Analytische Chemie
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- 2015 (2) (entfernen)
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- Embedded sensors (2) (entfernen)
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.
Challenging new constructions and ageing infrastructure are increasing the demand for permanent monitoring of loads and condition. Various methods and sensors are used for this purpose. But the technologies available today have difficulties in detecting slowly progressing locally confined damages. Extensive investigations or instrumentations are required so far for this purpose. In this study we present new sensors and data processing methods for ultrasonic transmission, which can be used for non-destructive long term monitoring of concrete. They can be mounted during construction or thereafter. Larger volumes can be monitored by a limited number of sensors for changes of material properties. The principles of ultrasonic transmission and influencing factors are presented. This latter include load, damages as well as environmental parameters as temperature or moisture. Various methods for data processing, e. g. coda wave interferometry are introduced. They allow the detection of very small changes in the medium. The embedded sensors are shown including mounting and operation. Application examples so far include small scale laboratory freeze-thaw experiments, localizing loads in larger concrete models, monitoring load effects on real structures as well as detecting acoustic events. Some sensors are operating already for several years. The sensors can be used as transmitter or receivers or switched between both roles. While most of the previous experiments have been active (at least one sensor serving as transmitter), new studies show that the sensors are useful as well for passive measurements, e. g. in acoustic emission or time reversal experiments. Besides application in civil engineering our setups can also be used for model studies in geosciences.