Passive Energy Dissipation (Dampers)

While seismic isolation works by reducing input forces, damping systems manage the effects of those forces. Passive dampers absorb energy within the structure to reduce movement once shaking has already begun.

WHAT THEY ARE AND HOW THEY WORK

Passive dampers are devices installed in structures that absorb and dissipate earthquake energy, reducing how much the building shakes and how much residual deformation remains. Unlike active systems, they don’t need power or control systems — they work naturally in response to motion.

They are widely used in mid-rise buildings, bridges, industrial structures, and retrofits of existing buildings. They complement seismic isolation to ensure immediate occupancy and reduce acceleration and drift.

VISCOUS FLUID DAMPER

A fluid viscous damper has a piston moving through a fluid (often silicone oil). As the structure shakes, the fluid flows through restrictors, a resistance force develops, and motion energy converts to heat. Force is related to relative velocity, effective across various motion amplitudes.

Materials: Steel piston and cylinder, silicone or glycols with additives, seals and valves to control flow.

Best used in: High-rise buildings, retrofit projects, moderate to severe seismic regions, and structures needing both drift and acceleration reduction.

Pros:

Energy dissipation increases with motion
Doesn’t add stiffness (minimal impact on natural frequency)
Effective for a wide range of earthquakes

Cons:

Can be expensive
Potential fluid leakage requires maintenance
Optimal performance depends on proper coefficient sizing

VISCOELASTIC SOLID DAMPER

In a viscoelastic solid damper, a rubbery material deforms and converts motion into heat. They behave like both a spring and a damper, storing and dissipating energy simultaneously.

Materials: Polymers sandwiched between steel plates.

How it works: Deforms and converts energy through hysteresis — the elastic part helps recover shape, viscous behavior dissipates seismic energy. Good at small to moderate displacements and can also contribute some stiffness.

Best used in: Mid-rise buildings, cold climates (some designs account for temperature), industrial structures, moderate seismic zones, and buildings where both vibration and small seismic forces matter.

Pros:

Combines damping and stiffness
Works well for both dynamic loads (wind + quake)
Material-based energy dissipation

Cons:

Highly temperature-sensitive
Performance can vary with frequency and temperature
Not as effective at large drifts

METALLIC DAMPER

Metallic dampers have steel elements shaped to yield plastically during seismic motion, absorbing energy through controlled deformation. Cyclic inelastic deformation absorbs energy — the damper itself undergoes controlled damage instead of the main structure. This is similar to how structural yielding dissipates energy, but isolated in dedicated devices.

Materials: Specially shaped steel bars (sometimes tubes), cut and arranged to control yielding.

Best used in: High-seismic regions, buildings where simple and robust dissipation is desired, and locations where survivability after an earthquake is not the only priority.

Pros:

Simple, reliable, relatively inexpensive
Performs well over many cycles
Good for large displacements

Cons:

Can permanently deform after strong events
Adds hysteretic stiffness (structural response affected)

FRICTION DAMPER

Friction dampers are devices where seismic motion causes two surfaces to slide against each other under controlled normal force (e.g., steel on PTFE). Energy is dissipated through frictional heat. Friction force develops independently of stiffness, and energy is dissipated as heat through sliding resistance.

Materials: Polished steel plates, low-friction inserts (PTFE), clamping mechanisms.

Best used in: Systems with large displacements, bridges and buildings with unpredictable load patterns, and retrofit projects.

Pros:e

Robust and reusable (no plastic damage necessary)
Less sensitive to temperature than some dampers

Cons:

Not as effective at small displacements
Requires predictable friction properties under load

ORIGINS

Early Concepts — Mid-20th Century: The idea of using devices to absorb vibration energy in structures emerged in the mid-1900s, inspired by automotive shock absorbers and materials research. Early research focused on adding devices to buildings to reduce dynamic response to wind and seismic loads.

1960s-1970s — Laying the Foundation: As structural dynamics and performance-based design matured, engineers began systematically studying how supplemental elements could dissipate energy separate from the main load-bearing structure. Metallic yielding devices and fluid dampers were among the first to be examined analytically and experimentally.

1980s — First Practical Applications: Passive dampers began to appear in real structures:

Viscous fluid dampers adapted hydraulic principles from vehicles
Viscoelastic materials, originally developed for vibration isolation in machinery and aerospace, were applied to buildings
Metallic (hysteretic) dampers became recognized for their ability to absorb seismic energy without damaging primary structural components

1990s — Expansion and Refinement: By the 1990s, comprehensive seismic codes began acknowledging supplemental damping systems as a formal design strategy. Friction dampers, already in use in mechanical systems, were introduced to structural engineering, offering dissipation through sliding mechanisms.

2000s-Present — Widespread Adoption: Passive dampers have become mainstream in seismic design, especially in high-rise buildings, bridges, retrofit projects, and critical facilities where reducing drift and accelerations is essential.

PERFORMANCE EVIDENCE

1994 Northridge Earthquake (M6.7): In analytical and retrofit studies following Northridge, buildings equipped with viscous fluid dampers demonstrated substantial reductions in inter-story drift and acceleration compared to undamped designs.

1995 Kobe Earthquake (M6.9): Research using recorded ground motions from Kobe applied to analytical building models showed that metallic dampers significantly reduced peak story drifts, and viscous dampers decreased accelerations and residual deformations. These results matched physical shake table tests and supported the use of hysteretic and fluid damping devices in future designs.

2001 Nisqually Earthquake (M6.8): Buildings instrumented with dampers (especially VFDs and friction systems) exhibited smoother velocity histories and lower peak responses compared to controls.

2011 Tōhoku Earthquake (M9.0): While seismic isolation captured much attention, performance studies of structures with supplemental damping systems subjected to Tōhoku motions showed that viscous fluid and friction damper systems maintained structural integrity, and drift levels and acceleration demands were significantly lower than in conventional frames.

WINNER OF THIS CATEGORY

Viscous fluid dampers are the best passive energy dissipation (dampers) for the design criteria of this project because they

Add damping without adding stiffness (critical for isolation compatibility)
Perform effectively across all earthquake intensities
Have proven success in major earthquakes (Northridge, Kobe, Tōhoku)
Pair perfectly with FPS isolators to control displacement

For detailed scoring comparisons, see the Shock Absorption Mechanisms spreadsheet below.