The definition of member transverse stiffeners enables you to define the boundary conditions for warping ω when calculating members with 7 degrees of freedom. You can specify the warp spring stiffness at a certain point directly or have it calculated automatically for available types (see also section resulting-stiffness resulting warp spring ).
Assignment to Member or Member Set
Member transverse stiffeners are organized in RFEM and RSTAB as a "Type for Members". Thus, you can assign the member transverse stiffeners to one or more members by using the Edit Member dialog box, by selecting them in the Member Transverse Stiffener dialog box, or via the input table.
Furthermore, it is possible to assign the member transverse stiffeners to a member set. The relative position of the stiffener types refers then to the length of the entire member set. Note that a member transverse stiffeners can be assigned either to a member or to a superordinate member set.
Stiffener Type and Location
In the Stiffener Type and Position section, specify all stiffener types and their locations. Click the
button to switch between the absolute and relative input of the position. Click the
button to sort the list according to the positions.
The following types are currently available:
- Flat stiffeners
- End plates at the member start and end
- Channel sections
- Angle sections (connection of both legs to the stiffened web)
- Connecting columns at the member start and end
- Warping restraints
Depending on the cross-section of the member, there may be restrictions in the assignment of the types. For general cross-sections (e.g. from RSECTION), only stiffeners of the type 'Warp spring' are permitted. If an incompatible stiffener type is assigned, a corresponding warning message is displayed.
Some stiffener types (such as flat stiffeners) require entering the stiffener position (left, right, or double-sided). In this case, the left side means the side lying in the negative y-direction.
Select the "Multiple" check box to add more stiffeners of the same type to a beam. In the parameters, you can now specify the number of stiffeners and the offset recurrence.
Parameters
In this section of the dialog box, you define the main properties of each stiffener type. In most cases, this requires the information about the material and dimensions of the stiffener.
If you have also activated one of the design add-ons Steel design or Aluminum design , the 'check box in the design Consider add-on' available. For more information on considering the transverse stiffeners in the design add-ons, see the corresponding chapters of the add-on manuals:
Warping Restraint
The resulting warp spring is automatically calculated for each transverse stiffener type and the present cross-section according to the entered parameters. The value is displayed in the lower dialog area, provided that there is a unique value for all situations. Otherwise, the maximum and minimum values are displayed in this field (for example, when using several members with different cross-section heights). The calculation formulas for different types of warping stiffeners can be found in the technical article Calculation of warping springs for consideration in the torsional buckling analysis for open cross-sections.
When specifying a warp spring, the entered stiffness is applied to the defined point. You can also use the rigid arching tension approach.
Calculation of members with 6 degrees of freedom
When calculating members with 6 degrees of freedom, member transverse stiffeners have no influence on the system stiffness. However, you can consider them when designing with the Steel Design and Aluminum Design add-ons by selecting the 'check box in the Design add-on Activate' (see also section parameters parameters ).