RF-LIMITS - Manual 5.xx/8.xx

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RF-LIMITS - Manual 5.xx/8.xx

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2.2 Limit Parameters

In module window 1.2, select the objects (member ends, members, nodes, etc.) and the limit values of the action effects.

Module window 1.2 Limit Parameters
Limit Description

In the first table column, enter the descriptions of the limit checks. To access the Limit Library use the [Library] button and that appear when you click into a table cell.

Dialog box Limit Library

At the moment, the library contains connections of the following companies: Sihga, Sherpa, Steico, Metsä Wood, Würth, Knapp and M-connect. Furthermore, the library contains connections which are authorized by DSTV (German Steel Engineering Association).

Connections of the library (selection)
Limit group Connection

Sihga

IdeFix group

Sherpa

Knapp

DSTV

IH group

With the button in the library you can define the relevant limit values for a new "limit element" (see Image 2.10).

 

Furthermore, it is possible to define a new Limit Group and Limit Table so that limit zones can be filtered quickly later.

Dialog box New Limit Group
Dialog box New Limit Table.
Dialog box Limit Detail
 

In the dialog box, you have also the possibility to add a picture to describe the limit value. Many manufacturers of connecting elements or CAD software offer graphics on their web pages.

It is always possible to adjust the limit groups or tables by using the button.

Frequently used limit elements can be marked as Favorite to find them quickly.

Object Type

In table column B, you can select the object type that is relevant for the limit. If the object does not fit to the corresponding limit, the type will be shown in blue.

Member End

For the first object type of the list you can define limit values (min/max) for the Internal Forces N, Vy, Vz, My, Mz, MT and the Cross-Section Dimensions (width and height).

Dialog box Limit Values for object type Member End (part of module window)

With the check boxes for Range Before, Range Between and Range After you decide if the zone is relevant

  • before the defined minimum value (Range Before)

For limit axial forces of e.g. Nmin = and Nmax = the program checks if the member axial force is smaller than 5 kN.

  • between both defined values (Range Between)

The zone between both limit values is verified in the check. In our example above, the program checks if the shear forces are available in the zone between ± 10 kN.

  • after the defined maximum value (Range After)

The check is done for the zone above the defined maximum value. In our axial force example above, the program checks if the tension force is greater than 10 kN.

when checking the internal forces, deformations or support forces.

 
Interaction

In addition, an interaction design is possible for the simultaneous action of the internal forces. This allows, amongst other things, to determine the influence of a biaxial bending. The internal forces are superimposed as follows:

The ratio from torsion is thus not squared.

Member

For this object type you can define the same limits like for the member ends. In contrast to the ends of a member, the limit area is checked on the entire member.

Nodal Support

The support force is checked in X-, Y- and Z-direction. A definition of the limit moments MX, MY and MZ is additionally possible. The ranges must be defined in the same way.

Node

For the Node object type you can check the rotations about the X-, Y- and Z-axes in addition to the displacements in X, Y and Z.

 

The following Knowledge Base Article describes how limits are defined for horizontal displacements of a building: https://www.dlubal.com/en/support-and-learning/support/knowledge-base/000833

Surface (Only RF-LIMITS)

All internal forces in surfaces (mx, my, mxy, vx, vy, nx, ny, nxy etc.) can be analyzed. The zones are defined in the same way.

List of Elements

In table column C, specify the numbers of the nodes, members, member ends, supports and surfaces that you want to check.

It is also possible to select the objects graphically in the RSTAB or RFEM work window by using the button.

Service Class

This column is only displayed if an analysis according to EN 1995-1-1 EN1995-1-1 or DIN 1052 DIN1052-2008 in module window 1.1 General Data has been defined. The service classes 1 to 3 are available for selection.

Factor Category

Also this table column is displayed only for EN 1995-1-1 or DIN 1052. The categories of the materials are described in Chapter 2.1.

Optimization

This table column offers the option to optimize the selected limits. The optimization can be performed in accordance with the defined Limit Group, Limit Table or Limit Detail.

Optimization options
Optimization from Library
Limit Group

When an optimization is set, you can define the corresponding Limit Group in table column G. Use the button to select the group.

Limit Table

Table column H manages the tables that are relevant for the optimization.

Limit Detail

In this column, the governing category details for the optimization are displayed.

 

These options simplify the selection -- particularly for the numerous DSTV connection types.

Comment

It is possible to enter a note in the last column which explains the limit parameter. It is also displayed in the printout report.

 

The data of module window 1.2 Limit Parameters can be exchanged with MS Excel and OpenOffice Calc by using the import and export functions. The buttons have the following meanings:

Buttons in module window 1.2 Limit Parameters
Button Description Function

Excel export

Exports content of the module window to MS Excel or OpenOffice Calc

Excel import

Imports content of a table from MS Excel or OpenOffice Calc

Export to library

Saves a new defined limit group

View mode

Switches to RFEM or RSTAB work window without quitting RF/-LIMITS