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Eingeladener Vortrag
- nein (56)
The active approach for non-destructive-testing in Civil Engineering (NDT-CE) with infraredthermography (IR), developed at the Federal Institute for Materials Research and Testing (BAM), is described in part one of this contribution. The active IR-approach is based on the principles of impulse- (IT) and pulse-phase-thermography (PPT). The concept is a direct result of a research project at the BAM in cooperation with the Technical University of Berlin (TUB) and was funded by the Deutsche Forschungsgemeinschaft (DFG). In the second part results of the new thermography-scanning system (thermo-scanner) of BAM on debonding of multi-layered structures, especially carbon fibre reinforced plates (CFRP) on concrete are presented. Both, the thermo-scanner developed at BAM, and the investigations carried out, are part of the
EU-Project Sustainable Bridges. In the third part of the paper the characteristic frequency of the optimum phase-contrast as a means for the characterization of defects depth in CE by means of PPT is introduced. A new quantitative approach is tested and discussed on concrete structures with defects of polystyrene and gas concrete.
Berlin Main Station is the largest multi-level station in Europe. Its daily passenger number amounts to over 300.000. Structures built for such a large number of people require a high-level safety standard. The station was built on the inner city site of the historic Lehrter Bahnhof. The conditions for building and start of operation were challenging by several reasons. The typical sandy ground with a high level of groundwater makes the permanent static stability of such a complex structure difficult. Several completed, ongoing, and planned construction activities in the immediate vicinity of the station influence the ground settlement of the whole area. On basis of the structural design an impact prediction was calculated, which expected certain vertical displacements particularly between the single columns of the outer concrete bridges of the building. These columns support the glass roof construction, which only allows a defined limit of displacement. In order to avoid damage, a concept for monitoring and adjusting potentially occurring displacements was developed for installation at the outer bridges of the station.
Condition assessment of old railway bridges, a scientific cooperation between Berlin and Wroclaw
(2009)
Two years ago, the East Prussian and the Low-Silesian Railway lines celebrated their 160th anniversaries. The history of both first railway connections in the Eastern railway network development in the whole region in the 19th century is presented together with information about the railway between Berlin and Wroclaw. Special attention is paid to the railway bridges built in this period. The first large iron bridges and typical masonry arch structures are presented. Special attention is paid to masonry arches. The condition appraisal of existing masonry arches requires new developed technical methodologies, effective tools and procedures for the description of the bridges current state and function. Their current technical condition as well as service-ability is described.
Für den Entwurf neuer Bauwerke gewährleistet die Einhaltung aktuell gültiger Normenwerke eine ausreichende Sicherheit. Diese Normen und die zugehörigen Lieferbedingungen gelten ausschließlich für Neubauten aus heute produzierten Stählen. Technische Regeln für die Begutachtung alter Materialien, wie sie zuletzt im Beiblatt 2-"Altstahl im Hochbau" von 1948 zur DIN 1050 "Stahl im Hochbau" [35] verankert waren, sind zurückgezogen worden. Bei der Bewertung alter Baukonstruktionen greift man häufig auf vorhandene Materialinformationen aus Bauwerksunterlagen, Vorschriften und Berechnungen, z.B. im Verantwortungsbereich der Deutschen Bahn AG, zurück. Die geltende Richtlinie der Modulfamilie 805.001 der Deutschen Bahn AG [21] erlaubt in Abschnitt 2, Absatz (2) sogar ausdrücklich die Nutzung alter Berechnungen und Vorschriften, wenn bei gleich bleibender Nutzung nur Eingriffe von untergeordneter Bedeutung, wie kleine Reparaturen oder lokale Verstärkungen, vorgenommen werden. Ein Eingriff in die Tragsicherheit des Bauwerkes ist nicht zulässig. Für umfassendere Maßnahmen und für Bauwerke außerhalb des Zuständigkeitsbereiches der Deutschen Bahn AG oder für die Bewertung der Konstruktionen bei Umnutzung bzw. bei umfangreichen Maßnahmen ist diese Ausnahme nicht anwendbar. Daraus ergibt sich für den auf die Beurteilung und Bewertung von bestehenden Bauwerken spezialisierten Ingenieur der Bedarf, alte Materialien, Bauweisen und Vorschriften zu kennen und zu verstehen. Aufwändige Versuchsserien an originalen Vollwand- und Fachwerkträgern zur Ermittlung von Schadensmechanismen im einstufigen Ermüdungsversuch werden vorgestellt. Sie resultieren in erweiterten Kenntnissen über Versagenskriterien für genietete Bauteile. Die Weiterentwicklung und Erprobung einander ergänzender zerstörungsfreier und minimal-invasiver (zerstörungsarmer) Verfahren verbessert die Schadensfrüherkennung an ermüdungsbeanspruchten Stahlkonstruktionen, z.B. bei Inspektionen. Intensive Materialuntersuchungen zur Mikrostruktur und zu mechanischen Materialparametern tragen zum Verständnis bestimmter, für moderne Stähle untypischer, Schadensmechanismen bei. Die interdisziplinäre Kooperation mit den Laboratorien der Abteilungen V, VIII und S bei der Analyse von Rissentstehung und Risswachstum erweitert die verfügbaren Kenntnisse über das Versagensverhalten alter Stähle und Stahlverbindungen. Aufbauend auf einer Darstellung der Entwicklung alter Bauweisen und Bauwerke, einer Literatur- und Normenanalyse zu Lieferbedingungen von Stahl für das Bauwesen und zu konstruktiven Details, so wie sie um die Jahrhundertwende zwischen dem 19. und 20. Jh. üblich waren, werden Materialuntersuchungen an alten Stählen, Ermüdungsversuche und Messungen an bestehenden Brückenbauwerken aus alten Stählen präsentiert. Innerhalb des Projektes gab es eine enge Zusammenarbeit mit Brückenbetreibern, die gewährleistete, dass die Ergebnisse aus Prüfungen, Forschung und Entwicklung direkt in die Praxis, aber auch in interne Vorschriften der Brückeneigner überführt werden konnten. So wurde in der Subgroup Remaining Fatigue Life of Bridge Structures der Gruppe ECOBRIDGE der Europäischen Eisenbahn Vereinigung UIC unter Beteiligung der BAM eine Machbarkeitsstudie [1] zusammengestellt. Auf dieser Basis erarbeitete ein bilaterales Konsortium der Schweiz und Deutschlands im Auftrag der Schweizerischen Bundesbahn und der Deutschen Bahn mit Ermüdungsspezialisten der RWTH Aachen, der EPFL Lausanne und der BAM einen Vereinheitlichten Sicherheitsnachweis für die Beurteilung alter Eisenbahnbrücken aus Stahl [2]. Der Abschlussbericht liegt seit 2001 im federführenden Institut für Stahlbau der RWTH Aachen vor. Die Überführung der Forschungsergebnisse in eine Richtlinie der Europäischen Konvention für Stahlbau (EKS) mit empfehlendem Charakter liegt als Entwurf [4] vor. Die Veröffentlichung nach abschließender Begutachtung durch namhafte auf Altstahl und Ermüdung spezialisierte Fachkollegen durch die EKS ist in Vorbereitung.
Opportunities and Limitation of Non-destructive Testing in Condition Assessment of Bridge Structures
(2009)
Condition assessment of old railway bridges, a scientific cooperation between Berlin and Wroclaw
(2009)
The construction process of the New Berlin Main Station, the former Lehrter Bahnhof, has been monitored from the beginning. In this station, the main European east-western railway connection crosses the northsouth railway lines. Four east-western bridges, built in the first construction phase, carry the platforms for international lines and suburban train tracks. The outer two bridges carry the supports of the relatively flat glass roof, too. Since the glass roof is very sensitive to vertical displacements, the authorities required a complex monitoring system. This case study describes long-term measurements with classical and enhanced innovative sensors to monitor vertical displacements of neighboring glass roof supports. Additionally, traditional strain gauges were embedded parallel to long-gauge length fiber-optic strain sensors in the near-surface concrete of the partial prestressed bridges to reliably survey possible changes.
The measurements on site go along with long-term laboratory tests on prestressed concrete beams. Researchers study load effects and long-term environmental influences on two large-scale model beams, inside and outside the laboratory.
The monitoring system has been working stable as an early warning system for any changes of the structural conditions since 2002. All data are available on line for both the project team and the owner.
Acoustic measurement methods
(2008)
Opportunities and limitation of non-destructive testing in condition assessment of bridge structures
(2009)
Messungen und Laborversuche an der schweißeisernen Spreebrücke an der Berliner Friedrichstraße
(2010)
The Berlin Main Station was built between 2000 and 2006. At the occasion of the 10th anniversary after the Berlin Main Station was officially opened to train traffic, a view back on eight years of monitoring was given. For the period of the construction with different load cases, the monitoring system was required by the Railway Authorities (Eisenbahnbundesam, EBA) to survey differential vertical displacements between neighbouring supports of the glas roof and the partially prestressed middle bridges. 128 sensors were installed.The data was published in the Internet with access restricted to the BAM scientists and the owner of the station, the German Railways DB AG.
Civil engineers, who are involved in nondestructive testing have to solve an essential task: the transfer of the results of NDT-research into practice. NDT in civil Engineering is a quite new discipline. The results must meet the needs of the infrastructure owners to convince them about the usefulness of NDT. The issue of reliability of the NDT-data was discussed.
The amount of new knowledge about bridges, materials they are made of, deterioration processes for the different materials, resulting defects, methods for early detection of them and related causes for damage increases day by day. Often the knowledge remains in the heads of ageing specialists leaving the inspection teams or universities. This paper presents a feasibility study about application of a new tool from artificial intelligence to model and organize bridge engineering knowledge from a domain expert´s view. Exemplarily, knowledge and not only data from bridge testing in the field and in the laboratory were formalized for the presentation of the functionality of ontologies.
Bridges represent a crucial part of traffic infrastructure networks for both, freight transport and transport of people. None the less, sometimes it is not easy for infrastructure owners to manage or extract data and knowledge of interest about specific bridges from bridge management systems, e.g. along a line. In case of search for a special material parameter or for a recent strengthening measure, the selection of the wanted information may be time consuming. The search process depends on the complexity of the selected issue.
The paper presents the applicability of ontologies, a new tool from artificial intelligence transferred to bridge engineering issues. Current modern ontologies consider the rules from the World Wide Web consortium (W3C), use a defined Web Ontology Language (OWL) and the Dublin Core Metadata Initiative (DCMI®) to describe the members of a domain and the relations between them in a machine readable manor. Any information, data as well as text information is broken down to a simple triple (RDF) in a subject- predicate- object relation to organize the link between them. Advantage over any type of data base is processibility due to the use of restrictions and axioms. Visualization plug-ins, as OntoGraph or GraphViz, can visualize the structure of the ontology or parts of it and the described relations.
In the recent years, ontology editors like e.g. Protégé, were developed to enable domain experts to structure a specific domain. The editor is still under development. None the less, the study shows exemplarily, how an ontology for riveted steel bridges could consider results from testing in the laboratory and in the field. Besides typical materials, typical damage processes defects and structures, applicable methods are formalized, classified and described. Queries using e.g. DL-Query may address tasks of interest and extract it from the ontology.
Active Thermography
(2016)
Active thermography is a nondestructive testing method for identification of near surface defects and signs of early deterioration. The presentation explains the potential and Limits of the method and the equipment for application to concrete structures. Advanced data analysis can increase the quality of imaging of the measurement. The method is usually applied once for analysis of the current condition. If applied periodically, the method can be used for observation of a deterioration process.
The amount of new knowledge about bridges, about the materials they are made of, deterioration processes for the different materials, typical defects, methods for early detection of them and related causes for damage increases day by day. Often the knowledge remains in the heads of ageing specialists leaving the inspection teams or universities. This paper presents a feasibility study about application of a new tool from artificial in-telligence, ontology, for modeling and organizing bridge engineering knowledge from a domain expert´s view. Exemplarily, knowledge and not only data from bridge testing in the field and in the laboratory were formalized for the presentation of the functionality of ontologies. The open source ontology editor Protégé was ap-plied to test the feasibility.
Cast iron arch bridges were built in the late 18th and early 19th century across Europe. After the famous Iron Bridge in the Ironbridge Gorge in Coalbrookdale in England, being now part of the UNESCO world heritage, many cast iron bridges followed and substituted timber bridges. A series of cast iron bridges has been built in central Europe, in Laasan, Breslau, (now Wrocław), in Berlin, Potsdam, Bad Muskau and Schwerin. The paper gives an overview about the current state of some remaining cast iron arch bridges, typical damage cases, material properties and rehabilitation. Most of the old cast iron arch bridges serve as pedestrian bridges. Some of these bridges have been strengthened to increase the traffic load. Different rehabilitation measures as substitution of parts of the bridges and strengthening using Carbon Reinforced Polymers (CFRP) are discussed.
Brücken zählen einerseits zu den ältesten Zeugnissen der Verkehrsgeschichte und sind andererseits ein wichtiger Bestandteil der Verkehrsinfrastruktur für unsere heutige Gesellschaft. Sie erfüllen eine wichtige Funktion bei Transport von Personen und Gütern und prägen das Stadtbild. Die Berliner Hoch- und Untergrundbahn, eröffnet im Februar 1902 nach 5 1/2 –jähriger Bauzeit, ist in der heutigen Berliner Denkmalliste als Denkmalbereich (Gesamtanlage) geschützt. Bereits seit 1980 waren die historischen Bahnhöfe entlang der Stammstrecke als Baudenkmale gelistet.
An der Stahlkonstruktion der Hochbahnviadukte zwischen Halleschem Tor und Prinzenstraße wurden während regulärer Inspektionen in den 1990ziger Jahren Risse dokumentiert. Die Berliner Verkehrsbetriebe (BVG) bezogen die Bundesanstalt für Materialforschung und –prüfung (BAM) sowie Ingenieurbüros in eine Diskussion über die optimale Lösung zur Sanie-rung und zum Erhalt der Hochbahnviadukte ein. Zahlreiche Versuche im Labor und Messungen vor Ort dienten der Optimierung der bevorzugten Sanierungsvariante. Die BVG für eine Lösung mit relativ geringem Eingriff in die Konstruktion. Das äußere Erscheinungsbild der Hochbahnviadukte im Berliner Stadtbild konnte durch die Sanierungsvariante der BVG erhalten werden.
The reliability of data, obtained from nondestructive testing depends on many different factors as e.g. the equipment, the human factor, the influence of material properties, geometrical accessibility of the given detail, the structure of the detail, but also from data acquisition, processing and interpretation. The presentation introduces to current possibilities for the quantification of measurement results received during nondestructive testing.
The amount of new knowledge about bridges, about the materials they are made of, deterioration processes for the different materials, typical defects, methods for early detection of them and related causes for damage increases day by day. Often the knowledge remains in the heads of ageing specialists leaving the inspection teams or universities. This paper presents a feasibility study about application of a new tool from artificial in-telligence, ontology, for modeling and organizing bridge engineering knowledge from a domain expert´s view. Exemplarily, knowledge and not only data from bridge testing in the field and in the laboratory were formalized for the presentation of the functionality of ontologies. The open source ontology editor Protégé was ap-plied to test the feasibility.
Active thermography
(2017)
Active thermography is introduced as tool for diagnostics in civil engineering structures. Aside from basic information, examples for applications of active thermography in different types of structures was presented. Active thermography was applied in historic structures to reveal former components or even ancient openings. Other examples present active thermography as a tool for nondestructive detection of debonding in CFRP strengthened structures. The way is explained, how the system was optimized for different materials.
Practical applications of recent BAM-research results of NDT and monitoring in civil engineering
(2018)
Nondestructive testing and monitoring was of mayor interest in BAM-research related to the survey of civil engineering structures during the last two decades. Three case studies about research projects carried out at BAM were presented. All three projects focussed on the survey of parameters and safety related tasks in bridge engineering and inspection. First, the monitoring of the Berlin main station was presented with focus on the sensors developed specifically for this project. The second case study presented and application of guided ultrasonic waves to CFRP-strengthened bridges. The method was sucsessully applied to two of four different strengthening measures carried out min. 10 years ago. The last project presented the feasibility study of a network consisting of simple Bluetooth modules to survey changes in the moisture content in sand and massive concrete.
The book chapter first analyses the history of higher education in Europe. Second step describes the current Bologna process. Finally, the rule of the Bundesanstalt für Materialforschung und -Prüfung (BAM) in supporting PhD-students during their research and preparation of theire theses in cooperation with Universities is described
Current measurement methods for dertermination of moisture analyse near-surface moisture distribution. During an externally funded research project, microwaves in the Bluetooth(R) frequency band width were utilized for Setting-up a module network. Without additional sensors, the feasibility study confirmed that threedimensional data can collected to obtain a threedimensional data set as basis for the estimation of moisture distribution inside massive building materials.
In 1882, the East-West suburban train viaduct was built through Berlin as part of the public traffic solution in the late 19th Century. Today, the only left over iron arch bridge is a pair of two arches Crossing the Spree river in the middle of Berlin. Before dismantling the former parallel two original pairs of iron arches and rebuilding new arches for the high-speed railway line through Berlin in 1997, BAM was involved in an extensive test program of the heritage iron arch structure. Especially the estimation of accumulated damage in critical details and the verification of the old material properties at early stage was important information to the bridge owners. The testing program included two strain and displacement measurement campaigns, non-destructive testing, materials testing and microscale metallographic analysis of critical details. The measured strain cycles were significant lower in number and size than expected. Most of the cycles were compression stress cycles only. The work was planned in Cooperation with the Berlin consultancy Professor Hilbers that was responsible for the design and calculation of the reconstruction measures. Additionally, after calculation of the possible reuse of the old arches, we compared measured data from strain measurements with the results from calculation.
The measured data and the calculated data show a good qualitative correlation.
Measurements, NDT and laboratory testing of the wrought iron bridge at Berlin-Friedrichstraße
(2010)
Dokumentation von Ermüdungsversuchen an genieteten Querträgern einer schweißeisernen Trogbrücke
(2001)
Ermüdungsversuche an alten genieteten Stahlbrücken: Beurteilung der verbleibenden Restnutzungsdauer von Querträgern einer originalen schweißeisernen Trogbrücke nach fast einhundert jähriger Nutzung. Verbindungen und Elemente des alten Bauwerks sind zunächst unter Verkehr und nach dem Abriss der Brücke im Labor getestet worden. Es kamen sowohl Dehnungsmessungen als auch zerstörungsarme bzw. Zerstörungsfreie Prüfverfahren zur Anwendung. Materialuntersuchungen, auch neuartige, wie z. B. Rissfortschrittversuche, Gefügeuntersuchungen und Zugversuche ergänzten die Untersuchungen.
Cast iron arch bridges were built in the late 18th and early 19th century across Europe. After the famous Iron Bridge in the Ironbridge Gorge in Coalbrookdale in England, being now part of the UNESCO world heritage, many cast iron bridges followed and substituted timber bridges. A series of cast iron bridges has been built in central Europe, in Laasan, Breslau, (now Wrocław), in Berlin, Potsdam, Bad Muskau and Schwerin. The paper gives an overview about the current state of some remaining cast iron arch bridges, typical damage cases, material properties and rehabilitation. Most of the old cast iron arch bridges serve as pedestrian bridges. Some of these bridges have been strengthened to increase the traffic load. Different rehabilitation measures as substitution of parts of the bridges and strengthening using Carbon Reinforced Polymers (CFRP) are discussed.
Cracks perpendicular to the surface may be initial indicators for a deterioration process of concrete structures. Moisture penetrates inside the structure and transports adverse chemicals. The paper presents an investigation about the reliability of available commercial non-destructive evaluation techniques to reliably estimate the depth of surface-breaking cracks in reinforced concrete structures. Aim of the study was the investigation of surface-braking cracks under laboratory conditions. Commercial acoustic devices as impact echo equipment, single ultrasonic transducers and arrays were applied even if they have not been developed for this purpose. The commercial software and descriptions for application was followed strictly to compare the function, precision and repeatability of the measurements. Both, perpendicular notches and cracks have been considered. The study was completed with a discussion about reference specimens. The study was the basis for formulation of gaps in research. The Electric Power Research Institute (EPRI) has initiated and funded a Project.
A toolbox with non-destructive testing methods for the condition assessment of railway bridges
(2006)
The unified economic structure of the European market requires a unified transport infrastructure to ensure seamless and barrierfree transportation of passengers and goods. The European commission is funding the European Integrated Project Sustainable Bridges to comply with future traffic demands. The main objective of the project is to reliably assess and upgrade the bridge infrastructure for the required increase of axle loads and transport volume. 32 Institutes from 12 countries develop unified procedures for the assessment and improvement of the existing railway bridge stock under the guidance and review of six major European railway companies.
Non destructive testing (NDT) is given a high priority. One of the work packages concentrates on the potential of advanced NDT-methods and creates a toolbox with advisable methods for the condition assessment of all types of railway bridges. Although NDT-methods are implemented in the quality assurance process in many industries, their application in the railway infrastructure is not common. Only a few countries have included selected NDT-methods into advanced condition assessment procedures for the management of their bridge stock.
This paper describes also current activities to enhance pulse-phase thermography, impulse-radar and acoustic methods. The advanced methods enable infrastructure owners to verify construction plans, to assess structures, repair and strengthening quality or to identify in-service damages. Latest development is an automated scanning system for combined acoustic and electromagnetic measurements. The results are then combined through data fusion techniques to further increase their value for the bridge owners.
In this research, laboratory experiments were carried out to investigate the feasibility of using ground penetrating radar (GPR) for corrosion detection and/or monitoring, and the mechanism of corrosion caused GPR signal changes, taking into account the influence of several parameters: Chloride, rebar size and cover depth. With the understanding of the mechanism, a novel method for detecting reinforcement corrosion in concrete with GPR is proposed, together with a series of signal processing toolkits for corrosion visualization and image comparison.
Monitoring accelerated corrosion in chloride contaminated concrete with ground penetrating radar
(2012)
Inspection of steel bridges
(2007)