Search

Auf dem Weg zur digitalen Brücke existieren bereits erste Lösungen, die den Lebenszyklus einer Brücke abbilden können. Für die Planung, den Bau und den Unterhalt stehen unterschiedlichste Werkzeuge, z. B. BIM, DIN 1076, SIB-Bauwerke, Monitoring etc. zur Verfügung, die jeweils mit unterschiedlichen Datenformaten arbeiten. Für ein intelligentes Erhaltungsmanagement müssen aber alle Daten mit den verschiedenen Datenformaten zusammengeführt, abgelegt und so verwaltet werden können, dass über den gesamten Lebenszyklus einer Brücke die Abbildung eines ganzheitlichen digitalen Zwillings eines Bauwerks möglich ist. Die Autoren haben dafür mit BBox den Prototyp einer Verwaltungsschale (VWS) auf Grundlage von Industrie 4.0 entwickelt. Damit wird das physikalisch-ingenieurtechnische Modell zur Zustandsbewertung der Brücke in den Mittelpunkt gestellt und der gesamte Lebenszyklus einer Brücke kann unabhängig von Datenformaten digital erfasst werden. Da der Aufbau der VWS durch die Granularität optimal strukturiert ist, bietet die Ablage und Einspeisung von Messdaten sowohl die Grundlage eines Live-Monitorings als auch den Grundstein für maschinelles Lernen (ML). Der Datenzugriff via S3-Schnittstelle erleichtert die Entwicklung von eigenen Prognosemodellen mit Informationsmustern (SHIP - Structural Health Information Pattern). Am Beispiel der Heinrichsbrücke Bamberg wird die praktische intelligente Umsetzung des Bauwerksmonitorings inkl. VWS mit Informationsmustern und ML gezeigt.

Zerstorungsfreie Prufverfahren liefern wichtige Informationen zur Beurteilung von Bauwerken. Mit ihnen konnen Materialeigenschaften bestimmt oder die innere Struktur von Bauteilen beschrieben werden. Fur letzteres werden in der Regel Volumenverfahren angewandt. Einen besonderen Stellenwert haben in der Praxis die Radar- und die Ultraschall-Echoverfahren. Ihre Anwendung erfordert lediglich eine einseitige Zuganglichkeit zum Bauteil. Zudem lassen sich zahlreiche unterschiedliche Prufaufgaben losen. Zum Stand der Technik gehoren beispielsweise die Ortung von Bewehrung und Spannkanalen, die Bestimmung der Dicke von Bauteilen oder die Fehlerlokalisierung. In diesem Beitrag wird gezeigt, wie mithilfe von Ultraschall-Echomessungen gesammelte Messwerte in ein quantitatives Messergebnis uberfuhrt werden konnen, das wiederum in ingenieurtechnische Berechnungen einfliesen kann. Einleitend werden die Prufmethode und die Messtechnik erlautert. Anschliesend wird das Vorgehen von der Auswertung der Messergebnisse bis zur Bestimmung der bautechnischen Kenngrose – Bauteildicke – gezeigt. Abschliesend wird die Methodik an einem Referenzprufkorper aus Polyamid demonstriert und den Ergebnissen von Messungen an Beton gegenubergestellt.

Durch die Einbeziehung von gemessenen Daten bei der Bewertung von bestehenden Bauwerken konnen Unsicherheiten bei der Beurteilung des Tragverhaltens reduziert werden, ohne das normative Zuverlassigkeitsniveau einzuschranken. Informationen sind die wesentliche Grundlage fur die Analyse der Zuverlassigkeit von Tragwerken. Umso wichtiger ist die Kenntnis uber die Prazision und die Richtigkeit der verwendeten Informationen. Aus messtechnischer Sicht kann ein Messwert, dem keine Messunsicherheit beigeordnet wurde, als wertlos erachtet werden. Liegt ein vollstandig dokumentiertes Messergebnis vor, so ist die Qualitat der gemessenen Information bekannt und deren Vergleichbarkeit gewahrleistet. In diesem Beitrag wird am Beispiel einer Spannbetonbrucke und zweier Grenzzustande gezeigt, wie Messergebnisse aus der zerstorungsfreien Prufung in probabilistische Nachweise von Bestandsbauwerken einfliesen konnen und welche Auswirkungen die Implementierung von gemessenen Daten bei der Bewertung von Bestandsbauwerken haben kann.

Gegenuber dem Neubauentwurf konnen bei der Bewertung von bestehender Bausubstanz Sicherheitsreserven genutzt werden, da Unsicherheiten, die beim Bau auftreten konnen, besser bekannt oder nicht mehr vorhanden sind. Konnen solche Unsicherheiten genauer bewertet werden, z. B. durch die Feststellung der genauen Lage der Spannglieder bei einer Spannbetonbrucke, so konnen Sicherheitsbeiwerte reduziert werden, ohne dass es dabei zu Auswirkungen auf das normativ festgelegte Zuverlassigkeitsniveau kommt. Mittlerweile sind Prufmethoden an Bauwerken wirtschaftlich einsetzbar und auch so leistungsfahig, dass die fur die Tragfahigkeit und Gebrauchstauglichkeit wesentlichen Parameter identifiziert werden konnen. Ein wesentlicher Punkt ist hierbei die Integration derartiger Messergebnisse in Rechenmodelle, die fur die Nachrechnung des Bauwerks verwendet werden. Dies konnen sowohl semiprobabilistische Rechenmodelle als auch vollprobabilistische Modelle sein. Bei semiprobabilistischen Methoden konnen aus den Messergebnissen Teilsicherheitsbeiwerte berechnet und abgeleitet werden, die dann in den bekannten Nachweisformaten gemas den Eurocodes und der Nachrechnungsrichtlinie berucksichtigt werden. Bei vollprobabilistischen Nachweisen konnen die Messdaten in Form von Verteilungsdichtefunktionen mit gemessenen Variationskoeffizienten direkt in das Rechenmodell eingehen. In einer dreiteiligen Aufsatzreihe werden die Messverfahren und die Nutzung der Ergebnisse bei der Nachrechnung vorgestellt. Der vorliegende Teil 1 zeigt die Moglichkeiten des Einsatzes von zerstorungsfreien Prufverfahren und bewertet deren Leistungsfahigkeit. Messen heist wissen. Dieses Wissen spiegelt die Realitat wider und soll den Tragwerksplaner bei der Entscheidungsfindung uber die Sicherheit und Zuverlassigkeit von Bestandsbauwerken unterstutzen.

In ultrasonic testing, the time of flight (ToF) of a signal can be used to infer material and structural properties of a test item. In dispersive media, extracting the bulk wave velocity from a received signal is challenging as the waveform changes along its path of propagation. When using signal features such as the first peak or the envelope maximum, the calculated velocity changes with the propagation distance. This does not occur when picking the signal onset. Borrowing from seismology, researchers used the Akaike information criterion (AIC) picker to automatically obtain onset times. In addition to being dependent on arbitrarily set parameters, the AIC picker assumes no prior knowledge of the spectral properties of the signal. This is unnecessary in ultrasonic through-transmission testing, where the signal spectrum is known to differ significantly from noise. In this contribution, a novel parameter-free onset picker is proposed, that is based on a spectral entropy criterion (SEC) to model the signal using the AIC framework. Synthetic and experimental data are used to compare the performance of SEC and AIC pickers, showing an improved accuracy for densely sampled data.

Ultrasonic inspection is a common tool for non-destructive testing in civil engineering (NDT-CE). Currently, transducers are coupled directly to the specimen surface, which makes the inspection time-consuming. Air-coupled ultrasound (ACU) transducers are more time-efficient but need a high pressure amplitude as the impedance mismatch between the air and the concrete is high and large penetration depth is needed for the inspection. Current approaches aim at eliminating the impedance mismatch between the transducer and the air to gain amplitude; however, they hardly fulfill the NDT-CE requirements. In this study, an alternative approach for ultrasound generation is presented: the signal is generated by a fluidic switch that rapidly injects a mass flow into the ambience. The acoustic field, the flow field, and their interaction are investigated. It is shown that the signal has dominant frequencies in the range of 35–60 kHz, and the amplitude is comparable to that of a commercial ACU transducer.

There is a continuing need for reassessments of existing bridges. The validity of reassessment results depends to a large extent on the information used for the calculations. In the meanwhile, the application of non-destructive testing (NDT) methods on concrete is suitable for gathering quantitative information about individual structures that are both relevant and accurate. Such measured information can be explicitly incorporated into probabilistic models used for the bridge reassessment. This way, the level of approximation of the considered model and therewith the validity of the reassessment results can be increased.

Post-tensioning systems provide safe and efficient construction solutions for long span bridges. Despite the improved grouting practices over the past decade, existing post-tensioning systems may have significant amount of grout defects, which could lead to corrosion of the strands. Condition assessment of post-tensioning systems is necessary to allow bridge owners to take timely, proactive actions to mitigate or prevent further deterioration and unanticipated tendon failures. A detailed experimental study conducted to assess the performance of nondestructive evaluation techniques in detecting grout defects within internal tendons is presented herein. Nondestructive evaluation techniques that include Ground Penetrating Radar, Impact Echo, Ultrasonic Tomography, and Ultrasonic Echo are evaluated in terms of detecting the location and severity of fabricated grout defects in a full-scale post-tensioned U-girder mock-up specimen. While Ground Penetrating Radar can identify the location and profile of the internal tendons, particularly metal ducts due to strong reflections, this method did not provide any information about the defect conditions within the tendon. Both Impact Echo and Ultrasonic Echo techniques are effective in identifying the location of grout defects, but could not differentiate between water, void, or compromised grout conditions. The study clearly demonstrates the need for NDE techniques that are applicable to anchorage regions, and that are capable of estimating the severity and nature of grout defects in internal tendons.

Measuring means knowing. The structural engineer’s Knowledge about structures is vitally important for the assessment of their structural safety. This contribution shows, how non-destructive testing methods can be used to collect valuable Information about existing structures. This value is expressed in this paper by the usability in probabilistic assessments and thus by the reliability of the information. The development of non-destructive testing methods in civil-engineering allows the realistic measurement and visualization of inner constructions of concrete components with a minimum of destructive interventions. The evaluation of the quality of measurement data is of fundamental importance for quantitative measurements in order to ensure the objectivity of testing and evaluation and to assess the reliability of the knowledge acquired. Both systematic and random deviations must be identified, quantified and taken into account to obtain statistically sound data. The Focus of this contribution is on the methodical path, how displayed measurement data can be processed into reliable knowledge. It is not about developing assessment methods but about providing necessary knowledge to increase their operational usability.

Air-coupled ultrasonic (ACU) testing has proven to be a valuable method for increasing the speed in non-destructive ultrasonic testing and the investigation of sensitive specimens. A major obstacle to implementing ACU methods is the significant signal power loss at the air–specimen and transducer–air interfaces. The loss between transducer and air can be eliminated by using recently developed fluidic transducers. These transducers use pressurized air and a natural flow instability to generate high sound power signals. Due to this self-excited flow instability, the individual pulses are dissimilar in length, amplitude, and phase. These amplitude and angle modulated pulses offer the great opportunity to further increase the signal-to-noise ratio with pulse compression methods. In practice, multi-input multi-output (MIMO) setups reduce the time required to scan the specimen surface, but demand high pulse discriminability. By applying envelope removal techniques to the individual pulses, the pulse discriminability is increased allowing only the remaining phase information to be targeted for analysis. Finally, semi-synthetic experiments are presented to verify the applicability of the envelope removal method and highlight the suitability of the fluidic transducer for MIMO setups.

Existing concrete structures were usually designed for lifetimes of several decades. The current and urgently required efforts to increase sustainability and protect the environment will likely result in extended service lives up to 100 years. To achieve such objectives, it is required to assess structures over their entire lifecycles. Non-destructive testing (NDT) methods can reliably support the assessment of existing structures during the construction, operational, and decommissioning phases. One of the most important and safety-relevant components of a prestressed concrete structure are the tendons. NDT methods such as the ultrasonic echo method are suitable for both the detection and the localization of the tendons, i.e., the measurement of their geometrical position inside the component. The uniqueness of structures, concrete heterogeneity, and varying amounts of secondary components such as the reinforcement represent obstacles in the application of these methods in practice. The aim of this contribution is to demonstrate a practicable procedure, that can be used in the field to determine the parameters required for the measuring data analysis without extensive knowledge about the investigated components. For this purpose, a polyamide reference specimen is used to show which steps are required to obtain reliable imaging information on the position of tendons from the measurement data. The procedure is then demonstrated on a concrete test specimen that covers various relevant and practice-oriented test scenarios, such as varying tendon depths and component thicknesses.

Each engineering decision is based on a number of more or less accurate information. In assessment of existing structures, additional relevant information collected with on-site inspections facilitate better decisions. However, observed data basically represents the physical characteristic of interest with an uncertainty. This uncertainty is a measure of the inspection quality and can be quantified by expressing the measurement uncertainty. The internationally accepted rules for calculating measurement uncertainty are well established and can be applied straightforwardly in many practical cases. Nevertheless, the calculations require the occasionally time-consuming development of an individually suitable measurement model. This contribution attempts to emphasize proposals for modelling the non-destructive depth measurement of tendons in concrete using the ultrasonic echo technique. The proposed model can serve as guideline for the determination of the quality of the measured information in future comparable inspection scenarios.

With the mandatory introduction of the May 2011 directive for reassessment of bridges in Germany, the administrations of the federal and state governments have the duty to prove the stability of their bridge stock. Verification of bridge stability will be realized with consideration of the newly increased traffic loads. Particularly in older bridges, the verification can only be achieved if calculative surplus load capacity of the original structural design is taken into account in the recalculation. One option for considering these reserves is the exact determination of the dead weight of the bridge. Within this case study, it will be demonstrated how the problem can be practically solved. In order to determine the dead weight of a concrete bridge, its volume has to be calculated. as a first step, a 3D laser scanner is used to record the internal geometry of a hollow box bridge girder. For the determination of the thickness of the concrete member, the non-destructive technique ultrasonic echo is applied. The construction must be segmented in approximately equidistant parts in order to be able to carry out an economic and efficient investigation. The description of the segmentation of the point cloud, carried out in a 2D model, was presented in the first part of the publication. The subject of this presentation is the merging of 2D cross sections into a 3D model, from which the weight of the bridge can be calculated.

The reassessment of bridges is becoming increasingly important. The basic requirement for analyses of structural safety is reliable knowledge about individual structures. This paper introduces the new approach to evaluate the quality of measured data gained from non-destructive testing (NDT) to provide reliable, objective, and relevant information about existing bridges. The purpose is to relate this validated knowledge to probabilistic analyses. Bridging the gap between NDT and numerical reassessments indicates reduced numerical uncertainties and residual service time extensions. This paper deals with an application of this approach using measurement data collected by ultrasonic technique at a prestressed concrete bridge.

The non-destructive testing methods available for civil engineering (NDT-CE) enable the measurements of quantitative parameters, which realistically describe the characteristics of existing buildings. In the past, methods for quality evaluation and concepts for validation expanded into NDT-CE to improve the objectivity of measured data. Thereby, a metrological foundation was developed to collect statistically sound and structurally relevant information about the inner construction of structures without destructive interventions. More recently, the demand for recalculations of structural safety was identified. This paper summarizes a basic research study on structural analyses of bridges in combination with NDT. The aim is to use measurement data of nondestructive testing methods as stochastic quantities in static calculations. Therefore, a methodical interface between the guide to the expression of uncertainty in measurement and probabilistic approximation procedures (e.g. FORM) has been proven to be suitable. The motivation is to relate the scientific approach of the structural analysis with real information coming from existing structures and not with those found in the literature. A case study about the probabilistic bending proof of a reinforced concrete bridge with statistically verified data from ultrasonic measurements shows that the measuring results fulfil the requirements concerning precision, trueness, objectivity and reliability.