Structural weakening and addition of damping is an approach previously proposed for the reduction of seismic forces and drifts in the retrofit of structures. It is also used in the design of new buildings with damping systems. While this approach is efficient, it does not significantly reduce and may even amplify inelastic excursions and permanent deformations of the structural system during a seismic event. This paper describes a negative stiffness device (NSD) that can emulate weakening of the structural system without inelastic excursions and permanent deformations. The NSD simulates yielding by engaging at a prescribed displacement and by applying a force at its installation level that opposes the structural restoring force. The NSD consists of (a) a self-contained highly compressed spring in a double negative stiffness magnification mechanism; and (b) a gap spring assembly (GSA) mechanism which delays the engagement of negative stiffness until the structural system undergoes a prescribed disp...

Negative Stiffness Device for Seismic Protection of Structures

Dynamics of Structures: Theory and Applications to Earthquake Engineering by Anil K. Chopra

Negative Stiffness Device for Seismic Protection of Structures 13-0005.pdf

Smart structures: Part II — Hybrid control systems and control strategies

Application of shape memory alloy dampers in the seismic control of cable-stayed bridges

Pseudo-negative-stiffness dampers or PNS dampers are controlled variable dampers that produce negative-stiffness hysteretic loops. Negative-stiffness hysteretic loops are advantageous since dampers are usually set parallel to structure's members, which have stiffness. By adding negative-stiffness hysteretic loops, artificial nonlinearity is obtained but the total force would not be larger than the member's stiffness force. Common passive dampers set parallel to structure's members will have the total force larger than the member's stiffness force. Moreover, applications of the PNS damping to the benchmark control problems for seismic response reduction are also reported. The benchmark structures, consisting of cable-stayed bridges, buildings, and highway bridges, are excited by various types of recorded ground motions. The application of PNS dampers to those benchmark structures shows that this strategy is effective in reducing seismic responses. Recently, the new negative-stiffness damper was innovated and its effectiveness was experimentally proven. Copyright © 2009 John Wiley & Sons, Ltd.

Advances in the development of pseudo-negative-stiffness dampers for seismic response control

Effectiveness of passive and semi-active seismic response control on a cable-stayed bridge was studied by numerical analyses. An existing cable-stayed bridge which has fixed-hinge connections between deck and towers is modeled and its connections were replaced by isolation bearings and dampers. The isolation bearings are of elastic and hysteretic type. The dampers are of linear and variable type. The variable damper uses semi-active control that incorporates a pseudo-negative stiffness algorithm. A pseudo-negative stiffness hysteretic loop produced by the variable damper, combined with a positive stiffness curve of the deck-tower connections, creates nearly rigid–perfectly plastic force–deformation characteristics with a large damping ratio. The damping ratio for the main mode of the bridge for both passive and semi-active control was also calculated. Soil-structure interaction and three-dimensional effects on structural responses were studied. Copyright © 2002 John Wiley & Sons, Ltd.

Passive and semi-active seismic response control of a cable-stayed bridge

The effectiveness of a variable damper employing pseudo-negative stiffness control on benchmark cable-stayed bridges was studied. Combination of a pseudo-negative stiffness hysteretic loop produced by the variable damper plus elastic stiffness of the deck-tower connections produces a hysteretic loop that approaches rigid perfectly plastic force–deformation characteristics with a large damping ratio. The advantage is that sensors are required only at damper connections to measure relative displacements. Moreover, the small amount of sensors and simple algorithm reduce the source of errors and uncertainties. Comparisons are made between passive, pseudo-negative stiffness, and active control for the phase II benchmark bridge. The results of pseudo-negative stiffness control are significantly better than those of passive control and comparable to those of active control. Copyright © 2003 John Wiley & Sons, Ltd.

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Application of pseudo-negative stiffness control to the benchmark cable-stayed bridge

Research shown in this paper is focused on the development of an autonomous semi-active control laws as simplified semi-active control algorithms for seismic response reduction. The strategy of the methods is to produce desirable hysteretic loops to absorb as much energy as possible by semi-active devices. The control method requires information only on the device's displacement and velocity.



The hysteretic loops produced by the semi-active control herein provide energy absorption capacity similar to those by friction dampers, while minimizing the disadvantages of the friction dampers, such as residual displacement after strong earthquakes and the generation of high-frequency in the damping forces.



The structure used for numerical simulation is the benchmark problem for control of base-isolated buildings. The results show that the simplified control strategy is effective for a variety of ground motions. Copyright © 2005 John Wiley & Sons, Ltd.

Negative stiffness friction damping for seismically isolated structures

This paper describes the results of a comprehensive analysis for tsunami disaster mitigation in Padang City, Indonesia. Assessment consists of several steps, starting from the construction of tsunami hazard maps based on the most probable earthquake scenario in the future. Results are then analyzed to determine the impact on residential population along potential evacuation routes. Next, from the standpoint of hazards, we move to the analysis of human‟s vulnerability during evacuation. The term “vulnerability” is associated with available evacuation time. Here, we conducted a static evacuation model using the GIS platform and a dynamic approach using multiagent paradigm. Results of evacuation modeling suggest that some residents may not have enough time to leave the tsunami inundation area before the first wave comes. We therefore propose using relatively high buildings as vertical evacuation sites. One of potential candidates that survived from a devastated earthquake with 7.6 Mw in 2009 is selected to be further analyzed its antiseismic deficiencies based on design ground motion obtained from micro-tremor analysis and synthesized recorded wave in Padang. As a result,
even though the building underwent some damage, the frame structure was able to withstand the shaking and keep the building from collapsing.

Mulyo Harris Pradono

Papers

Advances in the development of pseudo-negative-stiffness dampers for seismic response control

Passive and semi-active seismic response control of a cable-stayed bridge

Application of pseudo-negative stiffness control to the benchmark cable-stayed bridge

Negative stiffness friction damping for seismically isolated structures

Tsunami disaster mitigation by integrating comprehensive countermeasures in Padang city, Indonesia