Scaling and modeling the creep of Eucalyptus globulus

Abstract

Eucalyptus, with the commercial name of 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 of the water content in the wood material). The evaluation of bending creep was done in indoor / constant and transient humidity conditions. In the latter, mechano-sorptive effect, the creep bending tests were done for a period of 60 days with cycles of wetting-and-drying. Each cycle has 7 days of duration. Defect free specimens with dimensions of 20*20*400 mm3 (approximately to the scale 1:10) of Eucalyptus globulu. wood species were used. To fit the creep behaviour and extrapolate results for different periods (1, 10 and 50 years) a survey of different numerical models was done. Rational, parabolic and polynomial functions were chosen. In bending, Blue gum wood species presented a behaviour without a creep limit, therefore labile. Through the models used for extrapolations a significant variability was found for different periods. Values of the main standard of wood design (Eurocode 5) were exceeded. The most consistent mathematical model was the rational model because it is the one that has led to closer and stable results.

Keywords

• Blue gum
• creep limit
• eucalypts
• mechano-sorption
• model, test