TY - CONF A1 - Zinas, Orestis A1 - Schneider, Ronald A1 - Cuéllar, Pablo A1 - Schepers, Winfried A1 - Baeßler, Matthias A1 - Papaioannou, I. T1 - Potentials of probabilistic approaches in offshore foundation installation N2 - This presentation discusses the potentials of probabilistic methods in offshore foundation installation, from the perspective of probabilistic ground models and data-driven site characterization. We discuss about methodologies for utilizing site-specific geotechnical (CPT) and geological data, aiming to construct an integrated ground model that can predict stratigraphic profiles and useful for geotechnical design parameters at any location within a 3D domain. The predicted parameters and stratigraphy are then used to predict the probability of potential pile tip damage, upon collision with a boulder. T2 - Colloquium Buckling of Offshore Wind Energy Structures CY - Berlin, Germany DA - 14.02.2024 KW - Wind KW - Offshore KW - Buckling KW - Probabilistic KW - Ground PY - 2024 AN - OPUS4-59538 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zinas, Orestis T1 - 3D Probabilistic Site Characterization N2 - The aim of the study is to infer the soil stratification from the provided CPT and borehole data. We infer the soil type at any location within the domain of interest from the SBT index Ic (Robertson, 2009). This index can be directly related to the CPT data through an empirical correlation model. In addition, the soil classes contained in the borehole logs can be expressed as bounds on Ic. A log-transformation was applied to Ic, Y = ln(Ic), and Y was modelled by a 3D Random Field, with a fully Bayesian hierarchical Gaussian Process model to explicitly capture uncertainties. T2 - 19th eawe PhD Seminar CY - Hannover, Germany DA - 06.09.2023 KW - Wind Energy KW - Site-characterization KW - Probabilistic PY - 2023 AN - OPUS4-58940 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wiehle, Philipp A1 - Simon, Sebastian A1 - Baier, J. A1 - Dennin, L. ED - Forde, M. T1 - Influence of relative humidity on the strength and stiffness of unstabilised earth blocks and earth masonry mortar N2 - 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. KW - Earth block masonry KW - Load-bearing behaviour KW - Compressive strength KW - Moisture content KW - Sorption isotherm PY - 2022 U6 - https://doi.org/10.1016/j.conbuildmat.2022.128026 SN - 0950-0618 VL - 342 IS - Part A SP - 1 EP - 15 PB - Elsevier Ltd. AN - OPUS4-54949 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wiehle, Philipp A1 - Brinkmann, M. T1 - Material behaviour of unstabilised earth block masonry and its components under compression at varying relative humidity N2 - 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. KW - Compressive strength KW - Earth block masonry KW - Compression tests KW - Stress-strain relation KW - Relative humidity KW - Moisture content PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-562417 SN - 2214-5095 VL - 17 SP - 1 EP - 15 PB - Elsevier B.V. CY - Netherlands AN - OPUS4-56241 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wiehle, Philipp A1 - Brinkmann, M. T1 - Tragfähigkeit von Lehmmauerwerk - Experimentelle und numerische Analyse T1 - Load-bearing capacity of earth masonry – An experimental and numerical analysis N2 - Die Bemessung von tragendem Lehmmauerwerk erfolgt in Deutschland auf Basis der Lehmbau Regeln. Das dort verankerte Nachweisverfahren beruht auf einem globalen Sicherheitskonzept, welches aus zuverlässigkeitstheoretischer Sicht nicht mehr dem Stand der Technik entspricht. Auf Grund dessen wird das Bemessungskonzept für Lehmmauerwerk vom Deutschen Institut für Bautechnik (DIBt) voraussichtlich 2023 außer Kraft gesetzt. Ein statischer Nachweis von tragenden Lehmbauten wäre in Deutschland dann ausschließlich mit einer Zustimmung im Einzelfall (ZiE) oder vorhabenbezogener Bauartgenehmigung (vBg) möglich. Beides ist mit erheblichem Mehraufwand und höheren Kosten verbunden, was für den Lehmmauerwerksbau einen entscheidenden Nachteil im Vergleich zum konventionellen Mauerwerksbau darstellt. Um eine unkomplizierte Praxisanwendung von Lehmmauerwerk zu ermöglichen, werden innerhalb eines Forschungsvorhabens, welches von der Bundesanstalt für Materialforschung und -prüfung (BAM), dem Institut für Massivbau der Technischen Universität Darmstadt sowie dem Ingenieurbüro ZRS durchgeführt wird, auf Basis der Produktnormen für Lehmsteine und Lehmmauermörtel Grundlagen für ein aktualisiertes Bemessungskonzept entwickelt. Im Rahmen des Projekts wird ebenfalls untersucht, inwiefern die Bemessungsregeln nach den vereinfachten Berechnungsmethoden für unbewehrtes Mauerwerk gemäß DIN EN 1996-3 / NA auf den Lehmmauerwerksbau übertragbar sind. Falls eine Anwendung des normativen Nachweisverfahrens bei Lehmmauerwerk möglich ist, wäre zukünftig eine Aufnahme von Lehmsteinen und Lehmmauermörtel in den nationalen Anhang des Eurocode 6 denkbar, was eine bedeutsame Erweiterung des Anwendungsbereichs von Lehmmauerwerk zur Folge hätte. Diverse wissenschaftliche Untersuchungen konnten zeigen, dass bemessungsrelevante Festigkeits- und Verformungseigenschaften von Lehmmauerwerksbaustoffen stark von der vorherrschenden Materialfeuchte abhängen, welche im hygroskopischen Wassergehaltsbereich im Wesentlichen von der relativen Luftfeuchte (RLF) bestimmt wird. Auch die Zwischenergebnisse des laufenden Forschungsvorhabens zur Entwicklung eines Bemessungskonzepts für Lehmmauerwerk ergaben eine deutlich erkennbare Abhängigkeit zwischen der Materialfeuchte und den relevanten Festigkeits- und Verformungseigenschaften. Eine detaillierte Kenntnis des feuchteabhängigen Materialverhaltens von Lehmsteinen, -mörtel und -mauerwerk ist zwingend erforderlich, um ein konsistentes und zuverlässiges Bemessungskonzept für Lehmmauerwerk zu entwickeln. Im Rahmen des laufenden Forschungsprojektes werden deshalb umfangreiche Versuche zum Drucktragverhalten von Lehmsteinen und -mörtel sowie Lehmmauerwerk nach Konditionierung bei unterschiedlichen RLF durchgeführt und analysiert. Weiterhin werden auf Basis der experimentellen Ergebnisse numerische Modelle kalibriert, welche die detaillierte Analyse der Biegedrucktragfähigkeit von Lehmmauerwerk ermöglichen. In diesem Beitrag werden zunächst die bisherigen Zwischenergebnisse bezüglich der experimentell ermittelten feuchteabhängigen Materialkennwerte von Lehmsteinen, -mörtel und -mauerwerk dargelegt. Darauf aufbauend werden numerische Untersuchungen zur Bestimmung der Systemtragfähigkeit von Lehmmauerwerk unter Feuchteeinflusses durchgeführt und erläutert. N2 - The structural design of load-bearing earthen masonry in Germany is based on the Lehmbau Regeln. The verification procedure outlined in these regulations is based on a global safety concept that no longer corresponds to the state of the art from a reliability theory perspective. As a result, the structural design concept for earthen masonry will most likely be discontinued by the German Institute for Building Technology (DIBt) in 2023. A structural verification of load-bearing earthen buildings would then only be possible in Germany with an approval for individual cases (ZiE) or a project-related permit type (vBg). Both methods are associated with considerable additional work and higher costs, which is a decisive disadvantage for earthen masonry construction compared to conventional masonry construction. In order to enable a straightforward practical application of earthen masonry, the Federal Institute for Materials Research and Testing (BAM), the Institute for Solid Construction of the Technical University of Darmstadt and ZRS Engineers are laying the groundwork for an updated structural design concept based on the product standards for earth blocks and earthen masonry mortar. The project will also investigate the extent to which the design rules based on the simplified calculation methods for unreinforced masonry according to DIN EN 1996-3 / NA can be transferred to earthen masonry construction. If the normative verification procedure can be applied to earthen masonry, it would be conceivable to include earth blocks and earthen masonry mortar in the national appendix of Eurocode 6 in the future, which would result in a significant expansion of the field of application of earthen masonry. Various scientific studies have shown that the strength and deformation properties of earthen masonry building materials relevant to structural design are strongly dependent on the prevailing material moisture level, which is essentially determined by the relative humidity (RH) in the hygroscopic water content range. The interim results of the current research project for the development of a structural design concept for earthen masonry also showed a clearly recognisable dependency between the material moisture level and the relevant strength and deformation properties. Detailed knowledge of the moisture-dependent material behaviour of earth blocks, earthen mortar and masonry is absolutely essential to developing a consistent and reliable structural design concept for earthen masonry. Within the framework of the current research project, extensive tests on the pressure load bearing capacity of earth blocks and earthen mortar as well as earthen masonry after conditioning at different RH levels are therefore being carried out and analysed. Furthermore, numerical models are being calibrated on the basis of the experiment results, which facilitate a detailed analysis of the bending pressure bearing capacity of earthen masonry. This paper presents, firstly, the interim results obtained so far concerning the experimentally determined moisture-dependent material characteristics of earth blocks, earthen mortar and masonry. Based on this material, numerical investigations for determining the system bearing capacity of earthen masonry under the influence of moisture are carried out and explained. T2 - LEHM 2020 CY - Weimar, Germany DA - 30.10.2020 KW - Lehm KW - Earth KW - Tragfähigkeit KW - Mauerwerk KW - Feuchte KW - Load-bearing KW - Moisture KW - Strength PY - 2020 SP - 1 EP - 12 PB - Dachverband Lehm CY - Weimar AN - OPUS4-53231 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Viefhues, Eva A1 - Döhler, M. A1 - Zhang, Q. A1 - Hille, Falk A1 - Mevel, L. T1 - Subspace-based Damage Detection with Rejection of the Temperature Effect and Uncertainty in the Reference N2 - 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. T2 - International Operational Modal Analysis Conference CY - Copenhagen, Danmark DA - 13.05.2019 KW - Uncertainty KW - Statistical method KW - Subspace-based method KW - Temperature rejection KW - Model interpolation PY - 2019 SP - 1 EP - 11 AN - OPUS4-48240 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Viefhues, Eva A1 - Döhler, M. A1 - Simon, Patrick A1 - Herrmann, Ralf A1 - Hille, Falk A1 - Mevel, L. ED - Cunha, A. ED - Caetano, E. T1 - Stochastic subspace-based damage detection of a temperature affected beam structure N2 - Structural health monitoring (SHM) of civil structures often is limited due to changing environmental conditions, as those changes affect the structural dynamical properties in a similar way like damages can do. In this article, an approach for damage detection under changing temperatures is presentedand applied to a beam structure. The used stochastic subspace-based algorithm relies on a reference null space estimate, which is confronted to data from the testing state in a residual function. For damage detection the residual is evaluated by means of statistical hypothesis tests. Changes of the system due to temperature effects are handled with a model interpolation approach from linear parameter varying system theory. From vibration data measured in the undamaged state at some few reference temperatures, a model of the dynamic system valid for the current testing temperature is interpolated. The reference null space and the covariance matrix for the hypothesis test is computed from this interpolated model. This approach has been developed recently and was validated in an academic test case on simulations of a mass-spring-damper. In this paper, the approach is validated experimentally on a beam structure under varying temperature conditions in a climate chamber. Compared to other approaches, the interpolation approach leads to significantly less false positive alarms in the reference state when the structure is exposed to different temperatures, while faults can still be detected reliably. T2 - 10th International Conference on Structural Health Monitoring of Intelligent Infrastructure, SHMII 10 CY - Online meeting DA - 30.06.2021 KW - Damage detection KW - Subspace methods KW - Temperature effects KW - Model interpolation KW - Climate chamber KW - Laboratory beam structure PY - 2021 SP - 1 EP - 6 AN - OPUS4-52999 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Viefhues, Eva A1 - Döhler, M. A1 - Hille, Falk A1 - Mevel, L. T1 - Statistical subspace-based damage detection with estimated reference N2 - 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. KW - Damage detection KW - Uncertainty quantification KW - Statistical tests KW - Ambient excitation KW - Vibration measurement PY - 2022 U6 - https://doi.org/10.1016/j.ymssp.2021.108241 SN - 0888-3270 VL - 164 SP - 108241 PB - Elsevier Ltd. AN - OPUS4-52998 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Viefhues, Eva A1 - Döhler, M. A1 - Hille, Falk A1 - Mevel, L. T1 - Fault detection for linear parameter varying systems under changes in the process noise covariance N2 - 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. T2 - IFAC World Congress 2020 CY - Online meeting DA - 11.07.2020 KW - Linear parameter varying systems KW - Fault detection KW - Changing process noise KW - Subspace-based residual KW - Model interpolation PY - 2020 SP - 13858 AN - OPUS4-51617 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Viefhues, Eva A1 - Döhler, M. A1 - Hille, Falk A1 - Mevel, L. T1 - Fault detection for linear parameter varying systems under changes in the process noise covariance N2 - 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. T2 - 21st IFAC World Congress CY - Online meeting DA - 13.07.2020 KW - Linear parameter varying systems KW - Fault detectionchanging KW - Process noise KW - Subspace-based residual KW - Model interpolation PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-524652 SN - 2405-8963 VL - 53 IS - 2 SP - 13668 EP - 13673 PB - Elsevier AN - OPUS4-52465 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Viefhues, Eva A1 - Döhler, M. A1 - Hille, Falk A1 - Mevel, L. ED - Simani, S. ED - Patan, K. T1 - Asymptotic analysis of subspace-based data-driven residual for fault detection with uncertain reference N2 - 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. T2 - 10th IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes SAFEPROCESS 2018 CY - Warsaw, Poland DA - 29.08.2018 KW - Subspace-based method KW - Fault detection KW - Uncertainty in reference KW - Residual evaluation KW - Statistical tests KW - Vibration measurements PY - 2018 U6 - https://doi.org/10.1016/j.ifacol.2018.09.610 SN - 2405-8963 VL - 51 IS - 24 SP - 414 EP - 419 PB - Elsevier AN - OPUS4-46303 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Viefhues, Eva A1 - Döhler, M. A1 - Simon, Patrick A1 - Herrmann, Ralf A1 - Hille, Falk A1 - Mevel, L. T1 - Stochastic subspace-based damage detection of a temperature affected beam structure N2 - Structural health monitoring (SHM) of civil structures often is limited due to changing environmental conditions, as those changes affect the structural dynamical properties in a similar way like damages can do. In this article, an approach for damage detection under changing temperatures is presentedand applied to a beam structure. The used stochastic subspace-based algorithm relies on a reference null space estimate, which is confronted to data from the testing state in a residual function. For damage detection the residual is evaluated by means of statistical hypothesis tests. Changes of the system due to temperature effects are handled with a model interpolation approach from linear parameter varying system theory. From vibration data measured in the undamaged state at some few reference temperatures, a model of the dynamic system valid for the current testing temperature is interpolated. The reference null space and the covariance matrix for the hypothesis test is computed from this interpolated model. This approach has been developed recently and was validated in an academic test case on simulations of a mass-spring-damper. In this paper, the approach is validated experimentally on a beam structure under varying temperature conditions in a climate chamber. Compared to other approaches, the interpolation approach leads to significantly less false positive alarms in the reference state when the structure is exposed to different temperatures, while faults can still be detected reliably T2 - 10th International Conference on Structural Health Monitoring of Intelligent Infrastructure, SHMII 10 CY - Online meeting DA - 30.06.2021 KW - Damage detection KW - Subspace methods KW - Temperature effects KW - Model interpolation KW - Climate chamber KW - Laboratory beam structure PY - 2021 AN - OPUS4-53000 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Viefhues, Eva T1 - Subspace-based damage detection in engineering structures considering reference uncertainties and temperature effects N2 - Automated vibration-based damage detection is of increasing interest for structural health monitoring of engineering structures. In this context, stochastic subspace-based damage detection (SSDD) compares measurements from a testing state to a data-driven reference model in a statistical framework. In this thesis theoretical developments have been proposed to improve the robustness of SSDD for realistic applications conditions. First, a statistical test has been proposed considering the statistical uncertainties about the model obtained from the reference data. This leads to a precise description of the test’s distribution properties and damage detection thresholds. Second, an approach has been developed to account for environmental effects in SSDD. Based on reference measurements at few different environmental conditions, a test is derived with respect to an adequate interpolated reference. The proposed methods are validated in numerical simulations and applied to experimental data from the laboratory and outdoor structures. KW - Damage detection KW - Subspace methods KW - Vibrations KW - Uncertainty quantification KW - Environmental effects KW - Civil structures PY - 2021 SP - 1 EP - 191 CY - Universite de Rennes AN - OPUS4-55774 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Viefhues, Eva A1 - Döhler, M. A1 - Zhang, Q. A1 - Hille, Falk A1 - Mevel, L. T1 - Subspace-based Damage Detection with Rejection of the Temperature Effect and Uncertainty in the Reference N2 - 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. T2 - International Operational Modal Analysis Conference CY - Copenhagen, Danmark DA - 13.05.2019 KW - Un- certainty KW - Statistical method KW - Subspace-based method KW - Temperature rejection KW - Model interpolation PY - 2019 AN - OPUS4-48244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Viefhues, Eva T1 - Subspace-based damage detection handling temperature effects and uncertainty in the reference N2 - 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. T2 - Abteilungs-Vortragsseminar Abteilung 7 Bauwerksicherheit CY - Berlin, Germany DA - 28.11.2019 KW - Statistical method KW - Subspace-based method KW - Temperature rejection KW - Model interpolation KW - Uncertainty PY - 2019 AN - OPUS4-50195 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Viefhues, Eva A1 - Döhler, M. A1 - Hille, Falk A1 - Mevel, L. T1 - Fault detection for linear parameter varying systems under changes in the process noise covariance N2 - 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 con icts 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. T2 - 21st IFAC World Congress CY - Berlin, Germany DA - 13.07.2020 KW - Linear parameter varying systems KW - Fault detection KW - Changing process noise KW - Subspace-based residual KW - Model interpolation PY - 2020 AN - OPUS4-52366 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Titscher, Thomas A1 - van Dijk, T. A1 - Kadoke, Daniel A1 - Robens-Radermacher, Annika A1 - Herrmann, Ralf A1 - Unger, Jörg F. T1 - Bayesian model calibration and damage detection for a digital twin of a bridge demonstrator N2 - 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. KW - Damage detection KW - Finite element analysis KW - Load identification KW - Model updating KW - Estimation KW - System identification KW - Variational Bayesian statistics PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-574496 SN - 2577-8196 SP - 1 EP - 27 PB - Wiley CY - Hoboken, NJ AN - OPUS4-57449 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thiele, Marc A1 - Pirskawetz, Stephan T1 - Analysis of damage evolution in concrete under fatigue loading by acoustic emission and ultrasonic testing N2 - 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. KW - Concrete KW - Fatigue KW - Damage evolution KW - Ultrasonic testing KW - Acoustic emission PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-541891 SN - 1996-1944 VL - 15 IS - 1 SP - 341 EP - 355 PB - MDPI CY - Basel AN - OPUS4-54189 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiele, Marc A1 - Makris, Ralf ED - Aign, J. T1 - Reinforcement bar and reinforcement bar splicing systems under impact loading – Experimental tests and test specification N2 - Reinforced concrete is a widely used material for power generation structures, where load scenarios like impact loadings need to be considered. In this context mechanical splicing systems for the connection of reinforcement bars are of specific interest and impact resistance for the splicing systems has to be verified. High speed tensile tests need to be performed on splicing systems for reinforcement bars to confirm the capability of the coupler to resist impact loading. Furthermore, the ability of the reinforcement steel to dissipate energy by ductile behaviour with pronounced plastic strains should be confirmed by these tests. During the last decades comprehensive experiences were developed at BAM performing high speed tensile tests on reinforcement bars as well as on several splicing systems. For the lack of available standards defining these tests in detail an appropriate test procedure was developed and continuously optimized during this period at BAM. The test procedure is partially based on testing principles adapted from available standards. The main intention behind this test procedure is to perform high-speed tensile tests with a specific constant strain rate generated at the specimen. Furthermore, main objective was to establish a procedure to guarantee the comparability of test results for different diameter of reinforcement as well as for different types of couplers. Besides the pure execution of the high-speed tensile tests, the test specification also declares how to evaluate the measurements and the test results. Finally, some typical results will be presented in this contribution. T2 - SMIRT 26 CY - Potsdam, Germany DA - 10.07.2022 KW - Impact KW - Coupler systems KW - High-speed KW - Reinforcement PY - 2022 SP - 1 EP - 10 AN - OPUS4-55422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Thiele, Marc A1 - Makris, Ralf T1 - Specification for high-speed tensile tests on reinforcement bar coupler systems N2 - This document presents the specification for the execution and evaluation of high-speed tensile tests on reinforcement bar coupler systems. This specification was developed at BAM - Bundesanstalt für Materialforschung und -prüfung (Federal Institute for Materials Research and Testing, Germany) - following test principles from related international standards. The present document represents the latest status of the test specification. It is noted that until 2010 the test procedure was characterised on a test velocity based on L0. In an improved test conception and after intensive investigations in cooperation with industry partners, this procedure has been updated to consider instead a test velocity based on Lr, since this warrants more comparable and meaningful results. KW - Test specification KW - Coupler systems KW - High-speed KW - Tensile test KW - Reinforcement PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-525075 SP - 1 EP - 29 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin ET - V01 AN - OPUS4-52507 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -