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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.
Ultrasound sensors should be embedded into concrete for monitoring concrete properties. These new longitudinal wave sensors with a center frequency of 60 kHz were examined regarding their suitability for ultrasonic measurements in concrete structures in terms of emission characteristics, sensitivity and frequency ränge.
For the measurement of the radiation patterns, the sensors were embedded vertically and horizontally in concrete cylinders. The directivity pattern was measured using a laser vibrometer.
The sensitivity of the sensor was determined in water using different sensors of the same type. It shows changes in the signal amplitude as well as variations in the frequency ränge for different transmitter-receiver combinations.
The attenuation of the concrete affects the achievable resolution of the measurements and thus, the maximum possible spacing of the sensors within a concrete element. Experimental tests helped optimizing the distances with respect to the required resolution and the effort of embedding the sensors. The signal attenuation in the concrete was measured in the frequency ränge of 60 kHz in response to various degrees of reinforcement and grain size. For this purpose, the sensors were cast at different distances in the specimens studied. The recorded Signals were evaluated for their amplitude and frequency spectrum.
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.