The influence of freezing and heating on the nail withdrawal capacity of Norway spruce and European larch wood

Environmental conditions and temperature fluctuations can influence the properties of wood. Accordingly, the performance of wood connections such as nails could be affected by freezing and heating temperature. Thus, in the present work, the impact of freezing/heating temperatures on the nail withdrawal capacity of Norway spruce (Picea abies (L.) H. Karst.) and European larch (Larix decidua Mill.) was studied. Three types of wood nail: smooth, helically threaded, and annularly threaded were studied, and two different freezing/heating steps (- 15 degrees C/70 degrees C and - 25 degrees C/70 (?)degrees C) were implemented. Nail withdrawal capacity was determined in two anatomical directions, i.e., radial and tangential. The freezing/heating had a negative impact on the nail withdrawal capacity of both wood species. The highest decrease in withdrawal capacity was found in larch wood, where smooth nails driven in the tangential direction achieved a decrease of 73% at temperatures of - 15 ?degrees C/70 degrees C and a decrease of 69% at temperatures of - 25 degrees C/70 (?)degrees C. Smooth nails driven in the radial direction had a decrease in withdrawal capacity of 70% at temperatures of - 15 (?)degrees C/70 ?degrees C and 63% at temperatures of - 25 ?degrees C/70 (?)degrees C. Smooth nails driven in the tangential direction of spruce wood achieved a significant decrease in withdrawal capacity of 69% for temperatures of - 15 degrees C/70 degrees C and a 63% decrease at temperatures of - 25 degrees C/70 degrees C, while in the radial direction it was 54% at temperatures of - 15 degrees C/70 degrees C and 56% for temperatures of - 25 degrees C/70 degrees;C.