Vibration and Shock in Damped Mechanical Systems

Abstract. We monitored the displacement and seismic activity of an unstable vertical rock slice in a natural limestone cliff of the southeast Vercors massif, southeast France, during the months preceding its collapse. Displacement measurements showed an average acceleration of the movement of its top, with clear increases in the displacement velocity and in the discrete seismic event production rate during periods where temperature falls, with more activity when rainfall or frost occurs. Crises of discrete seismic events produce high amplitudes in periodograms, but do not change the high frequency base noise level rate. We infer that these crises express the critical crack growth induced by water weakening (from water vapor condensation or rain) of the rock strength rather than to a rapid change in applied stresses. Seismic noise analysis showed a steady increase in the high frequency base noise level and the emergence of spectral modes in the signal recorded by the sensor installed on the unstable rock slice during the weeks preceding the collapse. High frequency seismic noise base level seems to represent subcritical crack growth. It is a smooth and robust parameter whose variations are related to generalized changes in the rupture process. Drop of the seismic noise amplitude was concomitant with the emergence of spectral modes -that are compatible with high-order eigenmodes of the unstable rock sliceduring the later stages of its instability. Seismic noise analysis, especially high frequency base noise level analysis may complement that of inverse displacement velocity in earlywarning approaches when strong displacement fluctuations occur.

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“…The amplitude of the eigenmodes of a damped linear elastic system with one degree of freedom may be written (e.g. Snowdon, 1968;Jones, 2001):…”

Section: Emergence Of Eigenmodes In Noise Spectrummentioning

confidence: 99%

Pre-failure behaviour of an unstable limestone cliff from displacement and seismic data

Got

Mourot

Grangeon

2010

Nat. Hazards Earth Syst. Sci.

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“…The main task of the numerical experiment was to determine these frequency parameters , , , m M l L of a two-mass pendulum absorber, in which the frequency response graph system would have a symmetrical shape with equal values of maximum amplitudes at two frequencies 1  and 2  , one of which corresponds to the supporting body, and the otherdampers [5,11,14,20,30]. Physically, this means that the energy of forced oscillations for each cycle is divided equally between the supporting body and an absorber, which leads to a decrease in the amplitude of the level of forced oscillations of the carrier body.…”

Section: Numerical Analysismentioning

confidence: 99%

“…This applies in particular to the high-rise buildings, television towers, radio masts, chimneys [1][2][3][4][5][6][7][8][9][10][11], largepower transmission lines [12][13][14][15][16][17][18][19], carrying trunks of wind power plants, cable-stayed bridges [20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

“…In comparison with other passive devices suppression forced oscillations TMD-absorbers can be installed on high-rise buildings without special technical and design problems. Technical details of various designs TMD-absorbers differ on ways to ensure the damping of vibrations of the working body, which they implemented [2,3,10,11]. Methods for determining the optimum parameters of TMD-absorbers adjustment (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Mathematical Modeling of the Process of Vibration Protection in a System with two-mass Damper Pendulum

Hu¹,

Legeza²,

Dychka³

et al. 2017

IJISA

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“…Let each triplet of independent coordinates (x t , z t , 9j) corresponding to the interior nodes be denoted by a matrix vector of the form (a.) = (5) e.…”

Section: Development Of Analytical Models Coordinate Systemmentioning

confidence: 99%

Synthesis of shuttle vehicle damping using substructure test results

Kana

Huzar

1973

14th Structures, Structural Dynamics, and Materials Conference

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An empirical method is developed for predicting the modal damping of a combined parallel-stage Shuttle model by means of damping measurements performed on the individual substructures.Correlations are first determined for each component in terms of damping energy as a function of peak kinetic energy and modal amplitude. The results are then used to predict component damping energies corresponding to the respective kinetic energies and amplitudes that occur for the new modes of the combined System. Modal characteristics for the System, other than damping, are obtained by a real eigenvalue solution of dynamic equations developed by Hurty's procedure of substructures. System equations, which include component modal damping, are also solved by a complex eigenvalue approach for comparison with results of the empirical method.

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Vibration and Shock in Damped Mechanical Systems

Cited by 130 publications

References 0 publications

Pre-failure behaviour of an unstable limestone cliff from displacement and seismic data

Pre-failure behaviour of an unstable limestone cliff from displacement and seismic data

Mathematical Modeling of the Process of Vibration Protection in a System with two-mass Damper Pendulum

Synthesis of shuttle vehicle damping using substructure test results

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