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Frequently Asked Questions (FAQ)
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In order to evaluate user-defined points in addition to the result values on grid points and FE mesh nodes, there is the option to specify "Additional Surface Result Points" in RFEM 6. You can find them under "Types for Surfaces", as shown in Image 01.
The coordinates for these points are entered directly in the dialog box or selected in the model; see Image 02. Furthermore, it is necessary to assign the surface whose result values should be displayed.
In the Results navigator (the upper half), you can activate and deactivate the display of the manually specified result values. In the lower half of the Results navigator, you can set the display for grid points and/or surface result points; see Image 03.
When displaying the values in FE mesh points, the additional surface result points are deactivated.
Generally, the elements in RFEM 6 are rigidly connected by default. But by using special RFEM objects, we may change the way the model responds to the actions. For this purpose, we may use line hinges and line releases. The difference between them is explained below.
Line hinges change the characteristics of connections between surfaces. By using line hinges, we can allow for rotation between two surfaces on a selected edge or we may define a full translational release between elements.
Aside from these options, we can also define a spring stiffness in every direction or allow for nonlinearities in this hinge, a new feature compared to the previous RFEM program.
Moreover, line hinges allow for special options such as a slab-wall connection which is described here.
Line releases work similarly to line hinges, by changing the behavior of two connected elements, but unlike a hinge it also creates a new line and nodes in its place.
By using line releases, we can define/select more objects to be released rather than only connected surfaces. Line releases may be used to also include members and solids in their definition.
Similarly to line hinges, we can allow for rotation and translational releases between elements with options for a spring stiffness and nonlinearities.
The line release is a very powerful tool in managing more complicated geometries and connections between specific elements.
The fastest way to create a contact solid between two surfaces is to first copy the original surface by using the Step Links option.
In the new Step Links tab, select the "Link surfaces with solid" option. Select the template for this solid to be a standard Solid Type.
After copying and creating the new elements, select the Solid type to be a Contact. In the new tab, define the Contact Solid Type (for example, Full force transmission). Additionally, you will be able to select a pair of surfaces to have this contact. A list of available surfaces is generated automatically.
After defining the Contact Solid, it’s possible to change the side Surfaces to the type Without Thickness.
The surface/slab longitudinal reinforcement can be considered in the rib design by activating the Turns on/off automatic generation of longitudinal reinforcement items from surface reinforcement option (Image 01). The program automatically adds reinforcement from the connected surface. They are shown on the "Items" list but cannot be edited.
In RFEM 6 and the "Concrete Design", the fiber-reinforced concrete design can be carried out according to DIN EN 1992‑1‑1 in conjunction with the DAfStB guideline "Fiber Reinforced Concrete".
To activate the surface or member design using steel fiber reinforced concrete, it is sufficient to assign a material of the corresponding material type to the surface or member.
To do this, create a new material of the "Fiber Concrete" material type.
The concrete and lightweight concrete are designated with the "P1/P2" extension, which stand for Performance Class 1 and Performance Class 2.
The performance classes L1 and L2 are initially preset with the values 1.20 and 0.90 (see Image 02).
In order to be able to adapt these performance classes, you can activate a "user-defined material" in the "Main" tab of the material under the "Options".
Thus, the text boxes for L1 and L2 become accessible, so you can adjust the performance classes.
If you now perform the design with the material of the "Fiber Concrete" type in the "Concrete Design" add-on, the design checks modified or completed in the DAfStB guideline for the "fiber-reinforced concrete" design are adjusted. This modification of the design process can be found in the "Design Details", including the reference to the DAfStB guideline.
For this type of design, it is necessary to specify "normal reinforcement" (member reinforcement for a member, area reinforcement for a surface), otherwise the surfaces cannot be designed. This means that you can only add steel fibers to already reinforced components.
To calculate a slab with fiber-reinforced concrete only (without reinforcing steel), use the "Damage 2D/3D" material model.
A rib element can easily be modeled in RFEM 6 by changing the Member Type from "Beam" to "Rib" in the drop-down shown in Image 01.
Then, once a section and material is assigned in the Section tab, a new tab called "Rib" can be used to change a multitude of parameters.
Under the "Rib" tab, the rib alignment can be chosen along with one or two surfaces the rib is integrated with. Then, segments can be created using percentage (default) or lengths under the Ordinates column. These two options can be swapped by using the "Switch Relative/Absolute Ordinates" or "%" button. Segments allow you to divide the member and use different parameters for each section. That length is referenced in the next list of parameters.
The first parameter is the Definition Type where you can choose if you would like to adjust a Segment, Member, or User-Defined. User-Defined allows you to enter a custom length for Lref/8. Choosing member sets Lref to the length of the member. Segment sets Lref to the length of the segment.
Then, the "Width" parameters can either be entered manually, or they can be determined by referencing the length or EC2. These options can be seen in Image 02 along with the following parameters. Here are their definitions:
bint: Represents the internal integration width of the surface.
beff: Represents the effective width used in the Concrete Design add-on.
bmax: Represents the maximum possible value for bint and beff.
If the equal sign "=" button is selected, then beff will be set equal to bint.
You have selected "Rigid diaphragm" as the story slab stiffness in the Building Stories (Image 02). The "Rigid Diaphragm" is used to rigidly connect all components of a story in the floor plane with a rigid link. By doing so, the floor can no longer be defined with its real stiffness.
Therefore, surfaces with the "Load Transfer" stiffness type must be used (Image 03). It is not possible to create internal rigid links for surfaces with the stiffness type "Standard".
If line hinges are to be defined on several boundary lines of surfaces at the same time, the following procedure is recommended:
- Create a new line hinge in the Data Navigator under "Types for Lines", or in the menu "Insert → Types for Lines → Line Hinges → Dialog Box".
- Define degrees of freedom as desired.
- Use the "Pick" function to select the desired area and then the desired lines.
- Do not click "OK" to confirm the function, but select further surfaces and lines using the "+" symbol.
- As soon as all line hinges have been assigned, click "OK" to confirm the function.
Update: It is not necessary to click the "+" sign. After selecting a surface and the corresponding lines, you can simply select the next surface and the corresponding lines, and so on.
Under the Load Cases, select the Additional Settings tab, and activate the “Live load is less than or equal to 100 psf” option (Image 01).
Next, select the Design Situations tab and Edit Combination Wizard. Activate the “Exception 1 according to 2.3.1” option under the Standard Options (Image 02).
Under the Load Combinations tab, the load factor 0.5 is listed in the applicable COs (Image 03).
The default Design Situations (DS1 and DS2) do not include the seismic load combinations. To add the seismic COs, add new Design Situations with design situation type “Section 2.3 (LRFD), 6 and 7” and/or “Section 2.4 (ASD), 8 to 10” (Image 1).
Under the Load Combinations tab, the generated seismic COs are shown.
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Wind Simulation & Wind Load Generation
It's getting windy here! Send your structures to the digital wind tunnel using the stand-alone program RWIND 2. It simulates wind flows around structures, regardless of whether they are simple or complex.
You can easily import the generated wind loads acting on these objects into RFEM or RSTAB and use them for your further calculations.
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