Multidirectional Hysteretic Damper With Negative Stiffness

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Solution Overview

Problem

Existing vibration control solutions, such as dampers with negative stiffness, are limited by their unidirectional stress adaptation and inability to effectively handle multidirectional dynamic stresses like earthquakes or wind, which are stochastic and can occur in any direction, leading to inefficient energy dissipation and limited tunability.

Innovation Solution

A multidirectional hysteretic damper with negative stiffness is designed, comprising steel caps connected by a vertical connecting rod with a polyurethane spring and pre-tensioned ropes, allowing for adjustable negative stiffness and enhanced damping capabilities by utilizing oblique wires for stability and hysteretic damping, enabling effective energy dissipation across various directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If unidirectional dampers with negative stiffness are used, then negative stiffness control force is achieved, but multidirectional stress adaptation is lost

Engineering Contradiction:

Improvenegative stiffness control forceVSAvoidmultidirectional stress adaptation

Core Design Contradiction:

ForceVSAdaptability or versatility

Solution Approach 1:

The damper design transitions from unidirectional to multidirectional capability by introducing a spherical hinge connection that enables rotation in multiple directions. The connecting rod with spherical hinges at both ends allows the damper to adapt to stress vectors in any direction within the horizontal plane, while maintaining the negative stiffness control force through the same mechanical mechanism.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The damper is designed to perform multiple functions: it provides negative stiffness control force, adapts to multidirectional stresses, and dissipates energy through hysteresis. The universal design allows the same device to handle various stress directions and magnitudes, making it suitable for different vibration control applications without requiring direction-specific configurations.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Loss of energy

If friction-based isolators are used, then energy dissipation occurs, but sliding threshold must be exceeded first

Engineering Contradiction:

Improveseismic energy dissipationVSAvoidsliding threshold requirement

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The invention replaces the friction-based sliding mechanism with a hysteresis-based energy dissipation mechanism. Instead of requiring a threshold force to initiate sliding, the hysteretic damper provides continuous energy dissipation through its non-linear mechanical behavior, characterized by a hysteresis loop in the force-displacement relationship, which operates without a sliding threshold.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The damper utilizes changes in mechanical parameters during deformation to achieve energy dissipation. The hysteresis effect causes the force-displacement curve to form a closed loop, where the area enclosed represents energy dissipated per cycle. This parameter change approach allows energy dissipation to occur continuously during loading and unloading, without requiring threshold exceedance.

Inventive Principle:

Principle #35Parameter changes

3Force

If vertical isolation devices with springs are used, then vertical dynamic loads are handled, but negative stiffness and multidirectional capability are lost

Engineering Contradiction:

Improvevertical dynamic load handlingVSAvoidnegative stiffness and multidirectional capability

Core Design Contradiction:

ForceVSAdaptability or versatility

Solution Approach 1:

The damper design transitions from vertical-only isolation to multidirectional capability by introducing a spherical hinge connection that enables rotation in multiple directions. The connecting rod with spherical hinges at both ends allows the damper to adapt to stress vectors in any direction within the horizontal plane, while maintaining the negative stiffness control force through the same mechanical mechanism.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Loss of energy

If elastomeric elements are used for horizontal oscillation damping, then horizontal oscillations are dampened, but vertical isolation is compromised

Engineering Contradiction:

Improvehorizontal oscillation dampingVSAvoidvertical isolation effectiveness

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The vibration control system is segmented into separate functional components: the hysteretic damper handles vertical isolation and multidirectional energy dissipation, while the elastomeric element focuses specifically on horizontal oscillation damping. This segmentation allows each component to optimize its performance for its designated function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The damper significantly reduces structural stiffness and accelerations, amplifies equivalent damping, and provides adaptable performance across different stress levels and directions, achieving high vibration isolation efficiency with compact design and versatility.

Implementation Method 1

a vertical connecting rod (140) with a main body (141) and spherical hinges (145, 146) at its ends, which are rotatable in corresponding housings (125, 116) in the body of or rigidly connected to the respective facing bases (120, 110), a spring (170) arranged in one of the housings (125, 116)

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

The device consists of two steel caps, an upper one 110 and a lower one 120... a vertical connecting rod 140 with a main body 141 and spherical hinges (or 'heads') 145 and 146... a spring 170... pre-compression is achieved through the pre-tensioning of external ropes 180

Methodology Applied

Scientific EffectNegative stiffness:

Implementation Method 3

Methodology Applied

Scientific EffectHysteresis: Hysteresis

Implementation Method 4

enhanced damping capabilities by utilizing oblique wires for stability and hysteretic damping, enabling effective energy dissipation across various directions

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 5

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentUS20240401361A1Multidirectional hysteretic damper endowed with negative stiffness

Publication Date: 2024.12.05 UNIVERSITA DEGLI STUDI DI ROMA LA SAPIENZA

AI summary

Provided is a mechanical device to be connected in series or in parallel to a structure to be protected from dynamic stresses so as to vary mechanical features of the system and control the general dynamic behavior. The mechanical device is a multi-purpose rheological element employable in various applications including vibration isolation, vibration absorption, shock absorption, energy dissipation, and other applications based on rheological force-movement behavior.