Modelling Creep Behaviour of Blue Gum

Sofia Carvalho and Duarte B Lopes

Keywords

Blue Gum, creep, creep limit, Eucalyptus

Abstract

Blue gum is a viscoelastic material strongly influenced when under constant load (Creep), being this phenomenon in the context of displacements exacerbated with transient relative humidity (variations the water content in the material). The evaluation of mechano-sorptive effect in bending for 60 days long with cycles of wetting / drying (with 7 days 1 week of duration 1 cycle) according EN 1156 was done. Samples of Eucalyptus globulus Labill. wood species with dimensions of 20 20 400 mm (scale 1:10 app. RxTxL mm3, respectively) was used. To fit the creep behavior and extrapolate results for different periods (1, 10 and 50 years) a survey of different numerical models was done. In the tests, Blue gum wood specie presented a behavior in bending without a creep limit, therefore labile. A significant variability in different extrapolations (through models used) was found, exceeding the recommended values obtained through the rules of the main standard of wood design (Eurocode 5). Out of the six theoretical mathematical models used, one that has led to closer results, therefore more appropriate, was the parabolic model.

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