Influence of different factors on the buckling capacity of screws inserted in timber perpendicular to the grain

This paper investigates the buckling capacity of fully threaded screws inserted into timber members perpendicular to the grain, focusing on their role as reinforcement in compression perpendicular to grain scenarios. In such applications, the buckling behavior of the screws can be critical and is influenced by several parameters, including screw slenderness, insertion tolerances, wood moisture content, and density. To assess the impact of these factors, two experimental campaigns of single-screw compression tests were conducted independently at two different academic institutions. The experimental results support the development and validation of an alternative design model for the buckling of fully threaded screws, proposed as an improvement to the current formulation in the draft Eurocode FprEN 1995-1-1:2025. The primary objectives of this study are to quantify the influence of key variables and to evaluate the suitability of the proposed model for practical design applications.