## 7.2 Ingenieurbau

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#### Dokumenttyp

- Vortrag (169)
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- Zeitschriftenartikel (59)
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- Beitrag zu einem Sammelband (3)
- Dissertation (3)
- Tagungsband (Herausgeberschaft für den kompletten Band) (1)
- Forschungsbericht (1)

#### Schlagworte

- Fatigue (16)
- Damage detection (13)
- Ground vibration (12)
- Monitoring (11)
- Finite element method (10)
- Structural health monitoring (10)
- Concrete (7)
- Slab track (7)
- Soil-structure interaction (7)
- Truss structures (7)
- Axial force (6)
- Damage localization (6)
- Dynamic test (6)
- Grout (6)
- Numerical modelling (6)
- Offshore (6)
- Offshore wind turbines (6)
- Railway track (6)
- SHM (6)
- Vibration measurements (6)
- Windenergie (6)
- Field tests (5)
- Finite-element boundary-element method (5)
- Inspection (5)
- Inspection planning (5)
- Interface (5)
- Mitigation (5)
- Modal parameters (5)
- Model updating (5)
- Numerical model (5)
- Offshore foundations (5)
- Offshore wind energy (5)
- Optimization technique (5)
- Reliability (5)
- Subspace methods (5)
- Track damage (5)
- Train-induced ground vibration (5)
- Automated operational modal analysis (4)
- Boundary element method (4)
- Cracks (4)
- Cyclic loading (4)
- Ermüdung (4)
- Grouted connection (4)
- Hammer impact (4)
- Layered soils (4)
- Micromechanical modelling (4)
- Overhead transmission lines (4)
- Pfahlgründungen (4)
- Pile foundations (4)
- Repair (4)
- Resonance (4)
- Risk (4)
- Schadensdetektion (4)
- Statistical tests (4)
- Temperature rejection (4)
- Track-soil interaction (4)
- Train passage (4)
- Vehicle-track interaction (4)
- Vehicle-track-soil interaction (4)
- Wind turbine (4)
- Aerodynamic damping (3)
- Bitumen (3)
- Box-Behnken (3)
- Bridge transition zone (3)
- Compaction Grouting (3)
- Compressive strength (3)
- Contact problem (3)
- Continuous dynamic monitoring (3)
- Continuously inhomogeneous soils (3)
- Crack (3)
- Crack detection (3)
- DUCON® (3)
- Damage evolution (3)
- Deterioration (3)
- Ductility (3)
- E-modulus (3)
- Environmental/operational effects (3)
- Fire (3)
- Fly ash (3)
- Grouting (3)
- High-cycle (3)
- Impact (3)
- Jet erosion (3)
- LBM-DEM (3)
- Load vector (3)
- Metakaolin (3)
- Micro-reinforcement (3)
- Mobile elements (3)
- Numerical modeling (3)
- Offshore Pile Foundation (3)
- Offshore-Windenergieanlagen (3)
- Physical phenomenology (3)
- Pile bending stiffness (3)
- Pile foundation (3)
- Quasi-static and dynamic tests (3)
- Rehabilitation (3)
- Residual evaluation (3)
- Soil properties (3)
- Soil stiffness (3)
- Soil-building interaction (3)
- Statistical evaluation (3)
- Steel structures (3)
- Stereo photogrammetry (3)
- Structural Health Monitoring (3)
- Subspace-based method (3)
- Track vibration (3)
- Tragfähigkeit (3)
- Train passages (3)
- Tunnel (3)
- UHPC (3)
- Wind energy tower (3)
- ground vibration (3)
- mitigation (3)
- railway track (3)
- Aberfan flowslide (2)
- Accelerated ageing (2)
- Acoustic emission analysis (2)
- Acoustic emission testing (2)
- Ambient vibration (2)
- Amplitude-charge weight laws (2)
- Amplitude-distance laws (2)
- Analysis of variance (2)
- Assessment criteria (2)
- Axle box measurements (2)
- BIM (2)
- Bahnerschütterungen (2)
- Ballast track (2)
- Ballast tracks (2)
- Base isolation (2)
- Bauwerksüberwachung (2)
- Bayesian analysis (2)
- Betonautobahn (2)
- Big Data (2)
- Bodeneigenschaften (2)
- Bohrpfähle (2)
- Bridge (2)
- Brücken (2)
- Cable failure (2)
- Cable-stayed bridge (2)
- Compaction grouting (2)
- Compressive cyclic loading (2)
- Crack formation (2)
- Crack pattern (2)
- Crash-material (2)
- Crashkörper (2)
- Cyclic load (2)
- Cyclic loads (2)
- Damage Evolution (2)
- Datenmanagement (2)
- Design methods (2)
- Detection (2)
- Digital image correlation (2)
- Displacements (2)
- Downburst (2)
- Dynamic load test (2)
- Dynamic testing (2)
- Dynamische Pfahlprobebelastung (2)
- Elastische Gebäudelagerung (2)
- Energiedissipation (2)
- Energy (2)
- Energy dissipation (2)
- Erosion (2)
- Erosion onset (2)
- Erschütterungsursachen (2)
- Experimental testing (2)
- Explosion-induced ground vibrations (2)
- Explosionsbeanspruchung (2)
- Failure (2)
- Fassadenverankerung (2)
- Fatigue damage (2)
- Fault detection (2)
- Façade connector (2)
- Feature extraction (2)
- Finite element model updating (2)
- Force transfer (2)
- Frequenzbereiche (2)
- Generalized plasticity (2)
- Granular cohesion (2)
- Ground vibration measurements (2)
- Grouted Connection (2)
- Grouted connections (2)
- HTLS (2)
- Hammer tests (2)
- High temperature low sag conductors (2)
- High-Cycle (2)
- High-strength concrete (2)
- Imperfektion (2)
- Injection Sequence (2)
- Inspektion (2)
- Iron and steel truss structures (2)
- Joint capacity (2)
- Layered soil (2)
- Long-term loading (2)
- Long-term shrinkage (2)
- Luminescence (2)
- Messen im Bauwesen (2)
- Micro silica (2)
- Mix design (2)
- Mixed formulation (2)
- Model interpolation (2)
- Non-destructive testing (2)
- Non-synoptic wind event (2)
- Numerical simulation (2)
- Offshore Windenergieanlagen (2)
- Offshore wind energy converter (2)
- Offshore-Wind (2)
- Operational modal analysis (2)
- Overhead transmission line (2)
- Particle image velocimetry (2)
- Piles (2)
- Prediction (2)
- Prediction of explosion induced ground and building vibration (2)
- Railway (2)
- Railway measurement campaign (2)
- Railway vibration (2)
- Rechenmodelle (2)
- Ringversuch (2)
- SDDLV (2)
- SPH (2)
- Sand (2)
- Schwingungsbasierte Verfahren (2)
- Shear keys (2)
- Size effect (2)
- Slenderness effect (2)
- Soil-pile interaction (2)
- Sommerfeld effect (2)
- Static load (2)
- Static load test (2)
- Statische Pfahlprobebelastung (2)
- Statistical method (2)
- Strengthening strategy (2)
- Structural reliability (2)
- Subcritical debonding (2)
- Suction bucket (2)
- Supplementary cementitious materials (2)
- Tensile Capacity (2)
- Tensile capacity (2)
- Track damage monitoring (2)
- Train-track-bridge-interaction (2)
- Ultrasonic testing (2)
- Uncertainty (2)
- Uncertainty in reference (2)
- Under-ballast plate (2)
- Unterraummethoden (2)
- Value of information (2)
- Vehicle model (2)
- Vibration (2)
- Vibration measurement (2)
- Vibrations (2)
- Wavenumber integrals (2)
- Wavenumber method (2)
- Zugtragfähigkeit (2)
- Zyklisches Tragverhalten (2)
- floor vibration (2)
- modal analysis (2)
- track-soil interaction (2)
- undersleeper (2)
- wave analysis (2)
- 1-D insertion loss (1)
- 3D imaging (1)
- Acoplamiento Método de los Elementos de Contorno-Método de los Elementos Finitos (1)
- Ambient excitation (1)
- Amplitude-distance law (1)
- Analysis (1)
- Anwachsen (1)
- Assessment (1)
- Authorities approval process (1)
- Automated Modal Analysis for Tracking Structural Change during Construction and Operation Phases (1)
- Automated system identification (1)
- Axial and lateral design (1)
- Axial force identification (1)
- Axial pile capacity (1)
- Axle-load spectra (1)
- Bahnfahrwege (1)
- Ballast (1)
- Baustoffe (1)
- Bauteilprüfungen (1)
- Bauwerk-Boden-Wechselwirkung (1)
- Bayes'sche Analyse (1)
- Beanspruchungszustand (1)
- Bearing capacitiy (1)
- Bemessung (1)
- Bemessungskonzeptblast loads (1)
- Berechnung (1)
- Berechnungs- und Bemessungsverfahren - Analysis and calculation (1)
- Beton (1)
- Betonautobahnen (1)
- Blast loads (1)
- Blasting charge (1)
- Bodenerschütterungen (1)
- Boundary Element Method-Finite Element Method coupling (1)
- Brücke (1)
- Brückenübergangsbereich (1)
- Building materials (1)
- CPT (1)
- Cable dynamics (1)
- Changing excitation (1)
- Clay fill (1)
- Climate Chamber (1)
- Close range photogrammetry (1)
- Cohesionless granular soil (1)
- Cohesive granular media (1)
- Cohesive soils (1)
- Comparative study (1)
- Components of excitation (1)
- Compression (1)
- Conception and design (1)
- Conductor (1)
- Conductor cables (1)
- Conductors (1)
- Constitutive modeling (1)
- Coupled FE-SBFE model (1)
- Covariance analysis (1)
- Crack repair (1)
- Crashmaterial (1)
- Cyclic axial loading (1)
- Cyclic axial shearing (1)
- DEM-LBM simulation (1)
- Damage (1)
- Damage quantification (1)
- Daniels systems (1)
- Dauerhaftigkeit (1)
- Dauerüberwachung (1)
- Decision matrix analysis (1)
- Deckenschwingungen (1)
- Dehnungsmessung (1)
- Design (1)
- Design guideBauwerke - Buildings (1)
- Design practice (1)
- Detection of structural change (1)
- Deutschland (1)
- Digital Image Correlation (1)
- Digital Image Correlation (DIC) (1)
- Digital X-ray laminography (1)
- Digitale Bildverarbeitung (1)
- Discrete element method (1)
- Dispersionsmessung (1)
- Driving Versuche - Experimental set-ups (1)
- Drop height (1)
- Dynamic loading (1)
- Dynamic pile testing (1)
- Dynamic soil-structure interaction (1)
- Dynamik (1)
- Echtzeit (1)
- Einseitenschweißung (1)
- Eisenbahngleis (1)
- Elastic track elements (1)
- Emission (1)
- Energiewende (1)
- Entwurf und Konstruktion (1)
- Entwurf und Konstruktion - Conception and Design (1)
- Environmental (1)
- Environmental Effects (1)
- Environmental and operational effects (1)
- Environmental changes (1)
- Environmental/operational effect (1)
- Ermüdungsschäden (1)
- Erneuerbare Energien (1)
- Erosion of cohesive soils (1)
- Erosion phenomena (1)
- Erschütterungsprognose (1)
- Evaluation of crack fields (1)
- Evolutionary computing (1)
- Experimental optical techniques RIM-PLIF (1)
- Experimental verification (1)
- Experimentelle Untersuchung (1)
- Explosion (1)
- Extrinsic Fabry-Perot interferometer (1)
- FEBEM and simplified methods (1)
- FED (1)
- FEM-Simulation (1)
- Fahrwegschäden (1)
- Fahrzeug-Fahrweg-Wechselwirkung (1)
- Fatigue cracks (1)
- Fault isolation (1)
- Feldversuch (1)
- Fibre Bragg grating (1)
- Fibre optic strain sensor (1)
- Field measurements (1)
- Field test (1)
- Filter effect of the soil (1)
- Finite-Elemente-Modellkalibrierung (1)
- Flexible plate (1)
- Floor amplification (1)
- Fluidised geomaterials (1)
- Forschungsbericht (1)
- Foundation reduction (1)
- Fractional effective dose (1)
- Freileitung (1)
- Freileitungen (1)
- Frequency-wavenumber method (1)
- Fugenfüllsysteme (1)
- GPU parallel computation (1)
- GPU parallelisation (1)
- Gebäudemodelle (1)
- Gebäudeschwingungen (1)
- Gebäudeschwingungen, Deckenschwingungen, Wellenausbreitung (1)
- Gekoppeltes FE-SBFE-Modell (1)
- Geomechanics (1)
- Geomechanics of offshore foundations (1)
- Geometric trackbed irregularities (1)
- Grout Injection (1)
- Groutverbindung (1)
- Großprüfmaschinen (1)
- Hammerschlag (1)
- Hard object collisions (1)
- High temperature low sag (1)
- High temperature low sag (HTLS) conductors (1)
- Historische Brückenlager (1)
- Hochspannungs-Freileitungen (1)
- Hypothesis testing (1)
- Hypothesis tests (1)
- Impact test (1)
- In-situ measurements (1)
- Inclination (1)
- Increase (1)
- Inhomogeneous soils (1)
- Innovative Messtechnik (1)
- Instandhaltung (1)
- Integrity (1)
- Interacción dinámica suelo-estructura (1)
- Interface model (1)
- Inverse problem (1)
- Jet erosion test (1)
- Jet hydrodynamics (1)
- Klimakammer (1)
- Kontinuierlich (1)
- Kontrolle (1)
- Kostenoptimierung (1)
- LBM-DEM numerical simulation (1)
- LBM-DEM simulation (1)
- Laboratory tests (1)
- Laminography (1)
- Landslide propagation modelling (1)
- Langzeitmessung (1)
- Large concrete blocks (1)
- Large-scale field testing (1)
- Lebensdauerabschätzung (1)
- Lebewind (1)
- Liquefaction analysis (1)
- Load bearing behaviour (1)
- Load vectors (1)
- Load-carrying capacity (1)
- MOSYTRAF (1)
- Mass drop (1)
- Mast- und Turmbau - Masts and towers (1)
- Material Point Method (1)
- Material Point Method (MPM) (1)
- Material behavior (1)
- Material model (1)
- Material point method (1)
- Material point method (MPM) (1)
- Materialkennlinie (1)
- Measurement (1)
- Measurement campaigns (1)
- Measurements (1)
- Mechanical challenges (1)
- Mechanical systems (1)
- Mechanical tests (1)
- Messung (1)
- Microfine Cement (1)
- Microfine cement (1)
- Micromechanical LBM-DEM simulation (1)
- Microsilica (1)
- Minderung (1)
- Mitigation measures (1)
- Modal properties (1)
- Modal property (1)
- Mouthguard (1)
- Multi-beam method (1)
- Multi-beam model (1)
- Multi-beam-on-support model (1)
- Multimodal solution (1)
- Multiple linear (1)
- Multiple linear regression (1)
- Nichtlinearitäten (1)
- Non-ballasted track (1)
- Nonlinear Equation of Motion (1)
- Nonlinear Finite Element Formulations (1)
- Nonlinear finite element simulation (1)
- Nonlinearities (1)
- Normal strength concrete (1)
- Novelty analysis (1)
- Numerical computation (1)
- Numerical problem (1)
- Numerical response (1)
- OWEA (1)
- Offshore Windenergie (1)
- Offshore Windkraftanlagen (1)
- Offshore foundation (1)
- Offshore geotechnics (1)
- Offshore pile foundation (1)
- Offshore pile foundations (1)
- Offshore steel structures (1)
- Offshore structures (1)
- Offshore wind farms (1)
- Offshore-Gründung (1)
- Offshore-Gründungen (1)
- Offshore-Strukturen (1)
- Offshore-Windenergie (1)
- Offshore-Windenergieanlage (1)
- Onset of jet erosion (1)
- Optimierungsmethoden (1)
- Optimization strategies (1)
- Optimization techniques (1)
- PLIF-RIM optical techniques (1)
- Parametric excitation (1)
- Particle image velocimetry (PIV) (1)
- Perzyna viscoplasticity (1)
- Pfahl (1)
- Physical model testing (1)
- Physical testing (1)
- Pile Capacity (1)
- Pile ageing (1)
- Pile integrity test (1)
- Pile monitoring (1)
- Plate-soil interaction (1)
- Pore pressure accumulation (1)
- Prestressed concrete bridge (1)
- Principal Component Analysis (1)
- Principal component regression (1)
- Probabilitische Ingenieurmodelle (1)
- Prognose (1)
- Protective component (1)
- Prüfverfahren (1)
- RIM-PLIF techniques (1)
- Rail pad (1)
- Railway embankment (1)
- Railway induced ground vibration (1)
- Railway tracks (1)
- Rammpfähle (1)
- Rammung (1)
- Randelementmethode (1)
- Ratcheting convective cell (1)
- Rechenmodell (1)
- Reduction (1)
- Regular inspection (1)
- Reibung (1)
- Reinforced concrete (1)
- Reliability updating (1)
- Resistance (1)
- Resonancia en edificaciones (1)
- Resonant response (1)
- Risiko (1)
- Risikoanalyse (1)
- Risikobasierte Inspektionsplanung (1)
- Risikobasierte Maßnahmenplanung (1)
- Risk assessment (1)
- Rissdetektion (1)
- Risslumineszenz (1)
- Rissüberwachung (1)
- Riveted viaducts (1)
- Road (1)
- Robust tests (1)
- Sachschaden (1)
- Safety (1)
- Sand (hydraulic) (1)
- Scaled boundary finite element method (1)
- Scattered axle impulses (1)
- Schadenserkennung (1)
- Schienenverkehr (1)
- Schrauben (1)
- Schutzbauteil (1)
- Schweißnahtausbildung (1)
- Schwingungsmessungen (1)
- Schädigung (1)
- Seismic crosshole (1)
- Seismic tomography (1)
- Self-damping (1)
- Service life performance (1)
- Shearing (1)
- Shock absorbtion (1)
- Shrinkage (1)
- Shrinkage Reducing Admixture (1)
- Sleeper pad (1)
- Smoke (1)
- Smoothed particle hydrodynamics (1)
- Soft track elements (1)
- Soil erosion (1)
- Soil liquefaction (1)
- Soil-grout interface (1)
- Soil-water-structure interaction (1)
- Spannbetonbrücken (1)
- Spektralanalyse (1)
- Stabilität (1)
- Stahlbau (1)
- Stahlhochbau - Steel buildings (1)
- Stahlpfahl, gerammt (1)
- Stahlwasserbau - Steel structures for hydraulic engineering (1)
- State of stress (1)
- Statistical pattern recognition (1)
- Steel (1)
- Steel driven piles (1)
- Steel pile, driven in (1)
- Strain (1)
- Strain measurement (1)
- Strength (1)
- Stress state (1)
- Structural analyses (1)
- Structural health monitoring (SHM) (1)
- Structural modification (1)
- Structural performance (1)
- Structural reliability and risks (1)
- Structural systems (1)
- Structural vibration monitoring (1)
- Structure (1)
- Structure integrated sensor (1)
- Subset simulation (1)
- Subspace-based detection (1)
- Subspace-basierte Verfahren (1)
- Subspace-methods (1)
- Substructures (1)
- Superplasticizer (1)
- Supplementary Cementitious Materials (1)
- System (1)
- System identification (1)
- TOP (1)
- Tagung (1)
- Target stiffness (1)
- Temperatur (1)
- Temperature (1)
- Temperature effect (1)
- Temperature effect rejection (1)
- Temperature modeling (1)
- Temperatureinfluss (1)
- Test site (1)
- Tower-nacelle system (1)
- Toxicity (1)
- Track (1)
- Track beam (1)
- Track deformation (1)
- Track deterioration (1)
- Track settlement (1)
- Track-soil and vehicle-track resonances (1)
- Tragstrukturen (1)
- Train configuration (1)
- Train excitation (1)
- Train induced ground vibration (1)
- Train speed (1)
- Train-track interaction (1)
- Train-track-interaction (1)
- Tran speed (1)
- Transition zone (1)
- Turbulent Wind Excitation (1)
- Un- certainty (1)
- Uncertainty bounds (1)
- Under sleeper pads (1)
- Updated Lagrange Formulierung (1)
- Varying track stiffness (1)
- Verdichtungsinjektionen (1)
- Vibration behaviour (1)
- Vibration reduction (1)
- Vibration-based structural health monitoring system (1)
- Viscosity (1)
- Vorspannung (1)
- WKP (1)
- Wahrscheinlichkeit (1)
- Wave excitation (1)
- Wave-Tower interaction (1)
- Wellenausbreitung (1)
- Wellenfeldberechnung (1)
- Wellengeschwindigkeit (1)
- Westend bridge (1)
- Westendbrücke (1)
- Wheelset accelerations (1)
- Wiederkehrende Prüfung (1)
- Wind (1)
- Wind loading (1)
- Wind tunnel (1)
- Wind tunnel experiments (1)
- Windenergieanlage (1)
- Windfarm wake analysis (1)
- Workability (1)
- Zivile Sicherheit (1)
- Zugüberfahrt (1)
- Zustandsbewertung (1)
- Zyklik (1)
- elastische Gebäudelagerungen (1)
- fachwerkartige Stahltragwerken (1)
- risk, reliability, inspection planning, offshore wind turbines (1)
- sleeper pads (1)
- temperature (1)
- u-p-Formulierung (1)
- Überwachungsverfahren (1)

#### Organisationseinheit der BAM

- 7.2 Ingenieurbau (376) (entfernen)

Reliability analysis of deteriorating structural systems requires the solution of time-variant reliability problems.
In the general case, both the capacity of and the loads on the structure vary with time. This analysis can be approached by approximation through a series of time-invariant reliability problems, which is a potentially effective strategy for cases where direct solutions of the time-variant reliability problem are challenging, e.g. for structural systems with many elements or arbitrary load processes. In this contribution, we thoroughly Review the formulation of the equivalent time-invariant reliability problems and extend this approximation to structures for which inspection and monitoring data is available. Thereafter, we present methods for efficiently evaluating the reliability over time. In particular, we propose the combination of sampling-based methods with a FORM (first-order reliability method) approximation of the series system reliability problem that arises in the computation of the lifetime reliability. The framework and algorithms are demonstrated on a set of numerical examples, which include the computation of the reliability conditional on inspection data.

The subject of damage localization is an important issue for Structural Health Monitoring (SHM) particularly in mechanical or civil structures under ambient excitation. In this paper, the statistical subspacebased damage localization method has been applied on a benchmark application, namely a 1/200 scale model of the Saint-Nazaire Bridge, which is a cable-stayed bridge located on the Loire River near the river’s mouth. The employed damage localization method combines data-driven features with physical parameter information from a finite element model in statistical tests, avoiding typical ill-conditioning problems of FE model updating. Damage is introduced in the mockup for cable failures on some of the 72 cables. The purpose of the experiment is to assess the capability of damage assessment methods to find a cable failure.

Driven steel piles are commonly used as deep foundations for a wide range of engineering structures, particularly in the offshore branch. They are also an interesting example among the broad spectrum of geotechnical applications where the fluid-solid interaction at the pore-scale can play a major role for the macromechanical behaviour of the whole system.
In the context of the geotechnical practice for offshore wind-farm structures, both the industrial design and the actual dimensions of the large piles used as foundations in the seabed are often driven by factors such as the soil resistance to driving (SRD), which are still not well understood and often estimated based on mere empirical correlations or overly simplified one-dimensional models. In particular, the role of the micromechanical effects during the installation process (e.g. local dilatancy or contractancy) and their consequences on the pore pressure levels at the pile-tip and on the effective resistance to driving, are generally either disregarded or at most assumed to be covered by the simplified engineering “black-box” solutions.
Here, we propose a general framework to address such local aspects of a geotechnical application involving fluid-saturated soils while retaining the focus on the micro-scale phenomena. We advocate for an approach that combines the relative simplicity of the Discrete Element Method (DEM) for the solid mechanics with the capabilities of the Lattice Boltzmann Method (LBM) for the fluid dynamics. In this sense, we aim to compile some useful techniques and practical recommendations for an efficient GPU-based implementation of a micromechanical LBM-DEM simulation tool.

The shaft bearing capacity often plays a dominant role for the overall structural behaviour of axially loaded piles in offshore deep foundations. Under cyclic loading, a narrow zone of soil at the pile-soil interface is subject to cyclic shearing solicitations. Thereby, the soil may densify and lead to a decrease of confining stress around the pile due to microphenomena such as particle crushing, migration and rearrangement. This reduction of radial stress has a direct impact on the shaft capacity, potentially leading in extreme cases to pile failure. An adequate interface model is needed in order to model this behaviour numerically. Different authors have proposed models that take typical Interface phenomena in account such as densification, grain breakage, normal pressure effect and roughness. However, as the models become more complex, a great number of material parameters need to be defined and calibrated. This paper proposes the adoption and transformation of an existing soil bulk model (Pastor- Zienkiewicz) into an interface model. To calibrate the new interface model, the results of an experimental campaign with the ring shear device under cyclic loading conditions are here presented. The constitutive model shows a good capability to reproduce typical features of sand behaviour such as cyclic compaction and dilatancy, which in saturated partially-drained conditions may lead to liquefaction and cyclic mobility phenomena.

The increasing use of renewable energies leads to a constant search for optimised foundation concepts aiming to reduce the costs for offshore wind turbines. In an ongoing research project, we are developing a design approach for typical offshore driven piles based on the application of injections by compaction grouting directly at the pile shaft. Compaction grouting as a ground improvement technique has been used widely as a countermeasure against liquefaction, settlement and low bearing capacity of soil under new or already existing structures. It is performed by forcing highly viscous grout into the soil to displace and compact the surrounding soil without fracturing or penetrating it. Regarding this injection method, this paper gives a brief overview about general aspects such as appropriate soil characteristics and grouting parameters, grouting equipment and fields of application particularly in the offshore sector. This indicates the ability of our optimisation concept to provide an economic alternative to larger pile dimensions and a retrofitting technique, which is available during the entire lifetime of the foundation and can be deployed only in case of necessity (e.g. excessive deformations or insufficient structural stiffness after an extreme load event).
Besides the material feasibility and the constructive realisation of this improvement measure, the development of a corresponding verification concept is crucial in order to ensure the safety and durability of the retrofitted offshore piles. Here we will examine various verification concepts with their respective limitations in the framework of the limit state design. Furthermore, we will present the experimental findings from field tests in sand indicating the advantages of several local injections by compaction grouting for the enhancement of the load bearing behaviour of pile foundations. The test results were also used to validate a numerical model, developed with the finite element program PLAXIS, aiming to predict the expected bearing capacity for different injection scenarios (e.g. grout volume, location of injection points) along a pile shaft.

The aim of an ongoing research project is to develop a design approach for typical offshore driven piles (e.g. Jacket piles) based on the application of injections by compaction grouting directly at the pile shaft. The paper aims to present the results of laboratory and in-situ tests, which reveal the efficiency and the promising potential of the optimised foundation concept for a more economic dimensioning of pile foundations and to increase their bearing capacity in non-cohesive soil at any moment after installation.

Abstract. Three measurement campaigns of train-induced ground vibrations are evaluated for the vehicle-track-soil interaction. Ground vibrations, track vibrations and vehicle vibrations have been measured for train passages and impulse excitation and compared with theoretical results.
The soil and the track-soil system are calculated by wavenumber integrals. The influence of the vehicle is introduced by a substructure method. By comparing theory and measurement the different components of excitation force and ground vibration can be analysed, the quasi-static excitation, track-alignment errors, the out-of-roundness of wheels, the wheel and rail roughness, and moreover, scattered axle impulses and ineffective high-frequency parts of the wheelset accelerations and forces.

Measured train passages and hammer impacts in combination with track-soil calculation have been successfully used for the detection of damaged slab tracks. This approach is now extended to intact slab and ballast tracks. The vibrations of many tracks have been measured at several levels from rail, sleeper, track plate, base plate, base layer to the subsoil by velocity or acceleration sensors. The time histories have to be integrated once or twice to get the displacements. The displacement signals include an arbitrary time-dependent shift which must be eliminated or respected in the interpretation. On the other hand, the calculation of slab and ballast tracks have been done in frequency-wavenumber domain. The displacements along the track and the frequency-dependent compliance transfer functions can be calculated. The latter can be compared with the results of the hammer impacts on the track. The deformation of the track can be transformed to time histories for a whole train and compared to the measured train passages. Many slab (and ballast) tracks have been measured at different sites. The displacements of the tracks are presented, and the following parameters have been analysed in the measurement results: slab track vs. ballast track, different types of slab tracks, damaged slab tracks, different trains, switches at different measuring points, an elastic layer, the mortar layer, different soils at different places. The soil should have the dominant influence on the track-plate displacements. Slab and ballast track yield also big differences in maximum displacement and width of deformation. Some of the preceding aspects will be analysed in comparison of measurement and theory.

Methods have been presented for detailed studies of railway vibration and for the fast prediction of train-induced ground vibration. The ground vibration is generated by static or dynamic loads. The main purpose of this contribution was to show the influence of inhomogeneous soils on the different vibration components.
Layered soils, namely a soft layer on a stiffer half-space, yield a quite specific transmission behavior. The low-frequency and sometimes also high-frequency cut-off of the transfer function of the soil is demonstrated in theory and by experiments at many sites of which the soil model is approximated from dispersion and transfer function measurements. The layer frequency divides the frequency range in a low-frequency range, where the stiff half-space rules the low amplitudes, and a high amplitude high-frequency range which is mainly determined by the softer top layer. A thick soft layer yields a very low layer frequency, so that the higher soft soil amplitudes have a wider range down to low frequencies. A thin layer yields a high layer frequency, so that the high frequencies above this layer frequency are dominant. The higher the contrast between the stiff half-space and the soft layer is, the stronger the increase between the half-space and layer amplitudes, the more characteristic are the spectra of the soil transfer function. The range of measured soils has been from vS1 down to 125 m/s, vS2 up to 1000 m/s and the layer frequencies are within 10 Hz < f0 < 75 Hz. Moreover, during this measuring campaign in Switzerland, all 11 sites showed clearly the layer-on-half-space behaviour. The transfer functions of inhomogeneous soils have been used to predict the ground vibration due to dynamic axle loads which is usually thought to be the most important component.
The passage of static loads, in the contrary, results in very small vibration amplitudes for low train speeds, which can only be found at near distances and at low frequencies. They attenuate very rapidly with distance and lose very rapidly the higher frequency content. The passage of static axle loads can be included in the prediction of railway vibration just for completeness.
Special attention should be given to the case if the train runs with the Rayleigh-wave speed of the soil (Rayleigh train). The Rayleigh-train effect is strongest for a homogeneous half-space: At the near-field of the track the amplitudes are raised strongly compared to normal trains, and in addition, little attenuation with distance is observed. In case of a layered soil, the low-frequency cut-off reduces the frequency range and the amplitudes of the homogeneous quasi-static ground vibrations. Therefore, the Rayleigh-train effects are clearly reduced by a layered soil and they disappear if the layer frequency (for example for a thin layer) is higher than the frequency band of the axle impulse. The Rayleigh-train effect could completely disappear in a randomly inhomogeneous soil, but this has not been analysed so far.
The axle impulses from static loads can have an additional, quite different effect. They can be scattered by a randomly inhomogeneous soil so that a part (the scattered part) of the axle impulse can reach further distances from the track. This can establish a certain mid-frequency component of the ground vibration which becomes dominant in the far-field, and this important component exists for all train speeds. Experimental results from BAM and international measurements show the importance of the corresponding frequency range.
The mitigation of train induced ground vibration by elastic and stiff track elements has been analysed threefold. The vehicle-track interaction yields the reduction at high frequencies above the vehicle-track resonance. This is the standard effect. The filtering of trackbed errors by the bending stiffness of the track yields a certain mid-frequency effect. An even stronger mid-frequency effect is predicted for the mitigation of the scattered axle impulses by the bending stiffness and elastic elements of the track.

Es wird die Vorgehensweise erläutert wie die Notwendigkeit einer elastischen Gebäudelagerung geprüft wird. Es werden die Möglichkeiten und Schwächen vereinfachter Rechenverfahren dargestellt. Es folgen weitere Beispiele detaillierter Gebäudemodelle und ihres Schwingungsverhaltens. Schließlich greift eine aktuelle Bachelorarbeit die Fragestellung komplexen Gebäudeschwingungsverhaltens auf. Die letzte Folie zeigt dazu Gebäudemodelle, die an die konkreten Erschütterungsprognosen anknüpfen.

Within the presented research project, experimental and numerical investigations were performed to develop a thin-shelled, modular, mobile element system made of a micro-reinforced ultra-high-performance ductile concrete (DUCON®). Material parameters were experimentally determined to adapt the material model within the numerical analysis applying the Drucker-Prager relationship. Afterwards, for validation of the numerical models, quasi-static and high-velocity impact tests were performed on plate-like structures. Finally, a suitable geometry of transportable barrier elements will be designed, which provides a maximum of resistance against impact by a minimum of weight and a maximum of mobility.

A combined finite-element boundary-element method for the dynamic interaction of the soil with flexible structures such as single piles or complete wind energy towers has been developed. Flexible piles in different soils are analysed in frequency domain. The different parameters such as the stiffness of the soil, the bending stiffness and the radius of the hollow pile are analysed for their influence on the complex compliances. The results have been determined as specific power laws which are different for the different load cases (horizontal, rocking, coupling) and for the different soil models (Winkler, continuum with constant, root-parabolic and proportional-linear stiffness variation). The strongest influence of the soil stiffness can be found for the homogeneous soil and the horizontal component. Winkler soils have a weaker influence than the corresponding continuous soils. An offshore wind energy tower has been modeled and calculated for wind and wave loads.

Three measurement campaigns of train-induced ground vibrations are evaluated for the vehicle-track-soil interaction. Ground vibrations, track vibrations and vehicle vibrations have been measured for train passages and impulse excitation and compared with theoretical results. The soil and the track-soil system are calculated by wavenumber integrals. The influence of the vehicle is introduced by a substructure method. By comparing theory and measurement the different components of excitation force and ground vibration can be analysed, the quasi-static excitation, track-alignment errors, the out-of-roundness of wheels, the wheel and rail roughness, and moreover, scattered axle impulses and ineffective high-frequency parts of the wheelset accelerations and forces.

Three measurement campaigns of train-induced ground vibrations are evaluated for the vehicle-track-soil interaction. Ground vibrations, track vibrations and vehicle vibrations have been measured for train passages and impulse excitation and compared with theoretical results. The soil and the track-soil system are calculated by wavenumber integrals. The influence of the vehicle is introduced by a substructure method. By comparing theory and measurement the different components of excitation force and ground vibration can be analysed, the quasi-static excitation, track-alignment errors, the out-of-roundness of wheels, the wheel and rail roughness, and moreover, scattered axle impulses and ineffective high-frequency parts of the wheelset accelerations and Forces.

Two measurement campaigns of train-induced ground vibrations are evaluated for the vehicle-track-soil interaction. Ground vibrations, track vibrations and vehicle vibrations have been measured for train passages and impulse excitation and compared with theoretical results. The soil and the track-soil system are calculated by wavenumber integrals. The influence of the vehicle is introduced by a substructure method. By comparing theory and measurement the different components of excitation force and ground vibration can be analysed, the quasi-static excitation, track-alignment errors, the out-of-roundness of wheels, the wheel and rail roughness, and moreover, scattered axle impulses and ineffective high-frequency parts of the wheelset accelerations and forces.

The Stochastic Dynamic Damage Locating Vector (SDDLV) approach is a vibration-based damage localization method based on both a finite element model of a structure and modal parameters estimated
from output-only measurements in the damage and reference states. A statistical version of the Approach takes into account the inherent uncertainty due to noisy measurement data. In this paper, the effect of temperature fluctuations on the performance of the method is analyzed in a model-based approach using a finite element model with temperature dependent parameters. Robust damage localization is carried out by rejecting the temperature influence on the identified modal parameters in the damaged state. The algorithm is illustrated on a simulated structure.

Grouts have numerous applications in construction industry such as joint sealing, structural repair, and connections in precast elements. They are particularly favoured in rehabilitation of structures due to penetrability and convenience of application. Grouts for repair applications typically require high-performance properties such as rapid strength development and superior shrinkage characteristics. Sometimes industrial by-products referred as supplementary cementitious materials (SCM) are used with neat cement due to their capabilities to provide binding properties at delayed stage. Micro silica, fly ash and metakaolin are such SCMs, those can modify and improve properties of cement products. This study aims at investigating long-term mass loss and linear shrinkage along with long-term compressive and flexural strength for grouts produced from ultrafine cement and SCMs. A series of mixtures were formulated to observe the effect of SCMs on these grout properties. Properties were determined after 365 days of curing at 23oC and 55% relative humidity. The effect of SCMs on the properties are characterised by statistical models. Response surfaces were constructed to quantify these properties in relation to SCMs replacement. The results suggested that shrinkage was reduced by metakaolin, while micro silica and fly ash had positive effects on compressive and flexural strength, respectively.

Superplasticizer and Shrinkage Reducing Admixture Dosages for Microfine Cement in Grout Systems
(2019)

Grouts have numerous applications including crack repair as maintenance in construction industries. Microfine cements are intensively used for high strength mortar and grout products. They are ideal for injection grouting in structural repair. Such grouts should have suitable rheological properties to be injectable, especially those used in repair and rehabilitation. The use of superplasticizers (SP) in these products is thus becoming increasingly crucial to achieve favorable workability and viscosity properties. A difficulty in such grouts is the plastic shrinkage due to finer particles used. It is thus necessary to determine optimum SP and shrinkage reducing admixture (SRA) dosages for a microfine cement based grout. In this study, a saturation dosage was decided from two Polycarboxylate ether (PCE) based SPs in relation to neat cement using slump flow and rheological parameters. A range of grout mixtures was formulated containing micro silica (MS) and fly ash (FA), and tested for suitable rheological and mechanical parameters. Based on the results, a grout mixture with MS and FA was selected to determine optimum SRA content. According to the results, a SP dosage of 3% by weight of neat cement is sufficient to achieve saturation. The grout material including MS and FA can produce comparable properties to neat cement grout. MS is found to improve compressive strength within the range considered, whereas a higher FA content provides favourable rheological properties. Finally, a SRA dosage of 4%, which could reduce the shrinkage by about 43% after 28d days, is determined for the grout system.

Identifying optimal inspection and repair strategies for offshore jacket structures is a challenging task. We pre-sent an approach, which is based on recent developments in the field of risk-based operation and maintenance planning at the structural system level. The approach utilizes heuristics to define inspection and repair strate-gies at the system level and to reduce the search space of possible strategies. For each defined strategy, the expected service life cost of inspection, repair and failure is evaluated based on simulated inspection and re-pair histories. Subset simulation is applied to compute the conditional repair and failure probabilities required for this analysis. It also forms the basis for simulating inspection and repair histories. The strategy that mini-mizes the expected service life cost is the optimal one in the set of pre-selected strategies. The underlying condition and performance model accounts for the stochastic dependence among the deterioration states of the different structural elements and the structural redundancy. The approach is demonstrated in a case study considering a jacket-type frame. In this study, we essentially vary the inspection interval, the minimum num-ber of inspected components and the target reliability, and identify the combination that minimizes the ex-pected total service life cost.

Temperature variation can be a nuisance that perturbs vibration based structural health monitoring (SHM) approaches for civil engineering structures. In this paper, temperature affected vibration data is evaluated within a stochastic damage detection framework, which relies on a null space based residual. Besides two existing temperature rejection approaches – building a reference state from an averaging method or a piecewise method – a new approach is proposed, using model interpolation. In this approach, a general reference model is obtained from data in the reference state at several known reference temperatures. Then, for a particular tested temperature, a local reference model is derived from the general reference model. Thus, a well fitting reference null space for the formulation of a residual is available when new data is tested for damage detection at an arbitrary temperature. Particular attention is paid to the computation of the residual covariance, taking into account the uncertainty related to the null space matrix estimate. This improves the test performance, contrary to prior methods, for local and global damages, resulting in a higher probability of detection (PoD) for the new interpolation approach compared to previous approaches.

Temperature variation can be a nuisance that perturbs vibration based structural health monitoring (SHM) approaches for civil engineering structures. In this paper, temperature affected vibration data is evaluated within a stochastic damage detection framework, which relies on a null space based residual. Besides two existing temperature rejection approaches – building a reference state from an averaging method or a piecewise method – a new approach is proposed, using model interpolation. In this approach, a General reference model is obtained from data in the reference state at several known reference temperatures.
Then, for a particular tested temperature, a local reference model is derived from the general reference model. Thus, a well fitting reference null space for the formulation of a residual is available when new data is tested for damage detection at an arbitrary temperature. Particular attention is paid to the computation of the residual covariance, taking into account the uncertainty related to the null space Matrix estimate. This improves the test performance, contrary to prior methods, for local and global damages, resulting in a higher probability of detection (PoD) for the new interpolation approach compared to previous approaches.

The structural performance of many geotechnical systems (e.g. axially-loaded pile foundations), depends on the shearing resistance at the soil interface, which may govern the load bearing capacity of the foundation. Experimental investigations have shown that this interaction is mainly localised within a narrow shear band next to the structure. Under cyclic loading, a contraction of the soil at the interface may arise (net volume loss), possibly leading to a stress relaxation and thus to a reduction of the load bearing capacity (the so-called friction fatigue). Based on the constitutive similarities between soil continua and interfaces, we propose here the adaption of a Generalized Plasticity model for sandy soils for the numerical analysis of interface problems. In this contribution, the results of an experimental campaign for the parameter calibration of the constitutive model are presented. The tests have been conducted with a ring shear device involving different normal stresses, roughness of the steel plates as well as cyclic loading. The new modelling approach shows promising results and has the additional practical advantage that the interface zone and the soil continuum can both be described with the same constitutive model in general boundary value problems.

This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures.
The first lecture presents a brief introduction to the context and peculiarities of such foundations, and then focuses on the particular case of axially loaded piles. This part is most relevant for the relatively slender piles of the multi-pile substructures (i.e. jackets and tripods). A clear distinction between physical phenomenology and practical design is drawn here.
The second lecture continues with the case of lateraly loaded offshore piles, which bears most relevance for the case of the monopile foundations. Here again, a clear separation between physical reality and design methods is intended.
Finally, the last part of the second lecture introduces several advanced topics which lie outside the classical design approaches, namely the hydromechanical coupling effects (i.e. the excess pore-pressure generation around the monopiles), the cyclic pile fatigue and the so-called pile Setup (i.e. the time effects on the axial pile capacity). The relevance of the latter two topics is illustrated with experimental results from a field testing campaign on real large-scale piles.

Kontinuierliche Sensorbasierte Bauwerksmessungen leisten einen wichtigen Beitrag zur Sicherheit von Verkehrsbauwerken. Hierzu werden im Vorhaben AISTEC Referenzbauwerke und Referenzverfahren untersucht mit Schwerpunkt auf den Einfluss klimatischer Bedingungen. Der Vortrag stellt den aktuellen Projektstand des FB 7.2 vor.

Grouts are particularly favoured in rehabilitation of structures due to penetrability and convenience of application. Grouts for repair applications typically require high-performance properties such as rapid strength development and superior shrinkage characteristics. Sometimes industrial by-products referred as supplementary cementitious materials (SCM) are used with neat cement due to their capabilities to provide binding properties at delayed stage. Micro silica, fly ash and metakaolin are such SCMs, those can modify and improve properties of cement products. This study aims at investigating long-term mass loss and linear shrinkage along with long-term compressive and flexural strength for grouts produced from ultrafine cement and SCMs. A series of mixtures were formulated to observe the effect of SCMs on these grout properties. Properties were determined after 365 days of curing at 23 °C and 55% relative humidity. The effect of SCMs on the properties are characterised by statistical models. Response surfaces were constructed to quantify these properties in relation to SCMs replacement. The results suggested that shrinkage was reduced by metakaolin, while micro silica and fly ash had positive effects on compressive and flexural strength, respectively.

Automated modal analysis for tracking structural change during construction and operation phases
(2019)

The automated modal analysis (AMA) technique has attracted significant interest over the last few years, because it can track variations in modal parameters and has the potential to detect structural changes. In this paper, an improved density-based spatial clustering of applications with noise (DBSCAN) is introduced to clean the abnormal poles in a stabilization diagram. Moreover, the optimal system model order is also discussed to obtain more stable poles. A numerical Simulation and a full-scale experiment of an arch bridge are carried out to validate the effectiveness of the proposed algorithm. Subsequently, the continuous dynamic monitoring system of the bridge and the proposed algorithm are implemented to track the structural changes during the construction phase. Finally, the artificial neural network (ANN) is used to remove the temperature effect on modal frequencies so that a health index can be constructed under operational conditions.

Erschütterungen durch Industrie und Verkehr, Schwingungen von Gebäuden, Fundamenten und Gleisen hängen im hohen Maße vom jeweiligen unterliegenden Boden ab. Die Eigenschaften des Bodens ermitteln wir mit Wellenmessungen vor Ort. Die Wellen werden in der Regel mit einem Impulshammer erzeugt und mit Geophonen als Schwinggeschwindigkeits-signale gemessen. Geophone sind aktive Sensoren, die eine kleine Messspannung liefern. Ein 72-kanaliges Messsystem mit entsprechenden Messverstärkern ist im Messwagen der Arbeitsgruppe eingebaut. Es werden im Vortrag fünf verschiedene Auswertemethoden vorgestellt. Im einfachsten Fall versucht man die Laufzeit von einem Geophon zum andern auszumessen und damit die vorherrschende Wellengeschwindigkeit zu ermitteln. Wir haben Wellengeschwindigkeiten von 30 m/s für Moorboden bis 1000 m/s für Felsboden gemessen. Der Boden hat aber nicht nur eine Wellengeschwindigkeit, sondern mehrere frequenzabhängige Wellen-geschwindigkeiten. Dadurch wird aus einem kurzen Hammerschlag eine längere Schwingung (Zerstreuung, Dispersion). Für die Auswertung von dispersiven Wellen nutzt man die spektrale Analyse, zunächst mit zwei Aufnehmern (SASW Spectral Analysis of Surface Waves), später mit einer ganzen Messachse (Multi-Station SASW). Schließlich kann man eine ganze Messachse auch mit verschiedenen Transformationsmethoden auswerten wie die f,v-Methode und Spatial AutoCorrelation SPAC Methode. Alle diese Methoden wurden von uns auf Messreisen in Deutschland, Österreich und der Schweiz getestet. Durch die Approximation der frequenzabhängigen Wellengeschwindigkeiten erhält man ein passendes Bodenmodell. Zu diesem Bodenmodell kann man die Übertra¬gungsfunktionen für Hammer- und Zuganregung berechnen. Bei etlichen Mess¬orten wurden deutliche Merkmale einer Bodenschichtung beobachtet. Es ergibt sich eine Reduktion der tiefen Frequenzanteile durch den steifen unterliegenden Halbraum. Die weiche Deckschicht bestimmt das hochfrequente Verhalten.

Owners or operators of offshore wind farms perform inspections to collect information on the condition of the wind turbine support structures and perform repairs if required. These activities are costly and should be optimized. Risk-based methods can be applied to identify inspection and repair strategies that ensure an optimal balance between the expected total service life cost of inspection and repair, and the achieved risk reduction. Such an optimization requires explicit modeling of repairs. In this paper, the impact of different repair models on the results of a risk-based optimization of inspection and repair strategies is quantified in a numerical example considering a jacket-type steel frame subject to high-cycle fatigue. The example showed that, in this specific application, there is no need for detailed modeling of the behavior of repaired welded connections.

Damage detection and localization in civil or mechanical structures is a subject of active development and research. A few vibration‐based methods have been developed so far, requiring, for example, modal parameter estimates in the reference and damaged states of the investigated structure, and for localization in addition a finite element model. For structures in operation, temperature has been shown to be a major nuisance to the efficiency of such methods because the modal parameters are varying not only with damage but also due to temperature variations. For detection, a few rejection approaches have been developed. Besides the increased complexity, environmental variation is hardly taken into account in localization approaches. In this paper, we propose a sensitivity‐based correction of the identified modal parameters in the damaged state with respect to the temperature field in the reference state, on the basis of a sensitivity analysis with respect to temperature dependent Parameters of the finite element model in the reference state. The approach is then applied to the stochastic dynamic damage locating vector method, where its improved performance under nonuniform temperature variations is shown in a numerical application on a beam.

Global energy consumption will increase in the future necessitating both fossil fuels and renewable energy choices - especially wind energy. Such high energy demand requires installation of offshore energy structures, rigs, platforms and towers, which are susceptible to adverse environmental conditions along with maintenances. Due to their large size and remote locations, cylindrical grouted joints are often adopted between substructure and foundation in these offshore platforms and wind structures such as monopiles. However, these connections are composite structures with exterior sleeve, interior pile and infill mortar. Degradation and settlements were reported inside similar connections, which were installed in last three decades. Besides, grouting in the offshore sites were proven difficult to obtain ideal load bearing capacity. In-situ loading conditions were also found to be affecting the failure mechanism inside such connections. This study aims at characterizing the nature of cracks generated in these grouted connections under both static and cyclic loading. Scaled grouted joints were manufactured using a novel reusable mold, and connections were loaded to failure to visualize the main failure patterns. An assessment between failure under these two types of load is drawn along with comparison to previously available literature.

This talk provides a brief introduction on general engineering challenges for the offshore (marine) wind energy production, focusing on material, structural and hydromechanical aspects.
The talk begins with a broad overview on general trends for offshore wind-farms, with insights on some characteristic structural features and their associated loads. Then, some particular open issues for the foundation of the offshore wind turbines into the seabed are introduced. Here, different research approaches are discussed, from experimental investigations to coupled computational analysis at micro- and macroscopic scales.
In the second part of the seminar, both the hydromechanical Wave–Tower interaction and some general aspects of the windfarm aerodynamics (wake analysis) are discussed. Some modelling possibilities in the frame of CFD (computational fluid dynamics) are introduced and the relevance of such analyses for a proper windfarm layout optimization is pointed out.
Summing up, this seminar aims to show that: i) Numerical analysis of the turbine’s interaction with wind/waves and with the seabed is both useful and affordable. ii) Simplified models can provide an insight into windfarm aerodynamics. iii) Turbulent wake analysis is very relevant for the windfarm layout.

Fatigue in Concrete
(2019)

The current knowledge about fatigue behavior of concrete is still incomplete. This concerns especially the progress of fatigue which precedes the fatigue failure. An overview on the fatigue behaviour in concrete is given. Therefore, the process of fatigue itself under cyclic compressive loading was investigated in a systematic and comprehensive way. The aim of this investigation was to obtain a deeper insight and to provide a better understanding of the damage process occurring within the material during fatigue loading.

At present, to produce renewable energy offshore wind farms play an important role. The available space combined with the more valuable wind conditions make offshore locations very attractive for wind powered energy production. In Europe a significant number of offshore wind farms already exist, especially in the North and Baltic Sea. In future this trend will continue, and further offshore wind farms will be built. The majority of offshore wind turbines are mounted on steel foundation structures. Due to the high-cyclic loading by wind and waves fatigue stress plays a substantial role regarding structural safety.
Besides the consideration of fatigue within the design process, to monitor existing steel structures for potential fatigue cracks during their life time is a major topic and a challenge.
For the structures of the offshore wind turbines are large and partially under water effective reliable methods for the detection of fatigue cracks are required.
This contribution presents investigations on different crack detection methods applied at high-cycle fatigue tests on small-scale welded steel samples as well as on large-scale welded steel components. The tests were conducted at the BAM laboratories. For crack detection mainly three different methods were used and compared. The first method regards to the measurement of strain by conventionally strain gauges. Secondly, the crack luminescence was used as a new and effective optical method for surface monitoring. And finally, crack detection by pressure differentials of the inner and outer section of tubular steel elements was investigated. A comparison study will emphasize the advantages and disadvantages of the different methods and show which of the described methods is potentially more suitable for an application on real offshore wind structures.

This talk provides a brief introduction on general engineering aspects of offshore wind energy production. Some geomechanical issues for the foundation of OWTs into the seabed are introduced, while the results from experimental investigations and coupled computational analysis are discussed.
In the second part of the seminar, the hydromechanical Wave–Tower interaction is firstly discussed. Then, some general aspects of the windfarm aerodynamics are introduced. On the one hand, some modelling possibilities for the wake analysis of single turbines and turbine groups are discussed. And on the other hand the relevance of such analyses for a proper windfarm layout optimization is pointed out.
Concerning the geomechanical issues the talk shows that: i) The pile’s bearing capacity can degrade under cyclic loading (waves, wind, …). ii) The time effects can be relevant: Capacity improvement can be substantial, but also fragile. iii) There are cyclic PWP effects: Cyclic interaction with pore water may lead to soil softening and an uncoupled analysis (current design practice) is potentially unsafe.
And concerning the hydromechanical and aerodynamical design considerations, this seminar shows that: i) Numerical analysis of turbine’s interaction with wind/waves is useful and affordable. ii) Simplified models can provide insight into windfarm aerodynamics. iii) Turbulent wake analysis is very relevant for the windfarm layout.

Unterraumbasierte Detektion von Strukturschäden an Jacket-Gründungen von Offshore-Windenergieanlagen
(2018)

Die vorliegende Arbeit beschreibt die Adaption eines globalen, schwingungsbasierten Verfahrens zur frühzeitigen Erkennung von Strukturschäden an Gründungsstrukturen offshore installierter Windenergieanlagen (OWEA). Damit soll es, Betreibern von Offshore-Windparks ermöglicht werden, im Rahmen periodisch durchgeführter messtechnischer Überwachungsmaßnahmen mit einem gegenüber wiederkehrender Inspektionen wesentlich geringen Aufwand auftretende Schäden an der Struktur zuverlässig zu delektieren.
Das untersuchte und implementierte Verfahren basiert auf der Methode der stochastischen unterraumbasierten Schadensdetektion. Dabei erfolgt eine statistische Analyse des wiederkehrend messtechnisch aufgenommenen dynamischen Antwortverhaltens des mechanischen Systems. Mittels statistischem Test werden signifikante Änderungen in dessen Eigenstruktur und damit Schäden delektiert.
Im Rahmen der vorliegenden Arbeit wurden umfangreiche experimentelle als auch numerische Untersuchungen zur Sensitivität und Robustheit des beschriebenen Schadensindikators durchgeführt. Dazu sind zunächst an einem Labormodell mittels künstlich und reversibel eingebrachter Schäden grundlegende Analysen zu den Einflüssen signal- und verfahrensinhärenter Kenngrößen durchgeführt worden. Auf der Basis dieser Ergebnisse wurde im Anschluss mittels numerischer Analysen das Antwortverhalten von OWEA simuliert und der entwickelte Algorithmus zur Schadensdetektion an den so realisierten Datensätzen angewendet.
Anhand der Ergebnisse der Arbeit wird aufgezeigt, dass, vorausgesetzt die Windenergieanlage befindet sich in Parkposition, eine Detektion von schon geringen Schäden an Gründungs-strukturen mit dem beschriebenen Verfahren, auch unter Einsatz weniger Messaufnehmer, zuverlässig möglich ist.

The response of many geotechnical systems, whose structural behavior depends on shearing effect, is closely related to soil structure interaction phenomenon. Experimentally it is found that the localisation of these effect happens at a narrow soil layer next to the structure. Numerically, this behavior can be modelled through interface elements and adequate constitutive models. In this work, a constitutive model in the framework of Generalized Plasticity for sandy soils has been chosen to be adapted for the interface zone.
From the direct shear experiments a sandy soil at loose and dense states under different normal pressures is considered. The adapted constitutive model is able to reproduce contraction and dilatation of the soil according to its relative density and it shows a good agreement with the experimental data.

Risslumineszenz
(2018)

The response of many geotechnical systems, whose structural behavior depends on shearing effect, is closely related to soil structure interaction phenomenon. Experimentally it is found that the localisation of these effect happens at a narrow soil layer next to the structure. Numerically, this behavior can be modelled through inter-face elements and adequate constitutive models. In this work, a constitutive model in the framework of Gen-eralized Plasticity for sandy soils has been chosen to be adapted for the interface zone. From the direct shear experiments a sandy soil at loose and dense states under different normal pressures is considered. The adapted constitutive model is able to reproduce contraction and dilatation of the soil according to its relative density and it shows a good agreement with the experimental data.

The worldwide spread of windfarms brings new challenges, especially for concrete structures as a part of towers, connecting joints and foundations of wind turbines. High-cyclic loadings in such structures lead to a high relevance of the subject of fatigue. A proper assessment of the fatigue strength of concrete demands therefore a basis of reliable experimental data and the development of standardized testing methods. This article presents first results of an ongoing research program of BAM (Bundesanstalt für Materialforschung und -prüfung) which is a part of a joint project (WinConFat) funded by the German Federal Ministry for Economic Affairs and Energy. The subproject investigates the effects of size and slenderness of the specimens on the fatigue behaviour of high strength concrete at different stress levels. Not only the fatigue strength, but also the fatigue process itself is monitored by means of several measurement methods. Strain measurements are used to calculate the load dependent elastic modulus in the fatigue hysteresis as indicators for fatigue development. Furthermore, the application of non-destructive methods like acoustic emission analysis and ultrasonic measurement in laboratory tests gives a deeper insight into damage processes under cyclic loading. The results shall be used to improve design rules for concrete members under fatigue load and to develop or improve non-destructive techniques for in-service structural health monitoring.