Measurement results of train-induced vibrations are evaluated for characteristic frequencies, amplitudes and spectra, leading to a prediction which is based on transfer functions of the vehicle–track–soil system, the soil, and the building–soil system. The characteristic frequencies of train-induced vibrations are discussed following the propagation of vibrations from the source to the receiver: out-of-roundness frequencies of the wheels, the sleeper passage frequency, the vehicle–track eigenfrequency, the car-length frequency and multiples, axle-distance frequencies, bridge eigenfrequencies, the building–soil eigenfrequency, and floor eigenfrequencies. Amplitudes and spectra are compared for different train and track types, for different train speeds, and for different soft and stiff soils, where high frequencies are typically found for stiff soil and low frequencies for soft soil. The ground vibration is between the cut-on frequency due to the layering and the cut-off frequency due to the material damping of the soil, but the dominant frequency range also changes with distance from the track. The frequency band of the axle impulses due to the passing static loads obtains a signature from the axle sequence. The high amplitudes between the zeros of the axle-sequence spectrum are measured at the track, the bridge, and also in the ground vibrations, which are even dominant in the far field. A prediction software is presented, which includes all three parts: the excitation by the vehicle–track interaction, the wave transmission through the soil, and the transfer into a building.

Chapter 3.5 Entwurf und Bemessung von Gründungen für Offshore-Windenergieanlagen Stavros Savidis, Stavros SavidisSearch for more papers by this authorThomas Richter, Thomas RichterSearch for more papers by this authorFabian Kirsch, Fabian KirschSearch for more papers by this authorWerner Rücker, Werner RückerSearch for more papers by this author Stavros Savidis, Stavros SavidisSearch for more papers by this authorThomas Richter, Thomas RichterSearch for more papers by this authorFabian Kirsch, Fabian KirschSearch for more papers by this authorWerner Rücker, Werner RückerSearch for more papers by this author Book Editor(s):Univ.-Prof. Dr.-Ing. Karl Josef Witt, Univ.-Prof. Dr.-Ing. Karl Josef Witt Beratender Ingenieur, Kantstraße 10, 99425 WeimarSearch for more papers by this author First published: 17 January 2018 https://doi.org/10.1002/9783433607350.ch5Citations: 1 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary Der Großteil der Planungen für Offshore-Windparks in Deutschland betrifft Standorte innerhalb der ausschließlichen Wirtschaftszone (AWZ). Über die Zulassung von Windenergieanlagen in diesem Bereich entscheidet das Bundesamt für Seeschifffahrt und Hydrographie (BSH). Für die Gründung einer Offshore-Windenergieanlage (OWEA) stehen im Allgemeinen Flach- und Tiefgründungen zur Auswahl. Aber auch Kombinationen dieser Gründungstypen oder auch Sondergründungen sind denkbar. Die Verhältnisse von Wind, Wellen, Wassertiefen, Strömung, Aufbau des Untergrunds, Kolkbildung und Korrosion bilden die maßgebende Grundlage für den Entwurf und für die Bemessung der Tragstrukturen. Grundsätzlich sind in Bezug auf die geotechnischen Nachweise für sämtliche Gründungsarten die Grenzzustände der Tragfähigkeit und der Gebrauchstauglichkeit nachzuweisen. Im Beitrag werden für die wesentlichen Gründungsarten: Mehrpfahl-, Monopfahl-, Schwergewichts- und Suction-Gründungen die Besonderheiten der durchzuführenden Nachweise ausführlich beschrieben und auch auf die Erfordernisse eines Überwachungs-Monitoringkonzeptes eingegangen. Citing Literature Grundbau-Taschenbuch: Teil 3: Gründungen und geotechnische Bauwerke, 8. Auflage RelatedInformation

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. (C) 2014 Elsevier Ltd. All rights reserved.

The ground vibrations, which are generated by trains on different tracks, have been calculated by finite-element boundary-element models. The ballasted track is modelled in detail by the finite element method. The infinite soil is modelled by the boundary element method as a homogeneous or layered half-space. The track-soil system is coupled to a simple rigid mass model of the vehicle so that the vehicle-track interaction is completely included. Transfer functions are calculated in frequency domain without and with vehicle-track interaction, the compliance of the track and the mobilities of the soil at different distances from the track. Finally, the ratios between the ground vibration amplitudes with and without mitigation measures are calculated to quantify the effectiveness of the mitigation measures.Tracks with under-sleeper pads have been investigated in a wide parameter study for the RIVAS project. The main parameters that influence the reduction of ground vibration are the stiffness of the under-sleeper pad, the mass and the width of the sleeper. The softest sleeper pad yields the best reduction of the ground vibration. The influence of the sleeper mass is not so strong, as the characteristic frequency is ruled by the mass of the sleeper and the mass of the wheelset as well.

This paper presents the continuous dynamic measurements of an aging prestressed box-beam bridge during the period from 2000 to 2013, which consists of dynamic properties and environmental/operational factors, as well as the Variation of the extracted health features after removing the environmental/operational effects. Firstly, the variations of frequency estimates, temperatures and traffic loads from 2000 to 2013 are described. Subsequently, correlation analysis between them indicates the nonlinear influences of the temperature on the frequency estimates. The Multiple Linear Regression (MLR) method is used to remove the environmental/operational effects and the health index is proposed by performing the Novelty Detection analysis of the residual errors. Finally, the variations of the health index may indicate clear structural modifications that can be also characterized by the long term monitoring of the dynamic strain in the prestressed cable.

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. (C) 2014 Elsevier Ltd. All rights reserved.

Der vorliegende Bericht beschreibt Konzepte fur eine intelligente Brucke auf der Grundlage einer zuverlassigkeitsbasierten Zustandsbewertung unter Berucksichtigung von Bauwerksinformationen, welche aus Prufungen, Inspektionen und Uberwachung gewonnen werden. Das Bruckensystem wird durch ein Modell beschrieben, welches den zentralen Teil des Konzeptes darstellt. Das Modell wird in Schadigungsmodelle und ein Tragwerkssystem-Modell unterteilt. Dieses Modell wird a-priori durch die Eingangsdaten (welche etwa die Geometrie, die Materialien und die Verwendung der Brucke beschreiben) charakterisiert. Aus diesen ergeben sich dann auch die Ausgangsmodelle. Um die signifikanten Streuungen und Unsicherheiten adaquat abzubilden sind diese Modelle probabilistisch. Das Modell liefert eine sich kontinuierlich andernde probabilistische Zustandsbewertung. Die Zustandsbewertung gibt eine Aussage uber den Zustand und die Zuverlassigkeit des Bruckensystems und seiner Bauteile und dient als Grundlage fur die Planung und die Optimierung von Masnahmen. Die Verwendung von Resultaten aus Inspektionen, Prufungen und Uberwachungen erfolgt durch eine Aktualisierung der Modellparameter. Die Aktualisierung beruht auf der Methode der Bayes'schen Aktualisierung und wird auf der Grundlage der entwickelten Klassifizierung der Bauwerksinformationen mit entsprechenden Methoden durchgefuhrt. Dieses Verfahren erlaubt es, alle Informationen in konsistenter Weise in ein einziges Modell einfliesen zu lassen. Dabei wird die Genauigkeit und Aussagekraft der gewonnenen Daten und Beobachtungen explizit berucksichtigt. Durch die Aktualisierung der Modellparameter unter Berucksichtigung von Systemeffekten wird die Zustandsbewertung der Bauteile und des Bruckensystems aktualisiert. Das ermoglicht die Planung und die Optimierung von Masnahmen unter Berucksichtigung der Bauwerksinformationen. Auf diese Weise wird die intelligente Brucke mit Inspektionen und Uberwachungen zu einem adaptiven System, welches sich Veranderungen anpassen kann.

A prototype of wind turbines in 5 megawatt class was built and tested at the first German offshore wind energy test field 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 f(3n) 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.

This paper presents the development of a continuous dynamic monitoring system and its applications to different structures, with the purpose of understanding structural real behaviours under operational conditions and detecting early structural modifications.The first part of paper introduces a complete continuous dynamic system, consists of signal acquisition and communication, automated signal processing and management, investigation of the interaction between structures and its environmental/operational conditions, feature extraction and detection of structural modification.The rest of paper describes the applications of continuous dynamic monitoring system to different structures such as a wind turbine system and a highway bridge.

This paper deals with the system identification of a mechanical structure supported by nonlinear springs subjected to an external load. If all mechanical parameters of the system were known, the displacement of the system subjected to this load could be easily calculated. However, the monitoring applications often deal with the inverse problem. The loads and displacements of the system are known and certain mechanical parameters of the system are sought. The solution of such inverse problems can be difficult, especially when they have a nonlinear and multimodal character, which often makes them appear intractable at first sight.However, evolutionary computing can be applied to solve this inverse, nonlinear and multimodal problem. Sometimes a prior knowledge exists on certain system properties, which is difficult to implement into analytical or numerical solvers. This knowledge can play a decisive role in identifying the system properties and it can be easily included as a boundary condition when applying evolutionary algorithms. This article discusses how and under what conditions the unknown spring resistances can be identified. The practical application of this procedure is exemplified here with the mechanical system of a pile foundation. (C) 2015 Elsevier Ltd. All rights reserved.

Alternatively to common modal analysis as tool for detecting changes between a reference and an actual (possibly damaged) structural state, the subspace-based damage detection method has been developed in recent years and successfully adopted to test application data sets. Characteristic for that method is that instead of analyzing modal parameters, a statistical test with respect to changes of a dynamic signature of structural response is introduced. Therefor, a Gaussian residual vector is extracted from the subspace of an output only vibration data covariance matrix within the reference state. The paper describes the application of this damage detection method within a laboratory fatigue test on a steel frame structure. Aim of the investigation was to analyze the usability and efficiency of the detection method for realistic damage on carrying structures of wind energy turbines. In a second step, a numerical model of the lab test structure is developed and validated. Thus, a comparable numerical simulation of the fatigue damage detection was feasible and the accuracy of the simulation procedure could be verified. The present study describes the first step in a two-step approach for quantifying and optimizing fundamental characteristics of SHM systems for offshore wind turbine structures concerning a required number of sensors and their optimal location.

Offshore‐Pfähle in Mehrpfahlgründungsstrukturen wie Jacket‐Gründungen müssen nach der Rammung überwiegend zyklisch axialen Belastungen widerstehen. Die Abmessungen der Pfähle werden sowohl von der inneren Tragfähigkeit und dem Ermüdungsverhalten des Stahlquerschnittes als auch von der äußeren Tragfähigkeit und der Pfahl‐Boden‐Interaktion bestimmt. Aufgrund der großen Zahl von Pfahlgründungen, die für aktuelle und zukünftige Windparkprojekte benötigt werden, besteht ein dringender Bedarf, die Dimensionierung und die damit verbundenen Kosten des Einzelpfahles zu optimieren. Bezüglich der Pfahltragfähigkeit sind wichtige aktuelle Forschungsthemen eine mögliche Traglaststeigerung durch Anwachsen und die geeignete Abschätzung der zyklischen Degradation. Zur Untersuchung beider Effekte wurde eine großmaßstäbliche Versuchsanlage auf dem Testgelände BAM TTS in Horstwalde nahe Berlin errichtet. Auf diesem Versuchsfeld können große Stahlrohrammpfähle zyklisch druck‐ und zugbelastet werden. Zudem kann die Untersuchung von Alterungseffekten durch zeitlichen Versatz zwischen den Messkampagnen untersucht werden. Erste Ergebnisse zeigen einen Anstieg der Pfahltragfähigkeit bis zu ca. 60 % nach einer Standzeit von ca. 18 Monaten. Für die Degradation der Tragfähigkeit der zyklisch belasteten Pfähle zeigen die ersten vorläufigen Ergebnisse ein zum Teil unerwartetes Verhalten. Zusätzliche Untersuchungen werden derzeit zur weiteren Abklärung durchgeführt.

A comprehensive numerical model for the analysis of offshore foundations under a general transient loading is presented here. The theoretical basis of the model lies on the Swansea formulation of Biot’s equations of dynamic poroelasticity combined with a constitutive model that reproduces key aspects of cyclic soil behaviour in the frame of the theory of generalised plasticity. On the practical side, the adoption of appropriate finite element formulations may prevent the appearance of spurious numerical instabilities of the pore pressure field. In this respect, the use of a coupled enhanced-strain element is here proposed. On the other hand, the practicality of the presented model depends ultimately on its computational efficiency. Some practical recommendations concerning the solution strategies, the matrix storage/handling procedures and the parallel multi-processor computation are here provided. Finally, the performance of the model with a benchmark study case and its practical application to analyse the soil–structure interaction of an offshore monopile under a realistic transient storm loading are discussed.

The main degradation process at bridge transition zones due to traffic loads is the appearance of differential settlements. Abrupt stiffness changes, repeating traffic loads and relative displacements of the superstructure ends on bridges often aggravate this problem. In this contribution, a 3D finite element (FE) model extended with a boundary formulation in the frame of the scaled-boundary finite element method (SBFEM) for a transient analysis of train-track-bridge interaction is presented. This numerical model permits an assessment of bridge transition zone with respect to permanent deformations of the track. The main focus lies on the modeling strategies for the vehicle and their impact on suitable assessment criteria for bridge transition zones. For this purpose, two different modeling strategies for the vehicle, a moving load model and a multibody model, have been compared and discussed on the basis of the assessment criteria. The results indicate that the model of the vehicle has a minor effect for an assessment on the embankment, but that the assessment on the bridge may show significant differences depending on whether the inertial components of the vehicle (multibody model) are considered.