TY - JOUR A1 - Bremer, K. A1 - Wollweber, M. A1 - Weigand, F. A1 - Rahlves, M. A1 - Kuhne, Michael A1 - Helbig, R. A1 - Roth, B. T1 - Fibre Optic Sensors for the Structural Health Monitoring of Building Structures JF - Procedia Technology 26 N2 - In this work different fibre optic sensors for the structural health monitoring of civil engineering structures are reported. A fibre optic crack sensor and two different fibre optic moisture sensors have been designed to detect the moisture ingress in concrete based building structures. Moreover, the degeneration of the mechanical properties of optical glass fibre sensors and hence their long-term stability and reliability due to the mechanical and chemical impact of the concrete environment is discussed as well as the advantage of applying a fibre optic sensor system for the structural health monitoring of sewerage tunnels is demonstrated. KW - Structural Health Monitoring KW - crack sensor; fibre optic sensor; humidity sensor; SHM Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170331-30912 UR - http://www.sciencedirect.com/science/article/pii/S2212017316304121 SP - 524 EP - 529 ER - TY - JOUR A1 - Bore, Thierry A1 - Wagner, Norman A1 - Lesoille, Sylvie Delepine A1 - Taillade, Frederic A1 - Six, Gonzague A1 - Daout, Franck A1 - Placko, Dominique T1 - Error analysis of clay-rock water content estimation with broadband high-frequency electromagnetic sensors—air gap effect JF - Sensors N2 - Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling. KW - Wassergehalt KW - Ton KW - Zeitbereichsreflektometrie KW - Impedanzspektroskopie KW - Dielektrische Spektroskopie KW - water content measurement; TDR probe; clay-rock; dielectric spectroscopy; frequency domain finite element modeling Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170418-31248 UR - https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964200266&doi=10.3390%2fs16040554&partnerID=40&md5=26e537724db3b28e237009acde7676cd SP - 1 EP - 14 ER -