32878
2015
eng
260
272
89
article
Elsevier Ltd.
Oxford
1
--
--
--
Vibration-based structural health monitoring of a wind turbine system. Part I: Resonance phenomenon
This paper is focused on a resonance phenomenon of a wind turbine system in 5 MW class, on the basis of dynamic signals acquired continuously from the tubular tower under normal operational conditions during two years.
Firstly, technique specifications of the wind turbine system are introduced and a finite element model is developed to characterize the structural dynamic properties. The following part describes the continuous dynamic monitoring system integrated with an automated operational modal analysis procedure using the poly-reference Least Squares Complex Frequency domain (p-LSCF) method. Subsequently, variations and mutual relationships of environmental/operational factors such as vibration amplitude, temperature, wind speed, rotation speed of blades, pitch angle and nacelle direction are also presented. Finally, significant resonance is observed due to the fundamental frequency of the tower matching with the harmonic frequency induced by the rotation of three blades. As the rotation speed of rotor approaches to 8 rpm, the vibration amplitude of the tower increases significantly and the corresponding damping value decreases. With the further rising wind velocity, the rotation speed of blades stops increasing and the input energy just contribute to accumulate the vibration amplitude of tower. Such observation indicates the Sommerfeld effect that aggravates the resonance phenomenon. A vibration control device is necessary to minimize the excessive structural responses.
A companion paper will further discuss the environmental/operational effects on dynamic properties of the wind turbine system under the operational conditions.
Engineering structures
35955
10.1016/j.engstruct.2014.12.034
0141-0296
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000352671200020
26.03.2015
Wei-Hua Hu
Sebastian Thöns
Rolf Rohrmann
Samir Said
Werner Rücker
eng
uncontrolled
Vibration
eng
uncontrolled
Structural health monitoring
eng
uncontrolled
Wind turbine
eng
uncontrolled
Automated operational modal analysis
eng
uncontrolled
Resonance
eng
uncontrolled
Sommerfeld effect
7 Bauwerkssicherheit
7.2 Ingenieurbau
Verlagsliteratur
Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
32879
2015
eng
273
290
89
article
Elsevier Ltd.
Oxford
1
--
--
--
Vibration-based structural health monitoring of a wind turbine system. Part II: Environmental/operational effects on dynamic properties
The second part of these companion papers mainly researches environmental/operational influences on structural dynamic properties under normal operational conditions during two years, in order to extract a statistical based damage-sensitive indicator for health monitoring of a wind turbine system.
The correlation analyses between experimental identified frequencies, damping values as well as mode shapes and environmental/operational factors such as rotation speed of blades, wind speed, pitch angle, temperature and nacelle direction are presented. It is observed that the frequency estimates are influenced by the nacelle position, the activation of rotor, the rotation speed of blades and the wind speed as well as the temperature. Regarding to the damping estimates, they are mainly associated with variation of the aerodynamic damping due to the increasing wind speed. Besides, the resonance phenomenon is also observed in higher modes. The harmonic frequencies due to blades passing by tower are found and the corresponding damping value decreases. Moreover, the mode shapes in some modes are strongly affected by the position of the nacelle.
Subsequently, two types of simulated damage including the reduction of stiffness in both the rotor blade and the tubular tower are successfully detected by applying the Principal Component Analysis (PCA) based methods to these temperature-sensitive frequency estimates. Comparison of change of the extracted health features indicates that they are more sensitive with the tower damage.
Engineering structures
35956
10.1016/j.engstruct.2014.12.035
0141-0296
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000352671200021
26.03.2015
Wei-Hua Hu
Sebastian Thöns
Rolf Rohrmann
Samir Said
Werner Rücker
eng
uncontrolled
Vibration
eng
uncontrolled
Structural health monitoring
eng
uncontrolled
Wind turbine
eng
uncontrolled
Environmental/operational effects
eng
uncontrolled
Modal properties
eng
uncontrolled
Principal Component Analysis
eng
uncontrolled
Novelty analysis
eng
uncontrolled
Damage detection
eng
uncontrolled
Sommerfeld effect
eng
uncontrolled
Automated operational modal analysis
eng
uncontrolled
Resonance
7 Bauwerkssicherheit
7.2 Ingenieurbau
Verlagsliteratur
Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
32970
2014
eng
3619
3626
conferenceobject
1
--
--
--
Resonance phenomenon in a wind turbine system under operational conditions
A prototype of wind turbines in 5 megawatt dass was built and tested at the first German offshore wind energy test fteld in the North Sea. In order to investigate dynamic behaviors under a complex state of loads, a continuous dynamic monitoring System was implemented by Federal Institute for Material Research and Testing (BAM). It recorded structural responses and environmental/operational variables from November 2007 to October 2009.
This paper presents significant resonance phenomenon due to the interaction in the tower-nacelle System under operational conditions. Modal parameters are automatically estimated by the poly reference Least Square Complex Frequency domain (p-LSCF) method. Campbell plot demonstrates that a three-blade passage frequency and its multiples f3n match with the natural frequencies of the wind turbine System in several modal Orders. The damping estimates decrease and the Vibration amplitude increase significantly. A control System is necessary to minimize the excessive vibrations.
EURODYN 2014 - 9th International conference on structural dynamics (Proceedings)
36049
978-972-752-165-4
2311-9020
EURODYN 2014 - 9th International conference on structural dynamics
Porto, Portugal
30.06.2014
02.07.2014
13.04.2015
Wei-Hua Hu
Sebastian Thöns
Samir Said
Werner Rücker
eng
uncontrolled
Wind turbine
eng
uncontrolled
Tower-nacelle system
eng
uncontrolled
Resonance
eng
uncontrolled
Continuous dynamic monitoring
eng
uncontrolled
Automated operational modal analysis
7 Bauwerkssicherheit
7.2 Ingenieurbau
Verlagsliteratur
Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
44535
2018
eng
349
360
8
conferenceobject
RISE Safety
0
--
--
--
Risk Analysis for Road Tunnels – A Metamodel to Efficiently Integrate Complex Fire Scenarios
Fires in road tunnels constitute complex scenarios with interactions between the fire, tunnel users and safety measures. More and more methodologies for risk analysis quantify the consequences of these scenarios with complex models. Examples for complex models are the computational fluid dynamics model Fire Dynamics Simulator (FDS) and the microscopic evacuation model FDS+Evac. However, the high computational effort of complex models often limits the number of scenarios in practice. To balance this drawback, the scenarios are often simplified. Accordingly, there is a challenge to consider complex scenarios in risk analysis.
To face this challenge, we improved the metamodel used in the methodology for risk analysis presented on ISTSS 2016. In general, a metamodel quickly interpolates the consequences of few scenarios simulated with the complex models to a large number of arbitrary scenarios used in risk analysis. Now, our metamodel consists of the projection array-based design, the moving least squares method, and the prediction interval to quantify the metamodel uncertainty. Additionally, we adapted the projection array-based design in two ways: the focus of the sequential refinement on regions with high metamodel uncertainties; and the combination of two experimental designs for FDS and FDS+Evac.
To scrutinise the metamodel, we analysed the effects of three sequential refinement steps on the metamodel itself and on the results of risk analysis. We observed convergence in both after the second step (ten scenarios in FDS, 192 scenarios in FDS+Evac). In comparison to ISTSS 2016, we then ran 20 scenarios in FDS and 800 scenarios in FDS+Evac. Thus, we reduced the number of scenarios remarkably with the improved metamodel. In conclusion, we can now efficiently integrate complex scenarios in risk analysis. We further emphasise that the metamodel is broadly applicable on various experimental or modelling issues in fire safety engineering.
Proceedings from the Eighth International Symposium on Tunnel Safety and Security
978-91-88695-48-2
urn:nbn:de:kobv:b43-445354
International Symposium on Tunnel Safety and Security
Boras, Sweden
14.03.2018
16.03.2018
Florian Berchtold
Christian Knaust
Andreas Rogge
L. Arnold
Sebastian Thöns
eng
uncontrolled
Risk
eng
uncontrolled
Metamodel
eng
uncontrolled
CFD
eng
uncontrolled
Evacuation
eng
uncontrolled
Uncertainty
Ingenieurbau
7 Bauwerkssicherheit
Infrastruktur
Sicherheit von Industrieanlagen und Verkehrswegen
Fire Science
Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Graue Literatur
7.0 Abteilungsleitung und andere
https://opus4.kobv.de/opus4-bam/files/44535/Berchtold 18 - ISTSS data.pdf
44537
2018
eng
79
94
1
33
article
John Wiley & Sons, Inc.
Hoboken, NJ, USA
1
--
--
--
On the Value of Monitoring Information for the Structural Integrity and Risk Management
This article introduces an approach and framework for the quantification of the value of structural health monitoring (SHM) in the context of the structural risk and integrity management for systems. The quantification of the value of SHM builds upon the Bayesian decision and utility theory, which facilitates the assessment of the value of information associated with SHM. The principal approach for the quantification of the value of SHM is formulated by modeling the fundamental decision of performing SHM or not in conjunction with their expected utilities. The expected utilities are calculated accounting for the probabilistic performance of a system in conjunction with the associated structural integrity and risk management actions throughout the life cycle, the associated benefits, structural risks, and costs and when performing SHM, the SHM information, their probabilistic outcomes, and costs. The calculation of the expected utilities necessitates a comprehensive and rigorous modeling, which is introduced close to the original formulations and for which analysis characteristics and simplifications are described and derived. The framework provides the basis for the optimization of the structural risk and integrity management based on utility gains including or excluding SHM and inspection information. Studies of fatigue deteriorating structural Systems and their characteristics (1) provide decision Support for the performance of SHM, (2) explicate the influence of the structural component and system characteristics on the value of SHM, and (3) demonstrate how an integral optimization of SHM and inspection strategies for an efficient structural risk and integrity management can be performed.
Computer-Aided Civil and Infrastructure Engineering
10.1111/mice.12332
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000423078100007
21.03.2018
Sebastian Thöns
eng
uncontrolled
Monitoring
eng
uncontrolled
Structural Integrity and Risk Management
eng
uncontrolled
SHM
7 Bauwerkssicherheit
Infrastruktur
Sicherheit und Lebensdauer von Bauwerken
Verlagsliteratur
Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
7.0 Abteilungsleitung und andere
46964
2018
eng
255
268
3
28
article
Taylor & Francis
1
--
--
--
On Damage Detection System Information for Structural Systems
Damage detection systems (DDS) provide information of the structural system integrity in contrast to e.g. local information by inspections or non-destructive testing techniques. In this paper, an approach is developed and demonstrated to utilize DDS information to update the structural system reliability and to integrate this information in structural system risk and utility analyses. For this aim, a novel performance modelling of DDS building upon their system characteristics and non-destructive testing reliability is introduced. The DDS performance modelling accounts for a measurement system in combination with a damage detection algorithm attached to a structural system in the reference and damage states and is modelled with the probability of indication accounting for type I and II errors. In this way, the basis for DDS performance comparison and assessment is provided accounting for the dependencies between the damage states in a structure. For updating of the structural system reliability, an approach is developed based on Bayesian updating facilitating the use of DDS information on structural system level and thus for a structural system risk analysis. The structural system risk analysis encompasses the static, dynamic, deterioration, reliability and consequence models, which provide the basis for the system model for calculating the direct risks due to component failure and the indirect risks due to system failure. Two case studies with the developed approach demonstrate a high Value of DDS Information due to risk and expected cost reduction.
Structural Engineering international
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS_CPL&DestLinkType=FullRecord&UT=WOS:000451383100004
10.1080/10168664.2018.1459222
12.12.2018
Sebastian Thöns
M. Döhler
Lijia Long
eng
uncontrolled
Damage detection
eng
uncontrolled
Value of Information
eng
uncontrolled
Structural systems
eng
uncontrolled
Damage detection uncertainty
Ingenieurbau
7 Bauwerkssicherheit
Infrastruktur
Sicherheit und Lebensdauer von Bauwerken
Verlagsliteratur
Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
7.0 Abteilungsleitung und andere
46190
2018
eng
375
384
conferenceobject
0
--
--
--
The effects of SHM system parameters on the value of damage detection information
This paper addresses how the value of damage detection Information depends on key Parameters of the Structural Health Monitoring (SHM) system including number of sensors and sensor locations. The Damage Detection System (DDS) provides the information by comparing ambient vibration measurements of a (healthy) reference state with measurements of the current structural system. The performance of DDS method depends on the physical measurement properties such as the number of sensors, sensor positions, measuring length and sensor type, measurement noise, ambient excitation and sampling frequency, as well as on the data processing algorithm including the chosen type I error for the indication threshold. The quantification of the value of Information (VoI) is an expected utility based Bayesian decision analysis method for quantifying the difference of the expected economic benefits with and without information. The (pre-)posterior probability is computed utilizing the Bayesian updating theorem for all possible indications. If changing any key parameters of DDS, the updated probability of system failure given damage detection information will be varied due to different indication of probability of damage, which will result in changes of value of damage detection information. The DDS system is applied in a statically determinate Pratt truss bridge girder. Through the analysis of the value of information with different SHM system characteristics, the settings of DDS can be optimized for minimum expected costs and risks before implementation.
9th European Workshop on Structural Health Monitoring
9th European Workshop on Structural Health Monitoring
Manchester, UK
10.07.2018
Lijia Long
Sebastian Thöns
M. Döhler
eng
uncontrolled
SHM
eng
uncontrolled
Damage detection system
eng
uncontrolled
Value of information
Ingenieurbau
7 Bauwerkssicherheit
Infrastruktur
Sicherheit von Industrieanlagen und Verkehrswegen
Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Präsentation
7.0 Abteilungsleitung und andere
43624
2017
eng
1276
1284
conferenceobject
0
--
--
--
Damage Detection and Deteriorating Structural Systems
This paper addresses the quantification of the value of damage detection system and algorithm information on the basis of Value of Information (VoI) analysis to enhance the benefit of damage detection information by providing the basis for its optimization before it is performed and implemented. The approach of the quantification the value of damage detection information builds upon the Bayesian decision theory facilitating the utilization of damage detection performance models, which describe the information and its precision on structural system level, facilitating actions to ensure the structural integrity and facilitating to describe the structural system performance and its functionality throughout the service life. The structural system performance is described with its functionality, its deterioration and its behavior under extreme loading. The structural system reliability given the damage detection information is determined utilizing Bayesian updating. The damage detection performance is described with the probability of indication for different component and system damage states taking into account type 1 and type 2 errors. The value of damage detection information is then calculated as the difference between the expected benefits and risks utilizing the damage detection information or not. With an application example of the developed approach based on a deteriorating Pratt truss system, the value of damage detection information is determined,demonstrating the potential of risk reduction and expected cost reduction.
Proceedings of the 11th International Workshop on Structural Health Monitoring
978-1-60595-330-4
urn:nbn:de:kobv:b43-436244
International Workshop on Structural Health Monitoring
Stanford, CA, USA
12.09.2017
14.09.2017
Lijia Long
Sebastian Thöns
M. Döhler
eng
uncontrolled
Reliability updating
eng
uncontrolled
Structural reliability and risks
eng
uncontrolled
Damage detection
eng
uncontrolled
Value of information
Ingenieurbau
7 Bauwerkssicherheit
7.2 Ingenieurbau
Infrastruktur
Sicherheit und Lebensdauer von Bauwerken
Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Graue Literatur
https://opus4.kobv.de/opus4-bam/files/43624/2017_Long_SHM 2017_Titelblatt.pdf
48481
2019
eng
1
9
conferenceobject
0
--
--
--
Quantification of the posterior utilities of SHM campaigns on an orthotropic steel bridge deck
This paper contains a quantification and decision theoretical optimization of the posterior utilities for several options for monitoring campaigns on the particular case of fatigue life predictions of an orthotropic steel deck. The monitoring campaigns are defined by varying monitoring durations and phases. The decision analysis is performed with real data from the Structural Health Monitoring (SHM) of the Great Belt Bridge (Denmark) which, among others, consist of measured strains, pavement temperatures and traffic intensities. The fatigue loading prediction model is based on regression models linking daily averaged pavement temperatures, daily aggregated heavy-traffic Counts and derived S-N fatigue damages, all of them derived from the outcomes of different monitoring campaigns. A probabilistic methodology is utilized to calculate the fatigue reliability profiles of selected instrumented welded joints. The posterior utilities of SHM campaigns are then quantified by considering the structural fatigue reliability, various monitoring campaigns and the corresponding cost-benefit models. The decisions of identifying the optimal monitoring campaign and of extending the service life or not in conjunction with monitoring results are modelled. The optimal monitoring campaign is identified - retrospectively - by maximizing the expected benefits and minimize risks in dependency of the monitoring duration and the monitoring associated costs. The results, despite relying on a number of simplistic assumptions, pave the way towards the use of pre-posterior decision support to optimise the design of monitoring campaigns for similar bridges, with an overall goal to proof the cost efficiency of SHM approaches to civil infrastructure management.
Proceedings of Structural Health Monitoring 2019
IWSHM 2019, The 12th International Workshop on Structural Health Monitoring, Stanford, California, USA
Stanford, California, USA
10.09.2019
false
true
Lijia Long
I. F. Alcover
Sebastian Thöns
eng
uncontrolled
Quantification
eng
uncontrolled
SHM information
eng
uncontrolled
Steel bridge deck
Ingenieurbau
7 Bauwerkssicherheit
Infrastruktur
Sicherheit und Lebensdauer von Bauwerken
Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Graue Literatur
7.0 Abteilungsleitung und andere