A New Algorithm for the System Identification of Shear Structures

2012 ◽  
Vol 457-458 ◽  
pp. 495-499 ◽  
Author(s):  
Behnam Adhami ◽  
Hamed Niroumand ◽  
Karen Khanlari
Keyword(s):  
System Identification ◽  
Damage Detection ◽  
Frequency Characteristics ◽  
Mode Shapes ◽  
Noise Attenuation ◽  
Structural System ◽  
Coulomb Damping ◽  
Shear Structures ◽  
General Terms ◽  
Shear Structure

In general terms, the aim of "System Identification" is to determine the dynamic characteristics of mechanical systems. These characteristics include both frequency characteristics (frequencies, mode shapes, and damping ratios) and the system's characteristic matrices (the matrices of mass, viscous damping, stiffness, Coulomb damping or coefficients of friction, and the Duffing stiffness). In such fields as "Damage Detection" in structures, identification of the system's characteristic matrices is of the same importance as the identification of the frequency characteristics, or even more so, by identifying these matrices, the intended goals in Damage Detection can be achieved. In line with such identification, a new algorithm for the system identification of shear structures is presented in the paper. Taking into account the fundamental and significant effect of noise attenuation in boosting the levels of precision and the correctness of system identification, this method helps to achieve noise attenuation by trimming noisy records in the frequency domain, in parallel with the identification of the structural system. The efficiency and precision of the method have been examined through the application of a "closed loop solution" to a five storey model of shear structure.

scholarly journals Damage detection under temperature variability using closed-loop mode shapes

2020 ◽  
Author(s):  
Bilal Ali Qadri ◽  
Anders Schmidt Kristensen ◽  
Martin Dalgaard Ulriksen
Keyword(s):  
Damage Detection ◽  
Mode Shape ◽  
Closed Loop ◽  
Temperature Variability ◽  
Mode Shapes ◽  
Effect Of Temperature ◽  
Structural System ◽  
Outlier Analysis ◽  
Assignment Scheme ◽  
General Method

The dynamic characteristics of any structural system depend on the temperature. This poses a challenge in vibration-based damage detection, as temperature variability can mask damage-induced shifts in the vibration features. Different means for resolving the issue have been put forth, and two general method types can be distinguished; (i) those mitigating the effect of temperature variability on the features and (ii) those increasing the sensitivity to damage of the features. The present paper explores the use of features composed of closed-loop (CL) mode shapes, which combine attributes from both method groups by offering adequate sensitivity to damage and robustness to temperature variability. The CL mode shapes are designed using an eigenstructure assignment scheme formulated as a bi-objective optimization problem. The first objective is the reciprocal of the spectral norm of the CL mode shape Jacobian matrix, which is thus to be minimized to maximize the sensitivity to damage. The second objective, whose implementation hinges on the assumptions that temperature variability induces spatially uniform stiffness changes and that homogeneous sensing is employed, is a measure of how much the damping in each of the assigned CL modes deviates from a classical distribution. Since classically damped mode shapes obtained using homogeneous sensing are invariant under spatially uniform stiffness changes, the latter objective is minimized to promote robustness to temperature variability. The designed CL mode shape features can be used in any damage detection method, but in the paper we restrict the use to outlier analysis and assess the merit of the proposed scheme in the context of numerical examples. The damage detection results are compared to findings obtained using cointegration (a well-established method for mitigating the effect of temperature variability), and it is seen how the proposed scheme outperforms the cointegration-based method.

scholarly journals Damage Location Index of Shear Structures Based on Changes in First Two Natural Frequencies

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Hien HoThu ◽  
Akira Mita
Keyword(s):  
System Identification ◽  
Damage Detection ◽  
Natural Frequencies ◽  
Detection Method ◽  
Identification Methods ◽  
Damage Location ◽  
Shear Structures ◽  
Stiffness Reduction ◽  
Shear Building

A method of detecting the location of damage in shear structures by using only the changes in first two natural frequencies of the translational modes is proposed. This damage detection method can determine the damage location in a shear building by using a Damage Location Index (DLI) based on two natural frequencies for undamaged and damaged states. In this study, damage is assumed to be represented by the reduction in stiffness. This stiffness reduction results in a change in natural frequencies. The uncertainty associated with system identification methods for obtaining natural frequencies is also carefully considered. Some simulations and experiments on shear structures were conducted to verify the performance of the proposed method.

scholarly journals Ambient Vibration Testing of a Pedestrian Bridge Using Low-Cost Accelerometers for SHM Applications

Smart Cities ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 20-30 ◽  
Author(s):  
Azam Ali ◽  
Talha Sandhu ◽  
Muhammad Usman
Keyword(s):  
Finite Element ◽  
System Identification ◽  
Damage Detection ◽  
Low Cost ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Pedestrian Bridge ◽  
Finite Element Software ◽  
Ambient Vibration Testing ◽  
Good Comparison

Damage detection and structural health monitoring have always been of great importance to civil engineers and researchers. Vibration-based damage detection has several advantages compared to traditional methods of non-destructive evaluation, such as ground penetrating radar (GPR) or ultrasonic testing, since they give a global response and are feasible for large structures. Damage detection requires a comparison between two systems states, the baseline or “healthy state”, i.e., the initial modal parameters, and the damaged state. In this study, system identification (SI) was carried out on a pedestrian bridge by measuring the dynamic response using six low-cost triaxial accelerometers. These low-cost accelerometers use a micro-electro-mechanical system (MEMS), which is cheaper compared to a piezoelectric sensor. The frequency domain decomposition algorithm, which is an output-only method of modal analysis, was used to obtain the modal properties, i.e., natural frequencies and mode shapes. Three mode shapes and frequencies were found out using system identification and were compared with the finite element model (FEM) of the bridge, developed using the commercial finite element software, Abaqus. A good comparison was found between the FEM and SI results. The frequency difference was nearly 10%, and the modal assurance criterion (MAC) of experimental and analytical mode shapes was greater than 0.80, which proved to be a good comparison despite the small number of accelerometers available and the simplifications and idealizations in FEM.

Error analysis of structural system identification by observability method

2017 ◽  
Vol 109 (7) ◽  
pp. 3254-3261
Author(s):  
Jun LEI ◽  
Dong XU ◽  
José Antonio Lozano-Galant ◽  
María Nogal ◽  
José Turmo
Keyword(s):  
System Identification ◽  
Error Analysis ◽  
Structural System ◽  
Structural System Identification

A Study on Structural System Identification and Damage Detection for Free Vibration Response Using the Wavelet Transform

2015 ◽  
Vol 752-753 ◽  
pp. 1029-1034
Author(s):  
Asnizah Sahekhaini ◽  
Pauziah Muhamad ◽  
Masayuki Kohiyama ◽  
Aminuddin Abu ◽  
Lee Kee Quen ◽  
...  
Keyword(s):  
Free Vibration ◽  
Damage Detection ◽  
Vibration Response ◽  
Structural System ◽  
Modal Parameter ◽  
Modal Parameter Identification ◽  
Complex Morlet Wavelet ◽  
Structural System Identification ◽  
Free Vibration Response ◽  
Energy Components

This paper presents a wavelet-based method of identification modal parameter and damage detection in a free vibration response. An algorithm for modal parameter identification and damage detection is purposed and complex Morlet wavelet is chosen as an analysis wavelet function. This paper only focuses on identification of natural frequencies of the structural system. The method utilizes both undamaged and damage experiment data of free vibration response of the truss structure system. Wavelet scalogram is utilizes for damage detection. The change of energy components for undamaged and damage structure is investigated from the plot of wavelet scalogram which corresponded to the detection of damage.

Sign in / Sign up

Export Citation Format

Share Document