OVERVIEW OF CURRENT METHODS FOR CALCULATING SCREW JOINTS IN WOODEN STRUCTURES UNDER AXIAL TENSILE FORCES

Abstract

Designing wooden structures presents significant challenges, particularly in calculating joint connections. The design of these connections primarily depends on the magnitude of the forces acting on them. Research into the operation of screws under axial tensile forces dates back to the 1920s and 1930s, establishing the influence of pre-drilled holes and screw length on load-bearing capacity.

Subsequent studies have explored the factors affecting screw pull-out resistance, including screw diameter, wood density, screw length, pre-drilled hole diameter, the orientation of screwing (radial, tangential, or longitudinal), extraction speed, and lubrication during insertion. Currently, two methods for determining screw pull-out resistance are recognized: experimental, based on regression analysis, and theoretical, grounded in Volkersen’s theory.

An analysis of existing methods for calculating screw joints under axial tensile forces reveals that the standard procedure, which determines the load-bearing capacity, applies when the screw axis is angled between 30^o and 90^o to the wood grain and for screws with a diameter of 12mm or less. However, in situations where significant internal forces act on wooden structures, smaller diameter screws may not suffice. Today, a variety of screws are available with differing geometric parameters, such as diameter, thread pitch, and thread angle. Therefore, new calculation methods are needed to account for the unique performance characteristics of these modern screws.