Effects of multi-phase moisture conditioning on stiffness of nailed OSB-to-lumber connections

Single shear nailed oriented strandboard (OSB)-to-lumber connections were subjected to various moisture conditioning regimes between the times of fabrication and loading. This elucidated the relative importance of various phases in multi-phase moisture conditioning regimes as influences on the stiffness of such connections. Specimens were fabricated using spruce lumber in either a green or kiln-dried state and dry OSB. After fabrication, all specimens were conditioned to produce a 5 percent equilibrium moisture content (EMC) in the lumber components. During moisture cycling, the EMCs of the lumber members alternated between 5 and 12 percent. Moisture content of the lumber at the time a connection was fabricated had a strong influence on the extent to which the cycling of moisture in the joined materials influenced the stiffness of a connection. Moisture cycling, following an initial moisture conditioning, resulted in a substantial loss in the stiffness for a connection fabricated with kiln-dried lumber. For specimens fabricated with green lumber, there were no significant changes in the stiffness of a connection as a result of moisture cycling after the initial lumber drying. In practical terms, this study demonstrates the adverse influences on the stiffness of nailed OSB-to-lumber connections that result from using initially green lumber members, or exposing an initially dry assembly to humid service environments.

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