Design Supports & Deflection

For members or member sets with activated design properties, the Design Supports & Deflection tab is added to the edit dialog box. Here you can define the boundary conditions for the serviceability limit state design in steel design, as well as the specifications for the design of local transverse forces for cold-formed sections.

Dialog Box "Edit Member", Tab "Deflection and Design Supports"

Design Supports

Design supports allow for the segmentation of a member or member set for a deflection analysis. The design supports can be assigned via the table at all intermediate nodes of the object. Both nodes of the "Node on Member" type and standard nodes between the members of a member set are recognized.

Select a design support type from the list or create a new one using the button. You can use the button to edit the selected design support type. The button allows you to graphically select an already assigned design support from the model.

For hot-rolled steel sections, both the design support type 'General' and the type 'Steel' are suitable. If you use a design support for a member with a steel material, the 'Steel' type is preset.

Dialog Box "Edit Design Supports"

If you do not want to consider a design support for the segmentation, deactivate the 'Active for deflection design' option. For the deflection analysis, the specifications for the 'Support width' or 'Support depth' are not relevant.

If you want to perform the design of the local transverse forces (local compression, web crippling, or local buckling in the web) according to EN 1993-1-3, 6.1.7, AISI S100, or CSA S136 for cold-formed sections, define a new design support and select the type 'Steel' from the list.

Design Support for Designing Local Transverse Forces of Cold-Formed Sections

The 'Support width' w defines the length of the stiff bearing s_S. The 'Support depth' d, in contrast, has no influence on the design. The "Support" is therefore not a support in the actual sense, but rather serves to describe the geometric parameters for taking the load into account.

Specify the effect of the support with the 'Support from edge' list. The parameters "+z" and "-z" refer to the orientation of the local z-axis of the member. For example, if the load acts on the upper edge of the beam and the local z-axis points downwards, select the '-z/z'-axis' option. The load is thus assumed to be a compressive load for the section (with the '+z/z' axis' option, this would be a tensile load, as the load acts on the lower edge).

If there is an 'End support', select the corresponding check box and define the 'Overhang length' c. If the check box is cleared, the overhang length is considered to be infinite, so that c > 1.5 h_w.

Deflection Analysis

After assigning the design supports to a member or a member set, the resulting segments for the respective directions are listed in the Deflection Analysis section of the dialog box. For each design location in the respective segment, the displayed reference length is used to determine the limit value. The automatically determined reference lengths can be overwritten by selecting the "User-Defined Lengths" check box. Please note that if you subsequently change the member length in the model, the previously specified user-defined lengths are not adjusted automatically.

The deflection limit values can be specified in Serviceability Configurations for beams supported on both sides and for cantilevers. According to the defined design supports, the corresponding limit value is taken into account for each segment. A segment with design supports on both sides or with no design supports is regarded as a beam; a segment with a design support on one side is a cantilever.

In the design, you can consider a precamber for each segment and thus reduce the deflection value. The precamber is applied as a single-wave shape in the case of beam segments, and as a linear distribution in the case of cantilever segments. Enter the precamber z or y as a positive value if it is opposite the local member axis z or y. To design the resulting direction, the precamber components are converted into the resulting direction. In the case of design according to EN 1993‑1‑1, the precamber is only taken into account for quasi-permanent design situations.

Use Check direction to specify which deflection values are to be checked in the design. You can select the local axes y and z, as well as the resulting deflection, in the list.

By selecting the Displacement reference, you can influence the deflection values to be checked for the design. If an undeformed system is selected as the reference, the local deformation values u_y and u_z are taken directly from the results. With regard to the deformed member or member set ends, the deflection values for the design are reduced by the deformation values of the start and end nodes in order to be able to check the local deflections.