This model has been chosen to represent, with high accuracy, the creep in particleboard (Pierce and Dinwoodie 1977, Pierce et al.
Average initial elastic deflection, final creep deflection, and relative creep in PSL are summarized in Table 2.
t-Tests showed that the average final creep deflection and relative creep in PSL at 95 percent RH were significantly greater than those at 65 percent RH.
At cyclic RH levels and a constant temperature, both final creep deflection and relative creep in southern pine PSL were smaller than those in yellow-poplar PSL (Table 3), also revealing southern pine PSL has better creep resistance than yellow-poplar PSL.
However, RH varied in a greater range from 28 percent to 94 percent and possibly induced major effect on the creep in PSL.
It was found in all OSB products that relative creep in the parallel direction was much lower than that in the perpendicular direction, because MOE values in the parallel direction were considerably greater than those in the perpendicular direction.
This was because both outdoor temperature and RH fluctuated with higher frequency and magnitude to which creep in PSL was very sensitive.
As seen from Table 5, however, the relative creep values did not comply with this trend, implying that relative creep in PSL is independent of load levels in a certain range.
Modeling.--Under the constant RH and load levels just discussed, the estimated parameters of the four-element model for relative creep in PSL and the corresponding residual sum of squares (SS) and multiple coefficients of determination ([R.sup.2]) are summarized in Table 6.
A review of creep in wood: Concepts relevant to development long-term behavior predictions for wood structures.
Creep in chipboard-Part 1: Fitting 3- and 4- element response curves to creep data.
The bobbin-shaped specimens as developed earlier by Brooks et al  were adopted for testing of direct tensile strength, creep in tension and creep in compression at low stress.
where [c.sub.cl] and ct are the specific creep in compression (low stress) and in tension respectively.
[1.] Jiang, X, The Effect of Creep in Tension on Cracking Resistance of Concrete, Dissertation, Submitted for degree of M.Sc., Dept of Civil Engineering, Leeds University, 1997.