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Effects of Long-Term Outdoor Exposure on Properties of I-joists

Daniel Way, Jeffrey Morrell, Arijit Sinha


I-joists manufactured using wood composites are intended for dry service condition. Situations arise where I-joists are exposed to excessive weather conditions. This exposure to moisture can degrade structural properties of I-joists. In a follow-up to a previous published study (King et al 2014) looking at the short-term exposure to moisture (138 d), this study extends the exposure days further to 1351 d (approx. 3.5 yr) to gain an insight into property changes and fine-tune the degradation model presented by King et al (2014). Long-term exterior exposure was associated with continued declines in maximum load and deflection at maximum load, but the rate of property loss decreased as the exposure period was extended. Bending failure modes shifted back from web buckling to shear type failures at the web-web and web-flange joints.


Wood-composites, durability, moisture, regression model

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