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Moisture content monitoring in glulam structures by embedded sensors via electrical methods

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Abstract

In recent years, an increasing number of glulam structures have emerged in civil engineering, but their development is limited by durability issues. Degradations related to excessive moisture content (MC) or wetting/drying cycles were observed and can lead to severe structural damages. As a result, the development of continuous monitoring techniques of wood MC becomes essential. Currently, the mostly used MC control methods are based on electrical measurements (resistive or capacitive). Nevertheless, existing solutions are not practical to conduct measurements inside every lamella of glulam. In the light of these observations, it is proposed to transform glulam into “smart material” by embedding the MC monitoring system either inside or between lamellas, considering the major constraints of fabrication of this material (the small glue line thickness, the important bonding pressure, etc.). To achieve this, 4 measurement configurations using “pin-type” or “surface” electrodes were investigated with the following steps. First, a feasibility study was conducted to make sure of the good functionality of the measurement configurations. Thereafter, the selected configurations were used to monitor the MC variation (10–70%) in glulam specimens. At the same time, the influence of electrode spacing and bonding pressure on the electrical measurements was also investigated. Results show that the selected configurations are operational for the local MC measurement in the lamellas of glulam, regardless of the types of sensors used or the measured physical quantities (electrical resistance or capacitance). This study aims to provide valuable information for the future development of embedded MC monitoring system in glulam structures.

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Acknowledgements

The authors would like to thank the co-financers of this research project: la Région Midi-Pyrénées, le Conseil Général des Hautes-Pyrénées and le Grand Tarbes. Special thanks should also be addressed to Emannuel Laught for his contribution in developing the Giga-ohmmeter and to Tommy Vilella and Frédéric Leroy for their help in experimentation.

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Authors and Affiliations

  1. Institut Clément Ader (ICA), CNRS, UMR 5312, University of Toulouse, UPS, 1 rue Lautréamont, 65000, Tarbes, France

    Hang Li, Marianne Perrin & Florent Eyma

  2. PHASE Laboratory, EA 3028, University of Toulouse, UPS, 118 route de Narbonne, 31400, Toulouse, France

    Xavier Jacob & Vincent Gibiat

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  1. Hang Li
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  2. Marianne Perrin
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  3. Florent Eyma
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  4. Xavier Jacob
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Correspondence to Marianne Perrin.

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Li, H., Perrin, M., Eyma, F. et al. Moisture content monitoring in glulam structures by embedded sensors via electrical methods. Wood Sci Technol 52, 733–752 (2018). https://doi.org/10.1007/s00226-018-0989-y

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