Estimating Seismic Energy in Structure with Wavelet Transform

2010 ◽  
Vol 163-167 ◽  
pp. 3958-3963
Author(s):  
Mei Ling Xiao ◽  
Liao Yuan Ye ◽  
Yun Fen Li ◽  
Yan Li
Keyword(s):  
Wavelet Transform ◽  
Energy Input ◽  
Wavelet Coefficient ◽  
Ground Motions ◽  
Linear Structure ◽  
Seismic Energy ◽  
Acceleration Process ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Time Histories

This study proposed a wavelet method for estimating seismic energy in single-degree-of-freedom (SDOF) structure. With the recent development of wavelet-based procedures for structure seismic response, which the displacement and velocity of linear SDOF structure can be expressed with wavelet transform of acceleration process, it is easy to estimate seismic energy in SDOF linear structure, and strain, kinetic, damping energy and energy input based on wavelets introduced in a range of time and frequency assigned to the wavelet coefficient, Expressions have been derived for (i) the equation of motion. (ii)the wavelet coefficients of the response processes. By using these principles, a linear SDOF structure which subjected to 1988 LanCang-GenMa earthquake ground motions is analyzed, time-histories of strain, kinetic, damping energy and energy input for various ranges of frequencies are identified.

Inelastic Response of a Spectrum-Compatible Artificial Accelerogram

1989 ◽  
Vol 5 (3) ◽  
pp. 477-493 ◽  
Author(s):  
Michael E. Barenberg
Keyword(s):  
Response Spectrum ◽  
Ground Motions ◽  
Normalization Procedure ◽  
Target Response ◽  
Single Degree Of Freedom ◽  
Inelastic Response ◽  
Strong Ground Motions ◽  
Single Degree ◽  
Initial Frequency ◽  
Strong Ground

The validity of evaluating the inelastic response of a structure subjected to an artificial accelerogram in lieu of a suite of eight recorded ground motions is determined by analyzing the inelastic response of single-degree-of-freedom oscillators over a range of frequencies from 1.0 to 10.0 Hz. A normalization procedure to minimize the dispersion in the ductility response of the oscillators subjected to the recorded ground motions is investigated. The artificial accelerogram is derived by superimposing closely spaced sine waves in order to match a target response spectrum. The results show that the artificial accelerogram is expected to produce the same amount of damage as the average of the recorded strong ground motions for structures with an initial frequency of less than 5.0 Hz and close to the average for the entire suite of ground motions for structures with frequencies greater then 5.0 Hz.

Localization Phenomena of Nonlinear Vibrations in Three-Blade Wind Turbines

2013 ◽  
Author(s):  
Takashi Ikeda ◽  
Yuji Harata ◽  
Hisashi Takahashi ◽  
Yukio Ishida
Keyword(s):  
Wind Turbines ◽  
Degrees Of Freedom ◽  
Nonlinear Vibrations ◽  
Coupled System ◽  
Wind Pressure ◽  
Response Curves ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Frequency Responses ◽  
Time Histories

Vibration characteristics of three-blade wind turbines are investigated. The system is modeled by a coupled system of the flexible tower with two degrees of freedom and each blade with a single degree of freedom, and these blades are subjected to wind pressure which varies depending on the height from the ground. The vibrations of the three-blade wind turbines are theoretically analyzed to determine the natural frequency diagrams, frequency responses, stationary time histories and their FFT results. It is found that several peaks appear at the specific range of the rotational speed ω in the response curves because of both the wind pressure and the parametric excitation terms. In three-blade wind turbines, vibrations including predominant components of 3ω and its higher harmonics appear near these peaks. The response curves near the highest peak exhibit soft spring types due to the nonlinearities of the restoring moments of the blades. In the numerical simulations, “localization phenomena” in the blades, which vibrate at different amplitudes, are observed. The influence of an imperfection of the three blades is also examined.

On Equivalent Linearization Using Wavelet Transform

1999 ◽  
Vol 121 (4) ◽  
pp. 429-432 ◽  
Author(s):  
B. Basu ◽  
V. K. Gupta
Keyword(s):  
Wavelet Transform ◽  
Duffing Oscillator ◽  
Time Dependent ◽  
Equivalent Linearization ◽  
Equivalent System ◽  
Mean Square ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
The Mean ◽  
The Given

This paper proposes a wavelet-based formulation for linearizing a base-excited single-degree-of-freedom nonlinear system to a time-variant linear (TVL) system. The given system is assumed to be nonlinear in stiffness, and the time-dependent natural frequency of the equivalent system is proposed to he estimated through instantaneous minimization of the mean-square error. A duffing oscillator has been considered to illustrate the performance of the proposed TVL system.

Single Degree of Freedom Analysis of Steel Beams under Blast Loading

2014 ◽  
Vol 617 ◽  
pp. 92-95 ◽  
Author(s):  
Lucia Figuli ◽  
Daniel Papán
Keyword(s):  
Dynamic Analysis ◽  
Blast Wave ◽  
Exponential Decay ◽  
Pressure Wave ◽  
Steel Beams ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Time Histories ◽  
Blast Pressure Wave ◽  
Linear Decay

The paper deals with the analysis of steel beams subjected to blast load approximated as a one degree system of freedom (SDOF). It requires knowing the parameters of blast pressure wave, its effect on structure and the tools for the solution of dynamic analysis. The blast wave is estimated with linear decay and exponential decay using positive and negative phase. The results of SDOF model are compared with the corresponding experimental accelerations and strain time-histories. There is a described dynamic analysis for such structure.

Chaotic Responses of a Two-Degree-of-Freedom Elastic-Plastic Beam Model to Short Pulse Loading

1992 ◽  
Vol 59 (4) ◽  
pp. 711-721 ◽  
Author(s):  
J.-Y. Lee ◽  
P. S. Symonds ◽  
G. Borino
Keyword(s):  
Short Pulse ◽  
Direct Method ◽  
Degree Of Freedom ◽  
Beam Model ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Arch Action ◽  
Time Histories ◽  
Energy Plane ◽  
Two Degree Of Freedom

The paper discusses chaotic response behavior of a beam model whose ends are fixed, so that shallow arch action prevails after moderate plastic straining has occurred due to a short pulse of transverse loading. Examples of anomalous displacement-time histories of a uniform beam are first shown. These motivated the present study of a two-degree-of-freedom model of Shanley type. Calculations confirm these behaviors as symptoms of chaotic unpredictability. Evidence of chaos is seen in displacement-time histories, in phase plane and power spectral diagrams, and especially in extreme sensitivity to parameters. The exponential nature of the latter is confirmed by calculations of conventional Lyapunov exponents and also by a direct method. The two-degree-of-freedom model allows use of the energy approach found helpful for the single-degree-of-freedom model (Borino et al., 1989). The strain energy is plotted as a surface over the displacement coordinate plane, which depends on the plastic strains. Contrasting with the single-degree-of-freedom case, the energy diagram illuminates the possibility of chaotic vibrations in an initial phase, and the eventual transition to a smaller amplitude nonchaotic vibration which is finally damped out. Properties of the response are further illustrated by samples of solution trajectories in a fixed total energy plane and by related Poincare section plots.

Estimation of Hysteretic Energy of MDOF Structures Based on Equivalent SDOF Systems

2007 ◽  
Vol 340-341 ◽  
pp. 435-440
Author(s):  
Hong Nan Li ◽  
Feng Wang ◽  
Zhao Hui Lu
Keyword(s):  
Ground Motions ◽  
Estimation Method ◽  
Degree Of Freedom ◽  
Energy Relation ◽  
Energy Estimation ◽  
Single Degree Of Freedom ◽  
Hysteretic Energy ◽  
Single Degree ◽  
Energy Demands ◽  
The Relationship

It is important for obtaining the relationship between seismic energies of single degree-of-freedom (SDOF) systems and multiple degree-of-freedom (MDOF) structures in engineering. In this paper, the formula of hysteretic energy between the MDOF structures and equivalent SDOF systems is developed. Here is also presented the procedure for estimating hysteretic energy of MDOF structures subjected to severe ground motions employing the energy relation equation based on equivalent SDOF systems. Eight examples for two regular and six irregular MDOF structures show that the procedure to obtain the hysteretic energy demands of MDOF structures may be used as a simple and effective energy estimation method.

Evaluation of the Scaling Factor Bias Influence on the Probability of Collapse Using Sa(T1) as the Intensity Measure

2019 ◽  
Vol 35 (2) ◽  
pp. 679-702 ◽  
Author(s):  
Héctor Dávalos ◽  
Eduardo Miranda
Keyword(s):  
Lateral Displacement ◽  
Ground Motions ◽  
Scaling Factor ◽  
Intensity Level ◽  
Intensity Measure ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Target Intensity ◽  
Lateral Strength ◽  
Factor Bias

Amplitude scaling is a common approach to modify recorded ground motions to achieve a desired intensity level. The possible bias introduced by scaling the amplitude of ground motions when using the first-mode spectral ordinate as the intensity measure is evaluated using intensity-based analyses. This study evaluates whether upward scaling introduces bias in lateral displacement demands, but more importantly, in the probability of collapse. The latter, which is of utmost importance, has received little attention in previous studies. Analyses were conducted using degrading single-degree-of-freedom and multiple-degree-offreedom systems with different fundamental periods of vibration and normalized strengths subjected to different sets of recorded accelerograms requiring different scale factors to reach a target intensity. The results demonstrate that this type of amplitude scaling introduces a bias in which lateral displacement demands and collapse estimates are increasingly overestimated with an increasing scale factor and that the bias is strongly dependent on the period and lateral strength of the system. Furthermore, the bias is considerably larger in collapse risk estimates.

Spectral Variability and Its Relationship to Structural Response Estimated from Scaled and Spectrum-Matched Ground Motions

2016 ◽  
Vol 32 (4) ◽  
pp. 2191-2205 ◽  
Author(s):  
A. E. Seifried ◽  
J. W. Baker
Keyword(s):  
Response Spectrum ◽  
Ground Motions ◽  
Structural Response ◽  
Degree Of Freedom ◽  
Structural Systems ◽  
Spectral Variability ◽  
Single Degree Of Freedom ◽  
Inelastic Response ◽  
Single Degree ◽  
Spectral Dispersion

Conditional spectral dispersion ( CSD) is a measure of response spectrum variability that implicitly characterizes the variety of spectral shapes within a suite of ground motions. It is used here to explain the discrepancy between median structural demands estimated from different suites of scaled and spectrum-matched ground motions. Performing response history analyses with spectrum-matched ground motions is known to result in unconservatively biased median demand estimates in some cases. Herein, several suites of scaled ground motions with equivalent median intensities and varying levels of CSD are selected. A single suite of spectrum-matched ground motions is also created. These records are used to analyze the responses of inelastic single-degree-of-freedom and first-mode-dominated multiple-degree-of-freedom structural systems. Collapse capacities are also examined. A consistent trend between CSD and resulting median responses indicates that the bias phenomenon can be fully explained by an asymmetric relationship between conditional spectral ordinates at periods affecting inelastic response.

Simplified Method for Considering Dynamic Second-Order Effects of Elastic SDOF System under Earthquakes

2011 ◽  
Vol 295-297 ◽  
pp. 26-30
Author(s):  
Feng Xia Han ◽  
Zhi Jun Wang ◽  
Zong Ming Huang
Keyword(s):  
Ground Motions ◽  
Second Order ◽  
Order Effects ◽  
Single Degree Of Freedom ◽  
Static And Dynamic Analysis ◽  
Sdof System ◽  
Single Degree ◽  
Earthquake Ground Motions ◽  
Stiffness Reduction ◽  
Second Order Effects

The structures subjected to large displacement under ground motion may be severely influenced by the structural second-order effects. This paper studied the dynamic second-order effects of the single-degree-of-freedom (SDOF) system under earthquake ground motions. The following achievements have been made: (1) the stiffness reduction coefficients considering and effects under static and dynamic analysis were deduced; (2) through numerical analysis, the accuracy of the formulas was verified.

Sign in / Sign up

Export Citation Format

Share Document