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Eingeladener Vortrag
- nein (56)
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.
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 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.
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.
Opportunities and limitation of non-destructive testing in condition assessment of bridge structures
(2009)
Opportunities and Limitation of Non-destructive Testing in Condition Assessment of Bridge Structures
(2009)
Nuclear Power Plants have been in operation for ca. 50 years. Based on this experience, non-destructive testing tasks specific to thick and highly reinforced nuclear containment structures have materialized. The performance based Service life extension of existing NPPs also needs a measurement based decision to support continuing the service of the concrete part of the installations.
By nature, concrete is a very durable material and any natural Deterioration processes may take a long time to become critical to the structure. The experience of more than 50 years of service limits the testing tasks to a few ones which are not yet solved.
Research in NDT of concrete structures is performed by many research institutions all over the world with different technical and systematic approaches. Results are mainly obtained on laboratory specimens, sometimes additional field studies are reported. This research takes place independently without coordination and as a result, the outcomes mostly lack full comparability.
Software for data analysis has become indispensable and very powerful. This part of testing needs more attention when it comes to evaluate test results. Validation of NDE solutions is becoming a critical part in concrete structure testing.
Validation is by definition the proof that a customer´s requirements in the test are being met by the testing solution. This includes equipment, personnel qualification and data analysis. In the following tables, the research recommendation Validation is used in the sense, that proof of the performance of existing solutions needs to be adressed. In general, a validation methodology for NDE solutions for concrete testing in itself needs to be researched and established.
Comparability of research also needs an accepted and easily accessible reference. From experience, it is almost impossible to manufacture exact copies of test specimens at different locations. Round Robin tests are therefore needed to evaluate the performance of a test.
Data evaluation is generally done using dedicated software, sometimes Hardware dependant and not interchangeable between systems. Software is ever more increasingly becoming more powerful and sophisticated. An in-depth evaluation needs to address the comparability and validation of Software used for data analysis and evaluation. The vision of a unified software pool for NDE investigations would undoubtedly support research tremendously.
Quantitative NDE is mostly recommended to assess the condition of a structure. However, qualitative data can be very useful, especially for processes which change the material properties or deteriorate the structure (e.g. corrosion of reinforcement). The need for reliable baseline data is a key factor for such monitoring tasks.
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)