A connection formed using metal dowel fasteners may fail in a brittle or a ductile mode. The Eurocode 5 aims to design connections that fail in a ductile rather than a brittle manner; for example, the minimum spacings and end distances are imposed to prevent splitting failure.
The failure theory used for connections with metal dowel type fasteners is based on the assumption that the fastener and the timber behave essentially as rigid plastic materials.
The strength equations for connections formed using metal dowel type fasteners in timber where derived by Johansen, and are dependent on the geometry, the embedment strength of the timber material, the bending strength of the fastener, and the steel plate thickness (for those using steel plates). Other researchers have slightly modified the original Johansen’s equations to enhance the connection strength, including other effects; for example, the original equations used the fastener’s elastic yield moment, afterwards the elasto-plastic strength has been used, and friction and withdrawal effects were included.
The Eurocode 5 contains a set formulae, one for each relevant failure modes that can occur, with fasteners in single or double shear.
The strength equations known as Johansen’s equations and included in the Eurocode 5, approach the problem from the timber material’s perspective. They assume that the shear strength of the fasteners and the strength of the steel plates (if present) exceed the connection strength derived from the timber strength equations for the relevant fastener type.
The strength of the steel plates and shear strength of the fasteners must also be shown to exceed the connection strength, and it must be determined in accordance with the requirements of Eurocode 3.
If the connections is formed using pins, the strength check must be should be carried out in accordance with the requirements of the technical standard.
APF WoodJoint automatically performs all these verifications, but the user can easily disable them by activating the corresponding options in the settings dialog window.