Moisture monitoring in glulam timber structures with embedded resistive sensors: study of influence parameters
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Moisture monitoring in glulam timber structures with embedded resistive sensors: study of influence parameters Placide Uwizeyimana1 · Marianne Perrin1 · Florent Eyma1 Received: 26 February 2020 / Accepted: 17 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Today, a strong expansion in the construction of timber bridges is being promoted by the use of glulam. However, durability issues related to wetting/drying cycles limit their development. Timber bridge supervisors have therefore expressed their needs concerning continuous moisture content (MC) monitoring in timber structures. Checks on the MC of timber bridges are commonly based on the resistive method. A recent study carried out in the laboratory has shown the great potential of surfacetype electrodes for local MC measurement in the laminated timber of glulam. Nevertheless, many parameters influence MC measurements and no information exists concerning surface electrodes. The novelty of this paper is to make the MC measurements with surface-type electrodes more reliable and accurate. In this study, the influence of electrode size and boundary conditions was therefore investigated. The influence of embedded sensors on the bending strength and elastic modulus of glulam beams was also evaluated in order to validate the electrodes instrumentation. Then, the influence of temperature and MC on the electrical resistance was studied, allowing a calibration curve to be established. The results show that small electrodes reduce the measurement uncertainties and therefore permit a more reliable estimation of MC. The boundary conditions also influence the measurements and should be considered. The embedded electrodes have no significant influence on the bending strength and elastic modulus of glulam beams. Finally, based on the literature review, a model for estimating wood MC was established, considering temperature variation.
* Marianne Perrin Marianne.perrin@iut‑tarbes.fr 1
Institut Clément Ader (ICA), CNRS, UMR 5312, University of Toulouse, UPS, 1 rue Lautréamont, 65000 Tarbes, France
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Wood Science and Technology
Introduction In recent decades, the use of timber in civil engineering has become an interesting solution to sustainable development issues. Its renewable, natural and ecological nature allows it to be integrated more and more often in constructions. This material, which is a carbon sink, requires little energy for its production and transformation. It even helps to reduce carbon dioxide emissions (Leicher and Laz 2014). In addition, the development of innovative, high-tech products, such as glulam elements, has led to the strong increase in the use of timber bridges observed today (SETRA 2006). The high potential of glulam can be explained not only by its high mechanical strength compared to solid wood but also by the possibility of building large-span structures (SETRA 2006; Gross 2013; Crocetti 2016). Nevertheless, durability problems due to moisture content (MC) variations limit the dev
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