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- NDT (6)
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- Assessment of concrete structures (2)
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Infrastructure is subject to continuous ageing. This has given life cycle management of infrastructure an increasing role. Reliable inspection and monitoring tools are therefore an increasing demand. A combination of different non-destructive test methods is often necessary to receive reliable results for material characterization,
flaw detection and the determination of component specific geometry parameters.
Regarding concrete structures thickness measurements are combined with flaw detection and additional information about reinforcement and tendon ducts is required.
Therefore, a multi-sensor measurement approach is necessary with a high degree of automation. Otherwise a time consuming succession of manual measurements has to be performed which would prevent practical applications. A modular control and data acquisition approach is described and the application of two different automated measurement devices is shown. The BetoScan system consists of a self-navigating
mobile robot. The system is especially designed for the investigation of reinforced concrete floors exposed to de-icing salts. The data acquisition of the OSSCAR system a multi-sensor scanner is similar to the robot approach. These different applications are based on a similar kernel allowing the modular use of different contact and noncontact sensors. The described general concept of multi-sensor data acquisition and data analysis presented here is not limited to the field of civil engineering applications.
Automated multi-sensor systems in civil engineering for condition assessment of concrete structures
(2012)
Control and data acquisition of automated multi-sensor systems - two examples from civil engineering
(2010)
A new approach is presented to evaluate corrosion of steel bars in concrete by 1.5- and 2.6-GHz ground-penetrating radar (GPR) and a modified half-cell potential method. Changes in time-lapsed travel times, amplitudes, and peak frequencies that are associated with short-time Fourier transform spectrograms of the bar reflections were continuously measured. The year-long corrosion process of the reinforcement bar rapidly accelerated within a few days by impressing direct current across a pair of embedded reinforcement bars, which served as the anode and cathode. When corrosion started, the travel times, amplitudes, and frequency spectra of the bar reflection changed. The results were analyzed by dividing the material's response into three phases (NaCl contamination, depassivation, and corrosion). The writers attribute the phenomena of the first two phases to the ionic conduction and interfacial polarization effect, described in the low-frequency regime of complex dielectric permittivity outlined in the Maxwell-Wagner effect. The remaining phase corresponds with the appearance of large and multiple interfaces among steel, concrete, corrosion product, and cracks, in addition to the upward movement of the corrosion product to the concrete surface that intercepts wider radar footprints. The findings, based on time lapse measurements, provide a basis to further apply the GPR technique to spatial measurements in laboratory and field studies.
The combination of radio-frequency identification (RFID) tags with different types of sensors offers excellent potential for applications with regard to identification, diagnosis, and monitoring. This should be demonstrated by means of two examples of actual developments carried out by the Federal Institute for Materials Research and Testing (BAM). The Identification and diagnosis of concrete components is a major task in the maintenance of critical infrastructure, for instance concrete bridges with heavy traffic volume. A feasibility study investigates the application of RFID sensor systems for this task. The second example reviews the transportation of dangerous goods. Using modern technologies enables promising possibilities to reduce accidents and to avoid non-conformity with transportation regulations. Project results demonstrate an innovative technical solution for monitoring of dangerous goods transports with RFID sensor systems.