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An integrated study that explores the capability of Time-Frequency Analysis combined with another technique of signal analysis and system identification for damage detection purposes using only output signals is presented in this work.
The necessary background theory of Time-Frequency Analysis is presented, some definitions of damage and general a...
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... Here, α = 3 is selected for analysis [25,26]. ρ α norm is the normalized time-frequency distribution, which can be expressed as ...
The structure is said to be damaged if there is a permanent shift in the post-event natural frequency of a structure as compared with the pre-event frequency. To assess the damage to the structure, a time-frequency approach that can capture the pre-event and post-event frequency of the structure is required. In this study, to determine these frequencies, a local maximum synchrosqueezing transform (LMSST) method is employed. Through the simulation results, we have shown that the traditional methods such as the Wigner distribution, Wigner–Ville distributions, pseudo-Wigner–Ville distributions, smoothed pseudo-Wigner–Ville distribution, and synchrosqueezing transforms are not capable of capturing the pre-event and post-event frequency of the structure. The amplitude of the signal captured by sensors during those events is very small compared with the signal captured during the seismic event. Thus, traditional methods cannot capture the frequency of pre-event and post-event, whereas LMSST employed in this work can easily identify these frequencies. This attribute of LMSST makes it a very attractive method for post-earthquake damage detection. In this study, these claims are qualitatively and quantitatively substantiated by comprehensive numerical analysis.
... Here = 3 is selected for analysis [25,26]. ...
The natural frequency of buildings decreases during a strong-motion earthquake, and the structure loses its stiffness. As a result, understanding the damaging process in the structure owing to changes in structural properties is critical during a seismic excitation. The time-frequency technique can detect the damaged building’s time-varying frequency contents. Wigner distributions (WD), Wigner-Ville distributions (WVD), pseudo-Wigner-Ville distributions (PWVD), smoothed pseudo-Wigner-Ville distributions (SPWVD), and synchrosqueezing transforms (SST) have all become popular in recent years for a variety of earthquake engineering applications, including building damage detection. This study proposes the local maximum synchrosqueezing transform (LMSST) for detecting frequency shifts in buildings during strong earthquakes. The data presented in the research show that the suggested method outperforms as compared to the conventional time-frequency methods for detecting frequency shifting in earthquake-damaged structures.
... Aquí en particular se define el daño estructural como cambios (casi siempre permanentes) de propiedades estructurales como rigidez, resistencia, propiedades dinámicas o pérdidas de rendimiento estructural aceptable de acuerdo a criterios de comportamiento preestablecidos (Cano, 2008). ...
... Los sistemas estructurales con un grado de libertad tienen una única frecuencia y la señal de salida es principalmente monocomponente, sin embargo cuando el sistema es de múltiples grados de libertad, las frecuencias están asociadas a respuestas modales y las señales obtenidas tienen varias frecuencias (Cano, 2008). ...
... 2) donde ω d es la frecuencia circular amortiguada, ω n la frecuencia circular sin amortiguamiento y ξ el porcentaje de amortiguamiento crítico. Por lo tanto, para que ocurra un cambio de frecuencia significativo, se debe usar un factor de amortiguamiento excesivamente grande, por ejemplo, un factor de amortiguamiento del 30 % sólo produce un 5 % de cambio en la frecuencia (Cano, 2008). ...
Los métodos no invasivos para la detección de daños estructurales han ganado cada vez mayor importancia en los últimos años debido a los avances tecnológicos de instrumentación y procesamiento digital de señales. Las técnicas de monitoreo de salud estructural basadas en vibraciones permiten identificar la presencia y ubicación del daño a partir de cambios permanentes en las frecuencias fundamentales de las señales ya que estas están directamente relacionadas con la masa y rigidez de la estructura. Un método que se ha implementado con éxito enfocado a la detección de daño es la descomposición modal empírica (EMD) y otro método poco explorado en este campo de estudio, es el análisis singular espectral (SSA).
En este trabajo se describen en detalle ambas metodologías y se realiza un estudio de simulación con el objetivo de compararlas e identificar cual es más eficaz en la detección de daño estructural. Cabe mencionar que para facilitar la comparación entre los métodos, estos se aplicaron sobre un estudio de referencia conocido como benchmark SHM problem basado en datos de respuesta estructural simulados, desarrollado por el grupo de investigación IASC-ASCE (Asociación Internacional para Control Estructural y la Sociedad Americana de Ingeniería Civil) en monitoreo de la salud estructural, el cual permite analizar distintos patrones de daño. En términos generales el SSA es más eficaz en la detección de daño dado que no es necesario filtrar la señal original para poder detectar el daño.
... In Civil Engineering, Bonato et al. in 1998 [29] and 2000 [30] have proposed new methods based on Cohen class of TFDs for structural system identification. Some of other studies using square TFDs have been performed by Huerta-Lopez et al. [31], Zou and Chen [25], Bradford [21], Spanos et al. [32], Saldaña [33], Michel and Gueguen [34]. ...
This paper presents a new algorithm based on square time–frequency distribution to detect damages in concrete piers of railroad bridges. In addition, two new damage indices are proposed in this research. The algorithm and damage indices are described and corroborated using finite element model of Qotour railroad bridge. To create the finite element model according to the current condition of the Qotour railroad bridge, extensive in situ measurement results and laboratory tests were used. Some seismic damages were considered in the concrete piers of the model. The results indicate that the algorithm and damage indices can identify all damages from severe to small accurately. The proposed algorithm and damage indices are shown to be not sensitive to noise and even in case of noise-polluted response signal are working properly. The proposed algorithm only uses the response signals without the need for recording the excitation forces. In addition, according to the algorithm, there is no need to create an analytical model of the bridge for damage detection. This feature in modeling of bridge structures and especially complex bridge, which is associated with problems, is very useful. Copyright © 2014 John Wiley & Sons, Ltd.
... Por medio de la estimación de la distribución de densidad de probabilidad empírica (construido en torno a las frecuencias obtenidas en el MTFR), la diferenciación entre lo real y estructural externa o máquinas de frecuencias puede ser claramente identificada. La figura 20 muestra el plano de Tiempo frecuencia promedio y curva de densidad de probabilidad empírica propia de la estructura y las producidas por agentes externos(Tomado de Cano, 2008) . ...
... The most common of these methods are analysis in time-domain and analysis in frequency-domain, Fourier analysis. Recently other methods of signal analysis have been developed and although their basic principles have been established many years ago, only the evolutions of personal computers allow its current use (Saldana, 2008). These methods are analysis in time-frequency domain and analysis in time-scale domain. ...
Seismic waves that observed in earthquake records are non-stationary typical. To better understand the structure of the seismic signals, not only is enough to examine changes at time domain, also frequency domain is shows a component characteristics of the signal important. Therefore in recent years, different time-frequency analysis methods are used extensively. Time-Frequency analysis is suitable for non- stationary signal analysis and processing. Time-frequency analysis contains a signal in both time domain and frequency domain at the same time. In this study we applied and compared a linear and a quadratic two different time-frequency analysis methods short-time Fourier transform and Wigner-Ville distribution in December 25, 2012 Georgia earthquake record. As a result of this study, short-time Fourier transform method gave better results than the Wigner-Ville distribution.
... In strong events the duration of the signal varies from few milliseconds like in blast and explosions, to several hours like in high-wind speed events. -Frequency Laws: In the linear response the signal frequency might varies slightly, but in non-linear response regime the signal frequency is clearly time dependent (Cano 2008). In order to have into account the specific-signal characteristics, the structural performance indicator evaluate the behavior of each TFR from two type of signals: Ambient Vibration and Strong Events. ...
... A data base of signals recollected from structures subjected to strong motion was developed. The signals are classified according to the pattern frequency laws obtained of its TFRs (Cano 2008): (1) Linear response (without frequency changes), (2) Linear Response -linear stiffness degradation, (3)Linear Response exponential stiffness degradation, (4) Linear Response, instantaneous stiffness loss -linear stiffness degradation, (5) Linear Response, instantaneous stiffness loss -exponential stiffness degradation, (6) Linear Response exponential stiffness degradation -sudden instantaneous stiffness loss -exponential stiffness degradation or linear degradation, (7) Any precedent behavior and some frequency recovery to end of signal. ...
The main part of this paper is devoted to propose a new multicriteria method for an objective selection scheme of Time-Frequency Representations (TFRs) of signals from Earthquake Engineering and Civil Engineering (EE-CE) applications. The proposed method, consider four criteria, the first two are specifically oriented to EE-CE signals, while the last two has been proposed previously in the literature by other authors for general applications. An evaluation of the proposed multicriteria method to select a TFR from several Linear and Quadratic TFRs is shown using synthetic ambient vibration signals and real strong motion records.
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https://revistas.udistrital.edu.co/index.php/reving/article/view/20447/19565
Context: In recent years, thanks to technological advances in instrumentation and digital signal processing, noninvasive methods to detect structural damage have become increasingly important. Vibration-based structural health monitoring (SHM) techniques allow detecting the presence and location of damage from permanent changes in the fundamental frequencies of signals. A successfully employed method for damage detection is empirical mode decomposition (EMD). Another method, less used in this field of study, is singular spectral analysis (SSA). This paper describes both methods and presents a simulation study aimed at comparing them and identifying which one is more effective in detecting structural damage. Method: The methods of a reference study known as benchmark SHM were applied to facilitate the comparison. To evaluate the effectiveness of both methods, Monte Carlo simulation was employed. To control the random noise and other factors inherent to the simulation, the procedure was repeated 1.000 times for each type of damage. Results: In the case of severe damage, both methods showed a good performance. However, when the damage was slight, the changes in the fundamental frequency were not apparent. However, a significant change in the amplitude level was observed. In this case, SSA obtained the best results.
A hybrid time-frequency method known as Gabor-Wigner transform (GWT) is introduced in this paper for examining the time-frequency patterns of earthquake damaged buildings. GWT is developed by combining the Gabor transform (GT) and Wigner-Ville distribution (WVD). GT and WVD have been used separately on synthetic and recorded earthquake data to identify frequency shifting due to earthquake damages, but GT is prone to windowing effect and WVD involves ambiguity function. Hence to obtain better clarity and to remove the cross terms (frequency interference), GT and WVD are judiciously combined and the resultant GWT used to identify frequency shifting. Synthetic seismic response of an instrumented building and real-time earthquake data recorded on the building were investigated using GWT. It is found that GWT offers good accuracy for even slow variations in frequency, good time-frequency resolution, and localized response. Presented results confirm the efficacy of GWT when compared with GT and WVD used separately. Simulation results were quantified by the Renyi entropy measures and GWT shown to be an adequate technique in identifying localized response for structural damage detection. © 2015, Institute of Engineering Mechanics, China Earthquake Administration and Springer-Verlag Berlin Heidelberg.
