7.2 Ingenieurbau
Filtern
Dokumenttyp
- Vortrag (170)
- Beitrag zu einem Tagungsband (83)
- Zeitschriftenartikel (68)
- Posterpräsentation (10)
- Buchkapitel (4)
- Dissertation (4)
- Beitrag zu einem Sammelband (3)
- Sonstiges (2)
- Tagungsband (Herausgeberschaft für den kompletten Band) (1)
Sprache
- Englisch (260)
- Deutsch (84)
- Mehrsprachig (1)
Schlagworte
- Structural Health Monitoring (26)
- Ground vibration (20)
- Structural health monitoring (15)
- Fatigue (14)
- Brücken (11)
- Monitoring (11)
- Offshore (11)
- Offshore wind energy (11)
- Hammer impact (9)
- Impact (9)
- Train passage (9)
- Damage characterization (8)
- Model interpolation (8)
- Planar tomography (8)
- SHM (8)
- Structural systems (8)
- Vibration measurements (8)
- Building vibration (7)
- Damage detection (7)
- Deterioration (7)
- Layered soil (7)
- Reliability (7)
- Slab track (7)
- Soil-structure interaction (7)
- Train-induced ground vibration (7)
- Bahnerschütterungen (6)
- Compressive strength (6)
- Design methods (6)
- Grout (6)
- Inspection (6)
- Numerical modelling (6)
- Offshore wind turbines (6)
- Physical phenomenology (6)
- Pile foundations (6)
- Reinforced concrete structure (6)
- Datenmanagement (5)
- Environmental effects (5)
- Interface (5)
- Layered soils (5)
- Modalanalyse (5)
- Numeric simulation (5)
- Repair (5)
- Temperature rejection (5)
- Ultrasonic testing (5)
- Vibration (5)
- Windenergie (5)
- Bayesian updating (4)
- Container loading (4)
- Crack detection (4)
- Damage localization (4)
- Drop test (4)
- Erosion (4)
- Erschütterungen (4)
- Erschütterungsminderung (4)
- Excitation forces (4)
- Fault detection (4)
- Foundation load (4)
- Foundations (4)
- Gründungsstrukturen (4)
- High-strength concrete (4)
- Inspection planning (4)
- Mitigation (4)
- Offshore geomechanics (4)
- Probabilistic (4)
- Shell Buckling (4)
- Statistical tests (4)
- Steel structures (4)
- Subspace methods (4)
- Subspace-based method (4)
- Tunnel (4)
- Vehicle-track-soil interaction (4)
- Vibration measurement (4)
- Wind (4)
- Wind Energy (4)
- Ansys Autodyn (3)
- Attenuation (3)
- Axle impulses (3)
- BIM (3)
- Bauwerksüberwachung (3)
- Belastungsversuch (3)
- Box-Behnken (3)
- Bridge (3)
- Bridges (3)
- Brücke (3)
- Buckling (3)
- Compaction Grouting (3)
- Cracks (3)
- DUCON® (3)
- Deep foundations (3)
- Dispersionsmessung (3)
- Drucker-Prager (3)
- Ductility (3)
- E-modulus (3)
- Earth masonry (3)
- Elastische Gleiselemente (3)
- Emission (3)
- Erschütterungsprognose (3)
- Filter effects (3)
- Fly ash (3)
- Grouted connection (3)
- Grouting (3)
- Großer Fallturm Horstwalde (3)
- Irregular soil (3)
- Leichtbau (3)
- Linear parameter varying systems (3)
- Load vector (3)
- Maintenance (3)
- Material moisture (3)
- Metakaolin (3)
- Micro-reinforcement (3)
- Micromechanical modelling (3)
- Mobile elements (3)
- Model updating (3)
- Monopiles (3)
- Numerical modeling (3)
- Offshore Pile Foundation (3)
- Offshore Windenergieanlagen (3)
- Offshore foundations (3)
- Offshore wind turbine (3)
- Physical testing (3)
- Post-impact evaluation (3)
- Quasi-static and dynamic tests (3)
- Railway (3)
- Railway bridge (3)
- Randomly heterogeneous soil (3)
- Rehabilitation (3)
- Reinforced concrete (3)
- Risk (3)
- Scattering (3)
- Schwingungsdynamik (3)
- Soil erosion (3)
- Soil properties (3)
- Statistical evaluation (3)
- Statistical method (3)
- Stereo photogrammetry (3)
- Subspace-based residual (3)
- Temperature effects (3)
- Train speed (3)
- UHPC (3)
- Umwelteinflüsse (3)
- Vehicle-track interaction (3)
- Vibrations (3)
- Wellenausbreitung (3)
- Wellengeschwindigkeit (3)
- Zivile Sicherheit (3)
- 2-span bridge (2)
- AISTEC (2)
- Acceleration sensors (2)
- Achsfolgespektren (2)
- Acoustic emission testing (2)
- Amplitude-charge weight laws (2)
- Amplitude-distance laws (2)
- Analysis of variance (2)
- Apartment building (2)
- Artificial Intelligence (2)
- Artificial intelligence (2)
- Automatisierte schweißtechnische Fertigung (2)
- Axle sequence (2)
- Axle-sequence spectrum (2)
- Ballast track (2)
- Bauteile (2)
- Bauwerke (2)
- Bauwerksmonitoring (2)
- Bayes'sche Analyse (2)
- Bayesian System Identification (2)
- Bayesian analysis (2)
- Bayesian methods (2)
- Bayesian system identification (2)
- Bemessung (2)
- Big Data (2)
- Bitumen (2)
- Bodenübertragungsfunktion (2)
- Cable failure (2)
- Cable-stayed bridge (2)
- Changing process noise (2)
- Chemisoprtion (2)
- Climate chamber (2)
- Compressive Cyclic loading (2)
- Compressive cyclic loading (2)
- Computer Vision (2)
- Concrete (2)
- Coupled fluid-particle simulation (2)
- Coupler systems (2)
- Crack Luminescence (2)
- Crack formation (2)
- Crack pattern (2)
- Cyclic load (2)
- DEM (2)
- Damage identification (2)
- Design (2)
- Digital twin (2)
- Digitalisierung (2)
- Displacements (2)
- Drone (2)
- Earth block masonry (2)
- Elastische Elemente (2)
- Elastische Gebäudelagerung (2)
- Energy (2)
- Erschütterungsausbreitung (2)
- Evaluation (2)
- Explosion-induced ground vibrations (2)
- Faseroptik (2)
- Feuchte (2)
- Finite Elemente Simulation (2)
- Finite element models (2)
- Freight train (2)
- GPU parallel computation (2)
- Gaussian Process (2)
- Geotechnical site-characterization (2)
- Gleiströge (2)
- Ground vibration measurements (2)
- Grouted Connection (2)
- Halbraum (2)
- High-performance computing (2)
- High-speed (2)
- High-speed train (2)
- Immission (2)
- Injection Sequence (2)
- Irregular ballast (2)
- Irregularities (2)
- Jacket support structure (2)
- Jet erosion test (2)
- Klimakammer (2)
- Knudsen effect (2)
- LBM-DEM (2)
- Laboratory beam structure (2)
- Lehm (2)
- Long-term shrinkage (2)
- Luminescence (2)
- Macromechanical Sample Strength (2)
- Material tests (2)
- Mauerwerk (2)
- Measurement (2)
- Measurements (2)
- Messen im Bauwesen (2)
- Micro silica (2)
- Micromechanical Tensile Failure (2)
- Mix design (2)
- Modal Analysis (2)
- Moisture (2)
- Moisture content (2)
- Molecular diffusion (2)
- Non destructive testing (2)
- Non-Destructive Evaluation (2)
- Non-destructive testing (2)
- Numerical model (2)
- Office tower (2)
- Offshore Wind (2)
- Offshore Wind Energy (2)
- Offshore Windenergy Pile Buckling (2)
- Offshore geotechnics (2)
- Offshore wind (2)
- Offshore-Windenergieanlagen (2)
- Optimal Sensor Placement (2)
- Passenger train (2)
- Physisorption (2)
- Pile Foundation (2)
- Pile Tip Buckling (2)
- Prediction (2)
- Prediction of explosion induced ground and building vibration (2)
- Probability of Detection (2)
- Prädiktive Instandhaltung (2)
- Radar (2)
- Railway tunnel (2)
- Railways (2)
- Rechenmodelle (2)
- Reinforcement (2)
- Relative humidity (2)
- Repowering (2)
- Research data management (2)
- Residual evaluation (2)
- Resonance (2)
- Risslumineszenz (2)
- SDDLV (2)
- Safety (2)
- Scattered axle impulses (2)
- Schadensdetektion (2)
- Schwingungsbasierte Verfahren (2)
- Size effect (2)
- Slenderness effect (2)
- Soil-Structure-Interaction (2)
- Soil-pile interaction (2)
- Soil-wall-floor model (2)
- Static axle loads (2)
- Static load (2)
- Strength (2)
- Strukturmonitoring (2)
- Suction bucket (2)
- Supplementary cementitious materials (2)
- Surface-tunnel reduction (2)
- System Identification (2)
- System identification (2)
- Tensile Capacity (2)
- Time-variant reliability (2)
- Tomographic damage evaluation (2)
- Track damage (2)
- Track-soil interaction (2)
- Train excitation (2)
- Transmission (2)
- Uncertainty (2)
- Uncertainty in reference (2)
- Uncertainty quantification (2)
- Unterraummethoden (2)
- Value of Information (2)
- Vehicle–track interaction (2)
- Verkehrsinfrastukturen (2)
- Vollraum (2)
- Wellenausbreitung in der Tiefe (2)
- Wind Turbines (2)
- Wind energy (2)
- Wind turbine tower (2)
- Windenergieanlagen (2)
- Windenergy (2)
- Zuggeschwindigkeit (2)
- Zuverlässigkeit (2)
- 3D imaging (1)
- Achsimpulse (1)
- Acoustic emission (1)
- Acoustic emission analysis (1)
- Ambient excitation (1)
- Amplituden-Abstands-Gesetze (1)
- Analytical Design Methods (1)
- Asphalt (1)
- Assessment (1)
- Asymptotic local approach (1)
- Automated Modal Analysis for Tracking Structural Change during Construction and Operation Phases (1)
- Automated operational modal analysis (1)
- Automatic modal parameters identification (1)
- Automatisierte Fertigung (1)
- Automatisierte schweißtechniche Fertigung (1)
- Autonomous underwater vehicles (1)
- Axial load bearing (1)
- Axle loads (1)
- Axle pulses (1)
- BAM Windenergie Fügetechnik (1)
- Bahngleis (1)
- Base isolation (1)
- Baugrunddynamik (1)
- Bauwerk-Boden-Wechselwirkung (1)
- Bauwerksdiagnostik (1)
- Beanspruchungszustand (1)
- Belastungsfahrt (1)
- Belastungstest (1)
- Belastungszug (1)
- Benchmark (1)
- Beschleunigungssensoren (1)
- Beton (1)
- Betonautobahn (1)
- Betonautobahnen (1)
- Beulen (1)
- Bewertung (1)
- Bionik (1)
- Blast (1)
- Blast tests (1)
- Bodenschlitz (1)
- Bodenvariabilität (1)
- Boreholes (1)
- Boundary element (1)
- Boundary element method (1)
- Bridge monitoring (1)
- Bridge resonance (1)
- Bridge vibration (1)
- Bruchlastwechselzahlen (1)
- Brückensicherheit (1)
- Buckling piles circular shells (1)
- Buckling soil-structure-interaction offshore piles track (1)
- Building Information Modeling (1)
- Building and Construction (1)
- Building information modelling (1)
- Building response (1)
- Bulging (1)
- CFD (1)
- CPT (1)
- Cancellation (1)
- Cars (1)
- Cement-based composites (1)
- Cemented soil (1)
- Centerline solidification cracking (1)
- Chemisorption (1)
- Civil and Structural Engineering (1)
- Civil structures (1)
- Climate Chamber (1)
- Coating (1)
- Cohesive granular materials (1)
- Cohesive soils (1)
- Column/wall resonance (1)
- Combined finite-element boundary-element method (1)
- Compaction grouting (1)
- Compliance function (1)
- Components of excitation (1)
- Compression tests (1)
- Computational (1)
- Condensed Matter Physics (1)
- Conductor (1)
- Continuous soil (1)
- Continuously inhomogeneous geological media (1)
- Continuously inhomogeneous soils (1)
- Crack (1)
- Crack damage detection (1)
- Crack growth (1)
- Crack repair (1)
- Cyber security (1)
- Cyclic axial shearing (1)
- Cyclic degradation (1)
- DEM-LBM simulation (1)
- Damage Detection (1)
- Damage Identification (1)
- Damage evolution (1)
- Decision matrix analysis (1)
- Deckeneigenfrequenzen (1)
- Deckenschwingungen (1)
- Design models (1)
- Design practice (1)
- Detection (1)
- DiMoWind RDS-PP Maintenance Digital Twin Offshore Wind Energy (1)
- Digital Image Correlation (1)
- Digital Image Correlation (DIC) (1)
- Digital Models (1)
- Digital Twin (1)
- Digitale Zwillinge (1)
- Discrete Element Method (1)
- Discrete element method (1)
- Drop Test (1)
- Drop Tests (1)
- Drop tower (1)
- Druckfestigkeit (1)
- Druckschwellenversuch (1)
- Dynamic axle loads (1)
- Dynamic excitation (1)
- Dynamic loads (1)
- Dynamic soil properties (1)
- Dynamische Bodenkennwerte (1)
- Dynamische Bodensteifigkeit (1)
- Dämpfung (1)
- EERA Joint Program (1)
- Earth (1)
- Earth blocks (1)
- Earth material (1)
- Earthen hydraulic constructions (1)
- Earthen hydraulic infrastructures (1)
- Einflusslinie (1)
- Einflusslinien (1)
- Einfügungsdämmung (1)
- End-of-life decision making (1)
- Entscheidungsfindung (1)
- Environmental (1)
- Environmental Effects (1)
- Environmental and Operational Variability (1)
- Environmental changes (1)
- Environmental influence (1)
- Erhaltungsmanagement (1)
- Ermüdung (1)
- Ermüdungsprüfung (1)
- Ermüdungsschäden (1)
- Ermüdungsverhalten (1)
- Erneuerbare Energien (1)
- Erosion of cohesive soils (1)
- Erschütterungen im Fernfeld (1)
- Estimation (1)
- FEM (1)
- FEM analysis (1)
- Fahrzeug-Fahrweg-Boden-Wechselwirkung (1)
- Fallturm (1)
- Fatigue damage (1)
- Fatigue deterioration (1)
- Fatigue strength (1)
- Fault detectionchanging (1)
- Features (1)
- Fequency domain (1)
- Fiber optic sensing (1)
- Fibre optic sensors (1)
- Finite element (1)
- Finite element analysis (1)
- Finite element method (1)
- Finite element model updating (1)
- Finite elements (1)
- Finite-Elemente-Modellkalibrierung (1)
- Finite-element boundary-element method (1)
- Flexibility (1)
- Flexible car body (1)
- Flexible wheelset (1)
- Floor resonance (1)
- Floors (1)
- Fluid Dynamics (1)
- Fluid-structure interaction (1)
- Fluidized beds (1)
- Footbridge (1)
- Force reconstruction (1)
- Foundation Pile (1)
- Foundation reliability analysis (1)
- Freileitung (1)
- Frequency response function (1)
- GMNIA (1)
- GNSS (1)
- GPA (1)
- GPU Parallel computing (1)
- GPU parallelisation (1)
- Gebäudelagerung (1)
- Gebäudemodelle (1)
- Gebäudeschwingungen (1)
- Gekoppelte Fluid-Partikel Simulationen (1)
- General Materials Science (1)
- Geology (1)
- Geomechanics (1)
- Geomechanics of offshore foundations (1)
- Geometric vehicle and track irregularities (1)
- Geometrie (1)
- Global ambient vibrations (1)
- Granular Cohesive Materials (1)
- Granular Cohesive Materials, (1)
- Granular cohesion (1)
- Granular materials (1)
- Ground (1)
- Grout Injection (1)
- HAZID (1)
- HTLS (1)
- Hard impact (1)
- Harter Anprall an Stahlbetonstrukturen (1)
- High-Rise Building (1)
- High-rise building (1)
- High-rise buildings (1)
- Horizontal stress (1)
- Horizontal wind turbine (1)
- Hydraulic jet erosion (1)
- IEPE (1)
- Impact damage of reinforced concrete (1)
- Impact damage on reinforced concrete (1)
- Impact loading (1)
- Impakt (1)
- Impedanzmethode (1)
- Imperfektion (1)
- Impinging jet (1)
- Inclination angle (1)
- Inertial Interaction (1)
- Inertial interaction (1)
- Inhomogeneous soils (1)
- Innovative Messtechnik (1)
- Inspeciton (1)
- Inspektion (1)
- Instandhaltung (1)
- Interface model (1)
- Jet impingement (1)
- Kalibrierung (1)
- Kinematic Interaction (1)
- Kinematic interaction (1)
- Kraft auf den Boden (1)
- LBM-DEM coupling (1)
- LBM-DEM simulation (1)
- Laminar flow (1)
- Laminography (1)
- Large components (1)
- Laser beam welding (1)
- Lateral dynamic displacement (1)
- Lateral load bearing (1)
- Lattice Boltzmann Method (1)
- Lattice Boltzmann method (1)
- Leichtbauprinzipien (1)
- Lifetime Extension (1)
- Load Test (1)
- Load bearing behaviour (1)
- Load identification (1)
- Load tests (1)
- Load-bearing (1)
- Load-bearing behaviour (1)
- Local approaches (1)
- Long-span bridge (1)
- Low-frequency shaker (1)
- MEMS (1)
- Maintal Bridge Gemuenden (1)
- Maintalbrücke Gemünden (1)
- Maintenance Digital Twin Offshore Wind Energy (1)
- Marine geomechanics (1)
- Marine geotechnics (1)
- Maschinenbetrieb (1)
- Maschinenfundament (1)
- Material Point Method (1)
- Material Point Method (MPM) (1)
- Material model (1)
- Measurement campaigns (1)
- Mechanical challenges (1)
- Merkblatt (1)
- Messfahrt (1)
- Microfine Cement (1)
- Microfine cement (1)
- Micromechanical LBM-DEM simulation (1)
- Micromechanical analysis (1)
- Micromechanical simulation (1)
- Microsilica (1)
- Minderungsmaßnahmen (1)
- Mixed formulation (1)
- Modal analysis (1)
- Modal force spectrum (1)
- Modal load spectrum (1)
- Modal system identification (1)
- Model Building (1)
- Model Update (1)
- Model Updating (1)
- Model update (1)
- Modell-Update (1)
- Modellierung (1)
- Modes (1)
- Modes and waves (1)
- Modulus of elasticity (1)
- Monitoring-informed inspection and maintenance planning (1)
- Monopile (1)
- Monopile Buckling (1)
- Monopile installation risks (1)
- Movin load test (1)
- Multi-beam method (1)
- Multi-beam track model (1)
- Multiple impact (1)
- NDT (1)
- Nachgiebigkeiten (1)
- Nelson’s method (1)
- Normung (1)
- Numerical analysis (1)
- Numerical damage simulation (1)
- Numerical simulation (1)
- Numerical simulation of impact damage (1)
- Numerical simulations (1)
- Numerische Analysen (1)
- Obstacles (1)
- Offhore (1)
- Office building (1)
- Offshore Structures (1)
- Offshore Wind Energy Converter (1)
- Offshore Windenergie (1)
- Offshore pile foundation (1)
- Offshore pile foundations (1)
- Offshore steel structures (1)
- Offshore wind energy foundations (1)
- Offshore wind farm (1)
- Offshore wind farms (1)
- Offshore wind-turbine foundations (1)
- Offshore-Wind (1)
- Offshore-Windenergie (1)
- Offshore-Windkraftanlagen (1)
- Operational modal analysis (1)
- Optimal sensor placement (1)
- Optimierungsmethoden (1)
- Optimization techniques (1)
- Perfectly Matched Layer (PML) (1)
- Pfahlfußbeulen (1)
- Pfahlnachgiebigkeiten (1)
- Physisoprtion (1)
- Piaui state (1)
- Pile Buckling (1)
- Pile Capacity (1)
- Pile ageing (1)
- Pile bending stiffness (1)
- Pile foundation (1)
- Pile groups (1)
- Pile retrofit system (1)
- Pile-Tip-Buckling (1)
- Point Cloud (1)
- Predictive maintenance (1)
- Pressure (1)
- Probabilistic modelling (1)
- Probabilitische Ingenieurmodelle (1)
- Probability of detection (1)
- Probekörpergeometrien (1)
- Process noise (1)
- Prognose (1)
- Propagation from a tunnel (1)
- Quasi-static response; (1)
- Rail roughness (1)
- Railbridge (1)
- Railway induced vibration (1)
- Railway track (1)
- Railway tracks (1)
- Railway trafiic (1)
- Randelementmethode (1)
- Random dynamics and vibrations (1)
- Random stiffness variation (1)
- Rayleighwellendispersion (1)
- Rechenverfahren (1)
- Recovery experiments (1)
- Referenzbeispiel (1)
- Referenzkennzeichnungssystem (1)
- Remote sensing vibrometer (1)
- Residential building (1)
- Richtige Fahrzeugmasse (1)
- Richtlinie (1)
- Rigid vehicle model (1)
- Risiko (1)
- Risikoanalyse (1)
- Risk-based design (1)
- Risk-based maintenance planning (1)
- Rissprozes (1)
- Rissprozess (1)
- SHCC (1)
- SHM Environmental (1)
- SHM environmental bridges (1)
- Sandstone (1)
- Santa-marta (1)
- Scaling (1)
- Schadensüberwachung (1)
- Schallemission (1)
- Scherwellengeschwindigkeit (1)
- Schienenfahrweg (1)
- Schienenfahrwege (1)
- Schrauben (1)
- Schubmodul (1)
- Schwingungsmessungen (1)
- Schwingungsmonitoring (1)
- Schädigungsprozesse (1)
- Sensitivity vectors (1)
- Serra da cangalha (1)
- Shearing (1)
- Shell buckling (1)
- Shrinkage (1)
- Shrinkage Reducing Admixture (1)
- Sicherheit (1)
- Simple and fast prediction (1)
- Simple prediction (1)
- Simulation and experiment (1)
- Site-characterization (1)
- Soft impact (1)
- Soft track elements (1)
- Soil Struture Interaction (1)
- Soil classification (1)
- Soil forces (1)
- Soil stiffness (1)
- Soil-building interaction (1)
- Soil-building resonance (1)
- Soil-wall floor model (1)
- Soil-water-structure interaction (1)
- Sorption isotherm (1)
- Spannbeton (1)
- Spannstahlbruch (1)
- Spatially varying ground conditions (1)
- Spektralanalyse (1)
- Stability Buckling soil-structure-interaction piles offshore (1)
- Stabilität (1)
- State of stress (1)
- Static loading (1)
- Statistical correlations (1)
- Statistical pattern recognition (1)
- Statistische Auswertung (1)
- Statistische Korrelationen (1)
- Stiffness variation (1)
- Stochastic Subspace Damage Detection (1)
- Strain (1)
- Stress stiffening (1)
- Stress-strain relation (1)
- Stress–strain-relation (1)
- Structural Systems (1)
- Structural integrity (1)
- Structural integrity maintenance (1)
- Structural integrity management (1)
- Structural system identification (1)
- Störgrößen (1)
- Substructures (1)
- Suction Bucket (1)
- Superplasticizer (1)
- Supplementary Cementitious Materials (1)
- Support structures (1)
- Surface Foundation (1)
- Surface line (1)
- Sustainable binders (1)
- Switch (1)
- Systemidentifikation (1)
- TOP (1)
- TRC (1)
- Tagung (1)
- Temperature effect (1)
- Temperature effect rejection (1)
- Temperature modeling (1)
- Temperatureinflüsse (1)
- Tensile test (1)
- Test specification (1)
- Tip Buckling (1)
- Track and vehicle irregularities (1)
- Track beam (1)
- Track damage monitoring (1)
- Track damage quantification (1)
- Track deflection (1)
- Track displacements (1)
- Track filter (1)
- Track filtering (1)
- Track vibration (1)
- Tragfähigkeit (1)
- Tragstrukturen (1)
- Train configuration (1)
- Train passages (1)
- Train-induced vibration (1)
- Tran speed (1)
- Transfer fuction (1)
- Transfer function (1)
- Transverse butt weld (1)
- Trench (1)
- Truss structures (1)
- Tunnel line (1)
- Tunnel-pile transfer (1)
- Tunnel-to-surface reduction (1)
- Tunnelstrecke (1)
- Turnout (1)
- UAS (1)
- Un- certainty (1)
- Unbounded domain (1)
- Under-sleeper pads (1)
- Value of information (1)
- Variational Bayesian statistics (1)
- Varying soil stiffness (1)
- Varying stiffness (1)
- Varying track stiffness (1)
- Vibration analysis (1)
- Vibration excitation (1)
- Vibration monitoring (1)
- Viscosity (1)
- Vorspannung (1)
- Wahrscheinlichkeit (1)
- Water Science and Technology (1)
- Water-structure interaction (1)
- Wave propagation (1)
- Wave-Tower interaction (1)
- Wavenumber domain (1)
- Wavenumber integrals (1)
- Wavenumber method (1)
- Waves (1)
- Weld imperfections (1)
- Welded (1)
- Wellenfeldberechnung (1)
- Wheelset (1)
- Wheelset accelerations (1)
- Wind Energy Structures (1)
- Wind energy tower (1)
- Wind turbines (1)
- Wind-farm aerodynamics (1)
- Windenergieanlage (1)
- Windfarm wake analysis (1)
- Workability (1)
- Zerstreute Achsimpulse (1)
- acceleration sensors (1)
- building information modelling (1)
- calibration (1)
- elastische Gebäudelagerungen (1)
- environmental influences (1)
- fachwerkartige Stahltragwerken (1)
- layered soil (1)
- risk, reliability, inspection planning, offshore wind turbines (1)
- structural health monitoring (1)
- structural integrity management (1)
- support structures (1)
- temperature (1)
- transmission behavior (1)
- zerstreute Achslastimpulse (1)
- Übertragungsmatrizen (1)
- Übertragungsverhalten (1)
- Überwachung (1)
Organisationseinheit der BAM
- 7.2 Ingenieurbau (345) (entfernen)
Paper des Monats
- ja (5)
Temperature variation can be a nuisance that perturbs vibration based structural health monitoring (SHM) approaches for civil engineering structures. In this paper, temperature affected vibration data is evaluated within a stochastic damage detection framework, which relies on a null space based residual. Besides two existing temperature rejection approaches – building a reference state from an averaging method or a piecewise method – a new approach is proposed, using model interpolation. In this approach, a General reference model is obtained from data in the reference state at several known reference temperatures.
Then, for a particular tested temperature, a local reference model is derived from the general reference model. Thus, a well fitting reference null space for the formulation of a residual is available when new data is tested for damage detection at an arbitrary temperature. Particular attention is paid to the computation of the residual covariance, taking into account the uncertainty related to the null space Matrix estimate. This improves the test performance, contrary to prior methods, for local and global damages, resulting in a higher probability of detection (PoD) for the new interpolation approach compared to previous approaches.
The subject of damage localization is an important issue for Structural Health Monitoring (SHM) particularly in mechanical or civil structures under ambient excitation. In this paper, the statistical subspacebased damage localization method has been applied on a benchmark application, namely a 1/200 scale model of the Saint-Nazaire Bridge, which is a cable-stayed bridge located on the Loire River near the river’s mouth. The employed damage localization method combines data-driven features with physical parameter information from a finite element model in statistical tests, avoiding typical ill-conditioning problems of FE model updating. Damage is introduced in the mockup for cable failures on some of the 72 cables. The purpose of the experiment is to assess the capability of damage assessment methods to find a cable failure.
The Stochastic Dynamic Damage Locating Vector (SDDLV) approach is a vibration-based damage localization method based on both a finite element model of a structure and modal parameters estimated from output-only measurements in the damage and reference states. A statistical version of the Approach takes into account the inherent uncertainty due to noisy measurement data. In this paper, the effect of temperature fluctuations on the performance of the method is analyzed in a model-based approach using a finite element model with temperature dependent parameters. Robust damage localization is carried out by rejecting the temperature influence on the identified modal parameters in the damaged state. The algorithm is illustrated on a simulated structure.
Temperature variation can be a nuisance that perturbs vibration based structural health monitoring (SHM) approaches for civil engineering structures. In this paper, temperature affected vibration data is evaluated within a stochastic damage detection framework, which relies on a null space based residual. Besides two existing temperature rejection approaches – building a reference state from an averaging method or a piecewise method – a new approach is proposed, using model interpolation. In this approach, a general reference model is obtained from data in the reference state at several known reference temperatures. Then, for a particular tested temperature, a local reference model is derived from the general reference model. Thus, a well fitting reference null space for the formulation of a residual is available when new data is tested for damage detection at an arbitrary temperature. Particular attention is paid to the computation of the residual covariance, taking into account the uncertainty related to the null space matrix estimate. This improves the test performance, contrary to prior methods, for local and global damages, resulting in a higher probability of detection (PoD) for the new interpolation approach compared to previous approaches.
The subject of damage localization is an important issue for Structural Health Monitoring (SHM) particularly in mechanical or civil structures under ambient excitation. In this paper, the statistical subspacebased damage localization method has been applied on a benchmark application, namely a 1/200 scale model of the Saint-Nazaire Bridge, which is a cable-stayed bridge located on the Loire River near the river’s mouth. The employed damage localization method combines data-driven features with physical parameter information from a finite element model in statistical tests, avoiding typical ill-conditioning problems of FE model updating. Damage is introduced in the mockup for cable failures on some of the 72 cables. The purpose of the experiment is to assess the capability of damage assessment methods to find a cable failure.
The Stochastic Dynamic Damage Locating Vector (SDDLV) approach is a vibration-based damage localization method based on both a finite element model of a structure and modal parameters estimated
from output-only measurements in the damage and reference states. A statistical version of the Approach takes into account the inherent uncertainty due to noisy measurement data. In this paper, the effect of temperature fluctuations on the performance of the method is analyzed in a model-based approach using a finite element model with temperature dependent parameters. Robust damage localization is carried out by rejecting the temperature influence on the identified modal parameters in the damaged state. The algorithm is illustrated on a simulated structure.
Within the presented research project, experimental and numerical investigations were performed to develop a thin-shelled, modular, mobile element system made of a micro-reinforced ultra-high-performance ductile concrete (DUCON®). Material parameters were experimentally determined to adapt the material model within the numerical analysis applying the Drucker-Prager relationship. Afterwards, for validation of the numerical models, quasi-static and high-velocity impact tests were performed on plate-like structures. Finally, a suitable geometry of transportable barrier elements will be designed, which provides a maximum of resistance against impact by a minimum of weight and a maximum of mobility.
Es wird die Vorgehensweise erläutert wie die Notwendigkeit einer elastischen Gebäudelagerung geprüft wird. Es werden die Möglichkeiten und Schwächen vereinfachter Rechenverfahren dargestellt. Es folgen weitere Beispiele detaillierter Gebäudemodelle und ihres Schwingungsverhaltens. Schließlich greift eine aktuelle Bachelorarbeit die Fragestellung komplexen Gebäudeschwingungsverhaltens auf. Die letzte Folie zeigt dazu Gebäudemodelle, die an die konkreten Erschütterungsprognosen anknüpfen.
Two measurement campaigns of train-induced ground vibrations are evaluated for the vehicle-track-soil interaction. Ground vibrations, track vibrations and vehicle vibrations have been measured for train passages and impulse excitation and compared with theoretical results. The soil and the track-soil system are calculated by wavenumber integrals. The influence of the vehicle is introduced by a substructure method. By comparing theory and measurement the different components of excitation force and ground vibration can be analysed, the quasi-static excitation, track-alignment errors, the out-of-roundness of wheels, the wheel and rail roughness, and moreover, scattered axle impulses and ineffective high-frequency parts of the wheelset accelerations and forces.
Three measurement campaigns of train-induced ground vibrations are evaluated for the vehicle-track-soil interaction. Ground vibrations, track vibrations and vehicle vibrations have been measured for train passages and impulse excitation and compared with theoretical results. The soil and the track-soil system are calculated by wavenumber integrals. The influence of the vehicle is introduced by a substructure method. By comparing theory and measurement the different components of excitation force and ground vibration can be analysed, the quasi-static excitation, track-alignment errors, the out-of-roundness of wheels, the wheel and rail roughness, and moreover, scattered axle impulses and ineffective high-frequency parts of the wheelset accelerations and Forces.
Three measurement campaigns of train-induced ground vibrations are evaluated for the vehicle-track-soil interaction. Ground vibrations, track vibrations and vehicle vibrations have been measured for train passages and impulse excitation and compared with theoretical results. The soil and the track-soil system are calculated by wavenumber integrals. The influence of the vehicle is introduced by a substructure method. By comparing theory and measurement the different components of excitation force and ground vibration can be analysed, the quasi-static excitation, track-alignment errors, the out-of-roundness of wheels, the wheel and rail roughness, and moreover, scattered axle impulses and ineffective high-frequency parts of the wheelset accelerations and forces.
A combined finite-element boundary-element method for the dynamic interaction of the soil with flexible structures such as single piles or complete wind energy towers has been developed. Flexible piles in different soils are analysed in frequency domain. The different parameters such as the stiffness of the soil, the bending stiffness and the radius of the hollow pile are analysed for their influence on the complex compliances. The results have been determined as specific power laws which are different for the different load cases (horizontal, rocking, coupling) and for the different soil models (Winkler, continuum with constant, root-parabolic and proportional-linear stiffness variation). The strongest influence of the soil stiffness can be found for the homogeneous soil and the horizontal component. Winkler soils have a weaker influence than the corresponding continuous soils. An offshore wind energy tower has been modeled and calculated for wind and wave loads.
Superplasticizer and Shrinkage Reducing Admixture Dosages for Microfine Cement in Grout Systems
(2019)
Grouts have numerous applications including crack repair as maintenance in construction industries. Microfine cements are intensively used for high strength mortar and grout products. They are ideal for injection grouting in structural repair. Such grouts should have suitable rheological properties to be injectable, especially those used in repair and rehabilitation. The use of superplasticizers (SP) in these products is thus becoming increasingly crucial to achieve favorable workability and viscosity properties. A difficulty in such grouts is the plastic shrinkage due to finer particles used. It is thus necessary to determine optimum SP and shrinkage reducing admixture (SRA) dosages for a microfine cement based grout. In this study, a saturation dosage was decided from two Polycarboxylate ether (PCE) based SPs in relation to neat cement using slump flow and rheological parameters. A range of grout mixtures was formulated containing micro silica (MS) and fly ash (FA), and tested for suitable rheological and mechanical parameters. Based on the results, a grout mixture with MS and FA was selected to determine optimum SRA content. According to the results, a SP dosage of 3% by weight of neat cement is sufficient to achieve saturation. The grout material including MS and FA can produce comparable properties to neat cement grout. MS is found to improve compressive strength within the range considered, whereas a higher FA content provides favourable rheological properties. Finally, a SRA dosage of 4%, which could reduce the shrinkage by about 43% after 28d days, is determined for the grout system.
Kontinuierliche Sensorbasierte Bauwerksmessungen leisten einen wichtigen Beitrag zur Sicherheit von Verkehrsbauwerken. Hierzu werden im Vorhaben AISTEC Referenzbauwerke und Referenzverfahren untersucht mit Schwerpunkt auf den Einfluss klimatischer Bedingungen. Der Vortrag stellt den aktuellen Projektstand des FB 7.2 vor.
Grouts are particularly favoured in rehabilitation of structures due to penetrability and convenience of application. Grouts for repair applications typically require high-performance properties such as rapid strength development and superior shrinkage characteristics. Sometimes industrial by-products referred as supplementary cementitious materials (SCM) are used with neat cement due to their capabilities to provide binding properties at delayed stage. Micro silica, fly ash and metakaolin are such SCMs, those can modify and improve properties of cement products. This study aims at investigating long-term mass loss and linear shrinkage along with long-term compressive and flexural strength for grouts produced from ultrafine cement and SCMs. A series of mixtures were formulated to observe the effect of SCMs on these grout properties. Properties were determined after 365 days of curing at 23 °C and 55% relative humidity. The effect of SCMs on the properties are characterised by statistical models. Response surfaces were constructed to quantify these properties in relation to SCMs replacement. The results suggested that shrinkage was reduced by metakaolin, while micro silica and fly ash had positive effects on compressive and flexural strength, respectively.
This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures.
The first lecture presents a brief introduction to the context and peculiarities of such foundations, and then focuses on the particular case of axially loaded piles. This part is most relevant for the relatively slender piles of the multi-pile substructures (i.e. jackets and tripods). A clear distinction between physical phenomenology and practical design is drawn here.
The second lecture continues with the case of lateraly loaded offshore piles, which bears most relevance for the case of the monopile foundations. Here again, a clear separation between physical reality and design methods is intended.
Finally, the last part of the second lecture introduces several advanced topics which lie outside the classical design approaches, namely the hydromechanical coupling effects (i.e. the excess pore-pressure generation around the monopiles), the cyclic pile fatigue and the so-called pile Setup (i.e. the time effects on the axial pile capacity). The relevance of the latter two topics is illustrated with experimental results from a field testing campaign on real large-scale piles.
Automated modal analysis for tracking structural change during construction and operation phases
(2019)
The automated modal analysis (AMA) technique has attracted significant interest over the last few years, because it can track variations in modal parameters and has the potential to detect structural changes. In this paper, an improved density-based spatial clustering of applications with noise (DBSCAN) is introduced to clean the abnormal poles in a stabilization diagram. Moreover, the optimal system model order is also discussed to obtain more stable poles. A numerical Simulation and a full-scale experiment of an arch bridge are carried out to validate the effectiveness of the proposed algorithm. Subsequently, the continuous dynamic monitoring system of the bridge and the proposed algorithm are implemented to track the structural changes during the construction phase. Finally, the artificial neural network (ANN) is used to remove the temperature effect on modal frequencies so that a health index can be constructed under operational conditions.
The governing load bearing mechanism of multi-pile foundations is often the shaft friction. Under cyclic loading the soil particles next to the foundation rearrange and tend to compact leading to a decrease of the surrounding normal stress. The reduction of the normal stress leads to a lower threshold for shear stress (friction fatigue), which results in a degraded shaft bearing capacity. The common interface models used for numerical simulations (e.g. Mohr-Coulomb) are not able to capture such behavior. This work aims to develop an interface material model that incorporates such features of the contact behavior at the soil-structure interface.
The response of many geotechnical systems, whose structural behavior depends on shearing effect, is closely related to soil structure interaction phenomenon. Experimentally it is found that the localisation of these effect happens at a narrow soil layer next to the structure. Numerically, this behavior can be modelled through interface elements and adequate constitutive models. In this work, a constitutive model in the framework of Generalized Plasticity for sandy soils has been chosen to be adapted for the interface zone.
From the direct shear experiments a sandy soil at loose and dense states under different normal pressures is considered. The adapted constitutive model is able to reproduce contraction and dilatation of the soil according to its relative density and it shows a good agreement with the experimental data.
The response of many geotechnical systems, whose structural behavior depends on granular friction and a shearing effect with the ground, is characterized by a complex soil-structure interaction at their interfaces. Experimentally it is found that this interaction is highly non-linear, state-dependent and localized within a narrow layer of soil next to the structure, whereby cyclic loads can play a key role. Numerically, this behavior is often modelled with overly simplified models of interface elements that neglect cyclic effects within the soil. This work introduces a new perspective with an adequate constitutive model in the framework of Generalized Plasticity for sandy soils for an improved consideration of the interface mechanics.
Risslumineszenz
(2018)
Unterraumbasierte Detektion von Strukturschäden an Jacket-Gründungen von Offshore-Windenergieanlagen
(2018)
Die vorliegende Arbeit beschreibt die Adaption eines globalen, schwingungsbasierten Verfahrens zur frühzeitigen Erkennung von Strukturschäden an Gründungsstrukturen offshore installierter Windenergieanlagen (OWEA). Damit soll es, Betreibern von Offshore-Windparks ermöglicht werden, im Rahmen periodisch durchgeführter messtechnischer Überwachungsmaßnahmen mit einem gegenüber wiederkehrender Inspektionen wesentlich geringen Aufwand auftretende Schäden an der Struktur zuverlässig zu delektieren.
Das untersuchte und implementierte Verfahren basiert auf der Methode der stochastischen unterraumbasierten Schadensdetektion. Dabei erfolgt eine statistische Analyse des wiederkehrend messtechnisch aufgenommenen dynamischen Antwortverhaltens des mechanischen Systems. Mittels statistischem Test werden signifikante Änderungen in dessen Eigenstruktur und damit Schäden delektiert.
Im Rahmen der vorliegenden Arbeit wurden umfangreiche experimentelle als auch numerische Untersuchungen zur Sensitivität und Robustheit des beschriebenen Schadensindikators durchgeführt. Dazu sind zunächst an einem Labormodell mittels künstlich und reversibel eingebrachter Schäden grundlegende Analysen zu den Einflüssen signal- und verfahrensinhärenter Kenngrößen durchgeführt worden. Auf der Basis dieser Ergebnisse wurde im Anschluss mittels numerischer Analysen das Antwortverhalten von OWEA simuliert und der entwickelte Algorithmus zur Schadensdetektion an den so realisierten Datensätzen angewendet.
Anhand der Ergebnisse der Arbeit wird aufgezeigt, dass, vorausgesetzt die Windenergieanlage befindet sich in Parkposition, eine Detektion von schon geringen Schäden an Gründungs-strukturen mit dem beschriebenen Verfahren, auch unter Einsatz weniger Messaufnehmer, zuverlässig möglich ist.
Unterraumbasierte Detektion von Strukturschäden an Jacket-Gründungen von Offshore-Windenergieanlagen
(2018)
Die vorliegende Arbeit beschreibt die Adaption eines globalen, schwingungsbasierten Verfahrens zur frühzeitigen Erkennung von Strukturschäden an Gründungsstrukturen offshore installierter Windenergieanlagen (OWEA). Damit soll es, Betreibern von Offshore-Windparks ermöglicht werden, im Rahmen periodisch durchgeführter messtechnischer Überwachungsmaßnahmen mit einem gegenüber wiederkehrender Inspektionen wesentlich geringen Aufwand auftretende Schäden an der Struktur zuverlässig zu delektieren.
Das untersuchte und implementierte Verfahren basiert auf der Methode der stochastischen unterraumbasierten Schadensdetektion. Dabei erfolgt eine statistische Analyse des wiederkehrend messtechnisch aufgenommenen dynamischen Antwortverhaltens des mechanischen Systems. Mittels statistischem Test werden signifikante Änderungen in dessen Eigenstruktur und damit Schäden delektiert.
Im Rahmen der vorliegenden Arbeit wurden umfangreiche experimentelle als auch numerische Untersuchungen zur Sensitivität und Robustheit des beschriebenen Schadensindikators durchgeführt. Dazu sind zunächst an einem Labormodell mittels künstlich und reversibel eingebrachter Schäden grundlegende Analysen zu den Einflüssen signal- und verfahrensinhärenter Kenngrößen durchgeführt worden. Auf der Basis dieser Ergebnisse wurde im Anschluss mittels numerischer Analysen das Antwortverhalten von OWEA simuliert und der entwickelte Algorithmus zur Schadensdetektion an den so realisierten Datensätzen angewendet.
Anhand der Ergebnisse der Arbeit wird aufgezeigt, dass, vorausgesetzt die Windenergieanlage befindet sich in Parkposition, eine Detektion von schon geringen Schäden an Gründungs-strukturen mit dem beschriebenen Verfahren, auch unter Einsatz weniger Messaufnehmer, zuverlässig möglich ist.
Within the presented research project, experimental and numerical investigations were performed to develop a thin-shelled, modular, mobile element system made of a micro-reinforced ultra-high-performance ductile concrete (DUCON®). Material parameters were experimentally determined to adapt the material model within the numerical analysis applying the Drucker-Prager relationship. Afterwards, for validation of the numerical models, quasi-static and high-velocity impact tests were performed on plate-like structures. Finally, a suitable geometry of transportable barrier elements will be designed, which provides a maximum of resistance against impact by a minimum of weight and a maximum of mobility.
Within the presented research project, experimental and numerical investigations were performed to develop a thin-shelled, modular, mobile element system made of a micro-reinforced ultra-high-performance ductile concrete (DUCON®). Material parameters were experimentally determined to adapt the material model within the numerical analysis applying the Drucker-Prager relationship. Afterwards, for validation of the numerical models, quasi-static and high-velocity impact tests were performed on plate-like structures. Finally, a suitable geometry of transportable barrier elements will be designed, which provides a maximum of resistance against impact by a minimum of weight and a maximum of mobility.
Mit der Errichtung und der Inbetriebnahme des Windpark alpha ventus wurden umfangreiche Messungen an den Tragstrukturen und den Umgebungsparametern durchgeführt. Im Projekt Gigawind life wurde im TP1 ein Datenmanagementsystem zur kontinuierlichen und periodisch fortgeführten Datenauswertung für große Datenbestände (Big Data) entworfen und realisiert. Anhand von Performanceuntersuchungen konnte eine Verkürzung der Rechenzeit um den Faktor 10 in einem Rechencluster erreicht werden. Unter Anwendung einer Datenpipeline nach dem Publish/Subscribe Prinzip wird eine skalierbare Datenschnittstelle für Monitoringdaten vorgeschlagen.
Mit der Errichtung und der Inbetriebnahme des Windpark alpha ventus wurden umfangreiche Messungen an den Tragstrukturen und den Umgebungsparametern durchgeführt. Im Projekt Gigawind life wurde im TP1 ein Datenmanagementsystem zur kontinuierlichen und periodisch fortgeführten Datenauswertung für große Datenbestände (Big Data) entworfen und realisiert. Anhand von Performanceuntersuchungen konnte eine Verkürzung der Rechenzeit um den Faktor 10 in einem Rechencluster erreicht werden. Unter Anwendung einer Datenpipeline nach dem Publish/Subscribe Prinzip wird eine skalierbare Datenschnittstelle für Monitoringdaten vorgeschlagen.
This work describes a vibration-based structural health monitoring of a prestressed-concrete box girder bridge on the A100 Highway in Berlin by applying statistical pattern recognition technique to a huge amount of data continuously collected by an integrated monitoring system during the period from 2000 to 2013. Firstly, the general condition and potential damage of the bridge is described. Then, the dynamic properties are extracted from 20 velocity sensors. Environmental variability captured by five thermal transducers and traffic intensity approximately estimated by strain measurements are also reported. Nonlinear influences of temperature on natural frequencies are observed. Subsequently, the measurements during the first year are used to build a baseline health index. The multiple linear regression (MLR) method is used to characterize the nonlinear relationship between natural frequencies and temperatures. The Euclidean distance of the residual errors is calculated to build a statistical health index. Finally, the indices extracted from the following years gradually deviate; which may indicate structural deterioration due to loss of prestress in the prestressed tendons.
Grouting is a universal repair and strengthening technique, which is constantly used for structural remediation of concrete components, trenches, mine subsidence, dam joints, restoration of masonry structures, and geological stabilizations. Having an extremely small particle size of only few microns, ultrafine cements are ideal for grouting applications due to their superior permeability and compressive strength properties of the hardened cement paste compared to that of the less-expensive, but coarser ordinary Portland cements. Supplementary cementitious materials (SCMs) are often used to replace ultrafine cement in order to modify certain properties and to reduce costs. The aim of this experimental study is to investigate the effect of three supplementary materials: microsilica (MS), fly ash (FA), and metakaolin (MK) on the workability, and mechanical properties of an ultrafine cement based grout with a constant water-binder ratio and constant superplasticizer content. Maximum percentages of replacement with ultrafine cement were 6% by volume of cement for MS and 16% for FA, and MK. In general, results suggest that the workability is improved by addition of FA, whereas is reduced, when modified with MS and MK. The compressive strength of grout after cement replacement remains comparable to that of pure cement grout. However, there is a tendency of the MS to positively affect the compressive strength opposite to FA, whereas flexural strength is positively affected by FA. Based on the results, it is evident that grouts with Hägerman cone flow more than 500 mm and compressive strength of more than 90 MPa after 28 days can be produced.
Messen im Bauwesen 2018
(2018)
Der Tagungsband zur 10. Fachtagung „Messen im Bauwesen“ enthält die Beiträge der Autoren zum diesjährigen Thema „Messtechnische Anwendungen und deren Einbindung in digitale Bauwerksmodelle“ enthält.
Building Information Modeling (BIM) ermöglicht einen integralen Entwurfs-, Ausführungs- und Instandsetzungsprozess und verspricht Bauwerke von höherer Qualität bei niedrigeren Kosten und kürzeren Projektlaufzeiten. Was BIM aber im konkreten Anwendungsfall bedeutet, ist generell noch Teil eines umfassenden Diskussionsprozesses, insbesondere für die Integration der Ergebnisse von Bauwerksmessungen aus der Ausführungs- und Betriebsphase.
Die diesjährige Ausgabe der Tagung „Messen im Bauwesen“ befasst sich schwerpunktmäßig mit verschiedenen Aspekten des BIM in der bestehenden Baupraxis, beschreibt Technologien hinter BIM und zeigt die vielfältigen Möglichkeiten eines Einsatzes von Messverfahren sowohl in der Bauausführung als auch beim Lebenszyklusmanagement von Bauwerken auf. Auf Basis dieser Schwerpunktsetzung möchten wir wieder aus der Sicht des Bauingenieurs und des Geodäten von Praxisbeispielen aus Hoch- und Tiefbau berichten.
Die Vorträge sind zusammengestellt mit Blick insbesondere auf Bau- und Vermessungsingenieure in Ingenieurbüros sowie der Verwaltung in den Bereichen Planung, Ausführung und Betrieb von Infrastrukturbauwerken.
Surface erosion of a cohesive granular soil by a fluid flow is investigated numerically by coupling the Lattice Boltzmann Method (LBM) for the fluid phase and the Discrete Element Method (DEM) for describing the motion of the solid particles. In addition, inter-particles cohesion is insured by a contact model featuring a paraboloidal yield surface. The use of a fully resolved LBM-DEM coupling technique is currently limited due to the computational cost when simulating a large number of particles. This issue can be overcome using the graphics processing unit (GPU) thanks to ist massively parallel hardware architecture. Here, we first present a 2D GPU implementation of LBM-DEM coupling for a granular assembly. The GPU implementations are approximatively 30 times faster than a single core CPU version. Then, we apply the parallelization technique to practical erosional cases, namely the jet erosion test (JET) and the shear-driven erosion by a Couette flow. These numerical tests aim to relate micro parameters of a cohesive material (eg. cohesion) to macro parameters (eg. soil erodibility, mechanical strengths). Preliminary results show that micromechanical features indeed provide a novel insight of soil erosion phenomena.
The local asymptotic approach is promising for vibration-based fault diagnosis when associated to a subspace-based residual function and efficient hypothesis testing tools. It has the ability of detecting small changes in some chosen system parameters. In the residual function, the left null space of the observability matrix associated to a reference model is confronted to the Hankel matrix of output covariances estimated from test data. When this left null space is not perfectly known from a model, it should be replaced by an estimate from data to avoid model errors in the residual computation. In this paper, the asymptotic distribution of the resulting data-driven residual is analyzed and its covariance is estimated, which includes also the covariance related to the reference null space estimate. The importance of including the covariance of the reference null space estimate is shown in a numerical study.
Grouting is a universal repair and strengthening technique, which is constantly used for structural remediation of concrete components, trenches, mine subsidence, dam joints, restoration of masonry structures, and geological stabilizations. Having an extremely small particle size of only few microns, ultrafine cements are ideal for grouting applications due to their superior permeability and compressive strength properties of the hardened cement paste compared to that of the less-expensive, but coarser ordinary Portland cements. Supplementary cementitious materials (SCMs) are often used to replace ultrafine cement in order to modify certain properties and to reduce costs. The aim of this experimental study is to investigate the effect of three supplementary materials: microsilica (MS), fly ash (FA), and metakaolin (MK) on the workability, and mechanical properties of an ultrafine cement based grout with a constant water-binder ratio and constant superplasticizer content. Maximum percentages of replacement with ultrafine cement were 6% by volume of cement for MS and 16% for FA, and MK. In general, results suggest that the workability is improved by addition of FA, whereas is reduced, when modified with MS and MK. The compressive strength of grout after cement replacement remains comparable to that of pure cement grout. However, there is a tendency of the MS to positively affect the compressive strength opposite to FA, whereas flexural strength is positively affected by FA. Based on the results, it is evident that grouts with Hägerman cone flow more than 500 mm and compressive strength of more than 90 MPa after 28 days can be produced.
Identifying optimal inspection and repair strategies for offshore jacket structures is a challenging task. We pre-sent an approach, which is based on recent developments in the field of risk-based operation and maintenance planning at the structural system level. The approach utilizes heuristics to define inspection and repair strate-gies at the system level and to reduce the search space of possible strategies. For each defined strategy, the expected service life cost of inspection, repair and failure is evaluated based on simulated inspection and re-pair histories. Subset simulation is applied to compute the conditional repair and failure probabilities required for this analysis. It also forms the basis for simulating inspection and repair histories. The strategy that mini-mizes the expected service life cost is the optimal one in the set of pre-selected strategies. The underlying condition and performance model accounts for the stochastic dependence among the deterioration states of the different structural elements and the structural redundancy. The approach is demonstrated in a case study considering a jacket-type frame. In this study, we essentially vary the inspection interval, the minimum num-ber of inspected components and the target reliability, and identify the combination that minimizes the ex-pected total service life cost.
Die Risikoanalyse ist ein formales Verfahren zur Unterstützung von Entscheidungen unter Unsicherheit und Risiko. Es ermöglicht eine Optimierung von Maßnahmen zur Verhinderung unerwünschter Konsequenzen. Der Vortrag stellt die aktuellen Aktivitäten an der BAM in dem Feld Risikoanalyse technischer System vor.
Identifying optimal inspection and repair strategies for offshore jacket structures is a challenging task. We pre-sent an approach, which is based on recent developments in the field of risk-based operation and maintenance planning at the structural system level. The approach utilizes heuristics to define inspection and repair strate-gies at the system level and to reduce the search space of possible strategies. For each defined strategy, the expected service life cost of inspection, repair and failure is evaluated based on simulated inspection and re-pair histories. Subset simulation is applied to compute the conditional repair and failure probabilities required for this analysis. It also forms the basis for simulating inspection and repair histories. The strategy that mini-mizes the expected service life cost is the optimal one in the set of pre-selected strategies. The underlying condition and performance model accounts for the stochastic dependence among the deterioration states of the different structural elements and the structural redundancy. The approach is demonstrated in a case study considering a jacket-type frame. In this study, we essentially vary the inspection interval, the minimum num-ber of inspected components and the target reliability, and identify the combination that minimizes the ex-pected total service life cost.
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.
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.
The local asymptotic approach is promising for vibration-based fault diagnosis when associated to a subspace-based residual function and efficient hypothesis testing tools. It has the ability of detecting small changes in some chosen system parameters. In the residual function,the left null space of the observability matrix associated to a reference model is confronted to the Hankel matrix of output covariances estimated from test data. When this left null space is not perfectly known from a model, it should be replaced by an estimate from data to avoid model errors in the residual computation. In this paper, the asymptotic distribution of the resulting data-driven residual is analyzed and its covariance is estimated, which includes also the covariance related to the reference null space estimate. The advantages of the data-driven residual are demonstrated in a numerical study, and the importance of including the covariance of the reference null space estimate is shown, which increases the detection Performance.
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.
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 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.
Repair is an indispensable part of the maintenance of structures over their lifetimes. Structural grouting is a widely used remediation technique for concrete components, trenches, mine subsidence, dam joints, restoration of masonry structures, and geological stabilizations. A structural grout system should be injectable in narrow spaces and hence include ingredients with finer particles. Ultrafine cements are ideal for these type of demanding grouts due to their superior properties compared to that of the less expensive, but coarser ordinary Portland cement (OPC). Supplementary cementitious materials (SCMs) are often used to replace OPC clinker based binder in order to modify certain properties and to reduce costs. The most commonly used SCMs are fly ash (FA), and ground granulated blast furnace slag (GGBS). For various special applications microsilica (MS), and metakaolin (MK) are also used. Identifying the optimum replacement contents of OPC by SCMs are a challenge during the design of such grouts. The aim of this experimental study is to investigate the effect of the selected SCMs (FA, MS and MK) on the slump flow, time of efflux, viscosity, shrinkage, and compressive and flexural strength of ultrafine cement based grouts with constant water-binder ratio and superplasticizer content. The test program was formulated using Box-Behnken design principles. Maximum percentages of replacement with ultrafine cement was 6% by volume of cement for MS and 16% for FA, and MK. The results suggest that most investigated grouts have the potential to be used for structural applications. The appropriate quadratic models are then formulated through statistical tools and presented as response surfaces. The trends indicate that fly ash improves the rheological properties, whereas microsilica and metakaolin positively affect shrinkage and mechanical properties to some extent. Based on the influence of SCMs and priorities among the properties, Decision Matrix Analysis (DMA) is carried out to select the most suitable ones among the SCMs. The analysis suggests that microsilica and fly ash are more suitable as SCMs than metakaolin without affecting the properties.
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.
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 Untergrundsteifigkeit zu berücksichtigen? Als Referenzsituation ohne Minderungsmaßnahme? Der Beitrag bringt Rechenergebnisse zu abgefederten Gebäuden mit einfachen und komplexen (FE-) Modellen, Mess- und Rechenergebnisse zur Schwingungsübertragung von unabgefederten 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 Gebäudeparametern zur Reduktion der Deckenschwingungen. Den Ergebnissen bei der Erschütterungs-übertragung in Gebäude werden zwei ähnliche Beispiele zur elastischen Maschinenlagerung und zur elastischen Gleislagerung gegenübergestellt.
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 Minderungsma߬nahme? 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)
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.