| 研究実績の概要 |
Following determination of viscoelastic creep properties of surface and inner layer of Sugi and Hinoki boxed-heart timber, determination of mechano-sorptive creep properties of surface and inner layer of the timbers was then conducted at temperature of 20, 65, 80 and 90°C using cantilever creep test. A load of 20% from its rupture load was applied for the creep test at temperature of 20 and 65°C. In case of the creep test at temperature of 80 and 95°C, a load of 10% from its rupture load was applied at the free-end of the cantilever. Strain gauges was bonded at a fourth span on upper and bottom faces of the specimen. Deflection and strain were measured on the specimen subjected to load and cycling change of relative humidity (RH) in a temperature and humidity chamber for 36 h. Mechano-sorptive creep is defined as a function of cumulative moisture content change and a model consisted of one Kelvin unit and one dashpot connected in a series was used to determined mechano-sorptive creep properties of the timber. From the creep test results, it was found that temperature had significant effects on the creep properties of the timber. The creep compliance of surface and inner layer specimen of the timbers tended to increase as temperature increased. In addition, the largest deflection and creep rate of the specimen was observed at the first RH cycle. Fitting experimental data with model used in this research shows a good agreement. Therefore, model parameters obtained in this research were applicable for identification of mechano-sorptive creep properties of the timber.
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