The effect of water sorption/desorption on fatigue deflection of OSB

Abstract

Oriented strand board (OSB) is used as in-service loadbearing material. The impact of water sorption/desorption on the fatigue deflection is not fully understood yet. In this study, fatigue deflection of two types of OSB was studied when exposed to cyclic loading using the three point bending static method for 12 cycles. During cyclic loading, the specimens were wetted and dried before cycle 4, 7 and 10 respectively. Deflection and strain distributions were continuously recorded with digital image correlation (DIC) during the bending test. The results show that both recoverable and residual deflection mainly occurs in the first cycle. Water sorption/desorption can linearly increase the deflection of the specimens. Both large deflection and strain are prone to occur in a region 1–3 mm beneath the top surface. Large strains along the thickness direction induced during water sorption/desorption can be transferred from the top to the bottom surface of the specimens. Strain accumulation is an important factor of the decreasing loading capacity of OSB. Structural changes induced with shear strain could hurdle strain transferal along the thickness direction. Increasing water resistance and reducing structural defects are essential to guarantee proper strain transfer in OSB aiming at in-service loading conditions.