North Tonawanda, NY, United States
North Tonawanda, NY, United States

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Attary N.,Rensselaer Polytechnic Institute | Symans M.,Rensselaer Polytechnic Institute | Nagarajaiah S.,Rice University | Reinhorn A.M.,State University of New York at Buffalo | And 4 more authors.
Earthquake Engineering and Structural Dynamics | Year: 2015

A new passive seismic response control device has been developed, fabricated, and tested by the authors and shown to be capable of producing negative stiffness via a purely mechanical mechanism, thus representing a new generation of seismic protection devices. Although the concept of negative stiffness may appear to be a reversal on the desired relationship between the force and displacement in structures (the desired relationship being that the product of restoring force and displacement is nonnegative), when implemented in parallel with a structure having positive stiffness, the combined system appears to have substantially reduced stiffness while remaining stable. Thus, there is an 'apparent weakening and softening' of the structure that results in reduced forces and increased displacements (where the weakening and softening is of a non-damaging nature in that it occurs in a seismic protection device rather than within the structural framing system). Any excessive displacement response can then be limited by incorporating a damping device in parallel with the negative stiffness device. The combination of negative stiffness and passive damping provides a large degree of control over the expected performance of the structure. In this paper, a numerical study is presented on the performance of a seismically isolated highway bridge model that is subjected to various strong earthquake ground motions. The Negative Stiffness Devices (NSDs) are described along with their hysteretic behavior as obtained from a series of cyclic tests wherein the tests were conducted using a modified design of the NSDs (modified for testing within the bridge model). Using the results from the cyclic tests, numerical simulations of the seismic response of the isolated bridge model were conducted for various configurations (with/without negative stiffness devices and/or viscous dampers). The results demonstrate that the addition of negative stiffness devices reduces the base shear substantially, while the deck displacement is limited to acceptable values. This assessment was conducted as part of a NEES (Network for Earthquake Engineering Simulation) project which included shaking table tests of a quarter-scale highway bridge model. © 2014 John Wiley & Sons, Ltd.


Pasala D.T.R.,Rice University | Sarlis A.A.,State University of New York at Buffalo | Reinhorn A.M.,State University of New York at Buffalo | Nagarajaiah S.,Rice University | And 2 more authors.
Journal of Structural Engineering (United States) | Year: 2014

The acceleration and base shear of structures during strong ground motion can be attenuated by achieving bilinear-elastic behavior without any permanent displacement - also referred to as "apparent weakening." The negative stiffness device (NSD), used in this study, exhibits nonlinear-elastic negative stiffness behavior; by adding NSD to the elastic structure, the resulting structure-device assembly behaves like a bilinear-elastic structure. Peak acceleration and base shear experienced by the structures can be reduced by adding the negative stiffness device, and the additional deformations caused by the reduced stiffness can be contained by adding a viscous damper. This paper presents the experimental study on a three-story fixed-base structure (3SFS), acting as a single-degree-of-freedom (SDOF) system (because of bracing in the top two stories), that demonstrates the concept of apparent weakening in elastic structural systems. Two NSDs and a viscous damper are installed in the first story of 3SFS. To accentuate the advantages of incorporating NSD in structures, responses of four different systems - 3SFS, 3SFS with damper, 3SFS with NSD, and 3SFS with NSD and damper - are compared for a suite of ground motions. The behavior of all the three systems is also predicted analytically, and the predicted results are in excellent agreement with the experiments. Shake-table tests on 3SFS have confirmed that by adding the NSD and damper, acceleration and base shear of the structure are reduced by more than 30% and the displacement of the structure is reduced by more than 20%. © 2013 American Society of Civil Engineers.


Sarlis A.A.,State University of New York at Buffalo | Pasala D.T.R.,Rice University | Constantinou M.C.,State University of New York at Buffalo | Reinhorn A.M.,State University of New York at Buffalo | And 2 more authors.
Journal of Structural Engineering (United States) | Year: 2013

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 displacement. The NSD employs double chevron braces that self-contain the large vertical forces needed for the development of the horizontal negative stiffness without transferring these forces to the structure. This paper reports the development and operation of the NSD and presents analytical and computational tools that describe the behavior of the device. The principles of global control of structures using the NSD are presented in a companion paper. Additional papers present the results of testing of the device, and the results of analytical and experimental studies on the application of the device in a three-story conventional structure and a three-story seismically isolated structure. © 2013 American Society of Civil Engineers.


Sarlis A.A.,State University of New York at Buffalo | Sarlis A.A.,ExxonMobil | Pasala D.T.R.,Intecsea | Constantinou M.C.,State University of New York at Buffalo | And 3 more authors.
Journal of Structural Engineering (United States) | Year: 2016

The concept of apparent weakening by adding true negative stiffness to a structure has been previously introduced by the authors in order to reduce simultaneous drifts, accelerations, and displacements in a structure without yielding or permanent deformation in the main system. A novel negative stiffness device (NSD) that generates true negative stiffness has been developed, built, and tested and has been previously described by the authors in terms of operation and analytical and numerical modeling. This paper presents results that represent proof-of-concept for weakening with the use of the NSD based on the shake table testing of a 3-story seismically isolated structure, equipped with these devices complemented by viscous dampers. The NSD is shown to have a significant effect on the superstructure response by reducing floor accelerations, story drift, and the base shear and upon the addition of dampers, also results in a reduction in isolator displacements. Moreover, this paper provides validation of the analytical models that were previously developed by comparison of analytical and experimental results. © 2016 American Society of Civil Engineers.


Pasala D.T.R.,Rice University | Sarlis A.A.,State University of New York at Buffalo | Nagarajaiah S.,Rice University | Reinhorn A.M.,State University of New York at Buffalo | And 3 more authors.
Journal of Structural Engineering (United States) | Year: 2013

Yielding can be emulated in a structural system by adding an adaptive negative stiffness device (NSD) and shifting the yielding away from the main structural system, leading to the new idea of apparent weakening that occurs, ensuring structural stability at all displacement amplitudes. This is achieved through an adaptive negative stiffness system (ANSS), a combination of NSD and a viscous damper. By engaging the NSD at an appropriate displacement (apparent yield displacement that is well below the actual yield displacement of the structural system) the composite structure-device assembly behaves like a yielding structure. The combined NSD-structure system presented in this study has a recentering mechanism that avoids permanent deformation in the composite structure-device assembly unless the main structure itself yields. Essentially, a yielding-structure is mimicked with no, or with minimal, permanent deformation or yielding in the main structure. As a result, the main structural system suffers less acceleration, less displacement, and less base shear, while the ANSS absorbs these effects. This paper presents comprehensive details on development and study of the ANSS/NSD. Through numerical simulations, the effectiveness and the superior performance of the ANSS/NSD as compared with a structural system with supplemental passive dampers is presented. A companion paper presents the NSD and its mechanics in detail. © 2013 American Society of Civil Engineers.


Patent
New York University and Taylor Devices Inc. | Date: 2014-06-30

Negative stiffness systems and methods for seismic protection of a structure is described. A system can include a negative stiffness device having a first linkage pivotably connected to an anchor frame at a first pivot point and pivotably connected the movement frame at a second pivot point. The negative stiffness device can include a spring having a first end operably coupled to the anchor frame and a second end operably coupled to a movement frame. In a rest state, the spring can be compressed to exert a preload force to the first linkage and the anchor frame and not displace the first linkage and the movement frame. In an engaged state, the spring can be configured to apply a force to the first linkage such that the movement frame is displaced in a same lateral direction of a seismic load. The spring force can be amplified by the first linkage.


Taylor D.P.,Taylor Devices Inc.
Structural Design of Tall and Special Buildings | Year: 2010

The use of viscous dampers providing high damping levels within buildings is a relatively new application for a well-established and proven technology. The first modern use of damping technology in structural engineering occurred in the 1990s and has become increasingly popular today. Seminal research using viscous dampers to improve a structure's seismic response took place at the Multidisciplinary Center for Extreme Events Research (MCEER) at the State of New York at Buffalo in the early 1990s. This research documented excellent improvements in seismic capacity by simply adding dampers. Within a few years, highly effective computers and structural analysis/design software would arrive in the marketplace to properly model optimized damper designs. At this time, dampers began to be implemented on buildings and bridges, worldwide. Copyright © 2010 John Wiley & Sons, Ltd.


Schott F.H.,Fred H. Schott Engineering | Lee D.A.,Taylor Devices Inc. | Karns J.,MiTek | Symans M.D.,Rensselaer Polytechnic Institute
NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering | Year: 2014

Soft weak open front (SWOF) buildings often perform poorly in earthquakes. Two examples are buildings with a street facing garage, or commercial facilities with extensive open display windows. The poor performance of SWOF structures can consist of complete loss of use or even total collapse. This paper presents an approach to protecting such structures via the addition of an energy dissipation system (viscous dampers) such that peak inter-story drifts are limited to about 1% under relatively severe seismic events, thus keeping the deformations within the elastic range. With this addition of damping, earthquake survivability of this class of structures increases significantly. A series of seismic analyses are presented herein to demonstrate the potential performance of the damping system. In addition, a variety of damper installation configurations that provide enhanced energy dissipation are discussed.


Trademark
Taylor Devices Inc. | Date: 2014-12-17

Hydraulic shock absorbers; hydraulic dampers; hydraulic bumpers; liquid springs; hydropneumatic springs; crane and industrial dampeners and buffers having hydraulic shock absorbers; fluid viscous dampers and lock-up devices for protection of large structures subject to seismic or wind effects; mechanical, hydraulic, elastomer, and elastomer-hydraulic vibration isolators and dampers; shock isolators; vehicle suspension struts; and gun recoil absorbers.


Trademark
Taylor Devices Inc. | Date: 2014-12-17

Hydraulic shock absorbers; hydraulic dampers; hydraulic bumpers; liquid springs; hydropneumatic springs; crane and industrial dampeners and buffers having hydraulic shock absorbers; fluid viscous dampers and lock-up devices for protection of large structures subject to seismic or wind effects; mechanical, hydraulic, elastomer, and elastomer-hydraulic vibration isolators and dampers; shock isolators; vehicle suspension struts; and gun recoil absorbers.

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