Experimental tests on annular ringed shank nails for seismic resistant Cross-Laminated Timber (CLT) structures

This paper presents an experimental programme on Simpson Strong-Tie annular ringed shank nails, conducted at the Institute of Timber Engineering and Wood Technology, Graz University of Technology. The fastener under investigation is commonly used in cross-laminated timber (CLT) buildings to anchor typical metal connectors to the timber panels, and the understanding of its performances is of particular interest for the design of earthquake resistant timber structures. Shear tests in parallel and perpendicular direction to the face lamination of a CLT panel, and withdrawal tests, investigated the bearing capacity of a nail driven in the plane side of a CLT element. Furthermore, uniaxial tension tests and bending tests were performed on single fasteners to determine the ultimate tensile strength and the yielding moment, respectively. Mean and characteristic values of the mechanical properties were assessed in terms of strength, stiffness and ductility, and compared with the simplified calculation methods provided by the standards. Finally, a numerical model of the connection, considered as a non-linear spring with three degrees of freedom, is presented and calibrated on the experimental results. As an applicative example, the numerical model is used to simulate a shear and a tension test of a Simpson Strong-Tie AE116 angle bracket.