7.2 Ingenieurbau
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- Structural Health Monitoring (16)
- Offshore wind energy (9)
- Ground vibration (8)
- Brücken (7)
- Fatigue (7)
- Offshore (7)
- Design methods (6)
- Physical phenomenology (6)
- Pile foundations (6)
- Structural health monitoring (6)
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- 7.2 Ingenieurbau (169) (entfernen)
Severe mechanical fatigue conditions for worldwide proliferating windfarms are a Major challenge for high-performance concrete in towers, connecting joints and foundations of wind turbines. High-performance concrete offers potential for the application in offshore windfarms, not only regarding its good mechanical, but also chemical resistivity due to low diffusivity in the highly densified microstructure. For a more reliable fatigue assessment, monitoring based on nondestructive testing can be a valuable complement to design rules. Both approaches demand reliable experimental data, information about scalability and the development of standardized testing methods. This article presents results of an ongoing research program of BAM (Bundesanstalt für Materialforschung und -prüfung), which is a part of a joint national project (WinConFat) funded by the German Federal Ministry for Economic Affairs and Energy. The subproject implemented by BAM examines the fatigue behavior in dependence of size and slenderness for varying concrete strength at different stress levels. Besides fatigue strength, nondestructive testing is carried out additionally.
Methods used are strain measurement and ultrasonic testing. The change of strain, stiffness and ultrasonic pulse velocity in the fatigue process is discussed. Results disclose a deeper insight into the damage process under cyclic loading of high-performance concrete and contribute to improve nondestructive monitoring.
Mitigation measures of railway induced vibration have been demonstrated at the emission, transmission and immission part. It must be carefully observed that the correct masses and stiffnesses are used.
Typical mistakes have been shown,
- 1D models for vehicle-track interaction,
- impedance instead of stiffness for the infill material of a trench,
- rigid buildings or neglecting the soil-building interaction.
The dominant mid-frequency part of the ground vibration is due to the irregular soil.
Die Bundesanstalt für Materialforschung und -prüfung hat in den letzten 30 Jahren an vielen Orten Bahnerschütterungen gemessen. Dabei wurden immer auch Versuche zur Bestimmung der Bodeneigen-schaften durchgeführt, meist mit Hammeranregung, gelegentlich auch mit Schwingeranregung. Es werden verschiedene Auswertemethoden wie Seismogramm-Montage, Spektrale Analyse (SASW), Multistation Analysis of Surface Waves (MASW), f,v-Analyse (Dispersion aus zweifacher Fourier-Analyse), Spatial AutoCorrelation (SPAC, hier auch für deterministische Quellen) vorgestellt. Durch Approximation der frequenzabhängigen Wellengeschwindigkeiten (Dispersion) oder der gemessenen Übertragungsfunktionen erhält man ein passendes Bodenmodell. Zu diesem Bodenmodell kann man dann die Übertragungsfunktionen für Hammer- und Zuganregung berechnen. Mit allgemeinen oder spezifischen Achslastspektren werden dann die Bahnerschütterungen prognostiziert und mit den Messergebnissen verglichen. Bei etlichen Messorten, insbesondere in der Schweiz, wurden deutliche Merkmale einer Bodenschichtung beobachtet. Es ergibt sich eine deutliche Reduktion der tiefen Frequenzanteile durch den steifen unterliegenden Halbraum. Die weiche Deckschicht bestimmt das hochfrequente Verhalten. Hier bewirkt die Materialdämpfung des Bodens oft einen starken Amplitudenabfall, sowohl mit der Entfernung als auch mit der Frequenz. Für den verbleibenden mittelfrequenten Anteil wurde an mehreren Messorten die Amplituden-Fahrgeschwindigkeits-Gesetzmäßigkeiten untersucht. Es gibt konstante bis stark ansteigende Amplituden, und es zeigt sich auch hier, dass der geschichtete Boden von entscheidender Bedeutung ist.
The present contribution evaluates four measuring series made by the Federal Institute of Material Research and Testing for the relations between train speed and ground vibration amplitudes. This experimental evaluation is supported by the simulation of the train passages at the different sites by using appropriate excitation mechanisms and forces as well as layered soil models which have been derived from impact measurements at each site.
This presentation provides an overview on general issues related to erosive failures in civil constructions like hydraulic infrastructures and offshore foundations. A brief introduction to the related research activities of BAM in the field of offshore wind energy is first provided, and the general possibilities for micromechanical modelling approaches are outlined. Finally, the ongoing DFG-ANR research project COMET is introduced.
The identification of the dynamic behavior of structures, like bridges and towers, is relevant to address multiple issues. In many cases the dynamic parameters should be acquired only once or at a frequency that doesn’t justify the installation of distinct vibration sensors for a long-term monitoring. To identify modal frequencies of a structure, a drone based mobile sensing platform has been implemented. This sensing platform measures the relative displacement be-tween the structure and the drone, which also shows a strong dynamic behavior under wind tur-bulences. By regarding the dynamic model of the drone and additional measurements at the dis-tance sensor the absolute movement of the structure can be estimated based on the measured relative distance. This time domain data is a suitable input for various operational modal analysis algorithms. The system has been used to identify the dynamic properties of test and real structure, like a 1.5 MW wind turbine tower.