It is well known that timber elements (e.g. beams) exposed to varying moisture content are subject to induced eigen-stresses due to restraint of hygroexpansion. This is an issue not only concerning wood drying but also design of timber structures; although a timber construction element may look solid and without any visible cracks, eigen-stresses are always present as a consequence of uneven moisture distribution in both time and space. The magnitude and development of these stresses may be calculated using a constitutive model encompassing elastic, hygroexpansive and mechano-sorptive strain rates.In many engineering fields, statistical extreme value analysis of measured or calculated values is used to determine safety levels and probability of extreme events to occur. In this paper, annual maxima of calculated moisture induced stresses (based on daily recordings of relative humidity over more than 40 years) are analysed with basis on extreme stress levels using the GEV distribution. It is found that surface coating is effective in reducing moisture induced stress, and that the stress also decreases with decreasing cross-sectional width.
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