7.2 Ingenieurbau
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- Wind energy (2)
- Wind turbine tower (2)
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- Zuggeschwindigkeit (2)
- Zuverlässigkeit (2)
- 3D imaging (1)
- Achsimpulse (1)
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- Amplituden-Abstands-Gesetze (1)
- Analytical Design Methods (1)
- Asphalt (1)
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- Asymptotic local approach (1)
- Automated Modal Analysis for Tracking Structural Change during Construction and Operation Phases (1)
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- 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)
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- Baugrunddynamik (1)
- Bauwerk-Boden-Wechselwirkung (1)
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- Cement-based composites (1)
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- Civil structures (1)
- Climate Chamber (1)
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- Cohesive soils (1)
- Column/wall resonance (1)
- Combined finite-element boundary-element method (1)
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- Cyclic axial shearing (1)
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- DEM-LBM simulation (1)
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- Digital Models (1)
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- Discrete element method (1)
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- Drop Tests (1)
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- EERA Joint Program (1)
- Earth (1)
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- Einflusslinie (1)
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- Estimation (1)
- FEM (1)
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- Fahrzeug-Fahrweg-Boden-Wechselwirkung (1)
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- Fatigue strength (1)
- Fault detectionchanging (1)
- Features (1)
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- Finite element (1)
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- Finite element method (1)
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- Finite-element boundary-element method (1)
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- Flexible car body (1)
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- Floor resonance (1)
- Floors (1)
- Fluid-structure interaction (1)
- Footbridge (1)
- Force reconstruction (1)
- Foundation Pile (1)
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- Freileitung (1)
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- GMNIA (1)
- GNSS (1)
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- GPU Parallel computing (1)
- GPU parallelisation (1)
- Gebäudelagerung (1)
- Gebäudemodelle (1)
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- Geomechanics of offshore foundations (1)
- Geometric vehicle and track irregularities (1)
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- Global ambient vibrations (1)
- Granular Cohesive Materials (1)
- Granular Cohesive Materials, (1)
- Granular cohesion (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)
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- Inertial interaction (1)
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- Interface model (1)
- Jet impingement (1)
- Kinematic Interaction (1)
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- Kraft auf den Boden (1)
- LBM-DEM coupling (1)
- LBM-DEM simulation (1)
- Laminar flow (1)
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- Large components (1)
- Lateral dynamic displacement (1)
- Lateral load bearing (1)
- Lattice Boltzmann Method (1)
- Lattice Boltzmann method (1)
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- Long-span bridge (1)
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- Modulus of elasticity (1)
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- Monopile (1)
- Monopile Buckling (1)
- Monopile installation risks (1)
- Movin load test (1)
- Multi-beam method (1)
- Multi-beam track model (1)
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- Nachgiebigkeiten (1)
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- Obstacles (1)
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- Office building (1)
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- Offshore Wind (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 (1)
- Offshore wind-turbine foundations (1)
- Offshore-Wind (1)
- Operational modal analysis (1)
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- Optimierungsmethoden (1)
- Optimization techniques (1)
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- Quasi-static response; (1)
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- Sicherheit (1)
- Simple and fast prediction (1)
- Simple prediction (1)
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- Soft track elements (1)
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- Stability Buckling soil-structure-interaction piles offshore (1)
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- State of stress (1)
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- Stress-strain relation (1)
- Stress–strain-relation (1)
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- 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)
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- Vibration excitation (1)
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- Wind Energy Structures (1)
- Wind energy tower (1)
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- Wind-farm aerodynamics (1)
- Windenergieanlage (1)
- Windfarm wake analysis (1)
- Workability (1)
- Zerstreute Achsimpulse (1)
- building information modelling (1)
- elastische Gebäudelagerungen (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)
- zerstreute Achslastimpulse (1)
- Übertragungsmatrizen (1)
- Überwachung (1)
Organisationseinheit der BAM
- 7.2 Ingenieurbau (326) (entfernen)
Paper des Monats
- ja (4)
The new crack luminescence method offers the possibility of making fatigue surface cracks in metallic materials more visible during inspections through a special coating system. This coating system consists of two layers, whereby the first layer has fluorescent properties and emits visible light as soon as it is irradiated by UV light. The top layer is black and is designed to prevent the fluorescent layer from emitting if no crack develops in the underlying material. The technique proved particularly useful in a wide variety of fatigue tests of steel components under laboratory conditions. Moreover, it has the potential to be used in various industrial applications. To enable industrial deployment and integration into maintenance strategies, a concept study is developed in this contribution, resulting in a qualification framework that can serve as a foundation for determining the reliability of the crack luminescence system in terms of a probability of detection curve. Within this study, factors causing measurement variability and uncertainty are being determined and their influences assessed. Due to the extension of the system by a moving computer vision system for automated crack detection using artificial intelligence, additional long-term effects associated with structural health monitoring systems need to be incorporated into an extended probability of detection study as part of the technical justification. Finally, important aspects and findings related to design of experiments are discussed, and a framework for reliability assessment of a new optical crack monitoring method is presented, emphasizing the influence of various uncertainty parameters, including long-term effects such as system ageing.
The new crack luminescence method offers the possibility of making fatigue surface cracks in metallic materials more visible during inspections through a special coating system. This coating system consists of two layers, whereby the first layer has fluorescent properties and emits visible light as soon as it is irradiated by UV light. The top layer is black and is designed to prevent the fluorescent layer from emitting if no crack develops in the underlying material.
The technique proved particularly useful in a wide variety of fatigue tests of steel components under laboratory conditions. Moreover, it has the potential to be used in various industrial applications. To enable industrial deployment and integration into maintenance strategies, a concept study is developed in this contribution, resulting in a qualification framework that can serve as a foundation for determining the reliability of the crack luminescence system in terms of a probability of detection curve. Within this study, factors causing measurement variability and uncertainty are being determined and their influences assessed. Due to the extension of the system by a moving computer vision system for automated crack detection using artificial intelligence, additional long-term effects associated with structural health monitoring systems need to be incorporated into an extended probability of detection study as part of the technical justification.
Finally, important aspects and findings related to design of experiments are discussed, and a framework for reliability assessment of a new optical crack monitoring method is presented, emphasizing the influence of various uncertainty parameters, including long-term effects such as system ageing.
Almost all building materials in civil engineering have an open porosity and interact with or are affected by the environmental conditions. Structures might suffer from effects such as moisture adsorption, carbonation, corrosion, penetration of salt ions and chemical substances, etc. In the hygroscopic range, these processes are mostly driven by diffusion. Due to the confinement of small pores (< 1 µm), the Knudsen effect reduces the molecular diffusion. This reduction can become more significant in case of temporal changing pore systems because of physisorption of water vapor, carbonation, or chemisorption.
In this study, unstabilised earth blocks and earth masonry are investigated. In a first step, the pore size distribution of the blocks is measured and sorption isotherms are recorded in experiments. Besides the ordinary physisorption, the involved clay minerals undergo swelling or shrinking due to chemisorption. The following two effects must be considered: first, the reduction of the available pore space by the adsorbed water layer. For this, the Hillerborg sorption theory is used, which is a combination of the well-known Brunauer-Emmett-Teller sorption theory and the Kelvin equation. This allows the computation of adsorbed water layers even in curved pore geometries. Second, the variation of the initial pore size distribution due to chemisorption needs to be modelled. Based on these two models, the effective diffusion coefficient can be predicted. For validation, arrays of relative humidity sensors were embedded into a free-standing earth masonry wall. This monitoring was carried out over more than a year to have a broad variety of environmental conditions and was located in Berlin, Germany.
The prediction of the effective diffusion coefficient can also be transferred to other processes and allows the investigation of materials having temporarily changing pore systems. Examples are the carbonation of cementitious materials, alkali silica reaction, calcium leaching of long-lasting structures, etc. This effect becomes most prominent in the meso-pore range and might alter the effective diffusion coefficient by more than 100 %.
Almost all building materials in civil engineering have an open porosity and interact with or are affected by the environmental conditions. Structures might suffer from effects such as moisture adsorption, carbonation, corrosion, penetration of salt ions and chemical substances, etc. In the hygroscopic range, these processes are mostly driven by diffusion. Due to the confinement of small pores ( 1 m), the Knudsen effect reduces the molecular diffusion. This reduction can become more significant in case of temporal changing pore systems because of physisorption of water vapor, carbonation, or chemisorption.
In this study, unstabilised earth blocks and earth masonry are investigated. In a first step, the pore size distribution of the blocks is measured and sorption isotherms are recorded in experiments. Besides the ordinary physisorption, the involved clay minerals undergo swelling or shrinking due to chemisorption. The following two effects must be considered: first, the reduction of the available pore space by the adsorbed water layer. For this, the Hillerborg sorption theory is used, which is a combination of the well-known Brunauer-Emmett-Teller sorption theory and the Kelvin equation. This allows the computation of adsorbed water layers even in curved pore geometries. Second, the variation of the initial pore size distribution due to chemisorption needs to be modelled. Based on these two models, the effective diffusion coefficient can be predicted. For validation, arrays of relative humidity sensors were embedded into a free-standing earth masonry wall. This monitoring was carried out over more than a year to have a broad variety of environmental conditions and was located in Berlin, Germany.
The prediction of the effective diffusion coefficient can also be transferred to other processes and allows the investigation of materials having temporarily changing pore systems. Examples are the carbonation of cementitious materials, alkali silica reaction, calcium leaching of long-lasting structures, etc. This effect becomes most prominent in the meso-pore range and might alter the effective diffusion coefficient by more than 100 %.
The soil-foundation-structure interaction is always important when building vibrations due to train passages have to be considered. The frequency range for train vibrations is up to 100 Hz. Normally, soft surface soils are crucial so that the wavelength can be much smaller than the foundation dimensions. Three topics are of interest for the prediction and the under-standing of building vibrations. 1. The „kinematic interaction“ or the „added foundation ef-fect“, which is calculated either by the combined boundary-element finite-element method or by the wavenumber domain method, results in a reduction of the free-field vibration. The stiff-ness of the foundation resists the wave deformation, plates and walls for horizontally propa-gating waves or piles for vertically incident waves. 2. The „inertial interaction“ or the „added building effect“ yields an amplification around the vertical building resonance, which may be a rigid mode on the compliant soil or a flexible mode for high-rise buildings, and a reduction at higher frequencies. This has been analysed by detailed finite element models of apartment and office buildings. 3. Base isolation is a method to further reduce building vibrations. It is important to know the soil-foundation impedance for the possible reduction, as well as the correct building impedance. A high-rise building cannot be considered as a rigid mass model. It has a frequency-dependent behaviour with longitudinal waves travelling from the founda-tion to the top of the building which include the effect of floor vibrations. Experiences from building projects in Vienna, Frankfort and Berlin will give some additional results for the ex-citation from tunnel lines, the kinematic response of pile foundations, and the inertial re-sponse of the flexible multi-storey buildings.
The resonances of railway bridges have often been analysed for short bridges under periodical high-speed trains, for simply supported one-span bridges, for the fundamental bridge mode, and by time-domain analyses. Many time-consuming calculations have been performed to establish simplified rules for standards. In this contribution, the passage of different (existing, new and hypothetic) trains over different bridges will be analysed in frequency domain by using three separated spectra with the purpose to get a better physical insight in the phenomena. At first, the excitation spectrum of the modal forces is built by the mode shape and the passage time of the train over the bridge. The second spectrum is the frequency response function of the bridge which include the modal frequency, damping and mass. The third part is the spectrum of the axle sequence of an arbitrary train which is not limited to periodical or specific (conventional, articulated, regular or standard) trains and which does not include any bridge parameters. The final solution in frequency domain is obtained as the product of these three complex, strongly varying spectra for the dominating bridge mode or in general as the sum of these products over all relevant bridge modes. The time domain solution is obtained via the inverse Fourier transform, and the resulting time histories have been successfully compared with some measurement results. The method is applied to the vertical and torsional modes of a mid-long 1-span bridge on elastomeric bearings under standard train speeds, and to a long multi-span integral bridge under long periodical freight trains. Different resonance and cancellation effects have been found for systematically varied train speeds according to the axle sequence of the whole train which is dominated by the two locomotives in that case. To be more specific, the first torsional mode of the mid-span bridge is excited for a train speed of 100 km/h whereas the second bending mode is excited for a train speed of 160 km/h. In both cases, the other mode is suppressed by the minima of the axle-distance spectra. In addition, the case of the German high-speed train ICE4 and the very high-speed hyperloop case will be discussed briefly. In general, it is shown that resonance effects are also worth to be studied for freight and passenger trains with lower speeds.
Train-induced ground vibrations – The emission and transmission from tunnel and surface lines
(2023)
Train-induced ground vibrations are quite different for tunnel and surface lines. The excitation of the track and ground vibration by the vehicle-track-soil interaction maybe influenced by the stiffer track support of the tunnel invert. The excited waves are propagating on a different path compared to the surface line. The wave propagation in the interior of the soil is calculated by a wavenumber integral in a similar way as the propagation along the surface and a general reduction of < 0.5 has been found. An additional reduction has been found because of the missing Rayleigh wave. The different excitation of tunnel lines is analysed theoretically by the combined finite-element boundary-element method and some results about the influencing tunnel and soil parameters will be shown. Measurements have been made at the Mühlberg-Tunnel in Germany. The vibrations of the train, the track and the soil have been measured simultaneously at the tunnel and a nearby surface line. Spectra will be shown for different train speeds between 60 and 160 km/h. A clear reduction effect for the tunnel line compared to the surface line has been observed in a specific (train-speed-dependent) frequency range. This agrees well with the observations of other research institutes. The mid-frequency tunnel-surface reduction seems to be a consequence of the stiffer track structure which leads to a wider distribution of the axle loads. Therefore, the axle impulses due to the train passage are longer and have a lower frequency content. This will have an effect on the ground vibrations at some distance which are present in case of an irregular transmission path through a ballast and soil with varying stiffness. A similar reduction effect can also be found for other track forms where the axle impulses are distributed on a longer track segment, for example slab tracks, tracks with under ballast plates, under ballast mats or under sleeper pads.
The reduction in train-induced ground vibrations by different railway lines and by mitigation measures in the propagation path was analysed in a unified approach by two-dimensional finite element calculations. In general, there was no reduction at low frequencies, and the reduction be-came stronger with increasing frequencies. A maximum reduction of 0.1 at high frequencies was established with an open trench. Reductions between 0.7 and 0.2 have been found for the other sit-uations, filled trenches, walls, plates, and blocks, as well as for railway lines on dams, in cuts and in a tunnel. Bridges can produce amplifications due to their resonance frequencies, but also strong reductions due to massive bridge piers. The influence of some parameters has been analysed, such as the bridge span, the inclination of the dam and the cut, the stiffness of the soil, and the tunnel structure. The dynamic track stiffnesses of a surface, bridge, and tunnel track have been calculated using the 3D finite-element boundary-element method for comparison with corresponding meas-urements.
The soil-foundation-structure interaction is always important when building vibrations due to train passages have to be considered. The frequency range for train vibrations is up to 100 Hz. Normally, soft surface soils are crucial so that the wavelength can be much smaller than the foundation dimensions. Three topics are of interest for the prediction and the under-standing of building vibrations. 1. The „kinematic interaction“ or the „added foundation ef-fect“, which is calculated either by the combined boundary-element finite-element method or by the wavenumber domain method, results in a reduction of the free-field vibration. The stiff-ness of the foundation resists the wave deformation, plates and walls for horizontally propa-gating waves or piles for vertically incident waves. 2. The „inertial interaction“ or the „added building effect“ yields an amplification around the vertical building resonance, which may be a rigid mode on the compliant soil or a flexible mode for high-rise buildings, and a reduction at higher frequencies. This has been analysed by detailed finite element models of apartment and office buildings. 3. Base isolation is a method to further reduce building vibrations. It is important to know the soil-foundation impedance for the possible reduction, as well as the correct building impedance. A high-rise building cannot be considered as a rigid mass model. It has a frequency-dependent behaviour with longitudinal waves travelling from the founda-tion to the top of the building which include the effect of floor vibrations. Experiences from building projects in Vienna, Frankfort and Berlin will give some additional results for the ex-citation from tunnel lines, the kinematic response of pile foundations, and the inertial re-sponse of the flexible multi-storey buildings.
The resonances of railway bridges have often been analysed for short bridges under periodical high-speed trains, for simply supported one-span bridges, for the fundamental bridge mode, and by time-domain analyses. Many time-consuming calculations have been performed to establish simplified rules for standards. In this contribution, the passage of different (existing, new and hypothetic) trains over different bridges will be analysed in frequency domain by using three separated spectra with the purpose to get a better physical insight in the phenomena. At first, the excitation spectrum of the modal forces is built by the mode shape and the passage time of the train over the bridge. The second spectrum is the frequency response function of the bridge which include the modal frequency, damping and mass. The third part is the spectrum of the axle sequence of an arbitrary train which is not limited to periodical or specific (conventional, articulated, regular or standard) trains and which does not include any bridge parameters. The final solution in frequency domain is obtained as the product of these three complex, strongly varying spectra for the dominating bridge mode or in general as the sum of these products over all relevant bridge modes. The time domain solution is obtained via the inverse Fourier transform, and the resulting time histories have been successfully compared with some measurement results. The method is applied to the vertical and torsional modes of a mid-long 1-span bridge on elastomeric bearings under standard train speeds, and to a long multi-span integral bridge under long periodical freight trains. Different resonance and cancellation effects have been found for systematically varied train speeds according to the axle sequence of the whole train which is dominated by the two locomotives in that case. To be more specific, the first torsional mode of the mid-span bridge is excited for a train speed of 100 km/h whereas the second bending mode is excited for a train speed of 160 km/h. In both cases, the other mode is suppressed by the minima of the axle-distance spectra. In addition, the case of the German high-speed train ICE4 and the very high-speed hyperloop case will be discussed briefly. In general, it is shown that resonance effects are also worth to be studied for freight and passenger trains with lower speeds.