7.2 Ingenieurbau
Filtern
Erscheinungsjahr
- 2018 (40) (entfernen)
Dokumenttyp
- Vortrag (20)
- Beitrag zu einem Tagungsband (10)
- Posterpräsentation (4)
- Zeitschriftenartikel (3)
- Buchkapitel (1)
- Beitrag zu einem Sammelband (1)
- Dissertation (1)
Sprache
- Englisch (40) (entfernen)
Schlagworte
- Repair (4)
- Box-Behnken (3)
- Fatigue (3)
- Grouting (3)
- Interface (3)
- Statistical tests (3)
- Acoustic emission testing (2)
- Amplitude-charge weight laws (2)
- Amplitude-distance laws (2)
- Analysis of variance (2)
- Compressive cyclic loading (2)
- Compressive strength (2)
- Cracks (2)
- DUCON® (2)
- Ductility (2)
- E-modulus (2)
- Energy (2)
- Explosion-induced ground vibrations (2)
- Fault detection (2)
- Grouted Connection (2)
- Hammer impact (2)
- High-strength concrete (2)
- Impact (2)
- Micro-reinforcement (2)
- Mix design (2)
- Mobile elements (2)
- Non-destructive testing (2)
- Numerical model (2)
- Numerical modeling (2)
- Numerical modelling (2)
- Offshore (2)
- Prediction of explosion induced ground and building vibration (2)
- Quasi-static and dynamic tests (2)
- Rehabilitation (2)
- Residual evaluation (2)
- SHM (2)
- Size effect (2)
- Slab track (2)
- Slenderness effect (2)
- Soil properties (2)
- Soil-structure interaction (2)
- Stereo photogrammetry (2)
- Structural health monitoring (2)
- Supplementary cementitious materials (2)
- Track damage (2)
- UHPC (2)
- Ultrasonic testing (2)
- Uncertainty in reference (2)
- Vibration measurements (2)
- 3D imaging (1)
- Ballast track (1)
- Beanspruchungszustand (1)
- Boundary element method (1)
- Bridge (1)
- Cohesive soils (1)
- Compaction Grouting (1)
- Compaction grouting (1)
- Conductor (1)
- Crack detection (1)
- Crack repair (1)
- Cyclic axial shearing (1)
- DEM-LBM simulation (1)
- Damage detection (1)
- Decision matrix analysis (1)
- Design (1)
- Design methods (1)
- Design practice (1)
- Digital Image Correlation (1)
- Digital Image Correlation (DIC) (1)
- Environmental (1)
- Environmental changes (1)
- Erosion (1)
- Erosion of cohesive soils (1)
- Features (1)
- Finite element model updating (1)
- Finite-Elemente-Modellkalibrierung (1)
- Fly ash (1)
- Freileitung (1)
- GPA (1)
- GPU parallelisation (1)
- Geology (1)
- Geomechanics (1)
- Geomechanics of offshore foundations (1)
- Ground vibration measurements (1)
- Grout (1)
- Grout Injection (1)
- HTLS (1)
- Inspection planning (1)
- Interface model (1)
- Jet erosion test (1)
- LBM-DEM simulation (1)
- Laminography (1)
- Load bearing behaviour (1)
- Material Point Method (1)
- Material Point Method (MPM) (1)
- Material model (1)
- Metakaolin (1)
- Microfine cement (1)
- Micromechanical LBM-DEM simulation (1)
- Microsilica (1)
- Mixed formulation (1)
- Offshore Pile Foundation (1)
- Offshore pile foundation (1)
- Offshore pile foundations (1)
- Offshore wind energy (1)
- Offshore wind farms (1)
- Optimierungsmethoden (1)
- Optimization techniques (1)
- Physical phenomenology (1)
- Piaui state (1)
- Pile Capacity (1)
- Pile foundations (1)
- Pressure (1)
- Recovery experiments (1)
- Reinforced concrete (1)
- Reliability (1)
- Risk (1)
- Sandstone (1)
- Santa-marta (1)
- Schwingungsmessungen (1)
- Serra da cangalha (1)
- Shearing (1)
- Shrinkage (1)
- Soil erosion (1)
- Soil-pile interaction (1)
- State of stress (1)
- Statistical pattern recognition (1)
- Steel structures (1)
- Strength (1)
- Subspace methods (1)
- Subspace-based method (1)
- TOP (1)
- Temperature effect (1)
- Track vibration (1)
- Train configuration (1)
- Train passage (1)
- Train passages (1)
- Tran speed (1)
- Truss structures (1)
- Vibration measurement (1)
- Vibrations (1)
- Viscosity (1)
- Wave-Tower interaction (1)
- Windfarm wake analysis (1)
- Workability (1)
- fachwerkartige Stahltragwerken (1)
- temperature (1)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (40) (entfernen)
Eingeladener Vortrag
- nein (20)
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.
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.
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).