11.3 Supplemental damping devices
2 min read•july 25, 2024
are game-changers in earthquake engineering. They boost a building's ability to handle seismic loads, reducing damage and improving safety. These devices come in various types, each with unique ways of absorbing energy and enhancing structural performance.
From that use to that act like giant pendulums, these systems offer diverse solutions. They not only make buildings safer but also allow for more innovative designs, potentially revolutionizing how we construct in earthquake-prone areas.
Supplemental Damping Devices in Earthquake Engineering
Role of supplemental damping devices
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- Improve to seismic loads reducing displacement and acceleration minimizing structural and non-structural damage
- Increase capacity absorbing seismic energy reducing demand on primary structural elements (columns, beams)
- Enhance occupant comfort decreasing perceived building motion during earthquakes and strong winds
- Provide design flexibility allowing for lighter structural members enabling innovative architectural designs (tall slender buildings)
Types of damping devices
- Viscous dampers use fluid-based energy dissipation exhibiting (piston-cylinder systems)
- include and dissipating energy through material deformation or friction
- Tuned mass dampers (TMDs) employ large mass connected to structure counteracting building motion ()
- combine viscous and elastic properties for energy dissipation ()
- (BRBs) special type of hysteretic damper preventing buckling under compression (steel core in concrete casing)
Principles of damping devices
- Viscous dampers generate force proportional to velocity dissipating energy through fluid orificing
- Hysteretic dampers:
- Metallic yield dampers dissipate energy through plastic deformation of metals (lead, steel)
- Friction dampers dissipate energy through sliding friction between surfaces (brake-pad materials)
- Tuned mass dampers create inertial force opposing structural motion transferring energy between structure and damper mass
- Viscoelastic dampers dissipate energy through of viscoelastic materials combining viscous and elastic response
- Buckling-restrained braces dissipate energy through yielding of steel core while preventing buckling with external casing
Effects of supplemental damping
- Reduction in structural displacement decreasing minimizing (second-order effects)
- Decrease in structural acceleration reducing improving equipment and occupant safety
- Modification of potentially shifting resonance away from dominant earthquake frequencies
- Increased enhancing overall energy dissipation capacity of structure
- Reduction in lowering demand on foundations (smaller footings)
- Improved providing more stable energy dissipation over multiple cycles
- considerations allowing tailored response for different hazard levels (serviceability, life safety)
- Impact on altering internal force patterns in structural members
- Influence on requirements potentially reducing ductility demand on primary structural elements
Key Terms to Review (27)
Base Shear: Base shear is the total horizontal force that a building or structure experiences during seismic events, primarily caused by ground motion. It is crucial for understanding how a structure will respond to earthquakes, as it influences the design and analysis of structures, ensuring they can withstand seismic forces while maintaining stability.
Buckling-restrained braces: Buckling-restrained braces (BRBs) are structural elements designed to provide lateral stability to buildings during seismic events by absorbing and dissipating energy. These braces prevent buckling under compression by using a specially designed casing that allows the core material to yield while remaining stable, thus improving the overall resilience of structures. The use of BRBs enhances the effectiveness of supplemental damping systems and plays a significant role in retrofitting existing buildings to meet modern seismic standards.
Compression buckling: Compression buckling is a failure mode that occurs when structural elements, such as columns, are subjected to compressive loads, leading to sudden lateral deformation. This phenomenon is critical in the design and analysis of structures, as it can significantly reduce load-carrying capacity and lead to catastrophic failure if not properly addressed. Understanding compression buckling is essential when evaluating the stability of structural components and implementing effective reinforcement strategies.
Dynamic response: Dynamic response refers to the behavior of structures or systems when subjected to time-varying loads, such as those caused by earthquakes or wind. This term encompasses the way a structure reacts in terms of displacement, velocity, and acceleration during dynamic events, which is essential for ensuring safety and stability. Understanding dynamic response helps in the design of buildings and infrastructures that can effectively withstand the forces imposed by such events.
Effective damping ratio: The effective damping ratio is a dimensionless measure that quantifies how oscillations in a structure decrease over time due to energy dissipation mechanisms. This term becomes especially relevant in the context of supplemental damping devices, which enhance the energy dissipation capacity of structures during dynamic loading, such as earthquakes. By understanding and optimizing the effective damping ratio, engineers can improve the performance and safety of structures under seismic forces.
Energy dissipation: Energy dissipation refers to the process by which energy is transformed into a less usable form, often through mechanisms such as damping and friction, during dynamic loading events like earthquakes. This process plays a crucial role in structural engineering by helping to absorb and mitigate the forces exerted on structures, ensuring their stability and integrity during seismic events.
Floor accelerations: Floor accelerations refer to the rate of change of velocity experienced by the floors of a structure during dynamic loading events, such as earthquakes. This measure is crucial as it influences how forces are transmitted through the structure and affects the overall response during seismic events. Understanding floor accelerations helps engineers design buildings that can withstand these forces effectively, leading to safer structures in earthquake-prone areas.
Fluid mechanics: Fluid mechanics is the branch of physics that studies the behavior of fluids (liquids and gases) in motion and at rest. It encompasses the principles that govern fluid flow, pressure, and forces acting within fluids, making it essential for understanding how structures respond to dynamic loads, such as those caused by earthquakes.
Force distribution: Force distribution refers to how forces are spread out or transmitted through structures during events such as earthquakes. In the context of engineering, particularly when using supplemental damping devices, understanding force distribution is crucial for designing structures that can effectively absorb and dissipate energy, ultimately reducing the risk of failure during seismic activity.
Friction dampers: Friction dampers are devices used in structures to absorb and dissipate energy during seismic events by converting kinetic energy into thermal energy through friction. They enhance the performance of buildings by reducing the forces transmitted to the structure during earthquakes, making them crucial for improving safety and stability. The application of friction dampers helps to minimize structural damage and enhance the overall resilience of buildings against seismic activity.
Hysteretic behavior: Hysteretic behavior refers to the phenomenon where a material or system exhibits different responses to loading and unloading cycles, often leading to energy dissipation and non-linear deformation. This behavior is particularly important in structures during seismic events, as it impacts how buildings respond to ground motion, influencing both their design and performance under earthquakes. Understanding hysteretic behavior helps engineers predict how structures will behave and allows for the development of more resilient systems.
Hysteretic dampers: Hysteretic dampers are devices used in structures to absorb and dissipate energy during seismic events, effectively reducing vibrations and improving stability. These dampers utilize the hysteresis phenomenon, where the energy dissipated during loading and unloading is different, thus helping to minimize structural damage during earthquakes. They can be implemented in various forms, such as braces or linkages, to enhance the overall performance of buildings and bridges against seismic forces.
Interstory drift: Interstory drift refers to the relative lateral displacement between two adjacent floors of a building during seismic activity or lateral loading. This phenomenon is crucial to understand because excessive interstory drift can lead to structural damage, compromised safety, and failure of non-structural components within a building. It is particularly significant in the design and evaluation of buildings with respect to their performance during earthquakes, especially when considering supplemental damping devices that can help mitigate such movements.
Metallic yield dampers: Metallic yield dampers are energy dissipation devices used in structures to absorb and dissipate seismic energy during an earthquake. They work by deforming inelastically, meaning they undergo permanent deformation to reduce the forces transferred to the building. These dampers play a vital role in innovative structural systems and supplemental damping devices by enhancing the overall resilience of structures against seismic events.
Natural Frequency: Natural frequency is the frequency at which a system tends to oscillate in the absence of any external forces. Each structure has its own unique natural frequency based on its mass and stiffness, which can significantly influence how it responds to dynamic loads like earthquakes. Understanding natural frequency is crucial for analyzing how structures behave during seismic events, as it helps in predicting the potential for resonance and optimizing designs to ensure safety and stability.
P-delta effects: P-delta effects refer to the additional moments and forces in a structure that arise due to the displacement of the structure's center of mass during lateral loading, such as during an earthquake. This effect occurs when the lateral displacements cause vertical loads to create secondary moments, which can lead to increased demand on structural elements and affect their stability. Understanding p-delta effects is crucial for accurately analyzing structural performance, especially when using nonlinear static procedures and when designing supplemental damping devices.
Pendulum systems: Pendulum systems are supplemental damping devices used in structures to reduce the amplitude of vibrations caused by external forces such as earthquakes or strong winds. These systems consist of a mass suspended from a pivot point, allowing it to swing freely, thereby absorbing and dissipating energy from structural movements. The effectiveness of pendulum systems relies on the principle of inertia, as the swinging mass counteracts building motions, helping to stabilize the structure during seismic events.
Performance-Based Design: Performance-based design is an approach to earthquake engineering that focuses on meeting specific performance objectives during seismic events, rather than solely adhering to prescriptive building codes. This method emphasizes the functionality and safety of structures, allowing engineers to evaluate how buildings will perform under different seismic scenarios and ensuring that they meet the desired levels of resilience and safety.
Polymer-based materials: Polymer-based materials are substances made from long chains of molecules, known as polymers, that can exhibit various properties depending on their composition and structure. These materials are widely used in engineering applications due to their flexibility, lightweight nature, and ability to absorb energy, making them effective in damping vibrations and enhancing structural performance.
Shear Deformation: Shear deformation is the change in shape of a material due to the application of shear stress, which occurs when forces are applied parallel to a surface. This type of deformation is crucial in assessing how structures respond during seismic events, as it influences the overall stability and integrity of buildings and bridges when subjected to lateral forces like those experienced during earthquakes.
Structural Ductility: Structural ductility is the ability of a structure to undergo significant deformations without experiencing failure, particularly during extreme loading events such as earthquakes. This property allows structures to absorb and dissipate energy, enhancing their resilience against seismic forces. High ductility is crucial for maintaining structural integrity and ensuring that buildings can withstand large movements while still remaining safe for occupants.
Structural response: Structural response refers to how a building or structure reacts to external forces, particularly dynamic loads like earthquakes, wind, or vibrations. Understanding structural response is critical for assessing the performance and safety of structures during and after such events, which helps in designing effective monitoring systems and improving damping mechanisms.
Supplemental damping devices: Supplemental damping devices are engineered systems that help absorb and dissipate energy during seismic events, thereby reducing the amount of motion transmitted to structures. These devices work alongside the primary structural components to enhance the overall stability and performance of buildings during earthquakes. By mitigating vibrations, they can significantly lower the risk of damage and improve occupant safety.
Tuned mass dampers: Tuned mass dampers are devices used to reduce the amplitude of mechanical vibrations in structures, particularly during seismic events. They consist of a mass attached to a spring and a damper, tuned to a specific frequency to counteract the vibrations caused by external forces like earthquakes. This technology has significantly improved seismic design practices, allowing buildings to better withstand the forces generated by ground movement.
Velocity-dependent behavior: Velocity-dependent behavior refers to the response of materials or systems that changes based on the speed at which they are subjected to loads or forces. This concept is particularly important in structural engineering as it affects how damping devices interact with dynamic loads, especially during events like earthquakes.
Viscoelastic Dampers: Viscoelastic dampers are devices that utilize the viscoelastic properties of materials to absorb and dissipate energy, particularly during dynamic loading such as earthquakes. These dampers combine the characteristics of both solids and fluids, allowing them to deform under stress and return to their original shape, which helps reduce vibrations and enhance the stability of structures. They play a vital role in innovative structural systems and are key components of supplemental damping devices designed to enhance the seismic performance of buildings and bridges.
Viscous dampers: Viscous dampers are devices designed to dissipate energy from structural vibrations, particularly during seismic events, by converting kinetic energy into thermal energy through the flow of a viscous fluid. They play a crucial role in enhancing the performance of structures by reducing motion and stresses, thereby contributing to overall stability and safety during earthquakes. By absorbing energy, they help protect both the structure and its occupants from excessive movements that could lead to failure.