMD oscillates out of phase with the structure's natural frequency, effectively reducing the amplitude of the vibrations.

From a Bridge Engineering perspective dampers are often used to lower the amplitude of traffic vibrations that propagate through the structure, leading to fewer cracks and less deformation. These dampers are often in the form of bushings or elastomeric bearings. Elastomeric bearings are large rectangular blocks of rubber, or elastic material, with metal plates embedded to evenly distribute load into the rubber. This allows very heavy structures, such as bridge girders, to sit on top of them and dissipate kinetic energy in the form of vibrations through them. By reducing these vibrations, bridge life can be extended, which is crucial for achieving the service life requirement of 75 years in the Canadian Highway Bridge Design Code.

From a utility perspective, we have had to deal with vibration of tall steel structures as well as entire building supporting gear. For steel structures we do review vibration and employ dampers (sometime just a steel chain). For larger buildings which support equipment, we do not recommend use of steel or composite construction. Concrete mass contraction helps mitigate many of these problems.

"Vibration damping is one of the three existing methods of vibration control, the other two being reduction of vibration in its source and vibration isolation ... On the other hand, vibration damping, or dissipation of mechanical energy, is arguably the most important phenomenon one needs to understand in order to successfully apply vibration control." - Vibration Control for Optomechanical Systems, World Scientific, 2022, p.167.

In my experience, using any kinds of these advanced methods in the structures is so promising to save energy and material and cost. I advocate smart ideas to make an efficient design which is environment friendly.

Various measures of damping (damping coefficient, damping ratio, logarithmic decrement, loss factor) are discussed in Vibration Control for Optomechanical Systems, World Scientific, 2022, p. 32-34 and 40-43.

(2/2) Lastly, there's the logarithmic decrement, which is a bit like measuring the distance between two dance steps. It helps us understand how gracefully vibrations fade away. Think of it as the elegant transitions in a waltz, where each step leads to the next with perfect harmony. So, in the world of structural engineering, damping isn't just about turning down the volume; it's about orchestrating a beautifully balanced performance where vibrations move in sync with our structures, creating a masterpiece of stability and grace.

(1/2) Damping, in the world of vibrations, is like the volume knob that helps us control the intensity of a musical performance. We have various ways to measure this damping effect – it's like having different musical scales. First, there's the damping ratio, which tells us how close we are to that sweet spot where vibrations neither die out too quickly nor linger too long. It's a bit like finding the right balance in a dance – not too stiff, not too loose, just right. Next, we have the damping coefficient – this one's like our conductor, directing the orchestra of vibrations. It quantifies how much force is needed to slow down the vibrations when things get too lively. It's our way of ensuring the music doesn't get too loud or too soft.

Damping controls structural vibrations by converting kinetic energy into heat or other energy forms, thereby reducing oscillation amplitudes. By tuning the damping ratio, engineers can achieve desired vibration reduction—under, at, or over critical damping. The damping coefficient is calibrated in devices like dampers to exert the right force against motion, tailored to the structure’s response characteristics. The logarithmic decrement helps in assessing and designing the damping capacity needed for specific vibration patterns, ensuring structures withstand dynamic loads without excessive motion or noise.

If the vibration is caused by resonance of the structural member with the frequency of dynamic factor, it can be resolved by increasing or decreasing the mass or inertia of the structural member.As well as increasing the degrees of freedom with kipping stability. But if the vibration is caused by the direct connection between vibration generator with the structure, it can be effectively controlled by using rubber dampers between them. In general, concrete structures perform better to deal with vibration

There are other damping models which depend on more than just one factor, including magnetic field damping (taking advantage of eddy current), which depends on the displacement change rate along with the magnetic flux. This can provide a wider range of controlling structural response against external excitations.

To control vibrations in structures, engineers implement damping models suitable for the expected dynamic behavior. Linear viscous dampers, ideal for proportional damping needs, are commonly used for constant vibration frequencies. Nonlinear viscous dampers cater to varying forces, often seen in erratic loading scenarios. Hysteretic dampers are utilized where displacement and energy dissipation history play a role, such as in earthquake-resistant designs. Frequency-dependent dampers are applied when vibration frequencies can change, needing adaptable control. Correctly modeled damping ensures structural resilience by efficiently reducing vibrations.

Damping in structures is strategically designed to minimize vibrations by selecting and placing dampers that suit the structure's dynamic properties. Modal damping targets specific vibration modes, while optimal damping balances performance with cost and reliability. Tuned mass dampers are set to the structure's natural frequency to counteract vibrations. Passive dampers absorb energy with no external power, active dampers adapt to changes via external control, and semi-active offer a compromise, adjusting resistance according to structural response, enhancing stability and longevity without extensive energy requirements.

According to D.I.G. Jones' chapter in Shock and Vibration Handbook, edited by C.M. Harris, there are the following types of damping treatments: free-layer damping treatments, constrained-layer damping treatments, integral damping treatments, and tuned dampers. See also Vibration Control for Optomechanical Systems, World Scientific, 2022, Chapter 7: Vibration Damping. Active damping should be added to the list, see the same book, Chapter 9. Original designs of vibration-damping devices can be found on pages 196-203 and 242-243.

The dynamic compliance test is an effective way to estimate the damping in the mechanical system. See Vibration Control for Optomechanical Systems, World Scientific, 2022, Chapter 7, specifically in application to vibration-isolated platforms.

Damping mitigates structural vibrations by absorbing energy, thus reducing the amplitude and intensity of oscillations. It's tested through experiments or simulations to match design predictions with real-world behavior. Effective damping ensures that dynamic loads, like wind or seismic activity, don't cause damage or excessive movement. Engineers adjust damping in structures by analyzing test data and refining damping devices or materials, leading to safer, more stable buildings and infrastructure that can better withstand environmental forces and usage stresses.

A recommendation that I always take into account in the case of steel buildings (where damping is very critical) is the design and control of a mixed slab (steel-concrete) with Enough Stiffness. In my experience I have been able to notice that vibrations increase drastically (and comfort is affected) when the slab is thin. This goes hand in hand with the comment about "Modify properties", of course, for this to be possible it must be in the design phase. In the case of existing structures, the most logical thing seems to be the addition of external dampers.

Adding damping materials: Incorporating materials with high damping properties into the structure can help dissipate energy and reduce vibrations. Tuned mass dampers: Installing tuned mass dampers (TMDs) can be effective in reducing vibrations in structures. Passive damping systems: Implementing passive damping systems such as friction dampers or fluid dampers can absorb and dissipate energy from vibrations. Active or semi-active control systems: Active and semi-active control systems use sensors and actuators to detect and counteract structural vibrations. Structural modifications: Adding additional supports, braces, or stiffening elements can help increase damping and reduce vibrations.

It is a process that converts vibrational energy into heat, eliminating the vibrational energy through friction and other processes.?Increasing damping or stiffness can both reduce resonant vibration and the resulting noise by preventing the vibration from travelling through the structure.

Damping acts by reducing the speed of the displacement so then the amplitud of that displacement will be less on the following wave and the structure will stop moving. If there were no damping, the structure will oscillate forever. Damping can be provided by several ways. The very same structural material, wood provides 4 times more damping than concrete, then concrete damps a little more than steel. The soil can also damp the earthquake waves for foundations. Tune mass dampers can damp by vibrating on the oposite way of the force at the same vibration period. Damping can also be by dampers at the structure to reduce the displacement speed so then the second wave displacement.

Damping in structures is crucial for controlling vibrations. It can be achieved through techniques like using viscous materials, implementing tuned mass dampers, enhancing structural damping, employing active or passive damping systems, and applying friction dampers or constrained layer damping. These methods effectively dissipate vibrational energy and reduce structural vibrations.

In structures, when you go to advanced structures dynamics, the waves from shock, strut systems cause more complexities, the gyro style causes more waves. The solution when working in structural dynamics and systems of equations is mass, the more mass, the better your structure damping is. However, when you reach the structures natural frequency, pure mass damping becomes a problem of nor being able to stop the vibrations. When you use a gyro, you can counter the natural frequency by changing the gyro, the strut and shock systems can be artificially Changed to change the natural frequency. The best solution is mass. Strut shock systems and gyro systems or swinging pendulum systems take you out of a static and dynamic equilibrium rigid body.

One of the most recent technologies in dampers is the use of TMD Tunned Mass Dampers which is a huge weight that function to stabilize the building structure in existence of movement caused by vibrations. These TMDs are mostly hidden weight in the structure elements and most of the high-rise famous landmarks contain one.

(1/2) In Structural Engineering, the damping in conjunction with the structures (RCC/STEEL) plays a major role apart from the vibration controls. The sources of inherent damping from the structure itself are the masonry wall-rcc frame friction, joints cracking and vibration. Specifically, in an earthquake resistant design of structures the response spectrum of 5% damping is considered from the codes and standards. The amount of damping required to dissipate the Earthquake forces in the form of energy (strain energy for structures) plays the major role for performance of the structures.