## 7.2 Ingenieurbau

### Filtern

#### Dokumenttyp

- Vortrag (173)
- Beitrag zu einem Tagungsband (114)
- Zeitschriftenartikel (59)
- Posterpräsentation (18)
- Buchkapitel (11)
- 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)
- Offshore (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 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)
- Vibration (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)
- Bridges (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)
- Drone (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)
- Modal Analysis (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 measurement (2)
- Vibrations (2)
- Wavenumber integrals (2)
- Wavenumber method (2)
- Wind Turbines (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)
- EERA Joint Program (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)
- SHM Environmental (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)
- Stability Buckling soil-structure-interaction piles offshore (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 energy (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)
- buckling soil-structure-interaction offshore piles track (1)
- elastische Gebäudelagerungen (1)
- fachwerkartige Stahltragwerken (1)
- risk, reliability, inspection planning, offshore wind turbines (1)
- shm environmental bridges (1)
- sleeper pads (1)
- temperature (1)
- u-p-Formulierung (1)
- Überwachungsverfahren (1)

#### Organisationseinheit der BAM

- 7.2 Ingenieurbau (383) (entfernen)

Remediation of Cracks Formed in Grouted Connections of Offshore Energy Structures under Static Loads
(2018)

The future energy demand necessitates the exploration of all potential energy sources both onshore and offshore. Global trend has shifted towards offshore energy, which can be obtained from either carbon intensive or renewable options, hence requiring structures such as rigs, platforms, and monopiles. Most of these structures adopt easily installable construction techniques, where lower foundation need to be connected with the super structure by mean of grouted composite joints. Generally, these composite connections have exterior sleeve, interior pile and infill grout. Being located in remote offshore conditions, connections can experience considerable adverse loading during their lifetimes. Degradations were reported inside similar connections, which were installed in last three decades. Besides, grouting in the offshore sites may often be proven difficult, which eventually leads to reduced capacity of connections in the long run. Thus, repair and rehabilitation of such connections should be planned ahead to minimize operational delays and costs in the future. This study aims at characterizing the nature of crack generation in grouted connections and thereby identifying the potential of repair using suitable repair material. Scaled grouted joints were manufactured using a novel mold, and connections were loaded under static load to visualize the main failure pattern. The failure mechanism and loading capacity are found compatible to previous results from earlier literature. Grouted connection was then repaired using cementitious injectable grout. The effectiveness of the repair system is also discussed.

Automatic vibration-based structural health monitoring has been recognized as a useful alternative or addition to visual inspections or local non-destructive testing performed manually. It is, in particular, suitable for mechanical and aeronautical structures as well as on civil structures, including cultural heritage sites. The main challenge is to provide a robust damage diagnosis from the recorded vibration measurements, for which statistical signal processing methods are required. In this chapter, a damage detection method is presented that compares vibration measurements from the current system to a reference state in a hypothesis test, where data9
related uncertainties are taken into account. The computation of the test statistic on new measurements is straightforward and does not require a separate modal identification. The performance of the method is firstly shown on a steel frame structure in a laboratory experiment. Secondly, the application on real measurements on S101 Bridge is shown during a progressive damage test, where damage was successfully detected for different damage scenarios.

Safety evaluation of truss structures depends upon the determination of the axial forces and corresponding stresses in axially loaded members. Due to presence of damages, change in intended use, increase in service loads or accidental actions, structural assessment of existing truss structures is necessary. This applies particularly to iron and steel trusses that are still in use, including historic and heritage monuments. Precise identification of the stresses plays a crucial role for the preservation of historic trusses. The assessment measures require non–destructiveness, minimum intervention and practical applicability.
The axial forces in truss structures can be estimated by static calculations using the method of joints, method of sections or finite element method, if accurate information about parameters such as external loads, geometrical characteristics, mechanical properties, boundary conditions and joint connections are known. However, precise information about these parameters is difficult to be obtained in practice. Especially in the cases of historic constructions, reasonable assumptions about the uncertain parameters may not be acquired.
Motivated by the preservation of existing truss−type constructions composed of axially loaded slender members, the present work aims to develop a non–destructive methodology to identify the axial forces or corresponding stress states in iron and steel truss structures. The approach is based on vibration measurements and the finite element method combined with optimization techniques.
After a state of the art review, numerical and experimental studies were carried out on three partial systems of truss–type structures. The investigated systems included single bars, a two–bar truss−like system and a five–bar truss. They were developed step–by–step as built–up truss−type constructions that are constituted of individual members connecting at joints. The examined aspects included the effects of structural loading on the dynamic performance of truss structures, modelling of joint connections, mode pairing criteria, selection of updating parameters and definition of an objective function, as well as the use of different optimization techniques.
Concerning the axial force effects on the structural dynamic responses, the effects of the stress stiffening become more complicated for multiple–member truss systems with increasing complexity. The coexistence of both compressive and tensile forces in trusses has counteracting effects on the modal parameters. These effects cause variation of natural frequencies and interchange of modes when the loads or corresponding member forces are changed. To examine the axial force effects on the structures at different stress states, in the numerical study and laboratory experiments, loads were applied progressively to the investigated truss−like systems.
Regarding the modelling of joints for truss–type structures, the joint flexibility affects the structural dynamic responses. Therefore, the numerical models of truss−type structures include joint models with variable rotational springs to represent semi–rigid connections.
Considering the mode pairing criterion, the mode pairing is performed by adapting an enhanced modal assurance criterion with the calculation of the modal strain energy. The criterion allows the selection of desired clusters of degrees of freedom related to specific modes. With respect to the model updating strategies, the selection of updating parameters and the choice of an appropriate objective function are identified to be significantly important. In addition, three different optimization techniques were applied to compare their suitability for the inverse axial force identification and estimation of joint flexibility of truss structures. The results of the numerical study and laboratory tests show that nature–inspired optimization methods are considered as promising techniques.
A methodology consisted of a two–stage model updating procedure using optimization techniques was proposed for the determination of multiple member axial forces and estimation of the joint flexibility of truss–type structures. In the first stage optimization, the validation criterion is based on the experimentally identified global natural frequencies and mode shapes of the truss. Additionally, the axial forces in selected individual members of the truss are used. They are estimated from the natural frequencies and five amplitudes of the corresponding local mode shapes of the members using an analytically−based algorithm. Based on the results of the identified axial forces in the first stage, a second optimization procedure for the joint stiffnesses is performed. In this stage, the modal parameters of the global natural frequencies and mode shapes are used as validation criterion.
From the results of the laboratory experiments, the identified axial forces by the proposed methodology agree well with the experimentally measured axial forces of the investigated systems at different stress states. Moreover, based on the numerical verification, the identified joint stiffnesses indicate reasonably the joint flexibility in relation to the pinned or rigid conditions.
To assess the relevance of the proposed methodology on existing structures in real−life conditions, an in–situ experiment was carried out on a historic Wiegmann–Polonceau truss in the city of Potsdam. The in–situ experiment shows that uncertainties relating the mechanical and geometrical properties of historic trusses as well as the experimental sensor setup can influence the accuracy of the axial force identification. In the present work, recommendations are given for the development of a guideline of measuring concepts and assessment strategies applied to existing truss structures. The intention is to integrate the proposed methodology as part of the Structural Health Monitoring for historic truss–type constructions.

This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided in 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 cyclic pile fatigue and the so-called pile setup (i.e. the time effects on the axial pile capacity). The relevance of these two topics is illustrated with experimental results from a field testing campaign on real large-scale piles.

In structural parts under vibrational loading fatigue cracks can initiate and grow, which can lead to structural failure. Conventional non-destructive testing methods for crack detection provide just a snapshot of fatigue crack evolution, whereas crack luminescence coating realizes clear visibility of the entire crack formation. Fatigue causing cyclic tensile tests and examinations on special test bodies allowing control of the crack opening width demonstrate a high sensitivity of the coating.

Bei Monopfahlgründungen von Offshore-Windenergieanlagen wird die Verbindung zwischen Monopfahl und Übergangsstück als geschraubter Ringflansch ausgeführt. Die zunehmende Leistungsfähigkeit der Windenergieanlagen führt zu immer größeren Schnittgrößen in diesem Anschluss. In der Folge erhöhen sich nicht nur die Querschnittsabmessungen, sondern es kommen auch zunehmend größere Schrauben zum Einsatz. Da die einschlägigen Regelwerke zur Bemessung dieser Verbindungen nicht für Schrauben der Größen M64 oder M72 konzipiert wurden, stellt sich die Frage der Übertragbarkeit auf solche Anwendungsfälle.
Im Rahmen des Aufsatzes werden Einflüsse diskutiert, die eine Herabsetzung der Schraubentragfähigkeit verursachen könnten. Diese Einflüsse, vornehmlich geometrische Imperfektionen, werden systematisch untersucht und ergänzend in praxisrelevanten Beispielen bewertet. Die somit gewonnenen Erkenntnisse werden für die abschließende Beurteilung der großen Schrauben in Ringflanschverbindungen herangezogen.

Design challenges for offshore wind-farms. From foundation mechanics to wind-farm aerodynamics
(2018)

This talk provides a brief introduction on general engineering aspects of offshore wind energy production. Then 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.

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.

- Impact tests of concrete blocks
- High energy facility for laminographic testing
- Laminographic arrangement
- Cross-Laminography
- Measurement range extension by detector tiling
- Reconstruction methods
- Fast “shift averaging” method “next to base plane”
- reconstruction --> Removal of reinforcement indications
- 3D-Data analysis
- Crack-Segmentation by „Template Matching“

In this paper a shear test, which helps to study local behavior of the soil-pile interaction, is modelled numerically with the Finite Element Method as a 2D plane strain problem. A normal pressure on top and shear displacement on side were applied. So far, the material behavior was considered elastic for the sake of simplicity.
The effect of thickness on contact elements and the presence of in plane stress has been highlighted. The purpose of the paper is to find a suitable contact element which represents more close to reality a soil-pile interaction problem under cyclic axial loading. Moreover, an insight on the presence of in-plane stress shows that it needs to be considered cautiously.

The purpose of the work presented in this paper is to analyze locally (at the element level) the contact behavior of a soil-pile contact problem. Therefore, a 2D shear test is modeled using the Finite Element Method. The formulation of a 4 nodded zero-thickness interface element of Beer is chosen with a linear interpolation function. Four constitutive contact models adapted for contact problems have been implemented. The Mohr-Coulomb and Clough and Duncan models were chosen initially, due to the ease of implementation and few number of parameters needed. After, more complicated models in the framework of elasto-plasticity such as: Lashkari and Mortara were implemented for the first time into the finite element code of the shear test problem. They include other phenomena such as: relative density of soil, the stress level and sand dilatancy. From the results the relation between shear displacement and shear stress has been deduced. Finally, a discussion of the advantages and the drawbacks during computation of each model is given at the end.

The purpose of the work presented in this paper is to analyze locally (at the element level) the contact behavior of a soil-pile contact problem. Therefore, a 2D shear test is modeled using the Finite Element Method. The formulation of a 4 nodded zero-thickness Interface element of Beer is chosen with a linear interpolation function. Four constitutive contact models adapted for contact problems have been implemented. The Mohr-Coulomb and Clough and Duncan models were chosen initially, due to the ease of implementation and few number of parameters needed. After, more complicated models in the framework of
elasto-plasticity such as: Lashkari and Mortara were implemented for the first time into the finite element code of the shear test problem. They include other phenomena such as:
relative density of soil, the stress level and sand dilatancy. From the results the relation between shear displacement and shear stress has been deduced. Finally, a discussion of the advantages and the drawbacks during computation of each model is given at the end.

This paper deals with uncertainty considerations in damage diagnosis using the stochastic subspace-based damage detection technique. With this method, a model is estimated from data in a (healthy) reference state and confronted to measurement data from the possibly damaged state in a hypothesis test. Previously, only the uncertainty related to the measurement data was considered in this test, whereas the uncertainty in the estimation of the reference model has not been considered. We derive a new test framework, which takes into account both the uncertainties in the estimation of the reference model as well as the uncertainties related to the measurement data. Perturbation theory is applied to obtain the relevant covariances. In a numerical study the effect of the new computation is shown, when the reference model is estimated with different accuracies, and the performance of the hypothesis tests is evaluated for small damages. Using the derived covariance scheme increases the probability of detection when the reference model estimate is subject to high uncertainty, leading to a more reliable test.

This paper describes the experimental calibration of an existing Wiegmann–Polonceau roof truss based on modal parameters. Dynamic tests allowed the determination of the natural frequencies and mode shapes of the global truss and of individual truss members. The global and local modal configurations as well as coupled vibration of truss members are discussed. In addition, as truss members are axially loaded, the effect of stress stiffening on the modal parameters is considered. Moreover, several finite element models with different modelling assumptions for the details of the connections and member geometrical characteristics such as gusset plates and turnbuckles were developed. A suitable numerical model was chosen to represent the truss structural behavior. This paper focuses on the local measurement and analysis strategies applied to single truss members. The possibility of using a local analysis method, namely methods that consider individual members as part of a structure, is demonstrated to assess the behavior of the global truss structure. The comparison of the results after calibration reveals a very good correlation between the experimentally identified and numerically estimated modal parameters of the historic truss.

Measurements of downburst wind loading acting on an overhead transmission line in northern Germany
(2017)

Along an overhead transmission line in Northern Germany, a unique instrumentation of anemometers and force measurements is installed. Details of this test line with wind measurements along a horizontal axis are given. A recent event of a presumable downburst wind event is analyzed by means of available data and precedent works on thunderstorm analysis. The measured response of the conductors at the suspension tower is investigated and compared with time domain simulation of a finite element model.

The damage detection and repair control have become important tasks for ballast and slab tracks. Measurements which compare the damaged and the repaired status of the same track section at different times, or which compare a damaged and an intact track section at the same time, have been successfully performed at some sites in Germany. The loss of contact between the sleeper and the track plate, between the track plate and the base plate, and between the base plate and the base layer have been analysed. The soil properties of each site have been measured and have been used to establish realistic track-soil models. Theoretical results of the wavenumber domain and the finite-element boundary element method have been compared with the experimental results. The observed experimental and theoretical results, changes in the time histories of displacements and velocities due to train passages and in the transfer functions (receptances) due to hammer impacts, are encouraging that these measurements can be used to detect track damage.

Offshore wind energy towers are dynamically loaded by waves and wind. Pile foundations provide stiffness and damping and should be properly calculated. A combined finite-element boundary-element method for the dynamic interaction of flexible structures and the soil has been developed. The flexible structures such as single piles or complete wind energy towers are modeled by the finite element method whereas the homogeneous or layered soil is modeled by the boundary element method which uses the Green’s functions for interior loads in the layered half-space to establish the dynamic stiffness matrix of the soil. Soils with a stiffness that is continuously increasing with depth can be modeled as multi-layer soils with step-wise increasing stiffness. The effects of different parameters such as the stiffness of the soil, the axial and bending stiffness of the pile, and the radius of the cylindrical contact area will be analysed for the different components of excitation (vertical, horizontal, rotation and coupling). The results can be determined as specific power laws which are different for the different load cases and for the different soil models (Winkler support, homogeneous continuum, continuum with increasing stiffness). The dynamic effect of radiation damping will be analysed by the frequency-dependent compliance functions. A clear layering of the soil can cause noticeable changes in the dynamic compliances as reductions of the stiffness and the damping in certain frequency ranges (below and around layer resonance frequencies). The distribution of the displacements along the pile help to explain the observed laws. An example of an offshore wind energy tower has been modeled and calculated for wind, wave and weight loads. The resonances of the tower are usually limited by the radiation damping which is strongest for a soft soil.

Measurements on the vehicle-track interaction and the excitation of railway-induced ground vibration
(2017)

Two railway measurement campaigns have been performed in Germany and Switzerland which yield insight in the vehicle-track-soil interaction. The campaign in Germany has included simultaneous measurement of vehicle, track, and soil vibrations during train runs with 16, 25, 40, 63, 80, 100, 125, 140, 160 km/h, and impulse measurements of the passenger car, three track sections and the soil. Two ballast tracks, one on the soil surface and one on a concrete bridge, have been investigated as well as a slab track in a tunnel. Ten different sites in Switzerland have been measured for soil properties and train-induced ground vibrations, which allow to determine the excitation forces of the railway traffic. New axle-box measurements at some of the Swiss sites have been analysed to get further experimental evidence. All these measurements have been evaluated to characterize the excitation processes. Relations between vehicle vibration and ground vibration can be observed. The vehicle vibrations, namely the accelerations of the wheelsets, yield the dynamic forces due to the passage over the irregularities of the vehicle and the track. The ground vibrations are correlated to these dynamic forces to a certain extent. Some mid-frequency ground vibration amplitudes, however, are higher than expected from the dynamic excitation forces. The experimental observations can be explained by an irregular response to the passage of the static loads, that means the passage of the static loads over an irregular ballast or soil. This correct understanding of the excitation processes is important for the prediction as well as for the mitigation of railway induced ground vibrations.

This contribution presents some principles and some examples of the mitigation of railway-induced ground vibrations. The principles are different for the mitigation measures at the track, in the soil or at the building. Force transfer functions of isolated and un-isolated track-soil systems, reflected and transmitted wave amplitudes at walls and trenches in the soil, and the transfer of the (free-field) vibration amplitudes to the foundation amplitudes of the building are analysed. The mitigation effect can be calculated by exact or simplified formulas. Some examples with 3D (finite-element boundary-element), 2D (beam-on-support), and 1D track models, 2D and 1D soil models, detailed 3D building models and finite or infinite 1D wall-floor models are investigated to find out if simple models can be used for a satisfactory prediction of the mitigation effect. The 1D track examples show that the force transfer of the track without vehicle can be exactly calculated, whereas the total force transfer can be calculated approximately if appropriate wheelset masses per track length are used for the isolated and the un-isolated track. The mitigation effect of a filled trench is calculated by a 2D finite element model and the results compare with simple transmission formula if the stiffness per area rather than the wave impedances are used for the infill material. The base isolation of a building is analysed by a detailed 3D model and the results are similar to the analytic results of a single wall with floors on the soil. Other reduction measures as different floor and column dimensions are usually less effective so that the clearly best mitigation solution at a building is a partly or a complete base isolation.

The Federal Institute of Material Research and Testing (BAM) has collected some experience with the testing of damaged, repaired and newly constructed railway tracks. The experimental methods are hammer testing of the track at different positions, hammer testing of the soil, measurement of train passages, and in all cases, measurements with geophones at different positions. The measured signals are evaluated for wave velocities (dispersion of the soil or the track-soil system), for transfer functions (transfer admittances of the soil, compliances of the track in amplitude and phase), and one-third octave band spectra of the track response to hammer and train excitation. These methods are applied at different stages of the track construction. Before track construction, wave velocities and transfer functions of the sub-soil can indicate problems with soft soils. After track construction, a check of the acceptable state of the track can be done by comparison of many excitation positions and track sites. After a track damage (a lose sleeper or a lose plate of a slab track) and after its repair, the sensitivity of the different measurement quantities to different track errors and the achieved improvement of the repair can be determined. The contribution shows examples of all these track situations

Experiments have been performed at a test site with six different tracks with under-ballast plates. Hammer excitations of the soil and the tracks as well as train passages have been measured. The experimental observations are as follows. 1. The natural soil is stiff gravel whereas the railway dam consists of softer material. 2. The track compliance indicates a soft ballast if no train is present to provide a confining pressure. 3. The track response to the train passages can be split into a low-frequency region which is ruled by the static loads and a high-frequency region which is ruled by dynamic loads. 4. The track responses to hammer and track excitation indicate the presence of many voids between the sleepers and the ballast. 5. The ground vibrations are highly influenced by the soil. Due to the stiff soil at the site, the hammer and train induced spectra have a considerable high-frequency content. 6. A reduction of the ground vibration has been observed in a low-frequency range. The mitigation effects of an under-ballast plate are also investigated by calculations of a wavenumber domain model. The under-ballast plate has an effect at low frequencies where it distributes the static load over a longer track section. The impulse of the axle passage is longer and the frequencies are lower due to the plate stiffness. The axle impulses could yield a low-frequency ground vibration in an irregular soil with a randomly varying stiffness. This low-frequency part of the ground vibration (the scattered axle impulses) seem to be reduced by the under-ballast plate.

Erosive phenomena at the mesoscale – Perspectives and challenges using coupled LBM-DEM models
(2017)

The physical phenomena related to the erosion of granular materials by a fluid flow are ubiquitous and often present major challenges and threats to a wide range of civil engineering constructions and infrastructures. Catastrophic earth-dam failures and large sinkholes are just some of the possible outcomes of the different forms of erosion (a.o. surface erosion, suffusion, piping, backwards erosion, etc…). However, little is known about the actual mechanical origins of erosion, while the assessment of erodibility is generally performed by means of experimental tests and empirical correlations.
Here we provide a general overview of some current research models aiming to clarify the micromechanical phenomena and their macromechanical consequences taking place in different erosion scenarios. The employed numerical techniques rely on the coupling of two well-stablished particle methods for the fluid and solid phases, namely the Lattice Boltzmann Method (LBM) and the Discrete Element Method (DEM) respectively. Further ingredients of our numerical models include an elastoplastic cohesion model for intergranular solid bridges and a subcritical debonding model for the simulation of transient damage processes within the soil matrix.

Compaction grouting involves the injection under high pressure of a highly viscous grout into the soil to displace and compact the surrounding soil without fracturing it. This ground improvement technique has been used widely for settlement control, increasing liquefaction resistance or bearing capacity of soil under new or existing structures. The work presented here aims to show some numerical and experimental investigations being carried out to understand the compaction mechanism and the soil-grout interaction, which is crucial for a successful usage of this technique.
To investigate compaction grouting in the laboratory under various stress conditions, a large-scale testing chamber has been developed. The grout was injected directly at the transparent vertical window of the chamber in order to investigate the possibility to monitor the injection process with a camera to measure the in-plane soil displacements and strains by means of the PIV technique. The other aim of this study is to develop a numerical model, which should be able to deal with large displacements and deformations and to simulate the change in shape of the distinct soil-grout interface solely as a result of the interaction between the injected grout and the surrounding soil. Based on these considerations, as a numerical technique, we employ the implicit Material Point Method based on a mixed formulation, which is implemented in the open source Kratos Multiphysics framework. In contrast to standard FE formulations, the usage of the MPM avoids both the numerical instability caused by extensive mesh distortion and the high computational costs of remeshing. The main results focus on the different evolution of the grout bulb inside the soil under various stress states.

Current trend suggests that global energy consumption will increase in the future. This growing energy demand and advancement of technology lead to explore all potential offshore fossil and non-fossil energy sources, necessitating erection of exploration and production structures, rigs, platforms and towers, which are susceptible to adverse environmental conditions along with their maintenances. Cylindrical grouted joints provide suitable connections between steel substructure and foundation in these offshore platforms and wind structures especially monopiles for ease of installation. However, these are composite connections with exterior sleeve, interior pile and infill grout. The capacity of these connections is affected by number of factors. The literature over last four decades by numerous researchers has shown the development of these connections with increasingly higher capacities and influences on these capacities due to various factors. This paper provides a comprehensive review on the factors affecting the connection capacity along with technical challenges for the future. Critical aspects and shortcomings of the current connection systems and potential solutions may be sought after for these issues are also discussed.

Measurements of downburst wind loading acting on an overhead transmission line in Northern Germany
(2017)

Windeinwirkungen auf Freileitungen wurden in der Vergangenheit meist an exponierten Standorten bestimmt. In einem Langzeitversuch wurden seit 2012 an einer mit moderner Messtechnik ausgerüsteten 380-kV-Leitung der 50 Hertz Transmission GmbH, die im nicht besonders exponierten Gelände verläuft und somit den Leitungen im Netz entspricht, die Windgeschwindigkeiten entlang der Leiter und deren Auswirkungen auf die Stützpunkte gemessen. Die Messungen und die begleitenden Auswertungen bestätigen die heute verwendeten normativen Vorgaben für die Windwirkung auf die Leiter von Freileitungen, soweit dies in der relativ kurzen Zeit von fünf Jahren möglich ist.

The Federal Institute of Material Research and Testing (BAM) has collected some experience with the testing of damaged, repaired and newly constructed railway tracks. The experimental methods are hammer testing of the track at different positions, hammer testing of the soil, measurement of train passages, and in all cases, measurements with geophones at different positions. The measured signals are evaluated for wave velocities (dispersion of the soil or the track-soil system), for transfer functions (transfer admittances of the soil, compliances of the track in amplitude and phase), and one-third octave band spectra of the track response to hammer and train excitation. These methods are applied at different stages of the track construction. Before track construction, wave velocities and transfer functions of the sub-soil can indicate problems with soft soils. After track construction, a check of the acceptable state of the track can be done by comparison of many excitation positions and track sites. After a track damage (a lose sleeper or a lose plate of a slab track) and after its repair, the sensitivity of the different measurement quantities to different track errors and the achieved improvement of the repair can be determined. The contribution shows examples of all these track situations.

Measurements on the vehicle-track interaction and the excitation of railway-induced ground vibration
(2017)

The inverse identification of the stress state in axially loaded slender members of iron and steel truss structures using measured dynamic data is discussed. A methodology is proposed based on the finite element model updating coupled with nature-inspired optimization techniques, in particular the particle swarm optimization. The numerical model of truss structures is calibrated using natural frequencies and mode shapes from vibration tests, as well as additional information of the axial forces in selected truss members based on the experimentally identified modal parameters. The results of the identification are the axial forces or corresponding stresses in truss structures and the joint rigidity in relation to pinned and rigid conditions.

This paper is concerned with the inverse identification of the stress state in axially loaded slender members of iron and steel truss structures using measured dynamic data. A methodology is proposed based on the finite element model updating coupled with nature-inspired optimization techniques, in particular the particle swarm optimization. The numerical model of truss structures is calibrated using natural frequencies and mode shapes from vibration tests, as well as additional information of the axial forces in selected truss members based on the experimentally identified modal parameters. The results of the identification are the axial forces or corresponding stresses in truss structures and the joint rigidity in relation to pinned and rigid conditions. Attention is given to several examined aspects, including the effects of the axial tensile and compressive forces on the dynamic responses of trusses, mode pairing criteria, as well as modeling assumptions of joints and the use of a joint rigidity parameter. Considering the pairing of modes, it is performed by adapting an enhanced modal assurance criterion that allows the selection of desired clusters of degrees-of-freedom. Thus, information extracted from the measurements related to specific modes is utilized in a more beneficial way. For modeling of joints, the numerical model of a truss structure includes rotational springs of variable stiffness to represent semi-rigid connections. Moreover, a fixity factor is introduced for practical estimation of the joint flexibility. The effectiveness of the proposed methodology is demonstrated by case studies involving simulated and laboratory experimental data.

Das Ermüdungsverhalten einzelner Schweißverbindungen in Offshore-Strukturen ist stark korreliert. Diese Korrelation entsteht zum einen durch die Verwendung gleicher Prozesse und Materialien bei der Herstellung der Verbindungen, zum anderen sind die ermüdungswirksamen Lasten an verschiedene Hospots im Tragwerk ebenfalls von einander abhängig. Hieraus ergeben sich Systemeffekte, die es ermöglichen, durch stichprobenartige Inspektion des Zustandes einzelner Hotspots auf den Zustand der verbleibenden Hotspots im Tragwerk zu schließen. Auf dieser Grundlage können Inspektions- und Reparaturstrategien für ermüdungsbeanspruchte Offshore-Strukturen mit Hilfe von riskobasierten Methoden optimiert werden. In diesem Vortrag wird weiterführend ein Konzept zur Einbindung von globalen Monitoringergebnissen in die risikobasierte Inspektionsplanung vorgestellt.

Conventional methods of crack detection only provide a snapshot of the fatigue evolution at a specific location and in the moment of examination. The crack luminescence method realizes a clear visibility of the occurring cracks in loaded components during ongoing operation. Several different experiments show that due to the sensitive coating even the early stage of the crack formation can be detected what makes the crack luminescence helpful to determine the incipient crack opening behavior depending on load alternation. Due to the emitting of light under UV-radiation the crack gets clearly visible what makes continuous monitoring and automated crack detection possible. This can reduce costs and time needed for maintenance and inspection.

A novel method for risk-based optimization of inspection and repair strategies for deteriorating structural systems has recently been proposed. The method defines heuristics at the system level to reduce the number of possible strategies. For each defined strategy, it computes the updated system failure probability conditional on simulated inspection and repair histories, and evaluates the associated costs and risk. The expected total service life costs and risk for a strategy are finally determined using Monte Carlo simulation. The optimal strategy minimizes the expected total service life costs and risk. We intend to adopt this approach to optimize inspection, monitoring and repair activities for offshore wind park support structures. As a first step, we simulate – in analogy to an offshore wind park – the service life performance of an inspected group of jacket-type frames. The performance is quantified in terms of the group’s system failure probability conditional on simulated inspection and repair histories. The underlying system model accounts for the structural redundancy of the frames and the interdependence among their failure events due to similar loading conditions. The model also captures stochastic dependence among the deterioration states of the frames. As part of the simulation process the a-priori unknown outcome of any planned inspection is generated conditional on the outcome of all previous inspections.

The implementation of continuous dynamic monitoring systems in two bridges, in Portugal, is enabled to detect the occurrence of very significant environmental and operational effects on the modal properties of these bridges, based on automated processing of massive amounts of monitoring data collected by a set of accelerometers and thermal sensors over several years.
In order to remove or mitigate such environmental/operational effects with the purpose of damage detection, two different statistical methods have been adopted. One of them is the multiple linear regression by performing nonlinear correlation analysis between measured modal properties and environmental/operational variables. Another one is principal component regression based on the identification of the linear subspace within the modal properties without using measured values of environmental and operational variables.
This paper presents a comparison of the performance of these two alternative approaches on the basis of continuous monitoring data acquired from two instrumented bridges and simulated damage scenarios. It is observed that different methods show similar capacity in removing environmental effects, and the multiple linear regression method is slightly more sensitive to structural damage.

Here we investigate the physical mechanisms behind the surface erosion of a cohesive granular soil induced by an impinging jet by means of numerical simulations coupling fluid and grains at the microscale. The 2D numerical model combines the Discrete Element and Lattice Boltzmann methods (DEM-LBM) and accounts for the granular cohesion with a contact model featuring a paraboloidal yield surface. Here we review first the hydrodynamical conditions imposed by the fluid jet on a solid granular packing, turning then the attention to the impact of cohesion on the erosion kinetics. Finally, the use of an additional subcritical debonding damage model based on the work of Silvani and co-workers provides a novel insight into the internal solicitation of the cohesive granular sample by the impinging jet.

Erosion of soils affects both natural landscapes and engineering constructions as embankment dams or levees. Improving the safety of such earthen structures requires in particular finding out more about the elementary mechanisms involved in soil erosion. Towards this end, an experimental work was undertaken in three steps. First, several model materials were developed, made of grains (mostly glass beads) with solid bridges at particle contacts whose mechanical yield strength can be continuously varied. Furthermore, for most of them, we succeeded in obtaining a translucent system for the purpose of direct visualization. Second, these materials were tested against surface erosion by an impinging jet to determine a critical shear stress and a kinetic coefficient. Note that an adapted device based on optical techniques (combination of Refractive Index Matching and Planar Laser Induced Fluorescence) was used specifically for the transparent media. Third, some specifically developed mechanical tests, and particularly traction tests, were implemented to estimate the mechanical strength of the solid bridges both at micro-scale (single contact) and at macro-scale (sample) and to investigate a supposed relationship with soil resistance to erosion.

We focus here on the major and still relevant issue of soil erosion by fluid flows, and more specifically on the determination of both a critical threshold for erosion occurrence and a kinetics that specifies the rate of eroded matter entrainment. A state-of-the-art is first proposed with a critical view on the most commonly used methods and erosion models. It is then discussed an alternative strategy, promoting the use of model materials that allow systematic parametric investigations with the purpose of identifying more precisely the local mechanisms responsible for soil particle erosion and ultimately quantifying both critical onsets and kinetics, possibly through existing or novel empirical erosion laws. Finally, we present and discuss several examples following this methodology, implemented either by means of experiments or numerical simulations, and coupling erosion tests in several particular hydrodynamical configurations with wisely selected mechanical tests.

In this in vitro study, the protective qualities of different mouthguard types were examined during small hard object collisions. The aim was to investigate inconclusive aspects of hard inserts, nylon nets, and air spaces as reinforcements in the anterior region and the protection qualities of ethylene vinyl acetate (EVA).
Five different mouthguards with a labial thickness between 2 mm and 11 mm made of materials of varying stiffness were investigated. As a negative control, the same experiments were performed without a mouthguard. Different combinations of EVA and labial inserts ((polyethylene terephthalate glycol-modified [PETG]), nylon mesh, air space) were tested. Using a stainless steel pendulum device, blows of different energy (0.07-2.85 joules) were applied to the center of the crown of a pivoted tooth in a custom-built jaw model. A laser Doppler vibrometer measured the tooth deflection, while an acceleration sensor attached to the pendulum measured the braking accelerations.
Tooth deflection was reduced up to 99.7% compared to no mouthguard, and the braking acceleration was reduced up to 72.2% by increasing the mouthguards' labial thickness in combination with labial inserts of different stiffness and a built-in air space between the front teeth and the mouthguard. The mouthguards made of soft materials (EVA with nylon mesh) showed slightly better protection qualities than the more rigid mouthguards of similar thickness (PETG; P<.05). However, with increasing impact energy, their protective capacities decreased to a greater extent than the stiffer mouthguards.
The combination of increased labial thickness and labial inserts of varying stiffness and eventually an air space offers the best protection capacities for hard, small object collisions.

Suction Bucket Jackets (SBJ) are found as a suitable alternative to driven piles for the support of foundations for offshore wind energy converters. In the case of jackets or multipods, a predominant vertical load is to be expected. The effect of such a tensile loading is the generation of suction in the soil inside the bucket which leads to an increment of tensile capacity. This paper aims to study the bearing behaviour of a suction foundation by taking into account how the soil permeability and the loading rate influence the foundation behaviour. Moreover, after submitting the structure to a storm load, the bearing capacity is studied again, in order to see the effect of such a load on the bucket's bearing behaviour. This study is carried out by means of Finite Element numerical simulations based on the formulation of Biot's equations combined with a constitutive model that reproduces the key aspects of cyclic soil behaviour in the frame of Generalized Plasticity.