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Autor*in

  • Strangfeld, Christoph (71)
  • Bartholmai, Matthias (18)
  • Kruschwitz, Sabine (17)
  • Johann, Sergej (14)
  • Müller, Maximilian (8)
  • Klewe, Tim (6)
  • Nagel, Sarah Mandy (5)
  • Greenblatt, D. (4)
  • Wöstmann, Jens (4)
  • Mieller, Björn (3)
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Erscheinungsjahr

  • 2021 (3)
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Schlagworte

  • Embedded sensors (14)
  • Material moisture (11)
  • Structural health monitoring (11)
  • RFID sensors (9)
  • Concrete (8)
  • Building materials (7)
  • Corresponding relative humidity (7)
  • Feuchte (7)
  • Moisture (7)
  • Moisture measurements (7)
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Organisationseinheit der BAM

  • 8 Zerstörungsfreie Prüfung (71)
  • 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (61)
  • 8.1 Sensorik, mess- und prüftechnische Verfahren (20)
  • 8.0 Abteilungsleitung und andere (9)
  • 5 Werkstofftechnik (2)
  • 5.5 Technische Keramik (2)
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Non-destructive testing in civil engineering at BAM (2017)
Wiggenhauser, Herbert ; Kind, Thomas ; Mielentz, Frank ; Strangfeld, Christoph ; Völker, Christoph ; Wilsch, Gerd
Research and Development in Non-Destructive Testing in Civil Engineering at BAM has de-veloped over more than two decades. Highlights of present research are ultrasound phase array probes, ground penetrating radar applications for the assessment of existing structures and Laser Induced Breakdown Spec-troscopy (LIBS) to determine which chemical elements on the surface of a specimen are. RFID sensor devel-opments for wireless moisture monitoring and data fusion for the combined analysis of sensor data are fast developing areas. In addition, a selection of application cases is briefly described.
Embedded RFID-sensors for concrete bridge structures (2015)
Strangfeld, Christoph ; Stoppel, M. ; Bartholmai, Matthias ; Petrov, Sergej ; Fakhouri, A.
In the near future, it will be important to adopt innovative approaches and technologies in order to further guarantee the reliability and availability of the highway network. New tools are therefore needed in order 'to obtain in-depth information about the condition of bridges and its development early enough before significant, precarious damage cases occur. In 2011, the research program "Intelligente Brücken (Smart Bridges)" was launched by the BASt together with the BMVI to evolve systems for information and holistic evaluation for bridge structures as a supplement to the current inspection-based maintenance management. Several projects dealt with the topic in the last few years and provided guidelines and a solid basis to move towards a first implementation considering the input of all research projects carried out so far.
Einsatzfähigkeit von RFID-Tags zur Identifikation und Diagnose von Bauteilen in der intelligenten Straßeninfrastruktur (2015)
Strangfeld, Christoph
Airfoil in a high amplitude oscillating stream (2016)
Strangfeld, Christoph ; Müller-Vahl, H. ; Nayeri, C. N. ; Paschereit, C. O. ; Greenblatt, D.
A combined theoretical and experimental investigation was carried out with the objective of evaluating theoretical predictions relating to a two-dimensional airfoil subjected to high amplitude harmonic oscillation of the free stream at constant angle of attack. Current theoretical approaches were reviewed and extended for the purposes of quantifying the bound, unsteady vortex sheet strength along the airfoil chord. This resulted in a closed form solution that is valid for arbitrary reduced frequencies and amplitudes. In the experiments, the bound, unsteady vortex strength of a symmetric 18 % thick airfoil at low angles of attack was measured in a dedicated unsteady wind tunnel at maximum reduced frequencies of 0.1 and at velocity oscillations less than or equal to 50 %. With the boundary layer tripped near the leading edge and mid-chord, the phase and amplitude variations of the lift coefficient corresponded reasonably well with the theory. Near the maximum lift coefficient overshoot, the data exhibited an additional high-frequency oscillation. Comparisons of the measured and predicted vortex sheet indicated the existence of a recirculation bubble upstream of the trailing edge which sheds into the wake and modifies the Kutta condition. Without boundary layer tripping, a mid-chord bubble is present that strengthens during flow deceleration and its shedding produces a dramatically different effect. Instead of a lift coefficient overshoot, as per the theory, the data exhibit a significant undershoot. This undershoot is also accompanied by high-frequency oscillations that are characterized by the bubble shedding. In summary, the location of bubble and ist subsequent shedding play decisive roles in the resulting temporal aerodynamic loads.
Multimethodische Bestimmung von Feuchtegradienten in Estrich (2016)
Strangfeld, Christoph
Um den Feuchtegehalt von Fußbodenestrich vor der Verlegung von Holz- oder anderen Bodenbelägen zu bestimmen, werden zerstörende Prüfverfahren wie die Calcium-Carbid Methode (CM) oder das thermogravimetrische Darr-Verfahren eingesetzt. Diese liefern jedoch einmalig nur punktuelle Informationen und sind je nach Estrichtyp auch störanfällig. Zusammen mit Partnern aus Forschung und Industrie wurde an der BAM ein Ringversuch durchgeführt, dessen Ziel es war, verschiedene nach Möglichkeit zerstörungsfreie oder – arme Prüfverfahren hinsichtlich ihrer Genauigkeit und Sensitivität vor allem im Bereich der Belegereife zu testen. Hier dargestellt sind die Ergebnisse aufgenommen an einer Calciumsulphat-Estrich Probe vom Typ Knauf FE80 Largo mit drei Verfahren, die auch Aussagen über die Feuchtegradienten in die Tiefe zulassen. Die Proben wurden bei Konstant-Normklima mit T=23 °C und rH=50 % zur Trocknung gelagert.
Transmission characteristics of RFID sensor systems embedded in concrete (2016)
Bartholmai, Matthias ; Johann, Sergej ; Kammermeier, Michael ; Müller, Maximilian ; Strangfeld, Christoph
Completely embedded sensor systems for long-term operation offer innovative possibilities for structural health monitoring of concrete structures. Measuring of relevant parameters, e.g., temperature, humidity, or indication of corrosion can be performed with low energy sensors. This allows to implement passive RFID sensor systems without cable connection and battery, which are power supplied exclusively by the electromagnetic field from the external reader device. To evaluate characteristics and conditions of this concept, a systematical investigation of the transmission characteristics with variation of relevant parameters, as communication frequency, installation depth, type of concrete, moisture content, etc. is currently carried out in an interdisciplinary research project at BAM. First results are presented in this paper.
Moisture in screed: a non-destructive multi-sensor approach (2016)
Strangfeld, Christoph ; Kruschwitz, Sabine ; Wöstmann, Jens ; Nagel, Sarah Mandy ; Hase, Felix
Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23◦ C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes.
Moisture Measurements with RFID based Sensors in Screed and Concrete (2016)
Strangfeld, Christoph ; Johann, Sergej ; Müller, Maximilian ; Bartholmai, Matthias
To quantify the moisture in concrete, RFID based humidity sensors are embedded. Passive high frequency, ultra-high frequency RFID tags as well as active Bluetooth sensors are tested. After concreting, all sensors measure the corresponding relative humidity to monitor the concrete moisture. Two case studies are performed, embedding in an existing construction, i.e. the duraBASt test bridge, and embedding in cement based mortar in the laboratory. As basis for robust and long-life sensors in alkaline concrete, different casing materials are tested. Furthermore, signal strength measurements and their sensitivity to different moisture levels are performed.
Moisture Measurements with RFID based Sensors in Screed and Concrete (2016)
Strangfeld, Christoph
To quantify the moisture in concrete, RFID based humidity sensors are embedded. Passive high frequency, ultra-high frequency RFID tags as well as active Bluetooth sensors are tested. After concreting, all sensors measure the corresponding relative humidity to monitor the concrete moisture. Two case studies are performed, embedding in an existing construction, i.e. the duraBASt test bridge, and embedding in cement based mortar in the laboratory. As basis for robust and long-life sensors in alkaline concrete, different casing materials are tested. Furthermore, signal strength measurements and their sensitivity to different moisture levels are performed.
Moisture in screed: a non-destructive multi-sensor approach (2016)
Strangfeld, Christoph
Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23° C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes.
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