Wood Nail Research Articles

Properties of wood shear walls connected by wood nails

The performance of a wood wall connected by wood nails and twist nails was tested. It was found that during the monotonic load testing, the wood nails connected to the shear panel and stud at the column bottom broke when the deformation reached 12.1 mm. However, the primary failure mode was that the twist nails bent and the head cap became dented in the shear panel. For reciprocating loads, it was found that the wood nails experienced local fracture on the tensile side. The skeleton curve of the wood wall connected by twist nails showed a good trend of bearing capacity changes in both tension and compression sides. Based on the properties of the standard wood wall, a new T-shaped fastener was designed for the midply wood wall. The lateral performance of the reinforced standard wood shear wall and midply wood shear wall were tested. By adding T-shaped pull-up fasteners, sandwich wall structure and double row nails, the strength, stiffness, and ductility of the midply wood wall were substantially better than those of standard walls connected with twist nails using conventional pull-up fasteners.

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.

Wood nails to fix softwoods: characterization of structural deformation and lignin modification

Softwoods can be nailed with high density solid wood like Santos Rosewood (Machaerium scleroxylon) or nails made of densified laminated beech wood composite by hammering or shooting, for example with air nail guns, without pre-drilling. Shooting with about 30 m/s causes friction between nail surface and softwood matrix, heating up the interface to temperatures high enough to soften lignin. Re-condensation of softened lignin causes wood welding which doubles pull out strength in comparison to wood nails fixed without wood welding. Changes in lignin UV-absorption within the single cell wall layer and deformation of main anatomical features of spruce wood tissue are characterized by scanning UV microspectrophotometry (UMSP) whereas structural deformations of spruce wood tissue are revealed by X-ray micro-computed tomography (µ-CT).

Parameter interactions in two-block welding and the wood nail concept in wood dowel welding

The interactions between parameters found to be determinant in wood dowel welding by high speed rotation have been evaluated. Of these, the interactions that proved to be the most significant, in descending order, were rotation rate/dowel moisture content, followed by rotation rate/ethylene glycol, and finally, at a lower level of significance, the interactions rotation rate/dowel temperature, wood grain direction/wood species and dowel temperature/wood species. Of the individual factors, once the most determinant factor already optimized in previous studies, namely the dowel/hole diameter difference, was fixed, the most significant were wood grain direction, dowel moisture content (dryness) and wood species. The optimized process yielded excellent strength results. The regression equations developed were able to predict the strength obtainable. The torque for insertion of the dowel in the substrate hole has been measured for several cases and the results are presented. In no cases the value of the torque needed for insertion was excessive and insertion was, therefore, easy. Wood joints composed of two pieces of timber held together by a dowel welded to both of them were assembled for the first time. Two further new concepts have also been advanced and tested: (i) the conical dowel, to maximize welding area and (ii) the concept of the wood nail in which a slightly conical fast-rotating hardwood dowel is inserted rapidly into a softwood substrate into which no hole has been pre-drilled. X-ray densitometry of the samples prepared with the latter approach showed some interesting mechanical interlocking features that might contribute to dowel bonding in softwoods.