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Douglas P Taylor - One of the best experts on this subject based on the ideXlab platform.
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adaptive negative stiffness new structural modification approach for seismic protection
Journal of Structural Engineering-asce, 2013Co-Authors: D T R Pasala, A A Sarlis, Satish Nagarajaiah, A M Reinhorn, M C Constantinou, Douglas P TaylorAbstract:AbstractYielding 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 ...
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adaptive negative stiffness a new structural modification approach for seismic protection
Advanced Materials Research, 2013Co-Authors: Satish Nagarajaiah, D T R Pasala, A M Reinhorn, M C Constantinou, Apostolos A Sirilis, Douglas P TaylorAbstract: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 re-centering mechanism thereby avoids permanent deformation in the composite Structure-device assembly unless, the Main Structure itself yields. Essentially, a yielding-Structure is “mimicked” without any, or with minimal permanent deformation or yielding in the Main Structure. As a result, the Main structural system suffers less accelerations, less displacements and less base shear, while the ANSS “absorbs” them. 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 to a structural system with supplemental passive dampers is presented. A companion paper presents the NSD and its mechanics in detail.
Angelo Luongo - One of the best experts on this subject based on the ideXlab platform.
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nonlinear energy sink to control vibrations of an internally nonresonant elastic string
Meccanica, 2015Co-Authors: Daniele Zulli, Angelo LuongoAbstract:A nonlinear elastic string is considered here as a Main Structure to be passively controlled using a Nonlinear Energy Sink (NES). The string is internally nonresonant due to a point mass and an elastic spring applied at a free tip, and a distributed force with harmonic time-law is assumed. The Multiple Scale/Harmonic Balance method, already introduced for finite degree of freedom systems, is extended here in direct approach, being applied to the partial differential equations ruling the dynamics of the system. Amplitude modulation equations are obtained and discussion of some solutions, where the beneficial effect of the NES is evident, are made.
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dynamic analysis of externally excited nes controlled systems via a mixed multiple scale harmonic balance algorithm
Nonlinear Dynamics, 2012Co-Authors: Angelo Luongo, Daniele ZulliAbstract:A general, nonlinear, multi-d.o.f. Structure, excited by harmonic external force in 1:1 resonance with one of the modes of the system, is considered. The Structure is attached to an essentially nonlinear oscillator, with small mass and damping (Nonlinear Energy Sink, NES). The scope of the NES is to passively control the amplitude of vibrations of the Main Structure. A mixed Multiple Scale/Harmonic Balance Method (MSHBM) is proposed to get the differential equations describing the slow- and fast-flow dynamics of the whole Structure. The Main advantage of the procedure is that no complexification-averaging is required, so that the analysis is reconducted in the framework of the classical perturbation techniques.
Daniele Zulli - One of the best experts on this subject based on the ideXlab platform.
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nonlinear energy sink to control vibrations of an internally nonresonant elastic string
Meccanica, 2015Co-Authors: Daniele Zulli, Angelo LuongoAbstract:A nonlinear elastic string is considered here as a Main Structure to be passively controlled using a Nonlinear Energy Sink (NES). The string is internally nonresonant due to a point mass and an elastic spring applied at a free tip, and a distributed force with harmonic time-law is assumed. The Multiple Scale/Harmonic Balance method, already introduced for finite degree of freedom systems, is extended here in direct approach, being applied to the partial differential equations ruling the dynamics of the system. Amplitude modulation equations are obtained and discussion of some solutions, where the beneficial effect of the NES is evident, are made.
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dynamic analysis of externally excited nes controlled systems via a mixed multiple scale harmonic balance algorithm
Nonlinear Dynamics, 2012Co-Authors: Angelo Luongo, Daniele ZulliAbstract:A general, nonlinear, multi-d.o.f. Structure, excited by harmonic external force in 1:1 resonance with one of the modes of the system, is considered. The Structure is attached to an essentially nonlinear oscillator, with small mass and damping (Nonlinear Energy Sink, NES). The scope of the NES is to passively control the amplitude of vibrations of the Main Structure. A mixed Multiple Scale/Harmonic Balance Method (MSHBM) is proposed to get the differential equations describing the slow- and fast-flow dynamics of the whole Structure. The Main advantage of the procedure is that no complexification-averaging is required, so that the analysis is reconducted in the framework of the classical perturbation techniques.
D T R Pasala - One of the best experts on this subject based on the ideXlab platform.
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adaptive negative stiffness new structural modification approach for seismic protection
Journal of Structural Engineering-asce, 2013Co-Authors: D T R Pasala, A A Sarlis, Satish Nagarajaiah, A M Reinhorn, M C Constantinou, Douglas P TaylorAbstract:AbstractYielding 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 ...
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adaptive negative stiffness a new structural modification approach for seismic protection
Advanced Materials Research, 2013Co-Authors: Satish Nagarajaiah, D T R Pasala, A M Reinhorn, M C Constantinou, Apostolos A Sirilis, Douglas P TaylorAbstract: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 re-centering mechanism thereby avoids permanent deformation in the composite Structure-device assembly unless, the Main Structure itself yields. Essentially, a yielding-Structure is “mimicked” without any, or with minimal permanent deformation or yielding in the Main Structure. As a result, the Main structural system suffers less accelerations, less displacements and less base shear, while the ANSS “absorbs” them. 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 to a structural system with supplemental passive dampers is presented. A companion paper presents the NSD and its mechanics in detail.
Alexander F Vakakis - One of the best experts on this subject based on the ideXlab platform.
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DETC2003/VIB-48533 PASSIVE NONLINEAR ENERGY PUMPING IN COUPLED OSCILLATORS: STEADY STATE RESULTS
2020Co-Authors: Xiaoai Jiang, Michael D Mcfarland, Lawrence A Bergman, Alexander F VakakisAbstract:ABSTRACT We study theoretically and numerically the effect that a nonlinear energy sink (NES) has on the steady state dynamics of a weakly coupled system. The NES possesses essentially nonlinear (nonlinearizable) stiffness nonlinearity of the third degree. We find that, in contrast to the classical linear vibration absorber, the NES is capable of absorbing steady state vibration energy from the linear oscillator over a relatively broad frequency range. This results in localization of the steady state vibration in the NES, away from the directly forced subsystem. For a forward frequency sweep the localized branch of steady state motions is suddenly eliminated by a jump to a linearized low-amplitude motion, whereas, for a backward frequency sweep a reverse jump occurs. The difference in the frequencies of the two jumps introduces a nonlinear hysteresis loop. This work extends to the steady state case of earlier transient passive energy pumping results. The notion of passively transferring vibration energy to an a priori determined NES, weakly attached to a Main Structure, is novel. The use of essentially nonlinear energy sinks for passively absorbing energy from a linear Main Structure can form the basis of relatively simple and modular vibration and shock isolation designs of mechanical systems
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targeted energy transfers in vibro impact oscillators for seismic mitigation
Nonlinear Dynamics, 2007Co-Authors: Francesco Nucera, Lawrence A Bergman, Alexander F Vakakis, D M Mcfarland, Gaetan KerschenAbstract:In the field of seismic protection of Structures, it is crucial to be able to diminish ‘as much as possible’ and dissipate ‘as fast as possible’ the load induced by seismic (vibration-shock) energy imparted to a Structure by an earthquake. In this context, the concept of passive nonlinear energy pumping appears to be natural for application to seismic mitigation. Hence, the overall problem discussed in this paper can be formulated as follows: Design a set of nonlinear energy sinks (NESs) that are locally attached to a Main Structure, with the purpose of passively absorbing a significant part of the applied seismic energy, locally confining it and then dissipating it in the smallest possible time. Alternatively, the overall goal will be to demonstrate that it is feasible to passively divert the applied seismic energy from the Main Structure (to be protected) to a set of preferential nonlinear subStructures (the set of NESs), where this energy is locally dissipated at a time scale fast enough to be of practical use for seismic mitigation. It is the aim of this work to show that the concept of nonlinear energy pumping is feasible for seismic mitigation. We consider a two degree-of-freedom (DOF) primary linear system (the Structure to be protected) and study seismic-induced vibration control through the use of Vibro-Impact NESs (VI NESs). Also, we account for the possibility of attaching to the primary Structure additional alternative NES configurations possessing essential but smooth nonlinearities (e.g., with no discontinuities). We study the performance of the NESs through a set of evaluation criteria. The damped nonlinear transitions that occur during the operation of the VI NESs are then studied by superimposing wavelet spectra of the nonlinear responses to appropriately defined frequency – energy plots (FEPs) of branches of periodic orbits of underlying Conservative systems.
