Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (19)
- Beitrag zu einem Tagungsband (16)
- Vortrag (9)
- Forschungsdatensatz (5)
- Buchkapitel (3)
- Posterpräsentation (2)
- Beitrag zu einem Sammelband (1)
Sprache
- Englisch (55) (entfernen)
Schlagworte
- Non-destructive testing (17)
- Validation (11)
- NDT (10)
- Nondestructive testing (10)
- Air-coupled ultrasound (9)
- Bridge (8)
- Ultrasonic (8)
- Ultrasound (8)
- Concrete (7)
- Fluidics (6)
- Civil engineering (5)
- Measurement uncertainty (5)
- Reliability (5)
- Zerstörungsfreie Prüfung (5)
- Existing structures (4)
- Aeroacoustics (3)
- Concrete bridges (3)
- LiDAR (3)
- Non destructive testing and evaluation (3)
- Reconstruction algorithm (3)
- Acoustic-flow interaction (2)
- Assessment (2)
- Bistable amplifier (2)
- Bridge inspection (2)
- Corrosion (2)
- Durability assessment (2)
- Elastic wave (2)
- Ground penetrating radar (2)
- Laser Doppler vibrometer (2)
- Measurement (2)
- Procedure (2)
- Pulse echo method (2)
- Quality assurance (2)
- Reassessment (2)
- Reconstruction (2)
- Reference material (2)
- Reference specimen (2)
- Structural safety (2)
- Synthetic Aperture Focusing Technique (2)
- Tendon duct (2)
- Acousto-optic effect (1)
- Akaike information criterion picker (1)
- Bandgap quenching (1)
- Bauwesen (1)
- Bituminous material (1)
- Brücken (1)
- Building materials (1)
- Coda wave (1)
- Compressive Concrete Strength (1)
- Compressive concrete strength (1)
- Concrete Bridge (1)
- Concrete structures (1)
- Elastic reverse time migration (1)
- Elastic waves (1)
- Existing Concrete Structures (1)
- Existing bridges (1)
- Existing structure (1)
- Fluidic devices (1)
- Fluidic oscillators (1)
- Frequency modulation (1)
- Ground penetrating radar (GPR) (1)
- Harsh environment (1)
- Hilbert transform (1)
- Honeycomb (1)
- Horizontally polarized shear waves (1)
- Impact Echo (1)
- In-air ranging (1)
- Interlaboratory comparison (1)
- Istzustandserfassung (1)
- Kiesnest (1)
- Laserscanner (1)
- Life management (1)
- MIMO (1)
- Measurement Uncertainty (1)
- Metamaterial (1)
- Monitoring (1)
- Non-Destructive Testing (1)
- Non-Destructive Testing (NDT) (1)
- Non-destructive testing (NDT) (1)
- Non-destructive testing in civil engineering (1)
- Nuclear structures (1)
- Partial safety factor modification (1)
- Piezoelectric transducer (1)
- Prestressed concrete (1)
- Probabilistic (1)
- Probabilistic methods (1)
- Probabilistic reassessment (1)
- Probability of detection (1)
- Probability of detection (POD) (1)
- Puls-echo method (1)
- Pulse compression (1)
- Pulse echo technique (1)
- Pulse-echo method (1)
- Pulse-echo technique (1)
- Rebound Hammer (1)
- Rebound hammer (1)
- Rebound number (1)
- Reference data (1)
- Refracto-vibrometry (1)
- Reliability assessment (1)
- Road inspection (1)
- SAFT (1)
- Signal processing (1)
- Simulation (1)
- Sonic crystal (1)
- State-of-the-art (1)
- Stochastic modeling (1)
- Structural health monitoring (1)
- Synthetic aperture focusing technique (1)
- Time of flight (1)
- Time-of-flight measurements (1)
- Ultra sound (1)
- Ultraschall (1)
- Ultrasonic Echo (1)
- Ultrasonic Pulse Velocity (1)
- Ultrasonic echo (1)
- Ultrasonic echo technique (1)
- Ultrasonic pulse velocity (1)
- Ultrasonic tomography (1)
- Ultrasonic transducer (1)
- Uncertainty (1)
- Wave propagation (1)
- Zerstörungsfreie Prüfung im Bauwesen (1)
- ground penetrating radar (1)
- nuclear structures (1)
- ultrasonic (1)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (9)
The dataset presented contains ultrasonic data recorded in pulse echo mode. The investigated specimen is made of the isotropic homogeneous material polyamide and has a drill hole of constant diameter running parallel to the surface, which was scanned in a point grid using an automatic scanner system. At each measuring position, a pitch-catch measurement was performed using a sampling rate of 2 MHz. The probes used are arrays consisting of a spatially separated receiving and in-phase transmitting unit. The transmitting and receiving sides each consist of 12 point-shaped single probes. These dry-point contact (DPC) probes operate according to the piezoelectric principle at nominal frequencies of 55 kHz (shear waves) and 100 kHz (longitudinal waves), respectively, and do not require a coupling medium. The measurements are performed with longitudinal (100 kHz) and transverse (55 kHz) waves with different geometric orientations of the probe on the measurement surface. The data presented in the article provide a valid source for evaluating reconstruction algorithms for imaging in the low-frequency ultrasound range.
Development of an Accurate and Robust Air-Coupled Ultrasonic Time-of-Flight Measurement Technique
(2022)
Ultrasonic time-of-flight (ToF) measurements enable the non-destructive characterization of material parameters as well as the reconstruction of scatterers inside a specimen. The time-consuming and potentially damaging procedure of applying a liquid couplant between specimen and transducer can be avoided by using air-coupled ultrasound. However, to obtain accurate ToF results, the waveform and travel time of the acoustic signal through the air, which are influenced by the ambient conditions, need to be considered. The placement of microphones as signal receivers is restricted to locations where they do not affect the sound field. This study presents a novel method for in-air ranging and ToF determination that is non-invasive and robust to changing ambient conditions or waveform variations. The in-air travel time was determined by utilizing the azimuthal directivity of a laser Doppler vibrometer operated in refracto-vibrometry (RV) mode. The time of entry of the acoustic signal was determined using the autocorrelation of the RV signal. The same signal was further used as a reference for determining the ToF through the specimen in transmission mode via cross-correlation. The derived signal processing procedure was verified in experiments on a polyamide specimen. Here, a ranging accuracy of <0.1 mm and a transmission ToF accuracy of 0.3μs were achieved. Thus, the proposed method enables fast and accurate non-invasive ToF measurements that do not require knowledge about transducer characteristics or ambient conditions.
Corrosion of concrete reinforcement is one of the major damage mechanisms affecting both the load-bearing capacity and the serviceability of re-inforced concrete structures significantly. When externally discernible damages are observed during visual inspections on the structure, the extent of the damage inside the concrete is often already significant. Corrosion caused by carbonation often leads to severe discoloration of the surface or even large-area spalling of the concrete cover. In contrast, chloride-induced corrosion is usually difficult to observe visually but can cause much more serious damage in less time. The effect occurs locally and can lead to weakening of the cross-section of the reinforce-ment. This, in turn, can cause sudden structural collapses without prior notice.
In the meanwhile, various non-destructive and minimally invasive testing methods are available to evaluate the resistance to penetration of corrosion-pro-moting pollutants and to detect active corrosion. In this paper, a bridge crossing the river Regen is used as a case-study to demonstrate how the information ob-tained applying different testing methods can be combined and evaluated in the context of structural reassessments. Both the results of the permeability testing and the electrical resistance measurement are considered, as well as active corro-sion areas are localized using the half-cell potential mapping combined with the concrete cover measurement with the eddy current method and ground penetrat-ing radar. The results are evaluated using drill cores and in addition laser-induced breakdown spectroscopy was applied to obtain information about possible chlo-ride ion transport into the concrete.
"The reassessment of bridges continues to take great importance both nationally and internationally. A major challenge is to find computation models reflecting the actual properties of the considered structures sufficiently accurate. Besides regular inspections, the conduction of advanced measurements is suitable to generate reliable information about a structure to be assessed. Prior to incorporating measurement results in reassessment, the relevance, the trueness, and the precision of the measured information needs to be stated. On the one hand, the use of information whose quality has not been assessed can lead to errors with serious consequences. On the other, the measurement of irrelevant information is inefficient. Although the use of measured data in assessment is currently mostly unregulated, their appreciation in reliability analyses is beneficial since the built environment can be assessed more realistically. Utilizing NDT in reassessment has the potential to extend remaining lifetimes of a structure, save resources, and improve infrastructural availabilities. The power of judgment regarding the decision on the reliability of an existing structure can be increased.
In this contribution, an approach is outlined to process non-destructively gathered measurement data in a comparableway in order to include themeasured information in probabilistic reliability assessments of existing structures. An essential part is the calculation of measurement uncertainties. The effect of incorporating evaluated NDT-results is demonstrated by means of a prestressed concrete bridge and GPR measurements conducted on this bridge as a case-study. The bridge is assessed regarding SLS Decompression using the NDT-results."
Making optimal decisions about the reliability of existing structures requires that the information used in assessment adequately represents the properties and the condition of the structures. The knowledge gap regarding a structure to be assessed can be successively filled by individually purposeful observations on site. This paper gives an overview of an approach for utilizing nondestructively gathered measurement results in reliability assessment of existing structures. An essential part of measurement-based stochastic modeling of basic variables is the calculation of measurement uncertainties, which serves to establish confidence in measurement, to ensure the comparability of unambiguously expressed measurement results, and to quantify the quality of the measured information. Regarding the current discourse on how to treat information collected on-site in the context of assessment, the authors recommend that measurement uncertainty becomes an uncertainty component mandatorily to be represented in measurement-based stochastic models. The main steps of the proposed concept are presented, and the advantages of its application are emphasized by means of a prestressed concrete bridge as case study. The bridge is assessed regarding the serviceability limit state decompression using ultrasonic and radar data measured at the structure.
Each engineering decision is based on a number of more or less accurate information. In assessment of existing structures, additional relevant information collected with on-site inspections facilitate better decisions. However, observed data basically represents the physical characteristic of interest with an uncertainty. This uncertainty is a measure of the inspection quality and can be quantified by expressing the measurement uncertainty. The internationally accepted rules for calculating measurement uncertainty are well established and can be applied straightforwardly in many practical cases. Nevertheless, the calculations require the occasionally time-consuming development of an individually suitable measurement model. This contribution attempts to emphasize proposals for modelling the non-destructive depth measurement of tendons in concrete using the ultrasonic echo technique. The proposed model can serve as guideline for the determination of the quality of the measured information in future comparable inspection scenarios.
Existing concrete structures were usually designed for lifetimes of several decades. The current and urgently required efforts to increase sustainability and protect the environment will likely result in extended service lives up to 100 years. To achieve such objectives, it is required to assess structures over their entire lifecycles. Non-destructive testing (NDT) methods can reliably support the assessment of existing structures during the construction, operational, and decommissioning phases. One of the most important and safety-relevant components of a prestressed concrete structure are the tendons. NDT methods such as the ultrasonic echo method are suitable for both the detection and the localization of the tendons, i.e., the measurement of their geometrical position inside the component. The uniqueness of structures, concrete heterogeneity, and varying amounts of secondary components such as the reinforcement represent obstacles in the application of these methods in practice. The aim of this contribution is to demonstrate a practicable procedure, that can be used in the field to determine the parameters required for the measuring data analysis without extensive knowledge about the investigated components. For this purpose, a polyamide reference specimen is used to show which steps are required to obtain reliable imaging information on the position of tendons from the measurement data. The procedure is then demonstrated on a concrete test specimen that covers various relevant and practice-oriented test scenarios, such as varying tendon depths and component thicknesses.
The acquisition and appropriate processing of relevant information about the considered system remains a major challenge in assessment of existing structures. Both the values and the validity of computed results such as failure probabilities essentially depend on the quantity and quality of the incorporated knowledge. One source of information are onsite measurements of structural or material characteristics to be modeled as basic variables in reliability assessment. The explicit use of (quantitative) measurement results in assessment requires the quantification of the quality of the measured information, i.e., the uncertainty associated with the information acquisition and processing. This uncertainty can be referred to as measurement uncertainty. Another crucial aspect is to ensure the comparability of the measurement results.This contribution attempts to outline the necessity and the advantages of measurement uncertainty calculations in modeling of measurement data-based random variables to be included in reliability assessment. It is shown, how measured data representing time-invariant characteristics, in this case non-destructively measured inner geometrical dimensions, can be transferred into measurement results that are both comparable and quality-evaluated. The calculations are based on the rules provided in the guide to the expression of uncertainty in measurement (GUM). The GUM-framework is internationally accepted in metrology and can serve as starting point for the appropriate processing of measured data to be used in assessment. In conclusion, the effects of incorporating the non-destructively measured data into reliability analysis are presented using a prestressed concrete bridge as case-study.
Increasing requirements on the infrastructure caused by more and heavier traffic coincide with both the aging and the progressive degradation of bridge constructions. These exemplary issues lead to a non-negligible need for reassessments of existing bridges. Compared to the new building design, safety reserves can be used in the evaluation of such existing structures, since uncertainties that may arise during the design, construction and previous Service time are better known or no longer present. Uncertainties can be evaiuated more precisely by measurements. In the meantime, the application of advanced NDT-methods on concrete structures have become so capable, that crucial structure Parameters like certain material properties or geometrical dimensions can be quantified without significant destructive interventions. The measured data can be explicitly incorporated into the probabilistic computation models used for the bridge reassessment in form of random variables. Therewith, a previously insufficient model can be refined to achieve a higher level of approximation. This contribution emphasises two fundamental steps of the measured data based probabilistic reassessment: The sensitivity analyses to identify the cruciai Parameters and the needed accuracy of the related information as well as the comparison with expected uncertainties of non-destructively measured Parameters.
The purpose of this contribution is to introduce and to apply the developed approach of incorporating non-destructively gathered measurement results (instead of deterministic information and assumptions) into a reassessment model of a typical prestressed concrete road bridge and to outline the advantages. An essential part is the quality evaluation of the non-destructively measured information, that deals primarily with two questions. Could the object or parameter to be obtained reliably detected and if, how accurate are the inspection results achieved? Therefore, the importance of the combination of a probability of detection (POD)-approach and measurement uncertainty calculations is emphasized. With regard to the introduced case-study it is shown, for which structure parameters an assumption deviating from the actual (and measurable) situation has a particularly strong (and possibly arithmetically unfavorable) influence on the structural reliability. Measurements on such parameters are particularly beneficial for a reliable and robust reassessment. In conclusion, the individual reassessment results without consideration and with consideration of evaluated non-destructive inspection results are compared.