Load-Duration Effects in Westerm Hemlock Lumber

Results from a duration of load experiment on western hemlock 2 x 6-inch lumber, visually graded No. 2 and better, are presented. Constant and ramp loadings arm used and, to predict load duration behavior for other load histories, a damage accumulation model is developed and calibrated to the test results. The implications of the test and the damage model for the assessment of reliability of wood structures are discussed. The model's predictions are verified using additional test results from a rate-of-loading experiment with media times-to-failure in the range 0.04 seconds to 11.3 hours.