On strength and stiffness of screwed-in threaded rods embedded in softwood

Abstract

Screwed-in threaded rods with wood screw threads feature high axial capacity and stiffness and can be used as fasteners in highly resistant and stiff timber connections. The purpose of the present paper is to review the existing literature and design rules in the present version of Eurocode 5 (EN 1995-1-1) and European Technical Assessments, to identify gaps of knowledge and to provide some proposals for the strength and stiffness of threaded rods. A collection of experimental results is used to derive simple expressions for the withdrawal capacity and stiffness. Finally, theoretical expressions for the stiffness and the capacity of laterally-loaded threaded rods are provided.