Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-54969 Zeitschriftenartikel Savidis, S.; Bergmann, M.; Schepers, Winfried; Fontara, I.-K. Wave propagation in inhomogeneous media via FE/PML method The Perfectly Matched Layer (PML) method is an efficient approach to imposing radiation conditions at the bounded region of interest in case of wave propagation in unbounded domains. This paper presents and validates 3D FE/PML numerical schemes based on two different PML formulations for homogeneous and inhomogeneous geological media exhibiting discrete or continuous inhomogeneity. In the equation of motion for the PML domain the applied stretching behavior is expressed either as complex material properties or as complex coordinates. Both PML formulations are implemented in the FEM and verified against analytical solutions. Three different types of material inhomogeneity are considered: layered half-space, continuously inhomogeneous half-space with linear velocity profile and continuously inhomogeneous half-space with nonlinear velocity profile. Sensitivity analyses are conducted, and the performance of the developed numerical schemes is investigated taking into account a broad variation of the PML parameters. Recommendations are given for the optimal values of the PML parameters for the case of homogeneous and inhomogeneous geological media. Berlin Ernst & Sohn 2022 Geotechnik 45 2 98 107 10.1002/gete.202100028 2022-06-09 OPUS4-54949 Zeitschriftenartikel Wiehle, Philipp; Simon, Sebastian; Baier, J.; Dennin, L. Forde, M. Influence of relative humidity on the strength and stiffness of unstabilised earth blocks and earth masonry mortar Aim of this study is to provide information about moisture dependent material behaviour of unstabilised loadbearing earth blocks and mortars. Compressive strength and Young's modulus were investigated after conditioning in varying relative humidity reaching from 40 % up to 95 %. The material composition and physical properties were investigated to understand the influence of relative humidity onto the mechanical properties. A normalisation of strength and stiffness by the values obtained at 23 ◦C and 50 % relative humidity reveals a linear dependence of compressive strength and Young's modulus that is regardless of the material composition. Thus, it is possible to describe the influence of relative humidity onto the load-bearing behaviour of unstabilised earth masonry materials in a generally valid formulation. Elsevier Ltd. 2022 Construction and Building Materials 342 Part A 1 15 10.1016/j.conbuildmat.2022.128026 2022-06-08 OPUS4-55000 Zeitschriftenartikel Auersch, Lutz The role of vehicle dynamics in train-induced ground vibrations and the detection of irregular axle-pulse responses due to a varying track support stiffness Train-induced ground vibrations are all generated by the vehicle, by static or dynamic vehicle loads. The most important and most accepted excitation are the dynamic wheel loads from the passage over track irregularities. Dynamic wheel loads will be compared from parallel axle-box and ground vibration measurements at more than seven sites. Some low-frequency excitation of ground vibrations, typically between 10 and 30 Hz, cannot be found in the axle-box measurements. Therefore, other vehicle modes, such as rigid bogie modes, flexible carriage modes, rigid and flexible wheelset modes, have been analysed for additional excitation forces. These vehicle dynamics analyses give an explanation for higher axle-box results at high frequencies, but not for the excitation of the higher low-frequency ground-vibration component. Finally, the effect of the moving static train loads will be analysed. For a regular track and soil, the moving static train loads yield the quasi-static response which exists only in the low-frequency nearfield of the track. If the support stiffness is randomly varying along the track, the pulses on the track generate an additional low-frequency component which is called the irregular pulse responses. This component will be demonstrated by numerical analysis where all axle pulses are superposed in frequency domain. London Sage 2022 Proc IMechE Part F: J Rail and Rapid Transit 236 10 1218 1233 10.1177/09544097221086064 2022-06-13 OPUS4-56241 Zeitschriftenartikel Wiehle, Philipp; Brinkmann, M. Material behaviour of unstabilised earth block masonry and its components under compression at varying relative humidity block and mortar types is analysed with particular regard to the influence of varying relative humidity. The uniaxial compressive strength and deformation characteristics of unstabilised earth blocks and mortars as well as of unstabilised earth block masonry are studied in detail and compared to conventional masonry to evaluate whether the structural design can be made accordingly. An increase of 30 % points in relative humidity leads to a reduction of the masonry´s compressive strength between 33 % and 35 % whereas the Young´s modulus is reduced by 24-29 %. However, the ratio between the Young´s modulus and the characteristic compressive strength of earth block masonry ranges between E33/fk = 283-583 but is largely independent of the relative humidity. The results show that the mechanical properties of the investigated unstabilised earth block masonry are sufficient for load-bearing structures, yielding a masonry compressive strength between 2.3 MPa and 3.7 MPa throughout the range of moisture contents investigated. In general, the design concept of conventional masonry can be adapted for unstabilised earth masonry provided that the rather low Young´s modulus as well as the moisture dependence of both, compressive strength and Young´s modulus, are sufficiently taken into account. Netherlands Elsevier B.V. 2022 Case Studies in Construction Materials 17 1 15 urn:nbn:de:kobv:b43-562417 10.1016/j.cscm.2022.e01663 https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de 2022-11-14 OPUS4-56525 Zeitschriftenartikel Benseghier, Z.; Luu, L.-H.; Cuéllar, Pablo; Bonelli, S.; Philippe, P. On the erosion of cohesive granular soils by a submerged jet: a numerical approach This paper presents an erosion interpretation of cohesive granular materials stressed by an impinging jet based on the results of a micromechanical simulation model. The numerical techniques are briefly described, relying on a two-dimensional Lattice Boltzmann Method coupled with a Discrete Element Methods including a simple model of solid intergranular cohesion. These are then used to perform a parametric study of a planar jet in the laminar regime impinging the surface of granular samples with different degrees of cohesive strength. The results show the pertinence of using a generalized form of the Shields criterion for the quantification of the erosion threshold, which is valid for cohesionless samples, through empirical calibration, and also for cohesive ones. Furthermore, the scouring kinetics are analysed here from the perspective of a selfsimilar expansion of the eroded crater leading to the identification of a characteristic erosion time and the quantification of the classical erosion coefficient. However, the presented results also challenge the postulate of a local erosion law including erodibility parameters as intrinsic material properties. The paper then reviews the main limitations of the simulation and current interpretation models, and discusses the potential causes for the observed discrepancies, questioning the pertinence of using time-averaged macroscopic relations to correctly describe soil erosion. The paper concludes addressing this question with a complementary study of the presented simulations re-assessed at the particle-scale. The resulting local critical shear stress of single grains reveals a very wide dispersion of the data but nevertheless appears to confirm the general macroscopic trend derived for the cohesionless samples, while the introduction of cohesion implies a significant but systematic quantitative deviation between the microscopic and macroscopic estimates. Nevertheless, the micro data still shows consistently that the critical shear stress does actually vary approximately in linear proportion of the adhesive force. Springer 2023 Granular Matter 25 8 1 20 10.1007/s10035-022-01289-5 2022-12-12 OPUS4-54384 Zeitschriftenartikel Auersch, Lutz Different types of continuous track irregularities as sources of train-induced ground vibration and the importance of the random variation of the track support Irregularities of the track are a main cause of train-induced ground vibration, and track maintenance is of great importance. Although geometric irregularities at the wheel-rail contact are widely used, other types of irregularities, such as stiffness irregularities, irregularities from different track positions and irregularities in the wave propagation, were analysed in the present study. The track behaviour was investigated by a multi-beam-on-soil model. This track model is coupled with a vehicle model to calculate the vehicle-track interaction. The track model was also used for the track filtering, which transfers a track support error to the equivalent rail irregularity or, conversely, the sharp axle pulse on the rail to a smoother pulse on the soil. In the case in which this filtering varies randomly along the track, the pulses of the moving static load induce a certain ground Vibration component ("the scatter of axle pulses"). This effect was calculated by the superposition of axle pulses in the frequency domain and by a stochastic simulation. Simultaneous vehicle, track and soil measurements at a certain site were used to evaluate the different excitation and ground Vibration components. The agreement between calculations and axle-box and soil measurements is good. The ground vibrations calculated from rail irregularities and corresponding dynamic loads, however, clearly underestimate the measured ground vibration amplitudes. Only the static load that is moving over a varying track support stiffness can produce the important mid-frequency ground Vibration component by the scatter of axle pulses. Basel MDPI 2022 Applied Sciences 12 3 1 22 urn:nbn:de:kobv:b43-543846 10.3390/app12031463 https://creativecommons.org/licenses/by/4.0/deed.de 2022-02-23 OPUS4-54189 Zeitschriftenartikel Thiele, Marc; Pirskawetz, Stephan Analysis of damage evolution in concrete under fatigue loading by acoustic emission and ultrasonic testing The fatigue process of concrete under compressive cyclic loading is still not completely explored. The corresponding damage processes within the material structure are especially not entirely investigated. The application of acoustic measurement methods enables a better insight into the processes of the fatigue in concrete. Normal strength concrete was investigated under compressive cyclic loading with regard to the fatigue process by using acoustic methods in combination with other nondestructive measurement methods. Acoustic emission and ultrasonic signal measurements were applied together with measurements of strains, elastic modulus, and static strength. It was possible to determine the anisotropic character of the fatigue damage caused by uniaxial loading based on the ultrasonic measurements. Furthermore, it was observed that the fatigue damage seems to consist not exclusively of load parallel oriented crack structures. Rather, crack structures perpendicular to the load as well as local compacting are likely components of the fatigue damage. Additionally, the ultrasonic velocity appears to be a good indicator for fatigue damage beside the elastic modulus. It can be concluded that acoustic methods allow an observation of the fatigue process in concrete and a better understanding, especially in combination with further measurement methods. Basel MDPI 2022 Materials 15 1 341 355 urn:nbn:de:kobv:b43-541891 10.3390/ma15010341 https://creativecommons.org/licenses/by/4.0/deed.de 2022-01-05 OPUS4-53766 Zeitschriftenartikel Auersch, Lutz Resonances of railway bridges analysed in frequency domain by the modal-force-excitation, bridge-transfer and axle-sequence spectra In this article, the passage of different trains over different bridges will be studied for resonant excitation. The intensity of the resonance will be estimated in frequency domain by using three separated spectra. 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 the train. The influences of train speed, bridge length, bridge support, track irregularities, and train type on the resonance amplitudes will be analysed for each of these spectra separately for getting a better insight. A variety of axle-sequence spectra and corresponding rules will be presented for different vehicles and trains. As examples, the passage of a slow freight train over a long-span bridge, a normal passenger train over a medium-span bridge, and a high-speed train over a short bridge will be analysed. Corresponding measurements show the amplification, but also the cancellation of the subsequent axle responses. Namely in one of the measurement examples, the first mode of the bridge was amplified and the second mode was cancelled at a low speed of the train and vice versa at a higher speed. London Elsevier Ltd. 2021 Engineering Structures 249 1 9 10.1016/j.engstruct.2021.113282 2021-11-18 OPUS4-52998 Zeitschriftenartikel Viefhues, Eva; Döhler, M.; Hille, Falk; Mevel, L. Statistical subspace-based damage detection with estimated reference The statistical subspace-based damage detection technique has shown promising theoretical and practical results for vibration-based structural health monitoring. It evaluates a subspacebased residual function with efficient hypothesis testing tools, and has the ability of detecting small changes in chosen system parameters. In the residual function, a Hankel matrix of Output covariances estimated from test data is confronted to its left null space associated to a reference model. The hypothesis test takes into account the covariance of the residual for decision making. Ideally, the reference model is assumed to be perfectly known without any uncertainty, which is not a realistic assumption. In practice, the left null space is usually estimated from a reference data set to avoid model errors in the residual computation. Then, the associated uncertainties may be non-negligible, in particular when the available reference data is of limited length. In this paper, it is investigated how the statistical distribution of the residual is affected when the reference null space is estimated. The asymptotic residual distribution is derived, where its refined covariance term considers also the uncertainty related to the reference null space estimate. The associated damage detection test closes a theoretical gap for real-world applications and leads to increased robustness of the method in practice. The importance of including the estimation uncertainty of the reference null space is shown in a numerical study and on experimental data of a progressively damaged steel frame. Elsevier Ltd. 2022 Mechanical Systems and Signal Processing 164 108241 10.1016/j.ymssp.2021.108241 2021-07-26 OPUS4-52809 Beitrag zu einem Tagungsband Simon, Patrick; Schneider, Ronald; Baeßler, Matthias Yokota, H.; Frangopol, D. M. Bayesian system identification of a reinforced concrete beam subject to temperature variations based on static response data Changes in the measured response of structural systems can be an indication of structural damages. However, such changes can also be caused by the effect of varying environmental conditions. To detect, localize and quantify changes or damages in structural systems subject to varying environmental conditions, physics-based models of the structural systems have to be applied which explicitly account for the influence of ambient conditions on the structural behavior. Data obtained from the structural systems should be used to calibrate the models and update predictions. Bayesian system identification is an effective framework for this task. In this paper, we apply this framework to learn the parameters of two competing structural models of a reinforced concrete beam subject to varying temperatures based on static response data. The models describe the behavior of the beam in the uncracked and cracked condition. The data is collected in a series of load tests in a climate chamber. Bayesian model class selection is then applied to infer the most plausible condition of the beam conditional on the available data. CRC Press 2021 Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations Tenth International Conference on Bridge Maintenance, Safety and Management (IABMAS 2020) Online meeting 11.04.2021 15.04.2021 934 941 10.1201/9780429279119-125 2021-06-14 OPUS4-54557 Zeitschriftenartikel Herrmann, Ralf Digitalisierung sichert die Bauwerke von gestern und das Wissen von morgen Die moderne Gesellschaft in Deutschland und Europa profitiert von der hervorragenden baulichen Infrastruktur, die für uns viele Aspekte aus den Bereichen Mobilität, Energieversorgung, Transport, Umweltschutz, (Nah-)Erholung und Gefahrenabwehr zur Alltäglichkeit werden lassen und uns ein hohes Gefühl der technischen Sicherheit vermitteln. Viele der Annehmlichkeiten, wie beispielweise ein Hochgeschwindigkeitseisenbahnverkehrsnetz, zuverlässige Stromversorgung im europäischen Verbundsystem und ein immenser Personen-, Güter- und Warenverkehr auf der Straße, zu Wasser und in der Luft ist ohne eine leistungsfähige, resiliente und zuverlässige bauliche Infrastruktur undenkbar. Berlin Ernst & Sohn GmbH 2022 Bautechnik 99 3 161 162 10.1002/bate.202270303 2022-03-30 OPUS4-55492 Zeitschriftenartikel Simon, Patrick; Helmrich, M.; Herrmann, Ralf; Schneider, Ronald; Baeßler, Matthias; Lorelli, S.; Morgenthal, G. Maintalbrücke Gemünden: Bauwerksmonitoring und -identifikation aus einem Guss Die Infrastruktursysteme der Industriestaaten erfordern heute und in Zukunft ein effizientes Management bei alternder Bausubstanz, steigenden Lasten und gleichbleibend hohem Sicherheitsniveau. Digitale Technologien bieten ein großes Potenzial zur Bewältigung der aktuellen und künftigen Herausforderungen im Infrastrukturmanagement. Im BMBF-geförderten Projekt Bewertung alternder Infrastrukturbauwerke mit digitalen Technologien (AISTEC) wird untersucht, wie unterschiedliche Technologien und deren Verknüpfung gewinnbringend eingesetzt werden können. Am Beispiel der Maintalbrücke Gemünden werden ein sensorbasiertes Bauwerksmonitoring, bildbasierte Inspektion mit durch Kameras ausgestatteten Drohnen (UAS) und die Verknüpfung digitaler Bauwerksmodelle umgesetzt. Die aufgenommenen Bilder dienen u. a. als Grundlage für spätere visuelle Anomaliedetektionen und eine 3D-Rekonstruktion, welche wiederum für die Kalibrierung und Aktualisierung digitaler Tragwerksmodelle genutzt werden. Kontinuierlich erfasste Sensordaten werden ebenfalls zur Kalibrierung und Aktualisierung der Tragwerksmodelle herangezogen. Diese Modelle werden als Grundlage für Anomaliedetektionen und perspektivisch zur Umsetzung von Konzepten der prädiktiven Instandhaltung verwendet. Belastungsfahrten und historische Daten dienen in diesem Beitrag der Validierung von kalibrierten Tragwerksmodellen. Berlin Ernst & Sohn 2022 Bautechnik 99 3 163 172 urn:nbn:de:kobv:b43-554924 10.1002/bate.202100102 https://creativecommons.org/licenses/by/4.0/deed.de 2022-08-16 OPUS4-44285 Zeitschriftenartikel Schwedler, Michael; Dörfeldt, Stefan; Lüddecke, Falk; Seidel, Marc; Thiele, Marc Kurrer, Karl-Eugen Einflussfaktoren auf die Vorspannkraft von Schrauben mit Durchmessern bis M72 in Ringflanschverbindungen 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. Berlin Wilhelm Ernst und Sohn 2018 Stahlbau 87 2 149 161 10.1002/stab.201810571 2018-02-23 OPUS4-45471 Beitrag zu einem Tagungsband Auersch, Lutz; Said, Samir Strukturschwingungen und Schwingungsminderung - Bauwerksmodelle, Messungen vor Ort und auf dem Versuchsgelände der BAM 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. Düsseldorf VDI-Verlag VDI Wissensforum 2018 Baudynamik 2018, VDI-Berichte 2321 2321 978-3-18-092321-5 6. VDI Fachtagung Baudynamik Würzburg, Germany 17.04.2018 18.04.2018 421 434 2018-07-16 OPUS4-45127 Buchkapitel Döhler, Michael; Hille, Falk; Mevel, Laurent Ottaviano, Erika; Pelliccio, Assunta; Gattulli, Vincenzo Vibration-based monitoring of civil structures with subspace-based damage detection 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. 1. Cham Springer International Publishing 2018 Mechatronics for Cultural Heritage and Civil Engineering 978-3-319-68645-5 307 326 10.1007/978-3-319-68646-2 2018-06-11 OPUS4-51346 Zeitschriftenartikel Auersch, Lutz; Said, Samir Slab track behaviour under train passage and hammer impact - Measurements at different sites and calculated track interaction with continuous soils This contribution intends to give an overview on the vibration behaviour of slab tracks in comparison of measurements and calculations and also by comparison of different track types at more than ten different measuring sites. In theory, tracks on continuous soil are calculated by the frequency-wavenumber domain method. In experiment, geophone measurements are transformed to displacement results. Two aspects of track behaviour are considered, the frequency-dependant compliance of the track, measured by hammer impact, and the deflection under a passing axle load. In theory, the response to a single axle can be calculated, whereas in experiment, only the passage of the whole train can be measured. For comparison of theory and experiment, the calculated deflection under a single axle is superposed to get the response of the whole train. As a result, the slab track characteristics are completely different from the ballast track characteristics where each axle can be seen in the time histories. The slab track has a more global behaviour where only a whole bogie can be found in the track response and moreover, the two neighbouring bogies are not completely separated. The measurement of the different track elements (rail, sleeper, track plate, base layer) and the frequency-dependant compliances with possible resonances yield further information About the properties of the track elements. The calculations show that the soil has the dominant influence on the amplitudes and the width of the track-plate displacements. In the measurement results, the following parameters are analysed: slab track vs. ballast track, different types of slab tracks, damaged slab tracks, different trains, switches at different measuring points, voided sleepers, an elastic layer, the mortar layer, and different soils at different places. Finally, a good agreement between measured and calculated results is found for the normal and some special (damaged, floating) slab tracks. Gliwice International Institute of Acoustics and Vibration 2020 International journal of acoustics and vibrations 25 3 341 354 10.20855/ijav.2020.25.31622 2020-09-30 OPUS4-48181 Zeitschriftenartikel Kowitz, Astrid; Wu, Cheng-Chieh; Helmerich, Rosemarie; Hille, Falk; Kadoke, Daniel; Gründer, Klaus-Peter; Hauser, S.; Schwarzinger, H. Bland, S. Impact on a micro-reinforced UHPC: Experimental studies versus numerical modeling 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. Amsterdam Elsevier Ltd 2019 Materials Today: Proceedings 12 2 474 483 10.1016/j.matpr.2019.03.152 2019-06-07 OPUS4-48240 Beitrag zu einem Tagungsband Viefhues, Eva; Döhler, M.; Zhang, Q.; Hille, Falk; Mevel, L. Subspace-based Damage Detection with Rejection of the Temperature Effect and Uncertainty in the Reference 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. 2019 Proceedings of 8th International Operational Modal Analysis Conference International Operational Modal Analysis Conference Copenhagen, Danmark 13.05.2019 15.05.2019 1 11 2019-06-20 OPUS4-51115 Zeitschriftenartikel Nerger, Deborah; Hille, Falk; Moosavi, Robabeh; Grunwald, Marcel; Redmer, Bernhard; Kühn, T.; Hering, M.; Bracklow, F. Post-impact evaluation at RC plates with planar tomography and FEM Due to the wide range of applications, the easy production and the large field of use, reinforced concrete (RC) is a widespread building material. This variety of applications is reflected in a wide range of physical material properties. Not only therefor it still is a technical challenge to provide all necessary test conditions for experimentally reproducing dynamic effects under impact loading of RC structures. In this paper we present investigations on the thicknesses of RC plates under low and medium high velocity impact loading by a flat-tipped impactor. The planar tomography setup at BAM is used to visualize the impact damage and to characterize the damage features such as cracks, scabbing and spalling. Further, the comparison of tomography results with those of an applied numeric simulation analysis is used to verify the numeric models for future damage prognosis under impact loading. Using the results of both, the tomographic as well as the FE analysis, different damage features were investigated and compared regarding their validity. Crack damage plays a leading part and the significance of summarized crack values as well as their distribution is analyzed. The total damage value but also the determined damage distribution both provide an input for describing damage as a function of the impactor velocity and plate thickness. Elsevier 2020 Materials Today: Proceedings 1 10 10.1016/j.matpr.2020.05.671 2020-08-17 OPUS4-51051 Zeitschriftenartikel Hille, Falk; Sowietzki, D.; Makris, R. Luminescence-based early detection of fatigue cracks Classic non-destructive fatigue crack detection methods reveal the state of the fatigue damage evolution at the moment of application, generally not under operational conditions. The here introduced crack luminescence method realizes a clear visibility of the occurred and growing crack in loaded components during operation. Different established experiments show that due to the sensitive coating a crack Formation can be detected even in early stage under the premise the crack reached the surface. The coating consists of two layers with different properties and functions. The bottom layer emits light as fluorescence under UV radiation. The top layer covers the fluorescing one and prevents the emitting of light in case of no damage at the surface. In case of surface crack occurrence, the luminescent light is clearly noticeable by visual observations and also by standard camera equipment which makes automated crack detection possible as well. It is expected that crack luminescence can increase structural safety as well as reduce costs and time for inspections and preventive maintenance. Amsterdam Elsevier 2020 Materials Today: Proceedings 1 5 urn:nbn:de:kobv:b43-510517 10.1016/j.matpr.2020.02.338 https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de 2020-07-27 OPUS4-51210 Beitrag zu einem Tagungsband Auersch, Lutz A mid-frequency component of train-induced ground vibration due to scattered axle impulses and the irregularities of the soil and ballast The passage of the train is dominated by the impulses of the static axle loads. The response of the regular homogeneous and irregular soils has been calculated by the finite-element method in frequency domain. The superposition of the impulse responses yields the quasi-static component of the ground vibration which is restricted to very low frequencies and to the close near-field of the track. In case of an irregular soil or ballast of which the stiffness varies randomly in space, a mid-frequency ground vibration component is generated by the scattering of the axle impulses. Measurements will be shown which prove the existence of the mid-frequency ground vibration component and the unique explanation by the scattered axle impulses: many international measurements with a raised mid-frequency component, axle-box measurements with a too low mid-frequency dynamic load, amplitude-speed dependencies which are incompatible with irregularity-induced dynamic loads, and ground vibration reductions due to stiff track elements. Leuven KULeuven 2020 Proc. of ISMA/USD 2020 International Conference on Noise and Vibration Engineering (ISMA/USD) Online meeting 07.09.2020 09.09.2020 2611 2625 2020-09-14 OPUS4-51211 Beitrag zu einem Tagungsband Auersch, Lutz; Said, Samir; Rohrmann, R. Natural frequencies and modes of poles, beams, floors, road and rail bridges In the last three decades, the vibrations of many floors and bridges have been measured. The contribution shows some evaluation methods, experimental results and some modelling and theoretical results. Simple evaluation methods have been developed for single and coupled floors. Two coupled beams have been measured in good agreement with the theory. A more complex coupling model has been found for a large wooden floor in a castle consisting of six floor bays which correlates well with the measurements. Damaged and intact poles have been tested by their natural frequencies and damping values, and a fair correlation between the degree of damage and the shift of the frequency. Road bridges have been analysed in detail and some examples are presented. Railway bridges and trains are studied for resonant excitation. The risk of resonance can be estimated in frequency domain by using axle-sequence spectra of the train and the natural frequencies of the bridge. A measurement example shows the amplification, but even stronger the cancellation of the subsequent axle responses. Several high-speed trains and freight trains have been analysed for their potential resonance amplification. Leuven KULeuven 2020 Proc. of ISMA/USD 2020 International Conference on Noise and Vibration Engineering (ISMA/USD 2020) Online meeting 07.09.2020 09.09.2020 1573 1585 2020-09-14 OPUS4-50683 Zeitschriftenartikel Hu, W.-H.; Xu, Z.-M.; Liu, M.-Y.; Tang, D.-H.; Lu, W.; Li, Z.-H.; Teng, J.; Han, X.-H.; Said, Samir; Rohrmann, R. G. Estimation of the Lateral Dynamic Displacement of High-Rise Buildings underWind Load Based on Fusion of a Remote Sensing Vibrometer and an Inclinometer This paper proposes a novel method to estimate the lateral displacement of high-rise structures under wind loads. The coefficient β(x) is firstly derived, reflecting the relation between the structural lateral dynamic displacement and the inclination angle at the height x of a structure. If the angle is small, it is the ratio between the structural fundamental mode shape and its first-order derivative without influence of external loads. Several dynamic experiments of structures are performed based on a laser remote sensing vibrometer and an inclinometer, which shows that the fundamental mode is dominated in the structural displacement response under different types of excitations. Once the coefficient β(x) is curve-fitted by measuring both the structural lateral dynamic displacement and the inclination angle synchronously, the real-time structural lateral displacement under operational conditions is estimated by multiplying the coefficient β(x) with the inclination angle. The advantage of the proposed method is that the coefficient β(x) can be identified by lateral dynamic displacement measured in high resolution by the remote sensing vibrometer, which is useful to reconstruct the displacement accurately by the inclination angle under operational conditions 4052 Basel, Schweiz MDPI 2020 Journals Remote Sensing 12 7 1120 urn:nbn:de:kobv:b43-506833 10.3390/rs12071120 https://creativecommons.org/licenses/by/4.0/deed.de 2020-04-23 OPUS4-50613 Zeitschriftenartikel Brunier-Coulin, F.; Cuéllar, Pablo; Philippe, P. Generalized Shields criterion for weakly cohesive granular materials The erosion of natural sediments by a superficial fluid flow is a generic situation in many usual geological or industrial contexts. However, there is still a lack of fundamental knowledge about erosional processes, especially concerning the role of internal cohesion and adhesive stresses on issues such as the critical flow conditions for the erosion onset or the kinetics of soil mass loss. This contribution investigates the influence of cohesion on the surface erosion by an impinging jet flow based on laboratory tests with artificially bonded granular materials. The model samples are made of spherical glass beads bonded either by solid bridges made of resin or by liquid bridges made of a highly viscous oil. To quantify the intergranular cohesion, the capillary forces of the liquid bridges are here estimated by measuring their main geometrical parameters with image-processing techniques and using well-known analytical expressions. For the solid bonds, the adhesive strength of the materials is estimated by direct measurement of the yield tensile forces and stresses at the particle and sample scales, respectively, with specific traction tests developed for this purpose. The proper erosion tests are then carried out in an optically adapted device that permits a direct visualization of the scouring process at the jet apex by means of the refractive index matching technique. On this basis, the article examines qualitatively the kinetics of the scour crater excavation for both scenarios, namely, for an intergranular cohesion induced by either liquid or solid bonds. From a quantitative perspective, the critical condition for the erosion onset is discussed specifically for the case of the solid bond cohesion. In this respect, we propose here a generalized form of the Shields criterion based on a common definition of a cohesion number from yield tensile values, derived at both micro- and macroscales. The article finally shows that the proposed form manages to reconcile the experimental data for cohesive and cohesionless materials, the latter in the form of the so-called Shields curve along with some previous results of the authors which have been appropriately revisited. American Physical Society 2020 Physical Review Fluids 5 3 034308 10.1103/PhysRevFluids.5.034308 2020-04-01 OPUS4-49166 Buchkapitel Baeßler, Matthias; Cuéllar, Pablo; Victor, A.; Lüddecke, F. Triantafyllidis, T. Stability and large deformations of slender structures supported by soil materials The stability and geometric nonlinearities of slender structures are a major topic in structural design. While this topic is most relevant in the field of Structural Engineering, e.g. for steel or concrete structures, only few applications take the role of soil-structure-interaction explicitly into account. The focus of this paper is placed on the impact of soil support and its modelling for the buckling analysis based on examples both for pile foundations and for railway track stability. The general interaction between steel design and the geotechnical input will be addressed. The paper discusses and summarizes a range of subtopics based on experience and current research at the author's institute. Cham, Switzerland Springer IBF KIT 2020 Recent Developments of Soil Mechanics and Geotechnics in Theory and Practice; Lecture Notes in Applied and Computational Mechanics 91 978-3-030-28515-9 355 369 10.1007/978-3-030-28516-6 2019-10-01 OPUS4-49167 Beitrag zu einem Tagungsband Baeßler, Matthias; Bhuyan, Delwar; Hille, Falk; Viefhues, Eva; Döhler, M.; Mevel, L. Zingoni, Alphose Impact of environmental based effects on SHM strategies Environmental based perturbations influence significantly the ability to identify structural dam-age in Structural Health Monitoring. Strategies are needed to classify such effects and consider them appropri-ately in SHM. It has to be considered if seasonal effects just mask the structural response or if temperature itself correlates to a weakening of the structure. 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 considering environmental as well as damage-based changes of stiffness values. With the background of increasing affordability of sensing and computing technology, effort should be made to increase sensitivity, reliability and robustness of proce-dures, separating environmental from damage caused changes in SHM measures. The contribution describes an attempt to evaluate both general strategies, their advantages and drawbacks. In addition, two vibration moni-toring procedures are introduced, allowing for temperature-based perturbations of the monitoring data. Boca Raton CRC Press Department of Civil Engineering, University of Cape Town 2019 Advances in Engineering Materials, Structures and Systems: Innovations, Mechanics and Applications 978-1-138-38696-9 SEMC 2019 Cape Town, South Africa 02.09.2019 04.09.2019 Paper 324, 1 Paper 324, 6 10.1201/9780429426506 2019-10-01 OPUS4-50029 Zeitschriftenartikel Reimold, W. U.; Crosta, A. P.; Hasch, M.; Kowitz, Astrid; Hauser, N.; Sanchez, J. P.; Simoes, L. S. A.; de Sanchez, G. J.; Zaag, P. T. Shock deformation confirms the impact origin for the Cerro do Jarau, Rio Grande do Sul, Brazil, structure Cerro do Jarau is a conspicuous, circular morpho-structural feature in Rio Grande do Sul State (Brazil), with a central elevated core in the otherwise flat "Pampas" terrain typical for the border regions between Brazil and Uruguay. The structure has a diameter of approximately 13.5 km. It is centered at 30o12′S and 56o32′W and was formed on basaltic flows of the Cretaceous Serra Geral Formation, which is part of the Paraná-Etendeka Large Igneous Province (LIP), and in sandstones of the Botucatu and Guará formations. The structure was first spotted on aerial photographs in the 1960s. Ever since, its origin has been debated, sometimes in terms of an endogenous (igneous) origin, sometimes as the result of an exogenous (meteorite impact) event. In recent years, a number of studies have been conducted in order to investigate its nature and origin. Although the results have indicated a possible impact origin, no conclusive evidence could be produced. The interpretation of an impact origin was mostly based on the morphological characteristics of the structure; geophysical data; as well as the occurrence of different breccia types; extensive deformation/silicification of the rocks within the structure, in particular the sandstones; and also on the widespread occurrence of low-pressure deformation features, including some planar fractures (PFs). A detailed optical microscopic analysis of samples collected during a number of field campaigns since 2007 resulted in the disclosure of a large number of quartz grains from sandstone and monomict arenite breccia from the central part of the structure with PFs and feather features (FFs), as well as a number of quartz grains exhibiting planar deformation features (PDFs). While most of these latter grains only carry a single set of PDFs, we have observed several with two sets, and one grain with three sets of PDFs. Consequently, we here propose Cerro do Jarau as the seventh confirmed impact structure in Brazil. Cerro do Jarau, together with Vargeão Dome (Santa Catalina state) and Vista Alegre (Paraná State), is one of very few impact structures on Earth formed in basaltic rocks. Wiley 2018 Meteoritics & Planetary Science 54 10 2384 2394 10.1111/maps.13233 2019-12-16 OPUS4-50266 Zeitschriftenartikel Auersch, Lutz Characteristics of train passages over slab tracks from measurements and different track-soil models - Damage detection and ground vibration reduction The train passages over intact or damaged slab tracks on different soils have been calculated by the finite-element boundary-element or the wavenumber-domain method. The influence of track and soil parameters on the distribution of the track displacements and the soil forces has been analysed. The measured and calculated displacement time histories of train passages could be used to identify track damages such as lose sleepers or a lose track plate. The time histories and spectra of the soil forces can explain the measured ground vibration reduction of slab tracks. The calculated displacement and force distributions of slab tracks on continuous soils do not fulfil the Winkler hypothesis and Winkler models should not be used for track analysis. London Sage Institution of Mechanical Engineers 2020 Journal of Rail and Rapid Transport 234 2 142 160 10.1177/0954409719835036 2020-01-23 OPUS4-48843 Zeitschriftenartikel Bhuyan, Md Delwar Hossain; Gautier, G.; Le Touz, N.; Döhler, M.; Hille, Falk; Dumoulin, J.; Mevel, L. Vibration-based damage localization with load vectors under temperature changes Damage detection and localization in civil or mechanical structures is a subject of active development and research. A few vibration-based methods have been developed so far, requiring, for example, modal parameter estimates in the reference and damaged states of the investigated structure, and for localization in addition a finite element model. For structures in operation, temperature has been shown to be a major nuisance to the efficiency of such methods because the modal parameters are varying not only with damage but also due to temperature variations. For detection, a few rejection approaches have been developed. Besides the increased complexity, environmental variation is hardly taken into account in localization approaches. In this paper, we propose a sensitivity-based correction of the identified modal parameters in the damaged state with respect to the temperature field in the reference state, on the basis of a sensitivity analysis with respect to temperature dependent Parameters of the finite element model in the reference state. The approach is then applied to the stochastic dynamic damage locating vector method, where its improved performance under nonuniform temperature variations is shown in a numerical application on a beam. John Wiley & Sons, Ltd. 2019 Structural Control and Health Monitoring e2439, 1 16 10.1002/stc.2439 2019-09-04 OPUS4-48952 Zeitschriftenartikel Straub, D.; Schneider, Ronald; Bismut, E.; Kim, H.-J. Reliability analysis of deteriorating structural systems Reliability analysis of deteriorating structural systems requires the solution of time-variant reliability problems. In the general case, both the capacity of and the loads on the structure vary with time. This analysis can be approached by approximation through a series of time-invariant reliability problems, which is a potentially effective strategy for cases where direct solutions of the time-variant reliability problem are challenging, e.g. for structural systems with many elements or arbitrary load processes. In this contribution, we thoroughly Review the formulation of the equivalent time-invariant reliability problems and extend this approximation to structures for which inspection and monitoring data is available. Thereafter, we present methods for efficiently evaluating the reliability over time. In particular, we propose the combination of sampling-based methods with a FORM (first-order reliability method) approximation of the series system reliability problem that arises in the computation of the lifetime reliability. The framework and algorithms are demonstrated on a set of numerical examples, which include the computation of the reliability conditional on inspection data. Elsevier Ltd. 2020 Structural Safety 82 Paper 101877, 1 10.1016/j.strusafe.2019.101877 2019-09-16 OPUS4-48444 Beitrag zu einem Tagungsband Kullolli, Borana; Baeßler, Matthias; Cuéllar, Pablo; Rica, S.; Rackwitz, F. An enhanced interface model for friction fatigue problems of axially loaded piles The shaft bearing capacity often plays a dominant role for the overall structural behaviour of axially loaded piles in offshore deep foundations. Under cyclic loading, a narrow zone of soil at the pile-soil interface is subject to cyclic shearing solicitations. Thereby, the soil may densify and lead to a decrease of confining stress around the pile due to microphenomena such as particle crushing, migration and rearrangement. This reduction of radial stress has a direct impact on the shaft capacity, potentially leading in extreme cases to pile failure. An adequate interface model is needed in order to model this behaviour numerically. Different authors have proposed models that take typical Interface phenomena in account such as densification, grain breakage, normal pressure effect and roughness. However, as the models become more complex, a great number of material parameters need to be defined and calibrated. This paper proposes the adoption and transformation of an existing soil bulk model (Pastor- Zienkiewicz) into an interface model. To calibrate the new interface model, the results of an experimental campaign with the ring shear device under cyclic loading conditions are here presented. The constitutive model shows a good capability to reproduce typical features of sand behaviour such as cyclic compaction and dilatancy, which in saturated partially-drained conditions may lead to liquefaction and cyclic mobility phenomena. Glasgow, Scotland ASME 2019 OMAE 2019 2019 Conference: OMAE Glasgow, Scotland, UK 09.06.2019 14.06.2019 Article Number: UNSP V001T10A013 2019-07-15 OPUS4-52059 Zeitschriftenartikel Hüsken, Götz; Shamsuddoha, Md; Pirskawetz, Stephan; Hofmann, Detlef; Baeßler, Matthias; Kühne, Hans-Carsten Potential of a Repair System for Grouted Connections in Offshore Structures: Development and Experimental Verification Grouted connections are intensively used in offshore rigs, platforms as well as jacket and monopile offshore wind turbine structures. Being located in remote offshore conditions, these connections can experience considerable adverse loading during their lifetimes. Degradation was reported inside similar connections, which were installed in the last three decades. Grouting in the offshore sites may often be proven difficult, which eventually leads to reduced load-bearing 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 this study, scaled grouted connections were manufactured using a novel mould, whose integrity were monitored using digital image correlation (DIC). The connections were loaded under static load to visualize the main failure pattern using distributed fibre optic sensors and acoustic emission (AE) analysis. Grouted connections were then repaired using a cementitious injectable grout. The effectiveness of the grout injection was monitored using dye penetration technique. Finally, specimens are reloaded to identify the potential of such repair for grouted connections. Elsevier Ltd. 2021 Marine Structures 77 102934 10.1016/j.marstruc.2021.102934 2021-02-03 OPUS4-52107 Zeitschriftenartikel Auersch, Lutz; Said, Samir Dynamic track-soil interaction - calculations and measurements about slab and ballast tracks The dynamic behaviour of slab and ballast tracks has been investigated by measurements and calculations. Hammer impacts and train passages have been analysed. Measurements have been performed by geophones (velocity transducers) which have been time-integrated to displacements. The calculations are done in frequency-wavenumber domain for multi-beam-on-continuous soil models. The characteristics of the different tracks and track elements have been established in theory and experiment. The frequency-dependent compliances (displacement transfer functions) show clear rail-on-rail-pad resonances or highly damped track-soil resonances. Compared to the rail and sleeper, the track plate has much lower amplitudes. The slab track has usually the highest rail amplitudes due to soft rail pads. The train passage yields track displacements which are a superposition of the axle loads from the two neighbouring axles of a bogie and from the two bogies of two neighbouring carriages. This global behaviour is characteristic for the track plate of the slab track whereas the rails of the slab and the ballast track behave more local with only one bogie of influence. The measurements agree very well with the theory of the continuous soil in case of the six measured slab tracks and acceptably well for the six measured ballast tracks. The measurements allow to find appropriate model parameters and to check the models, for example the Winkler model of the soil has been found less appropriate as it reacts more locally. Hangzhou Zhejiang University Press Zhejiang University 2021 Journal of Zhejiang University-Science A 22 1 21 36 10.1631/jzus.A1900651 2021-02-11 OPUS4-49491 Zeitschriftenartikel Benseghier, Z.; Cuéllar, Pablo; Luu, L.-H.; Delenne, J.-Y.; Bonelli, S.; Philippe, P. Relevance of Free Jet Model for Soil Erosion by Impinging Jets The surface erosion of soil samples caused by an impinging jet can be analyzed using the jet erosion test (JET), a standard experimental test to characterize the erosion resistance of soils. This paper specifically addresses the flow characteristics of a laminar impinging jet over the irregular surface of granular beds to discuss the pertinence and relevance of commonly used empirical estimations based on a selfsimilar model of a free jet. The JET is here investigated at the microscale with a coupled fluid-particle flow numerical odel featuring the lattice Boltzmann method (LBM) for the fluid phase combined with the discrete element method (DEM) for the mechanical behavior of the solid particles. The hydrodynamics of a laminar plane free jet are confronted with the results from a parametric study of jet impingement, both on solid smooth and fixed granular surfaces, that take into account variations in particle size, distance from jet origin, and jet Reynolds number. The flow characteristics at the bed surface are here quantified, including the maximal values in tangential velocity and wall shear stress, which can be regarded as the major cause of particle detachments under hydrodynamic solicitation. It is shown that the maximal velocity at the impinged surface can be described by the free jet self-similar model, provided that a simple empirical coefficient is introduced. Further, an expression is proposed for the maximal shear stress in laminar conditions, including a Blasius-like friction coefficient that is inversely proportional to the square root of the jet Reynolds number. To conclude, finally, the JET erosion of different cohesionless granular samples is analyzed, confirming that the threshold condition at the onset of granular motion is consistent with the Shields diagram and in close agreement with previous experimental results. ASCE 2020 Journal of Hydraulic Engineering 146 1 04019047 10.1061/(ASCE)HY.1943-7900.0001652 2019-11-06 OPUS4-50230 Zeitschriftenartikel Benseghier, Z.; Cuéllar, Pablo; Luu, L.-H.; Bonelli, S.; Philippe, P. A parallel GPU-based computational framework for the micromechanical analysis of geotechnical and erosion problems This article deals with the relevance and practical feasibility of micromechanical simulations for their application to general geomechanical problems involving fluid-saturated granular assemblies, whether frictional or cohesive. A set of conceptual and numerical tools is here presented, advocating for a parallel computation using graphical processing units (GPUs) to treat large numbers of degrees of freedom with conventional Desktop computers. The fluid phase is here simulated with a particle-resolved approach in the frame of the Lattice Botzmann Method (LBM) while the granular solid phase is modelled as a collection of discrete particles from a Molecular Dynamics DEM perspective. The range of possible material behaviours for the solid granular phase is intended here to cover a broad spectrum from purely frictional to viscous cohesive materials with either brittle or transient debonding features. Specific details of the implementation and some validation cases are put forward. Finally, some exemplary applications in the fields of soil erosion and geotechnical profile installation are provided along with a discussion on the parallel performance of the presented models. The results show that a micromechanical approach can be feasible and useful in practice, providing meaningful insights into complex engineering problems like the erosion kinetics of a soil under an impinging jet or the penetration resistance of a deep foundation in a layered soil profile. Elsevier Ltd. 2020 Computers and Geotechnics 120 Paper 103404, 1 urn:nbn:de:kobv:b43-502309 10.1016/j.compgeo.2019.103404 https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de 2020-01-22 OPUS4-50335 Zeitschriftenartikel Hu, W.-H; Tang, D.-H.; Wang, M.; Liu, J.-L.; Li, Z.-H.; Lu, W.; Teng, J.; Said, Samir; Rohrmann, R. G. Resonance Monitoring of a Horizontal Wind Turbine by Strain-Based Automated Operational Modal Analysis A strain-based automated operational modal analysis algorithm is proposed to track the long-term dynamic behavior of a horizontal wind turbine under operational conditions. This algorithm is firstly validated by a scaled wind turbine model, and then it is applied to the dynamic strain responses recorded from a 5 MW wind turbine system. We observed variations in the fundamental frequency and 1f, 3f excitation frequencies due to the mass imbalance of the blades and aerodynamic excitation by the tower dam or tower wake. Inspection of the Campbell diagram revealed that the adverse resonance phenomenon and Sommerfeld effect causing excessive vibrations of the wind tower. Schweiz, Basel MDPI 2020 Energies 13 3 579 584 urn:nbn:de:kobv:b43-503350 10.3390/en13030579 https://creativecommons.org/licenses/by/4.0/deed.de 2020-02-06 OPUS4-52006 Zeitschriftenartikel Auersch, Lutz Train-induced ground vibration due to the irregularities of the soil Many measurements of train induced ground vibrations show high amplitudes for a certain mid-frequency range. This ground vibration component cannot be well explained by dynamic loads of the train. Many characteristics indicate that the axle impulses, which are scattered by an irregular soil, are the excitation. This new understanding of railway-induced ground vibration is verified by numerical analysis. The response of the regular homogeneous and irregular inhomogeneous soils has been calculated by the finite-element method in frequency domain. A specific superposition of the impulse responses has been invented including time shift, axle sequence, track filter and hanning filter. The superposition yields the quasi-static component of the ground vibration which is restricted to very low frequencies and to the close near-field of the track. In case of an irregular soil of which the stiffness varies randomly in space, the superposition yields a mid-frequency ground vibration component from the scattering of the axle impulses. The existence and the importance of this component can thus be demonstrated by the calculations. Some rules of the influence of distance, train speed, soil stiffness, strength and width of the stiffness variation have been derived from the calculations. Many measurements show the unique explanation of the mid-frequency ground vibration component by the scattered axle impulses. London Elsevier Ltd. 2021 Soil Dynamics and Earthquake Engineering 140 106438 10.1016/j.soildyn.2020.106438 2021-01-18 OPUS4-52465 Beitrag zu einem Tagungsband Viefhues, Eva; Döhler, M.; Hille, Falk; Mevel, L. Fault detection for linear parameter varying systems under changes in the process noise covariance Detecting changes in the eigenstructure of linear systems is a comprehensively investigated subject. In particular, change detection methods based on hypothesis testing using Gaussian residuals have been developed previously. In such residuals, a reference model is confronted to data from the current system. In this paper, linear output-only systems depending on a varying external physical parameter are considered. These systems are driven by process noise, whose covariance may also vary between measurements. To deal with the varying parameter, an interpolation approach is pursued, where a limited number of reference models - each estimated from data measured in a reference state - are interpolated to approximate an adequate reference model for the current parameter. The problem becomes more complex when the different points of interpolation correspond to different noise conditions. Then conflicts may arise between the detection of changes in the eigenstructure due to a fault and the detection of changes due to different noise conditions. For this case, a new change detection approach is developed based on the interpolation of the eigenstructure at the reference points. The resulting approach is capable of change detection when both the external physical parameter and the process noise conditions are varying. This approach is validated on a numerical simulation of a mechanical system. Elsevier 2020 IFAC-PapersOnLine: 21st IFAC World Congress 53 21st IFAC World Congress Online meeting 13.07.2020 2 13668 13673 urn:nbn:de:kobv:b43-524652 10.1016/j.ifacol.2020.12.868 https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de 2021-04-21 OPUS4-45922 Zeitschriftenartikel Shamsuddoha, Md; Hüsken, Götz; Schmidt, Wolfram; Kühne, Hans-Carsten; Baeßler, Matthias Ternary mix design of grout material for structural repair using statistical tools 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. Elsevier Ltd. 2018 Construction and Building Materials 189 170 180 10.1016/j.conbuildmat.2018.08.156 2018-09-13 OPUS4-46004 Beitrag zu einem Tagungsband Geißler, Peter; Cuéllar, Pablo; Hüsken, Götz; Kühne, Hans-Carsten; Baeßler, Matthias Insights into compaction grouting for offshore pile foundations 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. 2018 Proceedings of the ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering OMAE 2018 9 978-0-7918-5130-2 37th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2018) Madrid, Spain 18.06.2018 22.06.2018 V009T10A013, 1 9 2018-09-21 OPUS4-46059 Beitrag zu einem Tagungsband Baeßler, Matthias; Hille, Falk Powers, N.; Frangopol, D. A study on diverse strategies for discriminating environmental from damage based variations in monitoring data 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. CRC Press 2018 Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges 978-1-138-73045-8 IABMAS Melbourne, Australia 09.07.2018 13.07.2018 1557 1564 2018-09-27 OPUS4-46434 Beitrag zu einem Tagungsband Schneider, Ronald; Rogge, Andreas; Thöns, S.; Bismut, E.; Straub, D. Caspeele, Robby; Taerwe, Luc; Frangopol, Dan M. A sampling-based approach to identifying optimal inspection and repair strategies for offshore jacket structures 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. London Taylor & Francis Group 2019 Proceedings of the sixth international symposium on life-cycle civil engineering (IALCCE 2018) 978-1-138-62633-1 The sixth international symposium on life-cycle civil engineering (IALCCE 2018) Ghent, Belgien 28.10.2018 31.10.2018 1081 1088 2018-11-05 OPUS4-46812 Zeitschriftenartikel Hu, Wei-Hua; Tang, De-Hui; Teng, Jun; Said, Samir; Rohrmann, Rolf Structural health monitoring of a prestressed concrete bridge based on statistical pattern recognition of continuous dynamic measurements over 14 years 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. 4052 Basel, Schweiz MDPI 2018 sensors 18 12 4117, 1 28 urn:nbn:de:kobv:b43-468126 10.3390/s18124117 https://creativecommons.org/licenses/by/4.0/deed.de 2018-11-30 OPUS4-46303 Beitrag zu einem Tagungsband Viefhues, Eva; Döhler, M.; Hille, Falk; Mevel, L. Simani, S.; Patan, K. Asymptotic analysis of subspace-based data-driven residual for fault detection with uncertain reference 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. Elsevier International Federation of Automatic Control 2018 10th IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes SAFEPROCESS 2018 51 10th IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes SAFEPROCESS 2018 Warsaw, Poland 29.08.2018 31.08.2018 24 414 419 10.1016/j.ifacol.2018.09.610 2018-10-17 OPUS4-47511 Zeitschriftenartikel Teng, Jun; Tang, De-Hui; Zhang, Xiao; Hu, Wei-Hua; Said, Samir; Rohrmann, Rolf G. Automated modal analysis for tracking structural change during construction and operation phases 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. Basel, Switzerland MDPI AG 2019 Sensors 19 4 927, 1 23 urn:nbn:de:kobv:b43-475116 10.3390/s19040927 https://creativecommons.org/licenses/by/4.0/deed.de 2019-03-11 OPUS4-47831 Beitrag zu einem Tagungsband Shamsuddoha, Md; Hüsken, Götz; Schmidt, Wolfram; Kühne, Hans-Carsten; Baeßler, Matthias Superplasticizer and Shrinkage Reducing Admixture Dosages for Microfine Cement in Grout Systems 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. EDP Sciences 2019 MATEC Web of Conferences 278 2nd International Conference on Building Materials and Materials Engineering (ICBMM 2018) University of Lisbon, Portugal 26.09.2018 28.09.2018 Article Number 01001 urn:nbn:de:kobv:b43-478319 10.1051/matecconf/201927801001 https://creativecommons.org/licenses/by/4.0/deed.de 2019-04-17 OPUS4-47891 Zeitschriftenartikel Auersch, Lutz Compliance and damping of piles for wind tower foundation in nonhomogeneous soils by the finite-element boundary-element method 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. London Elsevier 2019 Soil Dynamics and Earthquake Engineering 120 5 228 244 10.1016/j.soildyn.2018.12.005 2019-05-08 OPUS4-58793 Zeitschriftenartikel Signorini, Cesare; Bracklow, Franz; Hering, Marcus; Butler, Marko; Leicht, Lena; Schubert, Thomas; Beigh, Mirza A.B.; Beckmann, Birgit; Curbach, Manfred; Mechtcherine, Viktor Ballistic limit and damage assessment of hybrid fibre-reinforced cementitious thin composite plates under impact loading Impact resistance of reinforced concrete (RC) structures can be significantly improved by strengthening RC members with thin composite layers featuring high damage tolerance. Indeed, to limit the well-known vulnerability of cement-based materials against impact loading, the synergistic effects of short fibres and continuous textile meshes as hybrid reinforcement has been proved to be highly beneficial. This paper addresses the characterisation of novel cement-based hybrid composites through accelerated drop-weight impact tests conducted on rectangular plates at different impact energies. Two distinct matrices are assessed, with particular interest in a newly developed limestone calcined clay cement (LC3)-based formulation. Important parameters quantifying energy dissipation capability, load bearing capacity and damage are cross-checked to compute the ballistic limit and estimate the safety-relevant characteristics of the different composites at hand. Although textiles alone can improve the damage tolerance of fine concrete to some extent, the crack-bridging attitude of short, well-dispersed fibres in hybrid composites imparts a certain ductility to the cement-based matrices, allowing a greater portion of the textile to be activated and significantly reducing the amount of matrix spalling under impact. Elsevier Ltd. 2023 Journal of Building Engineering 80 1 21 10.1016/j.jobe.2023.108037 2023-11-13 OPUS4-57019 Zeitschriftenartikel Sadowski, A.; Seidel, M.; Al-Lawati, H.; Azizi, E.; Balscheit, Hagen; Böhm, M.; Chen, Lei; van Dijk, I.; Doerich-Stavridis, C.; Kunle Fajuyitan, O.; Filippidis, A.; Winther Fischer, A.; Fischer, C.; Gerasimidis, S.; Karampour, H.; Kathirkamanathan, L.; Subramanian, S.; Topkaya, Cem; Wagner, H. N. R.; Wang, J.; Wang, J.; Kumar Yadav, K.; Yun, X.; Zhang, P. 8-MW wind turbine tower computational shell buckling benchmark - Part 1: An international 'round-robin' exercise An assessment of the elastic-plastic buckling limit state for multi-strake wind turbine support towers poses a particular challenge for the modern finite element analyst, who must competently navigate numerous modelling choices related to the tug-of-war between meshing and computational cost, the use of solvers that are robust to highly nonlinear behaviour, the potential for multiple near-simultaneously critical failure locations, the complex issue of imperfection sensitivity and finally the interpretation of the data into a safe and economic design. This paper reports on an international 'round-robin' exercise conducted in 2022 aiming to take stock of the computational shell buckling expertise around the world which attracted 29 submissions. Participants were asked to perform analyses of increasing complexity on a standardised benchmark of an 8-MW multi-strake steel wind turbine support tower segment, from a linear elastic stress analysis to a linear bifurcation analysis to a geometrically and materially nonlinear buckling analysis with imperfections. The results are a showcase of the significant shell buckling expertise now available in both industry and academia. This paper is the first of a pair. The second paper presents a detailed reference solution to the benchmark, including an illustration of the Eurocode-compliant calibration of two important imperfection forms. Oxford Elsevier Science 2023 Engineering failure analysis 148 1 23 10.1016/j.engfailanal.2023.107124 2023-02-20 OPUS4-56732 Zeitschriftenartikel Brinkmann, M.; Wiehle, Philipp Correlation between relative humidity and the strength and deformation characteristics of unstabilised earth masonry The mechanical properties of unstabilised earthen building materials are distinctively influenced by changes in material moisture content. However, this moisture-dependency often remains unconsidered in the calculation of the load-bearing capacity of earth constructions. This paper aims to derive a convenient way to sufficiently consider the impact of different material moisture contents on the mechanical properties of unstabilised earth masonry. Therefore, the influence of relative humidity and temperature on the strength and deformation characteristics of unstabilised earth blocks, earth mortar and earth masonry is evaluated by conducting compression tests under various climate conditions. The results show that the compressive strength and the modulus of elasticity are linearly correlated with the relative humidity, whereas changes in temperature at constant relative humidity have no significant influence. To account the distinct moisture-dependency, a general applicable modification factor for unstabilised earthen materials is provided, which enables the adjustment of the compressive strength and the modulus of elasticity in dependency of arbitrary hygroscopic material moisture contents. Elsevier BV 2023 Construction and Building Materials 366 22 1 11 10.1016/j.conbuildmat.2022.130048 2022-12-28 OPUS4-58725 Zeitschriftenartikel Eichner, Lukas; Schneider, Ronald; Baeßler, Matthias Optimal vibration sensor placement for jacket support structures of offshore wind turbines based on value of information analysis Information on the condition and reliability of an offshore jacket structure provided by a vibration-based structural health monitoring system can guide decisions on inspection and maintenance. When selecting the sensor setup, the designer of the monitoring system must assess its overall benefit compared to its costs before installation. The potential benefit of continuously monitoring the dynamic response of a jacket structure can be formally quantified through a value of information analysis from Bayesian decision theory. In this contribution, we present a framework for optimizing the placement of vibration sensors on offshore jacket structures by maximizing the value of information of the monitoring system. To solve the resulting discrete optimization problem, we adapt a genetic algorithm. The framework is demonstrated in a numerical example considering a redundant jacket-type steel frame. The numerical study shows that monitoring the vibration response of the frame is beneficial. Good sensor setups consist of relatively few sensors located towards the upper part of the frame. The adapted genetic algorithm performs similarly well as established sequential sensor placement algorithms and holds substantial promise for application to real jacket structures. Amsterdam Elsevier Ltd. 2023 Ocean Engineering 288 2 10.1016/j.oceaneng.2023.115407 2023-11-02 OPUS4-58669 Zeitschriftenartikel Hering, Marcus; Sievers, Jürgen; Curbach, Manfred; Beckmann, Birgit An Approach to Predicting the Ballistic Limit of Thin Textile-Reinforced Concrete Plates Based on Experimental Results In this article, a partial selection of experiments on enhancing the impact resistance of structural components with non-metallic, textile-reinforced concrete is discussed. The focus is on the experimental investigations in which the impact resistance of thin, textile-reinforced concrete plates is characterized. The article discusses the materials, fabrics and test setup used. For the experimental work, a drop tower from the Otto Mohr Laboratory, which belongs to the Technische Universtät Dresden, was used. Furthermore, the experimental results are presented and evaluated using different methods. Based on the collected data, a suitable approach to determining the perforation velocity of an impactor through the investigated thin, textile-reinforced concrete plates is shown. MDPI 2023 Buildings 13 9 1 14 urn:nbn:de:kobv:b43-586692 10.3390/buildings13092234 https://creativecommons.org/licenses/by/4.0/deed.de 2023-10-26 OPUS4-58161 Zeitschriftenartikel Liehr, A.; Wegener, T.; Degener, Sebastian; Bolender, A.; Möller, N.; Niendorf, T. Experimental Analysis of the Stability of Retained Austenite in a Low-Alloy 42CrSi Steel after Different Quenching and Partitioning Heat Treatments Quenching and partitioning (Q&P) steels are characterized by an excellent combination of strength and ductility, opening up great potentials for advanced lightweight components. The Q&P treatment results in microstructures with a martensitic matrix being responsible for increased strength whereas interstitially enriched metastable retained austenite (RA) contributes to excellent ductility. Herein, a comprehensive experimental characterization of microstructure evolution and austenite stability is carried out on a 42CrSi steel being subjected to different Q&P treatments. The microstructure of both conditions is characterized by scanning electron microscopy as well as X-ray diffraction (XRD) phase analysis. Besides macroscopic standard tensile tests, RA evolution under tensile loading is investigated by in situ XRD using synchrotron and laboratory methods. As a result of different quenching temperatures, the two conditions considered are characterized by different RA contents and morphologies, resulting in different strain hardening behaviors as well as strength and ductility values under tensile loading. In situ synchrotron measurements show differences in the transformation kinetics being rationalized by the different morphologies of the RA. Eventually, the evolution of the phase specific stresses can be explained by the well-known Masing model. Wiley 2023 Advanced Engineering Materials 25 17 1 16 urn:nbn:de:kobv:b43-581618 10.1002/adem.202300380 https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de 2023-09-06 OPUS4-57302 Zeitschriftenartikel Lehmann, F.; Hille, Falk Dauerüberwachung von Ingenieurbauwerken - Das neue Merkblatt B 09 der DGZfP Messtechnische Systeme zur Dauerüberwachung von Bauwerken ermöglichen Einblicke in deren reale Trag- und Verformungsverhalten. Die Planung und technische Umsetzung solcher Maßnahmen erfordern für die erfolgreiche Erfüllung der Aufgabenstellungen eine hohe Fachkompetenz, sowohl auf der planerischen Seite, als auch für die fachliche Bewertung von angebotenen Monitoringlösungen. Als Hilfestellung dafür wurde von der Deutschen Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) das Merkblatt „Dauerüberwachung von Ingenieurbauwerken" erarbeitet, welches nun verfügbar ist. In diesem Beitrag werden die Inhalte des neuen Merkblatts vorgestellt und dieses in die vorhandene Literatur eingeordnet. Ernst & Sohn 2023 Beton- und Stahlbetonbau 118 4 275 280 10.1002/best.202200122 2023-04-17 OPUS4-58513 Zeitschriftenartikel Auersch, Lutz The dynamic train-track interaction on a bridge and in a tunnel compared with the simultaneous vehicle, track, and ground vibration measurements at a surface line The vehicle-track interaction generates forces and consequently vibrations in the environment. The interaction has been analysed by the simultaneous measurements of vehicle, track and ground vibrations during test runs with varied train speeds. The special effects of the passage over a bridge and through a tunnel are studied and compared with the measurements on a conventional ballasted surface line. The maximum amplitudes, narrow band and one-third octave band spectra are presented for the axle-box accelerations and for the track, bridge and ground vibrations. The different frequencies and frequency bands are related to wheel out-of-roundness, track alignment errors, the sleeper passage and the wheelset-track resonance. An axle impulse component has been observed at the track, at the near-field soil and as a scattered version in the far field. Specific results can be found for the bridge track, where clearly speed-dependent bridge resonances occur due to the axle sequence of the train, and for the tunnel track where soft rail pads are responsible for a strong amplification around the wheelset-track resonance. On the other hand, the axle impulses are strongly reduced by the tunnel track, and the scattered axle impulse component is not as relevant as for the surface track. As a consequence, a strong mid-frequency amplitude reduction of the tunnel compared to the surface line has been measured for low and high train speeds by the Federal Institute of Material Research and Testing (BAM) and by other institutes. Basel, Schweiz MDPI 2023 Applied Sciences 13 19 1 23 urn:nbn:de:kobv:b43-585139 10.3390/app131910992 https://creativecommons.org/licenses/by/4.0/deed.de 2023-10-09 OPUS4-58502 Zeitschriftenartikel Auersch, Lutz Site-specific amplitude-distance laws, wave velocities, damping, and transfer functions of the soil from hammer impacts and application to railway-induced ground vibration - Similarities and mid-frequency differences The propagation of ground vibrations is theoretically analysed with frequency-wavenumber and simplified methods. Experimental methods are presented which can characterise the site-specific ground vibrations by wave velocities, stiffness and damping. Measurements with hammer and train excitation have been performed at several sites. The one-third octave spectra show the stiffness-dependent amplitudes and the low- and high-frequency filter effects due to the layering and the damping of the soil. Specific train effects, an additional high-frequency filter, the sleeper passage frequency, and an amplified mid-frequency component can be clearly found. The attenuation with distance is analysed in detail where the theoretical exponential and the empirical frequency-dependent power law are considered. Hammer and train excitation show the same site-specific effects which are mainly due to the stronger or weaker damping of the soil. The train attenuation is generally weaker than the hammer attenuation. The attenuation exponent of the power law, which is strongly dependent on the site and the frequency, is reduced for the train vibration by 0.3 to 0.5 in agreement with the theory. Reasons are discussed for the overall power law and for the dominating mid-frequency component. Springer 2023 Journal of Vibration Engineering & Technologies 1 17 urn:nbn:de:kobv:b43-585020 10.1007/s42417-023-01095-0 https://creativecommons.org/licenses/by/4.0/deed.de 2023-10-09 OPUS4-57449 Zeitschriftenartikel Titscher, Thomas; van Dijk, T.; Kadoke, Daniel; Robens-Radermacher, Annika; Herrmann, Ralf; Unger, Jörg F. Bayesian model calibration and damage detection for a digital twin of a bridge demonstrator Using digital twins for decision making is a very promising concept which combines simulation models with corresponding experimental sensor data in order to support maintenance decisions or to investigate the reliability. The quality of the prognosis strongly depends on both the data quality and the quality of the digital twin. The latter comprises both the modeling assumptions as well as the correct parameters of these models. This article discusses the challenges when applying this concept to realmeasurement data for a demonstrator bridge in the lab, including the data management, the iterative development of the simulation model as well as the identification/updating procedure using Bayesian inference with a potentially large number of parameters. The investigated scenarios include both the iterative identification of the structural model parameters as well as scenarios related to a damage identification. In addition, the article aims at providing all models and data in a reproducibleway such that other researcher can use this setup to validate their methodologies. Hoboken, NJ Wiley 2023 Engineering reports 1 27 urn:nbn:de:kobv:b43-574496 10.1002/eng2.12669 https://creativecommons.org/licenses/by/4.0/deed.de 2023-05-11 OPUS4-57244 Beitrag zu einem Tagungsband Gerards-Wünsche, Paul; Ratkovac, Mirjana; Schneider, Ronald; Hille, Falk; Baeßler, Matthias A framework for assessing the reliability of crack luminescence - an automated fatigue crack detection system 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. 2023 SPIE Conference Smart Structures + Nondestructive Evaluation 2023 978-1-5106-6086-1 SPIE Conference Smart Structures + Nondestructive Evaluation 2023 Long Beach, CA, USA 24.03.2023 28.03.2023 1 15 10.1117/12.2658390 2023-03-30 OPUS4-57957 Zeitschriftenartikel Auersch, Lutz Reduction in Train-Induced Vibrations—Calculations of Different Railway Lines and Mitigation Measures in the Transmission Path 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. Basel MDPI 2023 Applied Sciences 13 11 1 19 urn:nbn:de:kobv:b43-579573 10.3390/app13116706 https://creativecommons.org/licenses/by/4.0/deed.de 2023-07-24 OPUS4-58884 Zeitschriftenartikel Faghih-Naini, Sara; Kuckuk, Sebastian; Zint, Daniel; Kemmler, Samuel; Köstler, Harald; Aizinger, Vadym Discontinuous Galerkin method for the shallow water equations on complex domains using masked block-structured grids We evaluate masked block-structured grids for ocean domains which allow to represent small-scale geometric features without resorting to very small blocks or excessive mesh resolution. The considered approach aims to combine the geometric flexibility of unstructured meshes with the computational efficiency of stencil-based discretizations and is implemented and tested in a quadrature-free discontinuous Galerkin shallow water solver. We investigate the accuracy and the computational performance of the scheme on a range of realistic ocean domains meshed with blocks of different size and provide some comparisons to results obtained on unmasked block-structured grids and unstructured meshes. Elsevier 2023 Advances in Water Resources 182 1 11 10.1016/j.advwatres.2023.104584 2023-11-22 OPUS4-59099 Beitrag zu einem Tagungsband Ritz, Sebastian; Loewe, Anna; Bauer, Jan Specialties of HAZID-Study for Large Unmanned Underwater Vehicles This paper scopes the specialties of a hazard identification study for large and extra-large unmanned undersea vehicles (UUVs). A generic node/function structure is derived from different large and extra-large UUV designs, partially own vehicle designs from research projects, and partially from commercial vehicles. For each node, a short overview of its components and the proper function or operations is defined. A set of guide words is used to prompt a hazard discussion for each node, which identifies unwanted functions, resulting in potential hazards and unmitigated consequences. Related to the SafeMASS-Report from DNV, this work concentrates on selected topics of the bridge-related function on voyage, control & monitoring, and abnormal situations. For unmanned vehicles without any person on board, these three topics become more important for underwater vehicles with very limited connectivity or temporary disruptions of communication whereby an operator in a remote-control center could only be provided with rough vehicle or mission states. Therefore, vehicle control, whether in hard- or software, must handle most tasks belonging to the considered functions automatically or autonomously. Hence, the most appropriate reactions of the system to unwanted system behavior must be implemented. This HAZID study could, on the one hand, be used as background for such an implementation, and on the other hand, it is used to verify the implemented actions on the risks and hazards. IEEE 2023 OCEANS 2023 - Limerick OCEANS 2023 - Limerick Limerick, Ireland 05.06.2023 08.06.2023 1 10 10.1109/OCEANSLimerick52467.2023.10244358 2023-12-11