scholarly journals INVESTIGATION OF EFFECT OF USING NANO COATING ON WOODEN SHEDS ON DYNAMIC PARAMETERS

Wood Research ◽  
2021 ◽  
Vol 66 (6) ◽  
pp. 1006-1014
Author(s):  
SERTAÇ TUHTA ◽  
FURKAN GÜNDAY
Keyword(s):  
Silicon Dioxide ◽  
Ground Level ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Dynamic Parameters ◽  
Vibration Data ◽  
Nano Coating ◽  
High Adherence ◽  
Frequency Domain Decomposition ◽  
Ambient Excitation

In this article, the dynamic parameters (frequencies, mode shapes, damping ratios) of the uncoated wooden shed and the coated by silicon dioxide are compared using the operational modal analysis method. Ambient excitation was provided from micro tremor ambient vibration data on ground level. Enhanced frequency domain decomposition (EFDD) was used for output. Very best correlation was found between mode shapes. Nano-SiO2 gel applied to the entire outer surface of the red oak shed has an average of 14.54% difference in frequency values and 13.53% in damping ratios, proving that nanomaterials can be used to increase internal rigidity in wooden slabs. High adherence of silicon dioxide to wooden surfaces was observed as another important result of this study.

scholarly journals DETERMINATION OF THE EFFECT OF TiO2 ON THE DYNAMIC BEHAVIOR OF SCALED CONCRETE CHIMNEY BY OMA

2021 ◽  
Vol 55 (3) ◽  
Author(s):  
Sertaç Tuhta ◽  
Furkan Günday
Keyword(s):  
Titanium Dioxide ◽  
Outer Surface ◽  
Ground Level ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Dynamic Parameters ◽  
Vibration Data ◽  
Output Only ◽  
Frequency Domain Decomposition

In this article, the dynamic parameters (frequencies, mode shapes, damping ratios) of a scaled concrete chimney and the dynamic parameters (frequencies, mode shapes, damping ratios) of the entire outer surface of the 80-micron-thick titanium dioxide are compared using the operational modal analysis method. Ambient excitation was provided from micro tremor ambient vibration data at ground level. Enhanced Frequency Domain Decomposition (EFDD) is used for the output-only modal identification. From this study, very best correlation is found between the mode shapes. Titanium dioxide applied to the entire outer surface of the scaled concrete chimney has an average of 16.34 % difference in frequency values and 9.81 % in damping ratios, proving that nanomaterials can be used to increase the rigidity in chimneys, in other words, for reinforcement. Another important result determined in the study is that it has been observed that the adherence of titanium dioxide and similar nanomaterials mentioned in the introduction to concrete chimney surfaces is at the highest level.

scholarly journals Automated band selection for Bayesian FFT modal identification Based on RetinaNet

2021 ◽  
Vol 2078 (1) ◽  
pp. 012058
Author(s):  
Chen Wang ◽  
Zhilin Xue ◽  
Yipeng Su ◽  
Binbin Li
Keyword(s):  
Operation Time ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Band Selection ◽  
Data Sets ◽  
Civil Structures ◽  
Frequency Bands ◽  
Operational Conditions ◽  
Vibration Data

Abstract Bayesian FFT algorithm is a popular method to identify modal parameters, e.g., modal frequencies, damping ratios, and mode shapes, of civil structures under operational conditions. It is efficient and provides the identification uncertainty in terms of posterior distribution. However, in utilizing the Bayesian FFT algorithm, it is tedious to manually select frequency bands and initial frequencies. This step requires professional knowledge and costs most of time, which prevents the automation of Bayesian FFT algorithm. Regarding the band selection as an object detection problem, we design a band selection network based on the RetinaNet to automatically select frequency bands and a peak prediction network to predict the initial frequencies. The designed networks are trained using the singular value spectrum of measured ambient vibration data and verified by various data sets. It can achieve the human accuracy with much less operation time, and thus provides a corner stone for the automation of Bayesian FFT algorithm.

Extending Blind Modal Identification to the Underdetermined Case for Ambient Vibration

2012 ◽  
Author(s):  
Scot McNeill
Keyword(s):  
Natural Frequencies ◽  
Second Order ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Frequency Domain Method ◽  
Blind Identification ◽  
Vibration Data ◽  
Modal Damping ◽  
Six Dof

The modal identification framework known as Blind Modal Identification (BMID) has recently been developed, drawing on techniques from Blind Source Separation (BSS). Therein, a BSS algorithm known as Second Order Blind Identification (SOBI) was adapted to solve the Modal IDentification (MID) problem. One of the drawbacks of the technique is that the number of modes identified must be less than the number of sensors used to measure the vibration of the equipment or structure. In this paper, an extension of the BMID method is presented for the underdetermined case, where the number of sensors is less than the number of modes to be identified. The analytic signal formed from measured vibration data is formed and the Second Order Blind Identification of Underdetermined Mixtures (SOBIUM) algorithm is applied to estimate the complex-valued modes and modal response autocorrelation functions. The natural frequencies and modal damping ratios are then estimated from the corresponding modal auto spectral density functions using a simple Single Degree Of Freedom (SDOF), frequency-domain method. Theoretical limitations on the number of modes identified given the number of sensors are provided. The method is demonstrated using a simulated six DOF mass-spring-dashpot system excited by white noise, where displacement at four of the six DOF is measured. All six modes are successfully identified using data from only four sensors. The method is also applied to a more realistic simulation of ambient building vibration. Seven modes in the bandwidth of interest are successfully identified using acceleration data from only five DOF. In both examples, the identified modal parameters (natural frequencies, mode shapes, modal damping ratios) are compared to the analytical parameters and are demonstrated to be of good quality.

scholarly journals Identification, Model Updating, and Response Prediction of an Instrumented 15-Story Steel-Frame Building

2006 ◽  
Vol 22 (3) ◽  
pp. 781-802 ◽  
Author(s):  
Derek Skolnik ◽  
Ying Lei ◽  
Eunjong Yu ◽  
John W. Wallace
Keyword(s):  
Structural Damage ◽  
Model Updating ◽  
Three Dimensional ◽  
Response Prediction ◽  
Element Model ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Northridge Earthquake ◽  
Vibration Data ◽  
Modal Properties

Identification of the modal properties of the UCLA Factor Building, a 15-story steel moment-resisting frame, is performed using low-amplitude earthquake and ambient vibration data. The numerical algorithm for subspace state-space system identification is employed to identify the structural frequencies, damping ratios, and mode shapes corresponding to the first nine modes. The frequencies and mode shapes identified based on the data recorded during the 2004 Parkfield earthquake ( Mw=6.0) are used to update a three-dimensional finite element model of the building to improve correlation between analytical and identified modal properties and responses. A linear dynamic analysis of the updated model excited by the 1994 Northridge earthquake is performed to assess the likelihood of structural damage.

scholarly journals Estimation of Modal Properties of Low-Rise Buildings Using Ambient Excitation Measurements

2015 ◽  
Vol 2015 ◽  
pp. 1-18 ◽  
Author(s):  
K. K. Wijesundara ◽  
C. Negulescu ◽  
E. Foerster
Keyword(s):  
Damping Ratio ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Accurate Estimation ◽  
Vibration Measurements ◽  
Time Frequency ◽  
Modal Properties ◽  
Step Procedure ◽  
Ambient Vibration Measurements ◽  
Ambient Excitation

Continuous wavelet transform (CWT) has recently emerged as a promising tool for identification of modal properties through ambient excitation measurements of structures. However, it is difficult to obtain an accurate estimation of damping ratio directly from time-frequency decomposition of ambient vibration measurements using CWT. The main objective of this study is to introduce a new method called two-step procedure in the estimation of damping ratios using ambient vibration measurements. The two-step procedure involves the development of random decrement (RD) signature from the ambient vibration measurements, which is equivalent to the damped free vibration response of a structure under a given initial displacement and subsequently decomposition of time domain RD signature into time-frequency domain using CWT. The secondary objective of the study is to show that CWT is capable of identifying the natural periods and mode shapes of low-rise buildings using ambient vibration measurements. Furthermore, the two-step procedure is validated with two practical applications in a five-storey reinforced concrete structure with masonry infill walls and a three-storey masonry structure. Finally, a conclusion can be drawn that the two-step procedure yields a reasonably good estimation of damping ratio.

scholarly journals Obtaining Dynamic Parameters by Using Ambient Vibration Recordings on Model of The Steel Arch Bridge

2021 ◽  
Author(s):  
Azer A. Kasimzade ◽  
Sertaç Tuhta ◽  
Furkan Günday ◽  
Hakan Aydın
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Modal Analysis ◽  
Dynamic Characteristics ◽  
Operational Modal Analysis ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Dynamic Parameters ◽  
Analysis Method ◽  
Arch Bridge

Operational Modal Analysis (OMA) is a one of the most popular method to extract the dynamic characteristics from ambient vibration response signals. In this study, the dynamic characteristics of a model of steel arch bridge with a bolt connection constructed in a 6.10 m span and 1.88 m height laboratory were determined by finite element method and operational modal analysis methods. Firstly, finite element model was created in SAP2000 software of model steel system and dynamic characteristic were obtained numerically. Then, accelerometers were placed where the displacements are high on points of the system and dynamic characteristics were determined by operational modal analysis method. The aim of this study is to obtain the dynamic parameters (frequency, damping ratio, mode shapes) of the model of the steel arch bridge accurately and reliably by operational modal analysis method by making use of ambient vibrations in the laboratory conditions. For this purpose, analytical analysis of the model of the steel arch bridge with finite element method and the dynamic parameters obtained as a result of the operational modal analysis of the model steel arch bridge were compared. Also, the modal assurance criterion (MAC) was used. Good compatibility was recognized between the results obtained for experimental and numerical procedures in terms of both the natural frequency and the mode of vibration. At the end of this study, reasonable correlation is obtained between mode shapes, frequencies and damping ratios. Analytical and Operational modal frequencies differences between 0.139 %–7.170 %.

scholarly journals Building monitoring in Bishkek and Dushanbe by the use of ambient vibration analysis

2015 ◽  
Vol 58 (1) ◽  
Author(s):  
Bojana Petrovic ◽  
Dino Bindi ◽  
Marco Pilz ◽  
Matteo Serio ◽  
Sagynbek Orunbaev ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Residential Building ◽  
Short Description ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Dynamical Characteristics ◽  
Building Monitoring ◽  
Earthquake Model ◽  
Set Up ◽  
Frequency Domain Decomposition

<p>Within the framework of the EMCA - Earthquake Model Central Asia - project, the cities of Bishkek (Kyrgyzstan) and Dushanbe (Tajikistan) were selected for building monitoring using measurements of seismic noise to obtain the dynamical properties of the buildings. Eight buildings of different construction types, date of construction and building height, both, Soviet-era and recently constructed buildings, were instrumented for a period of a few hours. In this study, an overview of the experiment is given, including a short description of each monitored building’s structure and the performed installation. Preliminary results for a representative Soviet-era residential building in Dushanbe are presented. Modal analysis is performed using the Frequency Domain Decomposition (FDD) method to estimate the natural frequencies and the mode shapes. The wave propagation velocities in the two directions along the building axes are determined by an interferometric approach. Although the experimental set-up was not the optimal, valuable information about the dynamical characteristics of the buildings were still obtained.</p>

scholarly journals Forced Vibration Testing of a Four-Story Reinforced Concrete Building Utilizing the nees@UCLA Mobile Field Laboratory

2008 ◽  
Vol 24 (4) ◽  
pp. 969-995 ◽  
Author(s):  
Eunjong Yu ◽  
Derek Skolnik ◽  
Daniel H. Whang ◽  
John W. Wallace
Keyword(s):  
Reinforced Concrete ◽  
Harmonic Excitation ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Northridge Earthquake ◽  
Vibration Data ◽  
Field Laboratory ◽  
Concrete Building ◽  
Rc Building ◽  
Low Amplitude

The nees@UCLA mobile field laboratory was utilized to collect forced and ambient vibration data from a four-story reinforced concrete (RC) building damaged in the 1994 Northridge earthquake. Both low amplitude broadband and moderate amplitude harmonic excitation were applied using a linear shaker and two eccentric mass shakers, respectively. Floor accelerations, interstory displacements, and column and slab curvature distributions were monitored during the tests using accelerometers, linear variable differential transformers (LVDTs) and concrete strain gauges. The use of dense instrumentation enabled verification of common modeling assumptions related to rigid diaphragms and soil-structure-interaction. The first six or seven natural frequencies, mode shapes, and damping ratios were identified. Significant decreases in frequency corresponded to increases in shaking amplitude, most notably in the N-S direction of the building, most likely due to preexisting diagonal joint cracks that formed during the Northridge earthquake.

Dynamic Characteristics Evaluation on Portable Steel Frame due to Mass Irregularities

2020 ◽  
Vol 12 (9) ◽  
Author(s):  
Ahmad Fahmy Kamarudin ◽  
◽  
Azmi Ibrahim ◽  
Shahrul Niza Mokhatar ◽  
Mohd Hazreek Zainal Abidin ◽  
...  
Keyword(s):  
Dynamic Behaviour ◽  
Mass Action ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Research Centre ◽  
Torsional Mode ◽  
The North ◽  
Ambient Vibration Testing ◽  
Moment Resisting ◽  
Frequency Domain Decomposition

Application of irregular mass configuration in modern design era of buildings is unavoidable in order to serve various building functionality. The effect of mass irregularities was investigated on 5-storey portable moment resisting steel tower (PostFrame), against its dynamic behaviour. PostFrame was designed at five meter height and assembled on the strong floor in Jamilus Research Centre laboratory, UTHM. The predominant frequencies and mode shapes were determined on bare frame, uniform mass frame and mass irregularities’ frames. A total of four steel blocks at 800 kg were placed in uniform, ascending and alternating orientations on the first to fourth level of the PostFrame. Ambient vibration testing (AVT) was conducted using uni-axial accelerometer sensors. The sensors were aligned in bi-axial horizontal directions with respect to the North-South (NS) and East-West (EW) directions. ARTeMIS processing tool and Frequency Domain Decomposition (FDD) methods were used in the analysis of dynamic behaviour. Comparative findings were made between bare frame and mass action frame. Two translation mode shapes and torsional mode were illustrated by respective three predominant frequencies. Significant reduction of predominant frequency showed up to 37.79% between bare frame and frame with ascending mass orientation.Uniform mass orientation shows at the lowest percentage discrepancy percentage compared to others. Even though some changes have be found in predominant frequencies, but comparable mode shapes illustration were observed from all three predominant frequencies from all frame configurations.

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