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Response-only modal identification of structures using limited sensors
, Article Structural Control and Health Monitoring ; Volume 20, Issue 6 , 2013 , Pages 987-1006 ; 15452255 (ISSN) ; Ghahari, S. F ; Nateghi, F ; Taciroglu, E ; Sharif University of Technology
2013
Abstract
Herein, we propose a method based on the existing second-order blind identification of underdetermined mixtures technique for identifying the modal characteristics - namely, natural frequencies, damping ratio, and real-valued partial mode shapes of all contributing modes - of structures with a limited number of sensors from recorded free/ambient vibration data. In the second-order blind identification approach, second-order statistics of recorded signals are used to recover modal coordinates and mode shapes. Conventional versions of this approach require the number of sensors to be equal to or greater than the number of active modes. In the present study, we first employ a parallel factor...
Blind identification of soil-structure systems
, Article Soil Dynamics and Earthquake Engineering ; Volume 45 , February , 2013 , Pages 56-69 ; 02677261 (ISSN) ; Ghannad, M. A ; Taciroglu, E ; Sharif University of Technology
2013
Abstract
Surrounding soil can drastically influence the dynamic response of buildings during strong ground shaking. Soil's flexibility decreases the natural frequencies of the system; and in most cases, soil provides additional damping due to material hysteresis and radiation. The additional damping forces, which are in non-classical form, render the mode shapes of the soil-structure system complex-valued. The response of a soil-foundation system can be compactly represented through impedance functions that have real and imaginary parts representing the stiffness and damping of the system, respectively. These impedance functions are frequency-dependent, and their determination for different...
Probabilistic Identification of Soil-foundation Impedance Function Using Kalman Filter
,
M.Sc. Thesis
Sharif University of Technology
;
Mahsouli, Mojtaba
(Supervisor)
;
Ghahari, Farid
(Co-Supervisor)
Abstract
This paper puts forward a probabilistic approach for simultaneous identification of the dynamic stiffnesses of the soil-foundation and the foundation input motion of soil-structure systems from sparsely-measured structural responses. The soil-structure system in this approach is represented by a shear building resting on sway- and rocking-representative springs and dashpots. The proposed approach employs unknown-input extended Kalman filtering in time domain. This method is built upon Bayesian updating and accounts for two major sources of uncertainty in the problem: the process noise that account for the modeling errors and the measurement noise. In the proposed method, the state vector of...
Deep Learning Based Blind Recognition of Channel Code Parameters
,
M.Sc. Thesis
Sharif University of Technology
;
Saleh Kaleybar, Saber
(Supervisor)
;
Hashemi, Matin
(Co-Supervisor)
Abstract
In the communication systems, the raw signals of information are mainly encoded so as to prevent the detrimental effects of channel noises and distortions. After some processes, this encoded signal is passed through the channel. At the receiver side, the received signal has to be decoded to extract the information signal. In order to decode the received signal, the receiver require prior knowledge about the encoder parameters. The traditional approach is to send the encoder parameters along with the encoded signals. However, this transmission overhead might occupy a considerable amount of bandwidth since the type of coding may alter several times in a fraction of a second based on the...
Blind modal identification of structures from spatially sparse seismic response signals
, Article Structural Control and Health Monitoring ; Vol. 21, issue. 5 , May , 2014 , p. 649-674 ; Abazarsa, F ; Ghannad, M. A ; Celebi, M ; Taciroglu, E ; Sharif University of Technology
Abstract
Response-only identification of civil structureshas attracted much attention during recent years, as input excitations are rarely measurable for ambient vibrations. Although various techniques have been developed by which identification can be carried out using ambient responses, these techniques are generally not applicable to non-stationary excitations that structures experience during moderate-to-severe earthquakes. Recently, the authors proposed a new response-only modal identification method that is applicable to strong shaking data. This new method is highly attractive for cases in which the true input motions are unavailable. For example, when soil-structure interaction effects are...
Blind modal identification of non-classically damped systems from free or ambient vibration records
, Article Earthquake Spectra ; Volume 29, Issue 4 , 2013 , Pages 1137-1157 ; 87552930 (ISSN) ; Nateghi, F ; Ghahari, S. F ; Taciroglu, E ; Sharif University of Technology
2013
Abstract
A significant segment of system identification literature on civil structures is devoted to response-only identification, simply because lack of measurements of input excitations for civil structures is a fairly common scenario. In recent years, several researchers have successfully adapted a second-order blind identification (SOBI) technique-a method originally developed for "blind source separation" of audio signals-to response-only identification of mechanical and civil structures. However, this development had been confined to fully instrumented classically damped systems. While several approaches have been proposed recently for extending SOBI to non-classically damped systems, they all...
Detection of sudden structural damage using blind source separation and time-frequency approaches
, Article Smart Materials and Structures ; Volume 25, Issue 5 , 2016 ; 09641726 (ISSN) ; Kazemi, M. T ; Sharif University of Technology
Institute of Physics Publishing
2016
Abstract
Seismic signal processing is one of the most reliable methods of detecting the structural damage during earthquakes. In this paper, the use of the hybrid method of blind source separation (BSS) and time-frequency analysis (TFA) is explored to detect the changes in the structural response data. The combination of the BSS and TFA is applied to the seismic signals due to the non-stationary nature of them. Firstly, the second-order blind identification technique is used to decompose the response signal of structural vibration into modal coordinate signals which will be mono-components for TFA. Then each mono-component signal is analyzed to extract instantaneous frequency of structure. Numerical...