Moisture Effects on Load-Duration Behavior of Lumber. Part I. Effect of Constant Relative Humidity

Kenneth J. Fridley, R. C. Tang, Lawrence A. Soltis


The effect of moisture content on the load-duration behavior for structural lumber is presented. Select Structural and No. 2 Douglas-fir 2 by 4 specimens were tested in bending at relative humidities (RH) of 35%, 50%, and 95% with a constant temperature of 73 F maintained during the tests. Constant loads based on the 15th percentile of the static strength distribution for each grade at 73 F and 50% RH were used to load the beams. The results indicate a trend toward shorter times-to-failure at higher moisture contents subjected to equal mechanical stress ratios. The effect, however, was no more evident in the No. 2 grade specimens than in the Select Structural specimens. Survival rates were likewise reduced at higher humidities.


Load-duration;failure;relative humidity;moisture content;lumber

Full Text:



  • There are currently no refbacks.