Impact of moisture cycling on lateral resistance of resin-impregnated compressed beech nails in radiata pine timber

Abstract

Resin impregnated wood nails create an opportunity to use more renewable materials in place of metal fasteners, but there are few data on the effects of moisture cycling on performance. The properties of resin impregnated, compressed beech nails that had been subjected to repeated wetting and drying were compared with steel nails using radiata pine lumber. Sections cycled between ∼12 and ∼50% moisture content were destructively tested in shear. Capacity increased slightly with exposure to one moisture cycle for both connector types. Significant negative effects on wooden nail stiffness were only observed after 5 or 7 moisture cycles. Metal nails failed in a ductile fashion while the timber connectors failed in a brittle mode. The results suggest that wood fasteners can withstand some wetting, but repeated moisture cycling will be detrimental to performance.