Lumber and wood-based products are versatile construction materials that are susceptible to weakening as a result of applied stresses. To assess the effects of load duration and rate, experiments have been carried out by applying preset load profiles to sample specimens. This paper studies these effects via a damage modeling approach, by considering three models in the literature: the Gerhards and Foschi accumulated damage models, and a degradation model based on the gamma process. A statistical framework is presented for fitting these models to failure time data generated by a combination of ramp and constant load settings, and it is shown how estimation uncertainty can be quantified. The models and methods are illustrated and compared via a novel analysis of a Hemlock lumber dataset. Practical usage of the fitted damage models is demonstrated with an application to long-term reliability prediction under stochastic future loadings.
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The work reported in this paper was partially supported by FPInnovations and a CRD grant from the Natural Sciences and Engineering Research Council of Canada. The author is greatly indebted to Conroy Lum and Erol Karacabeyli from FPInnovations for introducing the author to this important area of research, sharing extensive advice during the conduct of this study, and providing the Forintek dataset analyzed herein. The author also thanks James V Zidek for helpful discussions during the preparation of the manuscript.
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Wong, S.W.K. Calibrating wood products for load duration and rate: a statistical look at three damage models. Wood Sci Technol 54, 1511–1528 (2020). https://doi.org/10.1007/s00226-020-01227-9