Determination of Screw and Nail Withdrawal Resistance of Some Important Wood Species

This paper deals with nail withdrawal strength of spruce (Picea abies L.) with a focus on its dependence on thermal modification. Nail withdrawal strength is a feature of wood that is very important in the construction of wooden buildings. There are many studies dealing with the nail withdrawal strength of natural wood; however, this feature is much less explored with respect to thermally modified wood. Spruce wood was thermally modified at three different temperatures (140, 180, and 240 °C), and the nail withdrawal strength was evaluated for three types of nails driven into three anatomical directions. Values of nail withdrawal strength of thermally modified wood were compared with values of control spruce wood. The effect of thermal modification was clear: with increasing temperature, gradually decreasing values of nail withdrawal strength were obtained. The highest values were found in the tangential direction, and the lowest occurred in the axial direction. Annularly threaded nails had the highest values of nail withdrawal strength, while helically threaded nails had the lowest results.

Section: Nail Withdrawal Strengthcontrasting

confidence: 84%

Section: Nail Withdrawal Strengthmentioning

confidence: 58%

Influence of thermal modification on nail withdrawal strength of spruce wood

Barcík¹,

Gašparík²,

Horejš³

2014

“…This has been confirmed by Aytekin (2008) and Akyildiz (2014), who found the highest values in the radial direction. In general, the lowest values are achieved in the axial direction, as confirmed by our results as well as those of Aytekin (2008). Fig.…”

Section: Screw Direct Withdrawal Load Resistancesupporting

confidence: 71%

Impact of Thermal Modification of Spruce Wood on Screw Direct Withdrawal Load Resistance

Gašparík¹,

Barcík²,

Borůvka³

et al. 2015

This paper reports on the dependence of screw direct withdrawal load resistance on thermal modification of spruce wood. Screw direct withdrawal load resistance was measured in native and thermally modified spruce wood. The thermal modification was performed at three different temperatures: 140, 180, and 220 °C. Tests were carried out using two types of screws in three anatomical directions. The effect of the thermal modification was unambiguous: the screw direct withdrawal load resistance decreased with increasing modification temperatures. The largest decline 44.2% was found in the axial direction and at a temperature of 200 °C, while the lowest decrease 4.1% was found in radial direction and at temperature 140 °C for conventional screws without pre-drilling. The highest values were identified in the radial direction, and the lowest in the axial direction. While conventional screws without pre-drilled holes may be regarded as the most suitable, the selfdrilling screws achieved the lowest values.

“…Connections may consist entirely of wood members, but frequently they involve connections of wood to steel or other members, where a wide variety of fastenings can be used: nails, spikes, screws, bolts, lag screws, drift pins, staples, and metal connectors of various types. In order to achieve the greatest rigidity and strength and longest serviceability, each type of fastening requires joint designs, which are adapted to the strength properties of the wood along and across the grain (Taj et al 2009;Aytekin 2008;Rammer 2010). Connections are equally important in furniture construction as in wooden structures, because they are the critical links between the elements of a structure, maintaining load path continuity and providing structural rigidity.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Heat Treatment on the Withdrawal Capacity of Screws in Spruce Wood

Kariž¹,

Kuzman²,

Šernek³

2013

The withdrawal capacity of screws in heat-treated spruce wood (Picea abies Karst.) was measured in the radial and tangential directions. Wood was heat-treated at temperatures of 150, 170, 190, 210, and 230 °C. Screw withdrawal capacity decreased as the degree of thermal modification was increased. Also, image analysis was used to measure the size of the deformed wood area around the screw, which increased with higher thermal modification temperatures. This leads to the practical recommendation that connections in heat-treated wood should be constructed with screws with larger diameters and deeper penetration. Moreover, larger spacing between screws is needed to ensure sufficient withdrawal capacity compared to non-treated wood.