In the Basic tab of the 'Serviceability configuration' dialog, you can specify the limit values that apply to the deformations of members and member sets.
The 'Design parameters' are divided into categories. They differ depending on the design standard.
Serviceability limit values
There are different design situation types for the serviceability limit state design (see Chapter Design Situations in the RFEM manual). When designing according to EN 1995-1-1, for example, a distinction is made between the characteristic and two quasi-permanent combinations. Four types are preset for NDS: The first limit state is of a general nature and applies to all load combinations. The other three types are based on the IBC standard [1]. For each combination type, you can define specific limit values for the deflections that apply for the directions of the member axes.
The limit values of the deformations are fundamentally related to the lengths of the components: The longer a member, the larger the deflections allowed. In the list next to the 'Definition type', you can select the form in which you want to define the limit value.
- Relative value: The limit value is defined in relation to the length of the member or member set.
- Absolute value: The value of the maximum deflection is specified directly.
- Sum of relative and absolute value: The limit value is composed of the sum of the relative value and the absolute value.
- Min. of relative and absolute value: The smaller value of the relative or absolute value is taken as the limit value.
- Max. of relative and absolute value: The larger value of the relative or absolute value is taken as the limit value.
Depending on the support of the component – 'Beam' with supports on both sides or 'Cantilever beam' with a support on one side – different limit values of the deflection are usually relevant. The type that applies to a specific segment is determined automatically based on the assigned design supports: A segment with design supports on both sides or without design supports is classified as a Beam, a segment with a design support on one side as a Cantilever beam. The design supports can be defined in the Design Supports & Deflection tab of the members and member sets.
If necessary, adjust the preset limit values for the deformation analysis of the objects.
If a precamber (initial deformation of the component during installation) is to be taken into account in the deformation analysis, you can specify this precamber in the properties of the member or member set (see Chapter Design Supports & Deflection). You can also define there whether the maximum displacements refer to the displaced segment ends or to the undeformed initial system.
Vibration (for EN, NTC)
The 'Vibration' category allows you to easily check the deformation for the vibration analysis with reference to a vibration amplitude. For this design, all design situations are considered to which the type SLS - Vibration is assigned 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 with the limit value in the respective axis direction.
