scholarly journals Ambient vibration testing and operational modal analysis of monopole telecoms structures

2021 ◽  
Author(s):  
Jose Alfonso Jimenez Capilla ◽  
Siu-Kui Au ◽  
James Mark William Brownjohn ◽  
Emma Hudson
Keyword(s):  
Time Windows ◽  
Analytical Models ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Stochastic Subspace Identification ◽  
Communication Structures ◽  
Modal Properties ◽  
Ambient Vibration Testing ◽  
Wind Response ◽  
The Uk

AbstractA structural health monitoring (SHM) system was developed to study the ambient response of monopole communication structures in the UK operated by Arqiva Ltd. The exercise had several purposes that included the evaluation of the SHM system itself and the system identification procedures applied to the data, followed by analysis of the evaluated modal properties to validate the current analytical models, structural assessments and standardised design procedures advising on dynamics actions. This paper describes the instrumentation and procedures used during monitoring of a lightweight flexible 14.5 m tubular tapered monopole supporting an array of mobile telecoms antennas. A Bayesian OMA (BAYOMA) approach is implemented to identify structural modal properties under different time windows as comparison for further assessments. Results from stochastic subspace identification are also obtained and compared. The correlation between modal properties and monitoring wind-response data reveals specific tendencies such as nonlinear stiffness behaviour, the existence of aerodynamic damping and typical directionality of the mode shapes with future implications for reformulation of current methods of assessing dynamics on monopole.

Dynamic characteristics of the Crowchild Trail Bridge

2000 ◽  
Vol 27 (5) ◽  
pp. 1046-1056 ◽  
Author(s):  
Carlos E Ventura ◽  
Tuna Onur ◽  
Pei-Chin Tsai
Keyword(s):  
Dynamic Characteristics ◽  
Natural Frequencies ◽  
Analytical Models ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Good Match ◽  
Structural Dynamic ◽  
Ambient Vibration Testing ◽  
Ambient Vibration Measurements

This paper presents the results of a study on the dynamic characteristics of the Crowchild Trail Bridge in Calgary, Alberta. This bridge is currently being monitored by members of the Intelligent Sensing for Innovative Structures Network (ISIS Canada). The effects of various modeling assumptions on the computed dynamic characteristics of the bridge are investigated and discussed in this paper. The dynamic characteristics of the bridge were determined by means of ambient vibration measurements and were used to calibrate a number of computer models developed by four different groups of engineers. The results of this study showed that in order to properly calibrate a model of the bridge for structural dynamic analysis, it is necessary to have not only a good match of experimental and analytical natural frequencies but also a good match of experimental and analytical mode shapes. Improper determination of dynamic characteristics of a bridge using analytical models could lead to erroneous conclusions on its expected behaviour under dynamic loading.Key words: ambient vibration testing, dynamic characteristics, bridge modeling, instrumentation, accelerometers, modal analysis.

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 Use ofIn-SituDynamic Measurements to Calibrate Analytical Models of RC-Elevated Water Tanks

2012 ◽  
Vol 19 (5) ◽  
pp. 903-914
Author(s):  
H.M. Lopes ◽  
C.S. Oliveira
Keyword(s):  
Water Supply ◽  
Analytical Models ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Water Supply Systems ◽  
Water Tank ◽  
Analysis And Design ◽  
Elevated Water ◽  
Water Tanks

Before establishing the priority settings for the reduction of seismic risk of water supply infrastructures, it is necessary to understand the dynamic behavior of elevated water tanks, which are components of those infrastructures. Among other information, the main frequencies of vibration of these structures must be estimated and the analytical models used in their analysis and design should reproduce the frequency values obtained by in-situ dynamic tests. This work focuses exclusively on reinforced concrete (RC) elevated water tanks (200–750 m^3 of water at heights of 30–40 m), which are very common structures in the water supply systems in Portugal since the mid XXth century. This type of structures can also be seen in many regions around the world. First, a nationwide survey was conducted to determine the most common typologies in the country in terms of structural layout. Second, an in-situ campaign using ambient vibration as input was performed for a group of selected structures to determine the main frequencies of vibration and to identify modal shapes and damping values. Third, a finite element model of several different typologies was developed using the water simply as a concentrated mass at the top; the elastic properties of the model of the structure including the foundation were calibrated, so that the frequencies of various mode shapes obtained by the analytical model would match the frequencies of the real structure. Finally, an expression was derived to estimate the fundamental frequency of a group of elevated water tank typologies based on the total mass at the top of the supporting structure, which include the water, the global lateral stiffness, and the height of the tank. This study, providing important information on the frequencies of vibration of RC-elevated water tanks, contributes in a definite way to the analysis and design of such water tanks.

Finite Element Model Updating of a PSC Box Girder Bridge Using Ambient Vibration Test

2010 ◽  
Vol 168-170 ◽  
pp. 2263-2270 ◽  
Author(s):  
Matthew Hiatt ◽  
Annika Mathiasson ◽  
John Okwori ◽  
Seung Seop Jin ◽  
Shen Shang ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Element Model ◽  
Ambient Vibration ◽  
Research Experience ◽  
Ambient Vibration Test ◽  
Modal Properties ◽  
Ambient Vibration Testing ◽  
Frequency Domain Decomposition

In this paper, in-field ambient vibration testing of a highway bridge in South Korea under traffic loadings has been conducted to update its finite element model for future predictive analysis and diagnosis purpose. The research results presented in this paper are outcomes from an international REU (Research Experience for Undergraduates) program in smart structures funded by US-NSF (National Science Foundation) and hosted abroad by the Korean Advanced Institute of Science and Technology (KAIST). The monitoring, modeling, and model updating of civil infrastructures are vital in maintaining new design and maintenance standards. Using the frequency domain decomposition (FDD), experimental modal properties of the structure were found and, after a finite element model was created and updated based on the modal properties. From the results, it has been concluded that (a) the FDD method successfully identified the modal characteristics of the structure from ambient vibration, (b) that model updating improved the accuracy of the finite element model, (c) Representing the structural supports as springs in the FEM improved the results from the ideally supported model.

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.

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 Experimental and Numerical Investigation on Dynamic Properties and Human-Induced Vibrations of an Asymmetric Steel-Plated Stress-Ribbon Footbridge

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Yi Zhang ◽  
Wei He ◽  
Jiewen Zhang ◽  
Hua Dong
Keyword(s):  
Dynamic Properties ◽  
Element Model ◽  
Ambient Vibration ◽  
Subspace Identification ◽  
Stochastic Subspace Identification ◽  
Deck Panels ◽  
Single Person ◽  
Ambient Vibration Testing ◽  
Measurement Results ◽  
Comprehensive Study

This paper presents a comprehensive study on dynamic properties and human-induced vibrations of a slender asymmetric steel-plated stress-ribbon footbridge via both experimental and analytical methods. Bridge modal test was conducted using both ambient vibration testing and impact methods. Modal properties of the bridge were identified based on stochastic subspace identification and peak-pick techniques. Results show that the bridge is characterized by closely spaced modes with low natural frequencies and small damping ratios (<0.002). A sophisticated finite element model that incorporates pretension of the stress ribbon and contribution of deck panels is developed and proven to be capable of reflecting the main dynamic characteristics of the bridge. Human-induced vibrations were measured considering synchronization cases, including single-person and small group walking as well as random walking cases. A theoretical model that takes into account human-structure interaction was developed, treating the single walking person as an SDOF system with biomechanical excited force. The validity of the model was further verified by measurement results.

scholarly journals Developing a Feature Extraction of Existing Structures Using an Ambient Vibration Test

2020 ◽  
Author(s):  
Hamed Sarmast ◽  
Hassan Haji Kazemi
Keyword(s):  
Dynamic Properties ◽  
Analytical Models ◽  
Ambient Vibration ◽  
Vibration Test ◽  
Vibration Testing ◽  
Destructive Testing ◽  
Ambient Vibration Test ◽  
Existing Structures ◽  
Ambient Vibration Testing ◽  
Using Data

The paper aims to extract the dynamic properties of existing structures without utilizing the analytical models. The ambient vibration testing could be used on any type of frame such as concrete, steel and masonry to investigate the structural vulnerability. The method could be the first stage and necessarily for the retrofit process. To achieve this aim, the ambient vibration testing can also be employed. The experimental data obtained from the method can be used to monitor the health, evaluating, and damage detection structures at present. The achieved data can be compared in future with the recorded signals at different times. So, the ambient vibration test was carried out on the building of Imam Hossein Hospital at Mashhad. Then, its dynamic characteristics of the acceleration records are obtained by using Data Acquisition System with three accelerometers in two perpendicular coordinates. The method is more accurate and practical compare with analytical models of the existing buildings. The ambient vibration test prevents of several points such as destructive testing or may irreparable damage to the building as well as high cost. Even, the ambient vibration test maybe required for every couple of decayed, when noticed of any changes in the condition of buildings after construction. These type of changes could be quality of concrete or welding or some changes in the location of walls that can be affected the dynamic specifications of the building. The method provides real lateral load pattern and actual modes that can evaluate existing condition of the building compare with the time of construction.

scholarly journals Establishing the fundamental period of light-frame wood buildings on the basis of ambient vibration tests

2018 ◽  
Vol 45 (9) ◽  
pp. 752-765 ◽  
Author(s):  
Ghazanfarah Hafeez ◽  
Ghasan Doudak ◽  
Ghyslaine McClure
Keyword(s):  
Seismic Analysis ◽  
Shear Walls ◽  
Field Testing ◽  
Primary Objective ◽  
Fundamental Period ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Rational Approach ◽  
Vibration Testing ◽  
Ambient Vibration Testing

This research project deals with dynamic field testing of light-frame wood buildings with wood-based shear walls. The primary objective of the investigation is to evaluate the building code formula for estimating light-frame wood building’s fundamental period for seismic analysis, through intensive field testing and numerical modeling. The project also aims to propose an alternative simplified rational approach to seismic analysis of these structures. The paper presents ambient vibration testing results of light-frame wood buildings in Canada. The dynamic characteristics of the measured buildings, such as natural frequency, mode shapes, and equivalent structural damping were obtained from frequency domain analysis of ambient motion records. Using a simplified method of period estimation based on the Rayleigh approximation while using the building mass and replacing the stiffness of shear walls by their length showed reasonable fit when compared with the finite element model results and ambient vibration testing measured periods. A formula was developed based on the regression analysis of the tested buildings. The expression is a function of building height, floor area, and shear wall length and it was shown to provide a reasonably good fit with the measured results.

Operational modal analysis of a multi-span skew bridge using real-time wireless sensor networks

2010 ◽  
Vol 17 (13) ◽  
pp. 1952-1963 ◽  
Author(s):  
MJ Whelan ◽  
MV Gangone ◽  
KD Janoyan ◽  
R Jha
Keyword(s):  
Real Time ◽  
Large Scale ◽  
Sampling Rate ◽  
Sensor Data ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Radio Waves ◽  
Operational Mode ◽  
Ambient Vibration Testing ◽  
Output Only

A large-scale field deployment of high-density, real-time wireless sensors networks for the acquisition of local acceleration measurements across a medium length, multi-span highway bridge is presented. The advantages, performance characteristics, and limitations of employing this emerging technology in favor of the traditional cable-based acquisition systems are discussed in the context of the in-service instrumentation and ambient vibration testing of a multi-span bridge. Of particular highlight in this study is the deployment of a large number of stationary rather than reference-based accelerometers to uniquely permit simultaneous acquisition of vibration measurements across the structure and thereby ensure consistent temperature, ambient vibration, and traffic loading. The deployment consisted of 30 dual-axis accelerometers installed across the girders of the bridge and interfaced with 30 wireless acquisition and transceiver nodes operating in two star topology networks. Real-time wireless acquisition at a per channel sampling rate of 128 samples per second was maintained across both networks for the specified test durations of 3 min with insignificant data loss. Output-only system identification of the structure from the experimental data is presented to provide estimates of natural frequencies, damping ratios, and operational mode shapes for 19 modes. The analysis of the structure under test provides a unique case study documenting the measured response of a multiple-span skewed bridge supported by elastomeric bearings. The feasibility of embedded wireless instrumentation for structural health monitoring of large civil constructions is concluded while highlighting relevant technological shortcomings and areas of further development required. In particular, previously undocumented obstacles relating to radio transmission of the sensor data using low-power 2.4 GHz wireless instrumentation, such as the effect of solid piers within the line-of-sight and the reflection of the radio waves on the surface of the water, are discussed.

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