DEGRADATION OF YIELD STRENGTH OF LATERALLY LOADED WOOD-TO-ORIENTED STRANDBOARD CONNECTIONS AFTER EXPOSURE TO ELEVATED TEMPERATURES
Keywords:Arrhenius activation energy, Douglas-fir, kinetics model, regression
AbstractWood to sheathing connections is crucial to lateral force resisting system of the wood-frame structure. Engineers are often faced with the challenge of predicting strength of a partially damaged structure after it has been exposed to elevated temperature during a fire. Numerical simulations to predict the residual strength need thermal degradation data and models for the material as well as the connections. Therefore, it is important to categorize connection response when exposed to elevated temperatures for a sustained period of time. This study addresses this issue by developing models to predict lateral yield strength degradation of wood to Oriented Strandboard (OSB) connection after exposure to elevated temperature. A total of 394 Douglas-fir to OSB connections were tested laterally as a function of 8 different temperatures and 8 exposure times within each temperature regime. Yield strength of the connection decreased as a function of temperature and exposure time. Rate of degradation was higher at higher temperatures. A regression-based statistical model was developed. Additionally, these results were fit to a 2-step simple kinetics model, based on the assumption of degradation kinetics following an Arrhenius activation energy model. The kinetics-based model was preferred over regression model as it fit the data better with one less parameter and predictions consistently matched the observed values for an independent data set.
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