Strength and Stiffness of Clear Douglas-Fir Exposed to the Mount St. Helens Volcanic Eruption

The objective of this study was to determine thermal and blast effects of the Mount St. Helens volcanic eruption on the clear bending strength and stiffness of Douglas-fir. Analysis of results showed that, although the material evaluated from two geographic areas within the blast zone had lower strength and stiffness than values published by ASTM, differences existed because of the generally lower specific gravity of the material. Old-growth timber in the sample showed somewhat higher values than did the limited sample of young-growth material. Wood located close to the surface of trees did not show the anticipated strength reduction when compared to unaffected wood of layers deeper inside the trees. The sample taken may be representative of a large area surrounding the volcano, but it may or may not reflect the effects much closer to the eruption center.

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