Rotational Stiffness of Timber-to-Timber Connections with Self-Tapping axially loaded Screws

Self-tapping axially loaded screws provide high load-carrying capacity and great stiffness. Due to these advantages, they were preferably applied to realise connections for tension members. While the translational stiffness of those connections can be estimated for engineering purposes sufficiently, knowledge about the rotational stiffness is still low. The investigations reported here show the influence of the inclination and the geometrical arrangement of the self-tapping screws on the rotational stiffness of connections for tension members. A test set-up was therefore developed. It enables that tensile forces and rotation are simultaneously effective and quantitatively independently of each other. The experimental results show that the inclination of the screws and the resulting compressive stress in the shear plane has a major influence on the rotational stiffness and that the stiffness of the screws themselves becomes less effective.