scholarly journals APPROXIMATE EIGEN MODES OF A SPHERICAL DOME IN ANTISYMMETRIC STATE AND THEIR APPLICATION TO LINEAR RESPONSE ANALYSIS

1994 ◽  
Vol 59 (466) ◽  
pp. 79-85 ◽  
Author(s):  
Shigehiro MOROOKA ◽  
Haruo KUNIEDA ◽  
Sang-Eul HAN
Keyword(s):  
Linear Response ◽  
Response Analysis ◽  
Spherical Dome ◽  
Antisymmetric State

The Use of ARMA Models in Earthquake Response Spectra

2006 ◽  
Author(s):  
Malek Brahimi ◽  
Sidi Berri
Keyword(s):  
Linear Response ◽  
Energy Demand ◽  
Arma Model ◽  
Response Spectra ◽  
Response Analysis ◽  
Arma Models ◽  
Maximum Displacement ◽  
Ductility Demand ◽  
Displacement Ductility ◽  
Hysteretic Energy

Structural design spectra are based on smoothed linear response spectra obtained from different events scaled by their peak values. Such an approach does not incorporate other characteristics of the excitation represented by measured data. This study investigate the use of non-stationary models which can be considered characteristic and representative of specific historical earthquakes. An earthquake record is regarded as a sample realization from a population of such samples, which could have been generated by the stochastic process characterized by an Autoregressive Moving Average (ARMA) model. ARMA models are developed for four major earthquakes after processing by a variance stabilizing transformation. Samples of acceleration records are generated for each event. In this earthquake modeling procedure, parameters describing the modulating function of the record and the stabilized series are estimated. Maximum displacement ductility demand and normalized hysteretic energy demand for linear and stiffness softening single degree of freedom system systems are computed for the samples generated for each event. The sensitivity and dependence of demand spectra on earthquake model characteristics are examined to develop a response prediction model. Non linear response analysis of the four events indicates that ARMA (2,1) process using samples of twenty simulated earthquakes provide a reliable description of the information contained within acceleration records. Empirical relationships for displacement ductility and Normalized hysteretic energy demand spectra are developed.

Lund’s Elliptic Orbit Forced Response Analysis: The Keystone of Modern Rotating Machinery Analysis

2001 ◽  
Author(s):  
R. Gordon Kirk
Keyword(s):  
Linear Response ◽  
Vibration Analysis ◽  
Rotating Machinery ◽  
Forced Response ◽  
Design Tool ◽  
Elliptic Orbit ◽  
Response Analysis ◽  
Flexible Rotor ◽  
Response Sensitivity ◽  
Machinery Design

Abstract A total understanding of rotating machinery vibration analysis requires evaluation of critical speed placement, forced response sensitivity to imbalance, linear onset of instability prediction and full non-linear response analysis. Of these four areas of analysis, only the first three are applied as a basic design tool in modern turbo-machinery analysis. The prediction of multi-mass flexible rotor steady-state elliptic orbit response, including bearing damping and support flexibility, has been and remains in this author’s opinion, to be the basic workhorse and keystone of machinery design. This has now been true for over 35 years. The person responsible for developing this basic method of analysis has been a longtime friend of many engineers worldwide. This paper is written to acknowledge this contribution, one of many in fact, made by Jorgen W. Lund and is presented in memory of his life’s work at this occasion of honoring his contributions to our profession. The utility of the analysis will be discussed and the powerful insight it gives to complex machinery dynamic behavior will be illustrated.

scholarly journals Kovacs-Like Memory Effect in Athermal Systems: Linear Response Analysis

Entropy ◽  
2017 ◽  
Vol 19 (10) ◽  
pp. 539 ◽  
Author(s):  
Carlos Plata ◽  
Antonio Prados
Keyword(s):  
Memory Effect ◽  
Linear Response ◽  
Response Analysis

Conceptual Analysis of the Non-Linear Forced Response of Aerodynamically Unstable Bladed-Discs

2013 ◽  
Author(s):  
Roque Corral ◽  
Juan Manuel Gallardo ◽  
Rahul Ivaturi
Keyword(s):  
Time Domain ◽  
Linear Response ◽  
Harmonic Excitation ◽  
Friction Model ◽  
Forced Response ◽  
Response Analysis ◽  
Non Linear ◽  
Aerodynamic Instability ◽  
Time Domain Response ◽  
The Time Domain

The response of aerodynamically unstable tuned bladed-discs with non-linear friction dissipation at blade-root attachments due to harmonic external excitation is studied. The bladed-disc is modeled using a simple mass-spring system and the effect of friction is modeled using a micro-slip friction model. The response is computed in time domain using a Runge-Kutta scheme. The time domain response is decomposed to obtain the evolution of traveling waves in the bladed-disc. Parametric studies have been conducted to study the non-linear response at different vibration amplitudes at high and low engine orders of excitation. It is seen that the non-linearity due to friction gives rise to a complicated interaction between the synchronous response of the system due to harmonic excitation and the non-synchronous response of the system due to aerodynamic instability. For low excitation levels the system behaves as in the pure flutter regime where a single, or at most a few, aerodynamically unstable modes may be found in the final state when a limit cycle is reached. When the forcing is large enough the aerodynamic instability is suppressed and only the non-linear response of the excited mode may be seen. It is concluded that the superimposition of the flutter and forced response analysis in terms of vibration amplitude is not valid and leads to prediction of vibration amplitudes significantly larger than that obtained when both phenomena are simulated together.

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