## 7.2 Ingenieurbau

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#### Referierte Publikation

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#### Schlagworte

- Fatigue (10)
- Finite element method (8)
- Monitoring (8)
- Ground vibration (7)
- Slab track (7)
- Grout (6)
- SHM (6)
- Soil-structure interaction (6)
- Windenergie (6)
- Concrete (5)
- Interface (5)
- Offshore (5)
- Track damage (5)
- Train-induced ground vibration (5)
- Vibration measurements (5)
- Boundary element method (4)
- Cracks (4)
- Damage detection (4)
- Field tests (4)
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- Micromechanical modelling (4)
- Numerical modelling (4)
- Offshore wind turbines (4)
- Pfahlgründungen (4)
- Pile foundations (4)
- Railway track (4)
- Repair (4)
- Structural health monitoring (4)
- Temperature rejection (4)
- Train passage (4)
- Truss structures (4)
- Vehicle-track-soil interaction (4)
- Axial force (3)
- Bitumen (3)
- Compaction Grouting (3)
- Contact problem (3)
- Damage evolution (3)
- Damage localization (3)
- Dynamic test (3)
- Ermüdung (3)
- Finite-element boundary-element method (3)
- Fire (3)
- High-cycle (3)
- Inspection (3)
- Inspection planning (3)
- LBM-DEM (3)
- Layered soils (3)
- Mitigation (3)
- Modal parameters (3)
- Model updating (3)
- Offshore Pile Foundation (3)
- Offshore-Windenergieanlagen (3)
- Optimization technique (3)
- Physical phenomenology (3)
- Schadensdetektion (3)
- Soil properties (3)
- Structural Health Monitoring (3)
- Train passages (3)
- Tunnel (3)
- ground vibration (3)
- mitigation (3)
- railway track (3)
- Acoustic emission analysis (2)
- Acoustic emission testing (2)
- Amplitude-charge weight laws (2)
- Amplitude-distance laws (2)
- Analysis of variance (2)
- BIM (2)
- Bahnerschütterungen (2)
- Ballast track (2)
- Ballast tracks (2)
- Bauwerksüberwachung (2)
- Betonautobahn (2)
- Big Data (2)
- Bodeneigenschaften (2)
- Bohrpfähle (2)
- Box-Behnken (2)
- Brücken (2)
- Cable failure (2)
- Cable-stayed bridge (2)
- Compressive cyclic loading (2)
- Compressive strength (2)
- Continuously inhomogeneous soils (2)
- Crack (2)
- DUCON® (2)
- Damage Evolution (2)
- Datenmanagement (2)
- Design methods (2)
- Detection (2)
- Digital image correlation (2)
- Displacements (2)
- Ductility (2)
- Dynamic testing (2)
- Dynamische Pfahlprobebelastung (2)
- E-modulus (2)
- Energy (2)
- Erosion (2)
- Erschütterungsursachen (2)
- Experimental testing (2)
- Explosion-induced ground vibrations (2)
- Failure (2)
- Fatigue damage (2)
- Finite element model updating (2)
- Fly ash (2)
- Frequenzbereiche (2)
- Generalized plasticity (2)
- Granular cohesion (2)
- Ground vibration measurements (2)
- Grouted Connection (2)
- Grouted connections (2)
- Grouting (2)
- HTLS (2)
- Hammer tests (2)
- High-Cycle (2)
- High-strength concrete (2)
- Impact (2)
- Injection Sequence (2)
- Inspektion (2)
- Iron and steel truss structures (2)
- Jet erosion (2)
- Load vector (2)
- Long-term shrinkage (2)
- Luminescence (2)
- Messen im Bauwesen (2)
- Metakaolin (2)
- Micro silica (2)
- Micro-reinforcement (2)
- Mobile elements (2)
- Model interpolation (2)
- Non-destructive testing (2)
- Numerical model (2)
- Numerical modeling (2)
- Numerical simulation (2)
- Offshore Windenergieanlagen (2)
- Offshore foundations (2)
- Offshore wind energy (2)
- Offshore wind energy converter (2)
- Offshore-Wind (2)
- Pile bending stiffness (2)
- Pile foundation (2)
- Prediction of explosion induced ground and building vibration (2)
- Quasi-static and dynamic tests (2)
- Railway vibration (2)
- Rehabilitation (2)
- Reliability (2)
- Residual evaluation (2)
- Ringversuch (2)
- Risk (2)
- SDDLV (2)
- Sand (2)
- Schwingungsbasierte Verfahren (2)
- Size effect (2)
- Slenderness effect (2)
- Soil stiffness (2)
- Statische Pfahlprobebelastung (2)
- Statistical evaluation (2)
- Statistical method (2)
- Statistical tests (2)
- Stereo photogrammetry (2)
- Strengthening strategy (2)
- Subcritical debonding (2)
- Subspace-based method (2)
- Suction bucket (2)
- Supplementary cementitious materials (2)
- Tensile Capacity (2)
- Tensile capacity (2)
- Track damage monitoring (2)
- Track vibration (2)
- Track-soil interaction (2)
- Tragfähigkeit (2)
- UHPC (2)
- Ultrasonic testing (2)
- Uncertainty (2)
- Under-ballast plate (2)
- Unterraummethoden (2)
- Value of information (2)
- Vehicle-track interaction (2)
- Vibration measurement (2)
- Wavenumber integrals (2)
- Wind energy tower (2)
- Zugtragfähigkeit (2)
- Zyklisches Tragverhalten (2)
- track-soil interaction (2)
- undersleeper (2)
- 1-D insertion loss (1)
- 3D imaging (1)
- Accelerated ageing (1)
- Aerodynamic damping (1)
- Ambient vibration (1)
- Amplitude-distance law (1)
- Analysis (1)
- Assessment (1)
- Authorities approval process (1)
- Axial and lateral design (1)
- Axial force identification (1)
- Axial pile capacity (1)
- Axle box measurements (1)
- Bahnfahrwege (1)
- Ballast (1)
- Base isolation (1)
- Bauteilprüfungen (1)
- Bauwerk-Boden-Wechselwirkung (1)
- Bayes'sche Analyse (1)
- Beanspruchungszustand (1)
- Bemessung (1)
- Berechnung (1)
- Beton (1)
- Betonautobahnen (1)
- Blasting charge (1)
- Bodenerschütterungen (1)
- Bridge transition zone (1)
- Brücke (1)
- Brückenübergangsbereich (1)
- Changing excitation (1)
- Clay fill (1)
- Climate Chamber (1)
- Close range photogrammetry (1)
- Cohesive granular media (1)
- Cohesive soils (1)
- Compaction grouting (1)
- Comparative study (1)
- Components of excitation (1)
- Conductor (1)
- Conductor cables (1)
- Coupled FE-SBFE model (1)
- Crack detection (1)
- Crack repair (1)
- Cyclic axial loading (1)
- Cyclic axial shearing (1)
- Cyclic loading (1)
- Cyclic loads (1)
- DEM-LBM simulation (1)
- Daniels systems (1)
- Dauerhaftigkeit (1)
- Dauerüberwachung (1)
- Deckenschwingungen (1)
- Dehnungsmessung (1)
- Design (1)
- Design practice (1)
- Deterioration (1)
- Deutschland (1)
- Digital Image Correlation (1)
- Digital X-ray laminography (1)
- Digitale Bildverarbeitung (1)
- Dispersionsmessung (1)
- Downburst (1)
- Drop height (1)
- Dynamic load test (1)
- Dynamic loading (1)
- Echtzeit (1)
- Eisenbahngleis (1)
- Elastische Gebäudelagerung (1)
- Energiewende (1)
- Environmental (1)
- Environmental Effects (1)
- Environmental changes (1)
- Ermüdungsschäden (1)
- Erneuerbare Energien (1)
- Erosion of cohesive soils (1)
- Erosion onset (1)
- Erosion phenomena (1)
- Erschütterungsprognose (1)
- Evaluation of crack fields (1)
- Explosion (1)
- FED (1)
- Fahrwegschäden (1)
- Fahrzeug-Fahrweg-Wechselwirkung (1)
- Fault detection (1)
- Fault isolation (1)
- Filter effect of the soil (1)
- Finite-Elemente-Modellkalibrierung (1)
- Forschungsbericht (1)
- Fractional effective dose (1)
- Freileitung (1)
- Freileitungen (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)
- Grout Injection (1)
- Grouted connection (1)
- Groutverbindung (1)
- Großprüfmaschinen (1)
- Hammerschlag (1)
- High temperature low sag (1)
- High temperature low sag (HTLS) conductors (1)
- High temperature low sag conductors (1)
- Hochspannungs-Freileitungen (1)
- Impact test (1)
- Inhomogeneous soils (1)
- Innovative Messtechnik (1)
- Instandhaltung (1)
- Integrity (1)
- Interface model (1)
- Jet erosion test (1)
- Joint capacity (1)
- Klimakammer (1)
- Kontinuierlich (1)
- Kontrolle (1)
- Kostenoptimierung (1)
- LBM-DEM numerical simulation (1)
- LBM-DEM simulation (1)
- Laminography (1)
- Large concrete blocks (1)
- Large-scale field testing (1)
- Lebewind (1)
- Load bearing behaviour (1)
- Load-carrying capacity (1)
- Long-term loading (1)
- MOSYTRAF (1)
- Mass drop (1)
- Material Point Method (1)
- Material model (1)
- Material point method (1)
- Material point method (MPM) (1)
- Measurement (1)
- Measurement campaigns (1)
- Mechanical systems (1)
- Mechanical tests (1)
- Messung (1)
- Microfine Cement (1)
- Microfine cement (1)
- Micromechanical LBM-DEM simulation (1)
- Minderung (1)
- Mitigation measures (1)
- Mix design (1)
- Mixed formulation (1)
- Multi-beam method (1)
- Nichtlinearitäten (1)
- Non-synoptic wind event (1)
- Nonlinear Equation of Motion (1)
- Nonlinear Finite Element Formulations (1)
- Nonlinear finite element simulation (1)
- Numerical computation (1)
- Numerical problem (1)
- OWEA (1)
- Offshore Windenergie (1)
- Offshore Windkraftanlagen (1)
- Offshore geotechnics (1)
- Offshore pile foundations (1)
- Offshore wind farms (1)
- Offshore-Gründungen (1)
- Offshore-Strukturen (1)
- Onset of jet erosion (1)
- Optimierungsmethoden (1)
- Optimization strategies (1)
- Optimization techniques (1)
- Overhead transmission line (1)
- Overhead transmission lines (1)
- PLIF-RIM optical techniques (1)
- Particle image velocimetry (1)
- Particle image velocimetry (PIV) (1)
- Pfahl (1)
- Physical model testing (1)
- Physical testing (1)
- Pile Capacity (1)
- Pile ageing (1)
- Piles (1)
- Prediction (1)
- Probabilitische Ingenieurmodelle (1)
- Prognose (1)
- Prüfverfahren (1)
- RIM-PLIF techniques (1)
- Railway embankment (1)
- Railway induced ground vibration (1)
- Railway measurement campaign (1)
- Railway tracks (1)
- Rammpfähle (1)
- Randelementmethode (1)
- Rechenmodell (1)
- Rechenmodelle (1)
- Regular inspection (1)
- Reinforced concrete (1)
- Reliability updating (1)
- Resistance (1)
- Risiko (1)
- Risikoanalyse (1)
- Risikobasierte Inspektionsplanung (1)
- Risikobasierte Maßnahmenplanung (1)
- Risk assessment (1)
- Rissdetektion (1)
- Risslumineszenz (1)
- Rissüberwachung (1)
- Road (1)
- Robust tests (1)
- Sachschaden (1)
- Safety (1)
- Scaled boundary finite element method (1)
- Scattered axle impulses (1)
- Schadenserkennung (1)
- Schienenverkehr (1)
- Schwingungsmessungen (1)
- Schädigung (1)
- Self-damping (1)
- Service life performance (1)
- Shear keys (1)
- Shearing (1)
- Shrinkage (1)
- Shrinkage Reducing Admixture (1)
- Smoke (1)
- Soft track elements (1)
- Soil erosion (1)
- Soil-building interaction (1)
- Soil-grout interface (1)
- Soil-pile interaction (1)
- Spannbetonbrücken (1)
- Stabilität (1)
- Stahlbau (1)
- State of stress (1)
- Static load test (1)
- Steel (1)
- Steel driven piles (1)
- Steel structures (1)
- Stress state (1)
- Structural analyses (1)
- Structural health monitoring (SHM) (1)
- Structural performance (1)
- Structural reliability (1)
- Structural reliability and risks (1)
- Subspace methods (1)
- Subspace-methods (1)
- Substructures (1)
- Superplasticizer (1)
- Supplementary Cementitious Materials (1)
- System (1)
- TOP (1)
- Tagung (1)
- Target stiffness (1)
- Temperatur (1)
- Temperature (1)
- Temperatureinfluss (1)
- Toxicity (1)
- Track beam (1)
- Track deterioration (1)
- Tragstrukturen (1)
- Train configuration (1)
- Train excitation (1)
- Train speed (1)
- Train-track interaction (1)
- Tran speed (1)
- Turbulent Wind Excitation (1)
- Un- certainty (1)
- Uncertainty in reference (1)
- Updated Lagrange Formulierung (1)
- Verdichtungsinjektionen (1)
- Vibration behaviour (1)
- Vibrations (1)
- WKP (1)
- Wahrscheinlichkeit (1)
- Wave-Tower interaction (1)
- Wavenumber method (1)
- Wellenfeldberechnung (1)
- Westend bridge (1)
- Westendbrücke (1)
- Wheelset accelerations (1)
- Wiederkehrende Prüfung (1)
- Wind (1)
- Wind tunnel experiments (1)
- Windfarm wake analysis (1)
- Zivile Sicherheit (1)
- Zugüberfahrt (1)
- Zustandsbewertung (1)
- Zyklik (1)
- elastische Gebäudelagerungen (1)
- fachwerkartige Stahltragwerken (1)
- floor vibration (1)
- modal analysis (1)
- sleeper pads (1)
- temperature (1)
- u-p-Formulierung (1)
- wave analysis (1)
- Überwachungsverfahren (1)

#### Organisationseinheit der BAM

- 7.2 Ingenieurbau (285) (entfernen)

Measurements of ground and track vibrations have been performed at a high-speed line in northern Germany. Impacts on the track and the ground, and passages of different trains with different speeds on different tracks have been measured. Transfer functions of the soil are presented and approximated by theoretical soil models. By using these transfer functions, the measured ground vibration between 2 to 64 m distance from the track can be transformed into a load spectrum which can be used for predictions at other sites. The method is compared to the soil-dependent method of an emission spectrum at a certain distance (8 m for example). The influence of train type, speed and track type is discussed on the base of the different emission quantities and the original measurements. The strong influence of the track, ballast track and slab track, is analysed by a theoretical model in wavenumber domain. The response of the track to the passage of the static load is reduced by the stiffness of the slab, the deformation of the track as well as the impulse acting on the soil. Usually, the impulse on the soil should result in a slow quasi-static movement of the soil, slower at further distances. In a heterogeneous soil, however, the impulses from the static loads scatter and keep parts of the higher impulse frequency band. In this case the reduced impulse spectra of the slab track will yield reduced ground vibration in a certain frequency band. Additional (BAM and international) measurements will be used to discuss this and possible other explanations for the different ground vibration differences.

Im ersten Teil werden Methoden der Wellenanalyse vorgestellt, Seismogramme, Multistation Analysis of Surface Waves (MASW), f,v-Analyse (Dispersion aus zweifacher Fourier-Analyse), Spatial AutoCorrelation (SPAC, hier auch für deterministische Quellen), und auf Messungen in Deutschland, Österreich und der Schweiz angewendet. Mit den Wellengeschwindigkeiten des Bodens werden die Berechnungsgrundlagen für die Erschütterungsausbreitung im Boden und die Bauwerk-Boden-Wechselwirkung geschaffen.
Der zweite Teil beschäftigt sich mit der Wellensynthese, das heißt mit der Berechnung von Wellenfeldern (aus Wellenzahlintegralen). Die Rechnungen können wesentlich vereinfacht werden, wenn man die Dimensionsanalyse und Symmetrieüberlegungen ausnutzt, so dass maximal fünf dimensionslose Verschiebungsfunktionen verbleiben (im Vollraum sind es sogar nur zwei Verschiebungsfunktionen, die sich einfach explizit angeben lassen). Es gibt Ähnlichkeiten zwischen den Halbraum-Amplituden an der Oberfläche, den Halbraum-Amplituden in der Tiefe und der Wellenausbreitung im Vollraum. Die berechneten Wellenfelder (als Terzspektren in verschie-denen Entfernungen von der Erschütterungsquelle) werden verwendet, um die gemessene Übertragungsfunktionen des Bodens zu approximieren und Erschütterungen von Zugvorbeifahrten zu prognostizieren. Auch dies wird an einigen Messorten vorgeführt. Dabei werden einige gemessene Besonderheiten der Eisenbahnerschütterungen mit dem geschichteten Aufbau des Bodens erklärt.
Der dritte Teil beschäftigt sich mit der Anwendung der Wellenfelder beziehungsweise der Punkt-lastlösungen beziehungsweise der Greenschen Funktionen in der Randelementmethode. Es wird ein einfaches Prinzip der Herleitung der Randelementmethode vorgeführt. Bei einer beliebigen Berandung benötigt man neben den Verschiebungswellenfeldern auch die Spannungswellen-felder. Eine einfache Berechnung der Spannungswellenfelder wird vorgeführt, die im Vollraum auf drei Spannungsfunktionen, ähnlich einfach wie die Verschiebungsfunktionen, führt. Durch die Kopplung der Randelementmethode mit der Finite-Element-Methode können dann Probleme der Bauwerk-Boden-Wechselwirkung gelöst werden.
Der vierte Teil beschäftigt sich schließlich mit der Freifeld-Wellenanregung unter einem Gebäude und der Wellenanregung im Gebäude. Dabei geht es um die Wechselwirkung der Freifeldwellen mit starren oder flexiblen Fundamenten (Pfählen, Fundamentplatten) und den Übertragungs-faktoren zwischen dem Freifeld und dem Gebäude. Bei der Wellenanregung in einem Büro-gebäude in Wien konnten die gleichen Methoden wie bei der Wellenanregung im Boden eingesetzt werden, Seismogramme, MASW, Übertragungsfunktionen und Amplituden-Abstandsgesetze.

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.

Use of DEM-LBM modeling to prove the relevance of free jet model for soil erosion by impinging jet
(2018)

The aim of this study is to provide a micromechanical insight into the mechanisms taking place during the erosion of a cohesive granular material driven by a fluid flow, the objectives are summarized as follows:
Perform numerical erosion tests.
Parallelization of the code (Gpu).
Extensive parametric analysis => rely micro parameters (eg. Cohesion) to macro parameters (eg. Soil erodibility, mechanical strengths).

The erosion phenomena is the main cause of the most serious incidents observed on earthen hydraulic structures such as dams and dikes. Thus, there is a real need to explore in depth and understand the mechanisms at work in such complex erosional processes for preventing similar risks.
The aim of this study is to provide a micromechanical insight into the mechanisms taking place during the erosion of a cohesive granular material driven by a fluid flow, the objectives are summarized as follows:
Perform numerical erosion tests.
Parallelization of the code (Gpu).
Extensive parametric analysis => rely micro parameters (eg. Cohesion) to macro parameters (eg. Soil erodibility, mechanical strengths).

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.

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.

Superplasticizer and shrinkage reducing admixture dosages for microfine cement in grout systems
(2018)

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.

Right from the beginning of applying SHM to bridge structures it was obvious that environmental based perturbations on the measurement significantly influence the ability to identify structural damage.
Strategies are needed to classify such effects and consider them appropriately in SHM. Various methods have been developed and analyzed to separate environmental based effects from damage induced changes in the measures. Generally, two main approaches have emerged from research activity in this fields: (a) statistics based tools analyzing patterns in the data or in computed parameters and (b) methods, utilizing the structural model of the bridge taking into account environmental as well as damage based changes of stiffness values.
With the back-ground of increasing affordability of sensing and computing technology, effort should be made to increase sensitivity, reliability and robustness of procedures, separating environmental from damage caused changes in SHM measures. The contribution describes both general strategies and points out their Advantages and drawbacks. As basis, a review on relevant methods was conducted. The aim of the study is to classify approaches for separating damage describing information from environmental based perturbations in dependency of the SHM objective. And such, it is intended to describe a best practice in designing concepts for Monitoring infrastructure, naturally effected by environmental influences.

In recent years, several high temperature low sag conductors (HTLS) have been developed and are now commercially available. Very few utilities have long-term experience with all the technologies. Moreover, most of the operational experience is at low temperatures. An independent testing program at maximum operational temperatures comparing most of the available technologies would provide useful guidance to utilities considering using such conductors.
This paper describes the approach and results of an international research project assessing the long-term reliability of a wide range of commercially available high temperature conductor systems. Each system was exposed to 4,400 hours of simultaneous mechanical and electrical stresses. A set of standard mechanical and electrical tests were carried out to determine any changes. A conventional ACSR conductor was also tested and provided a validation that the testing program was realistic.
The majority of the conductor systems performed satisfactorily. However the ACSS system joint resistance and the grease on the TACSR performed poorly.

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.

Explosion-induced ground vibrations have been measured at several places. Results about the wave propagation are shown in this contribution. The particle velocities of the soil have been measured at up to 1000 m distance from the explosion and are presented as time records (seismograms) and one-third octave band spectra (transfer functions). The results are compared with the results of hammer impacts. The seismograms clearly show different wave types, compressional waves of the air, the water and the soil, and the Rayleigh wave. The hammer impacts yield good results up to 100 m and incorporate higher frequencies at about 50 Hz, whereas the explosion results in a ground vibration with frequencies around 10 Hz and a longer range of influence. Explosion and hammer excitations are evaluated for the wave velocities of the soil by using the wavenumber and the spatial auto-correlation method. The attenuation of the ground vibration amplitudes A with distance r can well be presented by a power law A ~ r -q. This type of amplitude-distance law and the corresponding power q > 1 are substantiated in the contribution. The influence of the charge weight W is evaluated as an additional power law A ~ W -p for each measuring site. The power is found quite similarly around q 0.6 as all sites have a medium soft soil such as sand and clay. The obtained amplitude-charge-distance law can be used to predict the explosion-induced ground and building vibrations at other sites.

Die Grundidee einer Schwingungsminderung ist es eine tiefe Eigenfrequenz der Struktur zu erreichen, so dass höhere Frequenzen abgemindert werden. Das gilt für die Minderung an der Quelle, zum Beispiel einem Eisenbahngleis, und für die Minderung am Empfänger, dem Gebäude. Die Eigenfrequenz ermittelt man aus dem Verhältnis der Auflagersteifigkeit und der Masse. Wie ist die Masse bei einem Gebäude zu wählen? Und wie ist die Untergrund-steifigkeit zu berücksichtigen? Als Referenzsituation ohne Minderungsmaß¬nahme? Der Beitrag bringt Rechenergebnisse zu abgefederten Gebäuden mit einfachen und komplexen (FE-) Modellen, Mess- und Rechenergebnisse zur Schwingungsübertragung von unabge-federten Gebäuden. Es wird der Einfluss der Abstimmfrequenz, der Bodensteifigkeit und der „starren“ Gebäudemasse untersucht. Die komplexen Gebäudemodelle erlauben, neben der Berechnung einer elastischen Gebäudelagerung, auch die Variation von Gebäudepara¬metern zur Reduktion der Deckenschwingungen. Den Ergebnissen bei der Erschütterungs-übertragung in Gebäude werden zwei ähnliche Beispiele zur elastischen Maschinenlagerung und zur elastischen Gleislagerung gegenübergestellt.

This contribution presents experimental methods to detect track damage. At BAM (Federal Institute of Material Research and Testing), a measuring car with a measuring system of 72 channels, geophones, mountings, cables, harmonic and impulsive exciters is used for dynamic measurements of the track, the soil and buildings. An instrumented hammer allows force measurements and to evaluate transfer functions of the track, and the soil. Wave measurements are used to identify the soil characteristics. Train passages are measured at the track and for the train induced ground vibrations. In addition to these in situ options, tests of tracks or track elements can be performed in a large laboratory.

The authors are currently investigating the possibility to apply compaction grouting for offshore pile foundations (Jacket piles as well as monopiles) as a possible retrofitting technique for an optimised foundation concept. In this research project, we are developing a design approach aiming to predict the ideal amount and properties of a grout for a specific soil situation and desired improvement of pile bearing capacity after Installation and during service time. Both numerical and experimental tests have been carried out to investigate the injection process during which a highly viscous grout is injected into the soil under high pressure to displace and compact the surrounding soil without fracturing it. The implicit Material Point Method (MPM) based on a mixed formulation is the numerical technique chosen to deal with the expected large deformations and the arbitrary shape of the developing grout bulb. The usage of MPM prevents both the need of remeshing and the numerical instability induced by extensive mesh distortion. For validation with experimental results, we have constructed a testing chamber with one transparent sidewall. This chamber enables us to observe the injection process directly at the transparent vertical window and to measure the in-plane soil displacements and strains by means of the Digital Image Correlation (DIC) technique.
The results already reveal the interrelation of soil and grout properties for a successful usage of this common ground improvement technique.

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.

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

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.

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.

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.

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.

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.

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.