Dans la modélisation à long terme des structures en bois, plusieurs phé-nomènes sont pris en compte notamment la viscoélasticité, la mécano-sorption et le retrait gonflement. Le présent papier présente un protocole expérimental de découp-lage pour la compréhension des phénomènes rencontrés dans l'évolution de la flèche des poutres en bois soumises à des charges de longue durée. Pour cela, des essais de flexion quatre points ont été conduits en ambiance contrôlée sur des éprouvettes de petites dimensions dont nous mesurons la déflexion des faces supérieures et inférie-ures. L'analyse des résultats obtenus sur six mois en face supérieure et inférieure permet de découpler les phénomènes observés à savoir le retrait-gonflement transversal, l'effet verrou, la mécano-sorption orthotrope et la viscoélasticité.In long term modeling of mechanical behavior of timber elements, several phenomena have to be considered: mechano-sorption, viscoelasticity and shrinkage -swelling process are the major ones. This paper deals with an experimental procedure which separates and illustrates different phenomena observed on creep evolution of timber beams. For that purpose, a longitudinal four-point creep bending test was performed in controlled atmosphere on small samples by measuring upper and lower deflections. During six months, the result analysis allows a separation of swellingshrinkage effect, hygro-lock effect, orthotropic mechano-sorption and viscoelasticity.
Timber is a renewable material that should be more used for sustainable construction. While the mechanical behavior and durability of some species have been widely studied in the past, few studies are available for the Ozigo (Dacryodes buettneri) specie. This paper deals with the spatial variability of Ozigo beams subjected to long-term loadings and different environmental conditions. These beams were previously subjected to long-term creep in three environments (air-conditioned, unsheltered, and sheltered) at Masuku in the south-east of Gabon. Various specimens were extracted from these beams to determine its moisture content and subjected to three-point bending tests to obtain the modulus of elasticity and failure stress at various points in the space. The results obtained showed that, after long-term loadings, environmental exposure combined with mechanical loading, play a key role in the mechanical properties of the timber beams. A reduction of strength was found for the specimens extracted from the unsheltered and sheltered outdoor exposures in comparison with those extracted from the air-conditioned exposure. Concerning the spatial variability, statistical tests confirm that there is significant spatial correlation. It was also found that the spatial variation of properties in the beam is not stationary because it was affected by loading and support conditions.
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