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.

Effect of crack on free vibration of a pre-stressed curved plate

2021 ◽  
pp. 095440622199486
Author(s):  
Can Gonenli ◽  
Hasan Ozturk ◽  
Oguzhan Das
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Natural Frequency ◽  
Present Model ◽  
Mode Shapes ◽  
Load Parameter ◽  
Flexible Plate ◽  
Cantilever Plate ◽  
Finite Element Software ◽  
Aspect Ratios

In this study, the effect of crack on free vibration of a large deflected cantilever plate, which forms the case of a pre-stressed curved plate, is investigated. A distributed load is applied at the free edge of a thin cantilever plate. Then, the loading edge of the deflected plate is fixed to obtain a pre-stressed curved plate. The large deflection equation provides the non - linear deflection curve of the large deflected flexible plate. The thin curved plate is modeled by using the finite element method with a four-node quadrilateral element. Three different aspect ratios are used to examine the effect of crack. The effect of crack and its location on the natural frequency parameter is given in tables and graphs. Also, the natural frequency parameters of the present model are compared with the finite element software results to verify the reliability and validity of the present model. This study shows that the different mode shapes are occurred due to the change of load parameter, and these different mode shapes cause a change in the effect of crack.

scholarly journals Low Cost Frictional Seismic Base-Isolation of Residential New Masonry Buildings in Developing Countries: A Small Masonry House Case Study

2017 ◽  
Vol 11 (1) ◽  
pp. 1026-1035 ◽  
Author(s):  
Ahmad Basshofi Habieb ◽  
Gabriele Milani ◽  
Tavio Tavio ◽  
Federico Milani
Keyword(s):  
Finite Element ◽  
Seismic Vulnerability ◽  
Base Isolation ◽  
Low Cost ◽  
Element Model ◽  
Shaking Table ◽  
Fe Model ◽  
Isolation System ◽  
Finite Element Software ◽  
Non Linear

Introduction:An advanced Finite Element model is presented to examine the performance of a low-cost friction based-isolation system in reducing the seismic vulnerability of low-class rural housings. This study, which is mainly numerical, adopts as benchmark an experimental investigation on a single story masonry system eventually isolated at the base and tested on a shaking table in India.Methods:Four friction isolation interfaces, namely, marble-marble, marble-high-density polyethylene, marble-rubber sheet, and marble-geosynthetic were involved. Those interfaces differ for the friction coefficient, which was experimentally obtained through the aforementioned research. The FE model adopted here is based on a macroscopic approach for masonry, which is assumed as an isotropic material exhibiting damage and softening. The Concrete damage plasticity (CDP) model, that is available in standard package of ABAQUS finite element software, is used to determine the non-linear behavior of the house under non-linear dynamic excitation.Results and Conclusion:The results of FE analyses show that the utilization of friction isolation systems could much decrease the acceleration response at roof level, with a very good agreement with the experimental data. It is also found that systems with marble-marble and marble-geosynthetic interfaces reduce the roof acceleration up to 50% comparing to the system without isolation. Another interesting result is that there was little damage appearing in systems with frictional isolation during numerical simulations. Meanwhile, a severe state of damage was clearly visible for the system without isolation.

Investigation of stiffness of small wind turbine blade based on vibration analysis technique

2019 ◽  
Vol 44 (1) ◽  
pp. 49-59
Author(s):  
Nilesh Chandgude ◽  
Nitin Gadhave ◽  
Ganesh Taware ◽  
Nitin Patil
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Wind Turbine ◽  
Natural Frequency ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Element Analysis ◽  
Finite Element Software ◽  
Small Wind Turbine

In this article, three small wind turbine blades of different materials were manufactured. Finite element analysis was carried out using finite element software ANSYS 14.5 on modeled blades of National Advisory Committee for Aeronautics 4412 airfoil profile. From finite element analysis, first, two flap-wise natural frequencies and mode shapes of three different blades are obtained. Experimental vibration analysis of manufactured blades was carried out using fast Fourier transform analyzer to find the first two flap-wise natural frequencies. Finally, the results obtained from the finite element analysis and experimental test of three blades are compared. Based on vibration analysis, we found that the natural frequency of glass fiber reinforced plastic blade reinforced with aluminum sheet metal (small) strips increases compared with the remaining blades. An increase in the natural frequency indicates an increase in the stiffness of blade.

scholarly journals Numerical Modeling of Masonry Infilled Reinforced Concrete Building during Construction Stages Using ABAQUS Software

Buildings ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 181 ◽  
Author(s):  
Boudjamaa Roudane ◽  
Süleyman Adanur ◽  
Ahmet Can Altunışık
Keyword(s):  
Reinforced Concrete ◽  
Natural Frequencies ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Analysis Model ◽  
Reinforced Concrete Building ◽  
Finite Element Software ◽  
Comparison Results ◽  
Concrete Building ◽  
Abaqus Software

The effects of seismic actions on reinforced concrete (RC) structures are strongly influenced by the dynamic behavior of their materials. It is crucial to find a simple definition of the natural frequencies of reinforced concrete buildings, particularly in relation to both principal and secondary elements constructing the reinforced concrete building type. This paper firstly presents a comparison with the ambient vibration surveys. An analysis model of different stages of construction of the reinforced concrete masonry wall was compared using the finite element software. In the second step, structural responses of the model were investigated by means of static analysis. Three main types were examined: Bare frame for one, two and three storeys; brick-walled; and coated cases. Modal analysis is carried out by ABAQUS software starting from the deformed building, to provide the natural frequencies and mode shapes. For the natural frequencies, a good agreement is obtained between analytical and experimental results. Furthermore, the comparison results between different cases show that the application of the plaster work increases the lateral stiffness and has significant effects on the dynamic response of the buildings.

Modeling and Modal Analysis of Less-Teeth Gear Shaft

2013 ◽  
Vol 385-386 ◽  
pp. 192-195
Author(s):  
Dong Sheng Zhang ◽  
Jian Jun Zhang
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Modal Analysis ◽  
Helix Angle ◽  
Mode Shapes ◽  
Contact Ratio ◽  
Finite Element Software ◽  
Meshing Characteristics ◽  
Dynamic Meshing ◽  
Ansys Workbench

As the less-teeth gear has the less-teeth, the bigger helix angle and the more contact ratio etc. The research of dynamic meshing characteristics makes focus, and modal analysis is the basis of dynamic analysis. In order to get the modal analysis characteristics: firstly the parametric solid modeling is realized through the software of MATLAB and PRO/E; secondly multistage inherent frequencies and mode shapes are achieved by the finite element software of ANSYS Workbench.

Damage detection based on system identification of concrete dams using an extended finite element–wavelet transform coupled procedure

2017 ◽  
Vol 24 (18) ◽  
pp. 4226-4246 ◽  
Author(s):  
Sajjad Pirboudaghi ◽  
Reza Tarinejad ◽  
Mohammad Taghi Alami
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Wavelet Transform ◽  
System Identification ◽  
Damage Detection ◽  
Cohesive Crack ◽  
Modal Parameters ◽  
Concrete Dams ◽  
Extended Finite Element ◽  
Element Method

The aim of the present study is to propose a procedure for seismic cracking identification of concrete dams using a coupling of the extended finite element method (XFEM) based on cohesive crack segments (XFEM-COH) and continuous wavelet transform (CWT). First, the dam is numerically modeled using the traditional finite element method (FEM). Then, cracking capability is added to the dam structure by applying the XFEM-COH for concrete material. The results of both the methods under the seismic excitation have been compared and identified to damage detection purposes. In spite of predefined damage in some of the structural health monitoring (SHM) techniques, there is an advantage in the XFEM model where the whole dam structure is potentially under damage risk without initial crack, and may not crack at all. Finally, in order to evaluate any change in the system, that is, specification of any probable crack effects and nonlinear behavior, the structural modal parameters and their variation have been investigated using system identification based on the CWT. The results show that the extended finite element–wavelet transform procedure has high ability for the online SHM of concrete dams that by analysis of its results, the history of physical changes, cracking initiation time, and exact damage localization have been performed from comparing the intact (FEM) and damaged (XFEM) modal parameters of the structural response. In addition, any small change in the system is observable while the final crack profile and performance simulation of the dam body under strong seismic excitations have obtained.

Optimization Dressing Method of Amplitude Transformer Based on Finite Element

2013 ◽  
Vol 278-280 ◽  
pp. 315-318
Author(s):  
Ming Li Zhao ◽  
Bo Zhao ◽  
Yu Qing Wang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Resonant Frequency ◽  
Structural Parameters ◽  
Low Cost ◽  
Dressing Method ◽  
Finite Element Software ◽  
System Vibration ◽  
Vibration Performance ◽  
Element Method

The node position of amplitude transformer was determined by the finite element method, and the flange was designed at the nod position for conveniently installation. By the finite element software, the amplitude transformer with flange was optimized and dressed, and its structural parameters were determined. During the actual manufacturing process, it was used impedance analyzer to test its vibration performance, the testing results show that this system vibration performance is good, its resonant frequency is 34.771kHz, anti-resonant frequency is 35.008kHz. The above-mentioned results are very much coincided with the system natural frequency of 34.893kHz which is drew by finite element method. Compared to the traditional dressing this method has many advantages such as convenience, green, environmental protection, low cost and others.

Analysis of a damaged 12-storey frame-wall concrete building during the 2010 Haiti earthquake Part I: Dynamic behaviour assessment

2013 ◽  
Vol 40 (8) ◽  
pp. 791-802 ◽  
Author(s):  
Benoit Boulanger ◽  
Charles-Philippe Lamarche ◽  
Jean Proulx ◽  
Patrick Paultre
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Visual Assessment ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Vibration Frequencies ◽  
Haiti Earthquake ◽  
Ambient Vibration Tests ◽  
Modelling Assumptions

Despite all the damages encountered during the 2010 Haiti earthquake, the 12-storey reinforced-concrete Digicel building behaved well, sustaining only reparable damages. Visual assessment to characterize the damages sustained and ambient vibration tests (AVT) were carried out to identify the building’s key dynamics properties (natural vibration frequencies, mode shapes, and damping ratios). ETABS was used to generate finite element (FE) models before and after the AVT, to evaluate the capabilities of common modelling assumptions to predict the dynamic behaviour of structures. Nonautomated model updating was carried out to generate a model representing the building’s actual dynamic behaviour in its damaged state. The study showed that the finite element method (FEM) is reliable for predicting the dynamic behaviour of structures, but is very sensitive to the modelling assumptions. The models could predict the vibration frequencies precisely, but an accurate representation of the mode shapes required careful model updating.

scholarly journals Research on Laterally Restrained Built Up Steel Beam Under Dynamic Response

2019 ◽  
Vol 8 (6S4) ◽  
pp. 1057-1061
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Mode Shape ◽  
Extraction Methods ◽  
Analytical Investigation ◽  
Mode Shapes ◽  
Linear Perturbation ◽  
Steel Beam ◽  
Finite Element Software ◽  
Eigen Value

This paper presents the analytical investigation of laterally restrained built up steel beam under dynamic response using finite element software ABAQUS. The main objective of this study was to estimate the mode shapes and mode shape curvature of the laterally restrained built up steel beam. The three parameters such as modal frequencies, mode shapes and mode shape curvature are suggested for identifying the damages in built up steel beam. Damage assessment is done by linear perturbation free vibration study using finite element software ABAQUS. The frequency extraction methods for built up steel beam was done in ABAQUS to get the dynamic response. The Lanczos eigen solver was used for finding the mode shapes. Eigen value extraction, the natural frequencies and the corresponding mode shapes of a system were studied

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