Factors Influencing Natural Frequencies in a Prestressed Concrete Panel for Damage Detection

2014 ◽  
Vol 69 (3) ◽  
Author(s):  
L. D. Goh ◽  
A. A. Rahman ◽  
N. Bakhary ◽  
B. H. Ahmad
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Damage Detection ◽  
Prestressed Concrete ◽  
Natural Frequencies ◽  
Element Model ◽  
Modal Parameters ◽  
Actual Structure ◽  
Modal Test ◽  
The Finite Element Model

Modal parameters such as natural frequencies, mode shapes, and damping ratios are widely used as damage indicators in the field of vibration-based damage detection. These modal parameters can be easily obtained by conducting the modal test on the actual structure or from the finite element model. However, many publications are focusing only on the relationship between the modal parameters and the changes in structural properties for damage detection. There are a limited number of publications discussing on the factors that may affect the modal parameters for damage detection. Hence, this paper provides a study on the level of influence of several factors on the natural frequencies of a prestressed concrete panel. The factors that are considered in this study are the size of element used in the numerical model, the dimension of the structural element, and the prestressing force applied in the prestressed concrete panel. The natural frequencies computed from the finite element model are also verified with the actual measured natural frequencies that are determined through the modal test conducted in the laboratory. 

scholarly journals Experimental Studies on Finite Element Model Updating for a Heated Beam-Like Structure

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Kaipeng Sun ◽  
Yonghui Zhao ◽  
Haiyan Hu
Keyword(s):  
Finite Element ◽  
High Temperature ◽  
Finite Element Model ◽  
Natural Frequencies ◽  
Model Updating ◽  
Element Model ◽  
Modal Parameters ◽  
Finite Element Model Updating ◽  
Time Varying ◽  
The Finite Element Model

An experimental study was made for the identification procedure of time-varying modal parameters and the finite element model updating technique of a beam-like thermal structure in both steady and unsteady high temperature environments. An improved time-varying autoregressive method was proposed first to extract the instantaneous natural frequencies of the structure in the unsteady high temperature environment. Based on the identified modal parameters, then, a finite element model for the structure was updated by using Kriging meta-model and optimization-based finite-element model updating method. The temperature-dependent parameters to be updated were expressed as low-order polynomials of temperature increase, and the finite element model updating problem was solved by updating several coefficients of the polynomials. The experimental results demonstrated the effectiveness of the time-varying modal parameter identification method and showed that the instantaneous natural frequencies of the updated model well tracked the trends of the measured values with high accuracy.

Deep neural networks–based damage detection using vibration signals of finite element model and real intact state: An evaluation via a lab-scale offshore jacket structure

2020 ◽  
pp. 147592172093261 ◽  
Author(s):  
Zohreh Mousavi ◽  
Sina Varahram ◽  
Mir Mohammad Ettefagh ◽  
Morteza H. Sadeghi ◽  
Seyed Naser Razavi
Keyword(s):  
Neural Network ◽  
Finite Element ◽  
Finite Element Model ◽  
Damage Detection ◽  
Deep Neural Network ◽  
Element Model ◽  
Frequency Data ◽  
Vibration Signals ◽  
Intact State ◽  
The Finite Element Model

Structural health monitoring of mechanical systems is essential to avoid their catastrophic failure. In this article, an effective deep neural network is developed for extracting the damage-sensitive features from frequency data of vibration signals to damage detection of mechanical systems in the presence of the uncertainties such as modeling errors, measurement errors, and environmental noises. For this purpose, the finite element method is used to analyze a mechanical system (finite element model). Then, vibration experiments are carried out on the laboratory-scale model. Vibration signals of real intact system are used to updating the finite element model and minimizing the disparities between the natural frequencies of the finite element model and real system. Some parts of the signals that are not related to the nature of the system are removed using the complete ensemble empirical mode decomposition technique. Frequency domain decomposition method is used to extract frequency data. The proposed deep neural network is trained using frequency data of the finite element model and real intact state and then is tested using frequency data of the real system. The proposed network is designed in two stages, namely, the pre-training classification based on deep auto-encoder and Softmax layer (first stage), and the re-training classification based on backpropagation algorithm for fine tuning of the network (second stage). The proposed method is validated using a lab-scale offshore jacket structure. The results show that the proposed method can learn features from the frequency data and achieve higher accuracy than other comparative methods.

Hydroelastic Modal Analysis of the Perforated Cylindrical Shell in SMART

2011 ◽  
Author(s):  
Youngin Choi ◽  
Seungho Lim ◽  
Kyoung-Su Park ◽  
No-Cheol Park ◽  
Young-Pil Park ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Dynamic Characteristics ◽  
Natural Frequencies ◽  
Element Model ◽  
Mode Shapes ◽  
Steam Generators ◽  
Structure Interaction ◽  
The Finite Element Model ◽  
Reactor Internals

The System-integrated Modular Advanced ReacTor (SMART) developed by KAERI includes components like a core, steam generators, coolant pumps, and a pressurizer inside the reactor vessel. Though the integrated structure improves the safety of the reactor, it can be excited by an earthquake and pump pulsations. It is important to identify dynamic characteristics of the reactor internals considering fluid-structure interaction caused by inner coolant for preventing damage from the excitations. Thus, the finite element model is constructed to identify dynamic characteristics and natural frequencies and mode shapes are extracted from this finite element model.

A Method to Determine the Boundary Conditions of the Finite Element Model of a Slender Beam Using Measured Modal Parameters

1996 ◽  
Vol 118 (3) ◽  
pp. 474-478 ◽  
Author(s):  
Wang Fengquan ◽  
Chen Shiyu
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Finite Element Model ◽  
Interpolation Method ◽  
Element Model ◽  
Accurate Method ◽  
Modal Parameters ◽  
Computation Method ◽  
Modal Parameter ◽  
The Finite Element Model

In this paper, a method used to determine the boundary conditions of the Finite Element Model of a slender beam with measured structure modal parameters is presented. On deriving the method, the finite element model theory for dynamic calculating is used. Combined with the modal parameters from experiment, an FEM-modal parameter equation to determine the boundary conditions is put forward. For solving the equation, three methods are given. The first is the accurate method. The second is the full mode computation method by means of generalized inverse matrix. The third is the interpolation method of frequency. A numerical simulation with computer is given and the results of calculation fully verify the effectiveness of the method offered and also verify that the accuracy of the method is satisfying. Finally, an applied example is given and the results of calculation fully verify the effectiveness of the method offered.

scholarly journals Applied theory of bending vibration of the piezoelectric and piezomagnetic bimorph

2020 ◽  
Vol 10 (03) ◽  
pp. 2050007
Author(s):  
Do Thanh Binh ◽  
V. A. Chebanenko ◽  
Le Van Duong ◽  
E. Kirillova ◽  
Pham Manh Thang ◽  
...  
Keyword(s):  
Finite Element ◽  
Variational Principle ◽  
Boundary Conditions ◽  
Finite Element Model ◽  
Natural Frequencies ◽  
Element Model ◽  
Applied Theory ◽  
Bending Vibration ◽  
Steady Vibrations ◽  
The Finite Element Model

Based on the variational principle, equations and boundary conditions for transverse steady vibrations of a bimorph consisting of a piezoelectric and piezomagnetic layers are obtained. The results of calculations of natural frequencies are compared with the finite element model of the device in ACELAN.

Modal Analysis for the Powertrain of Electric Vehicle by Finite Element Method

2013 ◽  
Vol 437 ◽  
pp. 140-145
Author(s):  
Fei Fei Chen ◽  
Peng Yu ◽  
Tong Zhang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Finite Element Model ◽  
Modal Analysis ◽  
Element Model ◽  
Element Calculation ◽  
Modal Test ◽  
Vibration Properties ◽  
Automotive Powertrain ◽  
The Finite Element Model

The finite element model of an electric automotive powertrain is the basis of the research on its vibration and noise. In this paper, the vibration properties of dynamically-loaded housing are first obtained based on finite element calculation,which is testified by the modal test .It provides the reference for the establishing of electric automotive powertrain.

Model Analysis of Car’s Body-in-White Based on FEA

2011 ◽  
Vol 354-355 ◽  
pp. 454-457
Author(s):  
Yuan Wang ◽  
Li Xu ◽  
Xi Liang Dai ◽  
Sheng Hui Peng
Keyword(s):  
Finite Element ◽  
Optimal Design ◽  
Finite Element Model ◽  
Element Model ◽  
Model Analysis ◽  
The Body ◽  
Dynamic Parameters ◽  
Modal Test ◽  
Body In White ◽  
The Finite Element Model

In this paper, the finite element model of some car’s body-in-white is established in Hypermesh. The model analysis is executed based on the element model in ANSYS. Through the model analysis the dynamic parameters of the body-in-white are obtained. At the same time，the modal test of a real car body is implemented. The reliability of the finite element model is validated based on the modal test. The results show that the stiffness of the body-in-white is great enough and it can provide optimal design for future designers.

Nonlinear Energy Sink for Whole-Spacecraft Vibration Reduction

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Kai Yang ◽  
Ye-Wei Zhang ◽  
Hu Ding ◽  
Tian-Zhi Yang ◽  
Yang Li ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Natural Frequencies ◽  
Vibration Reduction ◽  
Nonlinear Energy Sink ◽  
Element Model ◽  
Equivalent Model ◽  
Energy Sink ◽  
The Finite Element Model ◽  
Nonlinear Energy

A nonlinear energy sink (NES) approach is proposed for whole-spacecraft vibration reduction. Frequency sweeping tests are conducted on a scaled whole-spacecraft structure without or with a NES attached. The experimental transmissibility results demonstrate the significant reduction of the whole-spacecraft structure vibration over a broad spectrum of excitation frequency. The NES attachment hardly changes the natural frequencies of the structure. A finite element model is developed, and the model is verified by the experimental results. A two degrees-of-freedom (DOF) equivalent model of the scaled whole-spacecraft is proposed with the two same natural frequencies as those obtained via the finite element model. The experiment, the finite element model, and the equivalent model predict the same trends that the NES vibration reduction performance becomes better for the increasing NES mass, the increasing NES viscous damping, and the decreasing nonlinear stiffness. The energy absorption measure and the energy transition measure calculated based on the equivalent model reveals that an appropriately designed NES can efficiently absorb and dissipate broadband-frequency energy via nonlinear beats, irreversible targeted energy transfer (TET), or both for different parameters.

scholarly journals DEVELOPMENT OF A DESIGN METHOD FOR DETERMINING THE ATTACHMENT OF THE EXHAUST MOUNTING MOUNTS

Akustika ◽  
2019 ◽  
Vol 34 ◽  
pp. 141-147
Author(s):  
Rakhmatjon Rakhmatov ◽  
Vitaliy Krutolapov ◽  
Valeriy Zuzov
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Strain Energy ◽  
Natural Frequencies ◽  
Design Method ◽  
Exhaust System ◽  
Element Model ◽  
Vehicle Body ◽  
Vibration Modes ◽  
The Finite Element Model

The article presents the developed method of determining the attachment points of the mounts of the exhaust system to the vehicle body. The requirements for the construction of a finite element model of the exhaust system are presented, the finite element model of the exhaust system is created, the results of natural frequencies and vibration modes and the strain energy of the structure are shown.

Simulation of Damage Scenarios in an FRP Composite Suspension Footbridge

2005 ◽  
Vol 293-294 ◽  
pp. 599-606 ◽  
Author(s):  
R.A. Votsis ◽  
M.M. Abdel Wahab ◽  
M.K. Chryssanthopoulos
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Natural Frequencies ◽  
Element Model ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Limit States ◽  
Damage Scenarios ◽  
Frp Composite ◽  
Initial Strains

Simulations of damage scenarios were carried out using a finite element model of a newly constructed FRP composite footbridge, the Wilcott footbridge. This footbridge represents a new generation of suspension footbridges that have lightweight decks made of pultruded glass fibre reinforced polymer (GFRP) composite elements. It offers several advantages over conventional steel or concrete footbridges, e.g. speed of installation, high resistance to corrosion and saving in weight and foundations. On the other hand, its lightness and slenderness make it more sensitive to dynamic effects, both at serviceability and ultimate limit states. A finite element model using 3-D beam elements was constructed and damage scenarios were simulated and introduced in the model. The natural frequencies, mode shapes as well as time responses due to pedestrian loading were predicted. Different size of delamination in the composite deck was simulated at various locations along the bridge. The sensitivity of natural frequencies and mode shapes due to delamination were assessed by comparing the results of the damaged deck to those of the reference intact deck. The effect of changes in the cables’ initial strains on the modal parameters was also examined, and the sensitivity of modal parameters to cable degradation was assessed.

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