Creep of various structural members in ambient conditions, 2: Estimation of future deflections considering initial moisture content
2004
Aratake, S. (Miyazaki-ken. Government Office (Japan)) | Arima, T.
Bending creep tests of various structural members were conducted with changes of loading conditions, and a method for estimating creep deflection considering initial moisture content was investigated. The specimens used were sugi (Cryptomeria japohica D. Don) sawn lumber, Douglas-fir (Pseudotsuga menziesii Franco) sawn lumber and sugi glulam. The specimens were 10.5 cm in width, 24.0 cm in depth, and 400 cm in length. The results are summarized as follows : 1) Although all of the sawn specimens had initial moisture contents above the air-dried state, their creep tendencies became almost the same as those of the air-dried specimens (sugi glulam) after they reached the air-dried state. 2) When long-term deflection with changes of loading conditions is calculated using the superposition theory (SP) there is every possibility that the long-term deflechon is overestimated if the power law which includes mechanosorptive deflection (MSD) is applied to the basic SP curve. 3) The creep deflection under various loading conditions of sawn specimens, which were initially above the airdried state, can be expressed by SP on condition that the power law of air-dried specimens is applied to the basic SP curve and the defined MSD in the process of desorption is added to the SP. 4) The values of relative creep pf sugi glulam were rather on the safe side in comparison with the coefficient of creep deflection (C sub(CP)) determined in " Standard for Structural Design of Timber Structures", regardless of the adapted stress levels and the types of adhesive. On the other hand, the relative creep of sawn specimens whose moisture content was initially above the air-dried state was much higher than the CCF ,
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