10.5 Geometry

In Window 1.5 Geometry, you can specify the details for the connection of the selected members.

This window is divided into two parts: On the left, the input parameters of the connection node are displayed; on the right, they are illustrated by graphics. The upper graphic shows a system sketch of the current parameter, the lower graphic shows a 3D visualization of the node.

The graphic buttons are explained in Table 3.1.

The window is adapted to the joint type. In the following, the entries for the Front to side type are presented. This connection is the most common type of design for slant screws.

If there is an eccentricity for the Member alignment in the model, it can be imported from RFEM or RSTAB. You can use the Edge options to specify a user-defined eccentricity. However, this eccentricity is not transferred to the main program. Thus, the eccentricity does not influence the internal forces, just the geometric boundary conditions of the connection.

For the connected member, the plane x-y or x-z can be selected as the Joint plane. Depending on the specification, the pair of screws is rotated accordingly. The graphic window shows the arrangement of the screws dynamically.

The Define parameters of screws option allows you to define the screws automatically, manually, or in a library. The library of fasteners (see Figure 10.11) can be opened in the text box below by using the button.

The Thread type can be selected from the list.

When you define the screws manually, note the following:

• The Diameter d_st of the screw must have at least 6 mm and a maximum of 12 mm.
• The Screw length l_st is freely definable. However, the screw must not protrude from the wood.
• The Head length l_h is limited to a maximum of 50 mm.
• The Minimal angle between the screw and grain α_lim must be between 0° and 90°. According to [2] 8.7.2, this angle may not be smaller than 30° (default setting). However, some manufacturers also offer the option to apply flatter angles according to the technical approval.
• The Characteristic withdrawal capacity F_ax,Rk can be calculated according to [2] Equations (8.38), (8.40a), or (8.40b). Alternatively, this value can be taken from the technical approval of a screw manufacturer.
• The Characteristic compressive resistance capacity f_c,k in the buckling design of the bolt is assumed to be 50 kN.
• According to the technical approval, the Characteristic tensile strength of the screw f_tens,k is assumed to be 20 kN.

• The Screws configuration can be selected from the list.
• With the Both screws from connected member side option, you can control the screw-in direction of the screws (see Figure 10.12).
• The Screws centered on shear plane option allows you to create an offset of height from the connected member to the main beam.

• Defining drill point determines whether the screw is connected from the bottom or top edge.
• If the screw is not placed in the center of the shear plane, you can enter the Drill point distance, the distance from the head of defining screw to the shear plane, and the distance from head of following screw to the shear plane in the text boxes.
• After that, define the Number of screws. There can be at most 20 pairs of screws if the alignment is crosswise or 20 screws if the alignment is parallel.

• If more than one screw pair or, in case of a parallel alignment, more than one screw is defined, information about the screw spacings is required. The Method of screws placement can take the minimum or maximum edge distances or user-defined specifications into account.

On our website, you can find a technical article that explains how to determine the screw forces for a secondary beam connected to a torsionally rigid main beam: