Fully threaded screws vs. partially threaded screws
Partially threaded screws
Timber-to-timber
Partially threaded screws enable a stable connection of two components. The thread must be completely in the lower component (2). Partially threaded screws pull the upper component (1) onto the lower component (2) during the installation process. In case of axial loading the head pull-through and thread pull-out (withdrawal) shall be considered.
Stressed in shear
Partially threaded screws are mainly used for timber-to-timber connections. One area of application can be regarded within-timber-to timber joints stressed in shear, such as of connecting floor and wall elements made of cross laminated timber.
Pressure
Concerning screw-press gluing in timber construction, partially threaded screws with washer head, such as the RAPID® WH, are applied in order to ensure not only position stability, but also a well-balanced distribution of pressure within the glue joint.
Metal-to-timber
For example, the robust RAPID® Dual screws are used in conjunction with steel sheets to secure posts in the corresponding beam sockets.
Fully threaded screws
Applications
RAPID® FT screws are used for a wide range of applications. In structural metal-to-timber or timber-to-timber connections the screws are applied perpendicular to the surface or inclined, designated as active fasteners. To reinforce timber element capacity the screws are applied as passive fastener to increase tension or compression perpendicular to grain resistance at transverse connections, openings and more.
Screw cross
If loads act in only one specific direction, it is advisable to use screws arranged in parallel, as the load-bearing capacity is significantly increased by the frictional resistance in the composite joints. Regarding general loading directions, applying screws crosswise is highly advisable. Further applications can be seen in reinforcing of structural components against stresses perpendicular to grain or shear.
Support reinforcements
RAPID® FT CS screws in combination with supporting steel plates enable a significant increase of the bearing capacity of the supports.
Metal-to-timber
Another example of use are connections with outer steel plates. The steel plates have a specific hole geometry to ensure position stability and a tight fit of the screws heads. The screws are inserted with controlled torque for a well-balanced load transfer. In this context it is highly advisable to avoid tension stresses perpendicular to grain within the timber components via overlapping of the screw tips.