In the Basic tab of the 'Serviceability Configuration' dialog, you set the limit values that apply to deformations of members and member sets.
The 'Design Parameters' are subdivided into categories. They vary according to the design standard.
Serviceability Limit Values
Different design situation types exist for serviceability checks (see Chapter Design Situations of the RFEM manual). For example, in accordance with EN 1993-1-1, there is a distinction between the characteristic, frequent, and quasi-permanent combination. For each combination type, you can set specific limit values for deflections, which apply to the directions of the member axes.
The deformation limit values are generally related to the lengths of the components: The longer a member is, the greater deflections are permissible. In the list next to the 'Definition Type', you can select how you want to define the limit value.
- Relative value: The limit value is defined related to the length of the member or member set.
- Absolute value: The value of the maximum deflection is set directly.
- Sum of relative and absolute value: The limit value is the sum of the relative and absolute value.
- Min. of relative and absolute values: The smaller value of relative or absolute value applies as the limit value.
- Max. of relative and absolute values: The larger value of relative or absolute value applies as the limit value.
Depending on the support of the component – double-sided supported 'Beam' or single-sided supported 'Cantilever' – different deflection limit values are usually relevant. The type applicable to a specific segment is automatically determined based on the assigned design supports: A segment with design supports on both sides or without design supports is considered a Beam, a segment with a design support on one side is considered a Cantilever. You can set the design supports in the Design Supports and Deflection tab of members and member sets.
If necessary, adjust the preset limit values for the deformation checks of the objects.
Vibration (for EN, NTC)
Entering the restriction for the vibration check enables you to simply verify a vibration amplitude. During the check, all design situations of the 'Vibration' category are verified (selection is made in the Design Situations table). It is assumed that these are corresponding load combinations or result combinations containing the maximum values of the vibration amplitudes in the form of deflections. These are compared to the inputted limit value.
Limitation of Web Plate Breathing (for EN, NTC)
For the frequent SLS combination, a check of the web slenderness according to EN‑1993‑2, Section 7.4 can be activated. Depending on the chosen option, the limit value is applied for railway bridges or for road bridges for the check. If you have assigned Member Transverse Stiffeners to the object to be designed and activated them for the design add-on, the distances between the transverse stiffeners will be used during the web plate breathing check. The reference length for the check is set as the reference length Lz from the Design Supports and Deflection tab.
