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• ### I would like to design an aluminum or lightweight structure. Is it possible to use RFEM or RSTAB for this?

Both RFEM and RSTAB can be the solution . For both programs, there are standards available with which the aluminum and light-weight structures can be calculated and designed.
In addition to Eurocode 9 with numerous National Annexes, the American standard ADM 2020 is also available.

Further add-on modules for membrane and cable constructions complete the options.

###### Main Programs RFEM or RSTAB
The main programs RFEM or RSTAB are used to define structures, materials, and actions.

If you also want to analyze membrane and cable structures, you need RFEM . When it comes to pure beam structures, the purchase of RSTAB is sufficient. In any case, RFEM is the more diverse option because it can be equipped and extended with the corresponding add-on modules for all materials and designs.

###### Available standards
• RF-FORM-FINGING/RF-CUTTING-PATTERN (only for RFEM)
Determines the shape and cutting pattern for cutting membranes
• RWIND Simulation
Complex analysis of any structures in the digital wind tunnel with transfer of load cases to RFEM or RSTAB for further processing.
###### Dynamic analysis
If it is necessary to perform seismic analysis or vibration designs of a building, the RF‑/DYNAM Pro add-on modules provide special tools for determining natural frequencies and mode shapes, for an analysis of forced vibrations, a generation of equivalent loads, or for a nonlinear time history analysis.

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If you have any question about the Dlubal Software programs, please do not hesitate to contact our sales department.
• ### Does the program use different values of modulus of elasticity for different temperatures? How to activate it?

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Temperature-dependent stress-strain properties of an elastic isotropic material can be defined in a diagram or imported from [Excel]. These properties are considered for member and surface elements subjected to thermal load (changes or differences in temperature).

The Reference temperature defines stiffnesses for the members or surfaces that have no temperature loads. For example, if a reference temperature of 300 °C is set, the reduced elastic modulus of this point of the temperature curve is applied to all members and surfaces.

The Options dialog section allows you to control if the Poisson's ratios that are applied to the complete temperature diagram are identical. Clear the check box to access the Poisson's Ratio table column for individual entries.

You have to select and define the Temperature/Modulus diagram by your own.

• ### How can I set the deformation coefficient kdef in the program?

The setting for the deformation coefficient kdef can already be made in the model data. There, you can specify the deformation coefficient manually or select it based on the service class.

The deformationfactor k def is considered in the load combinations for serviceability in the program (similar to DIN EN 1995-1-1, 2.2.3).

For the design of mixed structures made of timber materials, see FAQ 4325 .

• ### I would like to move some elements. When moving, my members are deleted, what is the reason?

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You have probably created nodes that were automatically generated by the program and thus locked.

You can unlock these nodes by selecting the nodes and then editing them. There you will find the option to unlock the nodes.

• ### I am using COM interface and Grasshopper for the calculation of complicated structures. For this task I need to create NURBS lines. Could you explain how NURBS should be set? For example what kind of data should be provided for Knots?

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In the FAQ downloads you'll find a sample code how to set NURBS surfaces. The knot vector KnotsX, KnotsY determines how the control points affect the NURBS curve. The number of knots is equal to the number of nodes plus order.

• ### How do I activate the modeling of pipelines?

The RF-PIPING add-on module is available for modeling pipelines. This add-on module is an extension of RFEM. The functions of the piping module are activated when the piping analysis is activated in the General Data dialog box, Options tab.
• ### How is the load distributed to the members in the angular axis method if members are excluded from the load application?

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A surface load of 1 kN/m² delimited by nodes 1 to 4 is only applied to member 3 (Figure 1).

The entries made in the load generator are shown in Figure 02. There is no correction of the distribution according to the moment equilibrium (Figure 3).

The generated member load is shown in Figure 4. This is calculated as follows:

q = 1.00 kN/m² (area load)

h1 = 4.00 m

h2 = 6.00 m

btot = 12.00 m

$\mathrm\alpha\;=\;\arctan\left(\frac{{\mathrm h}_2\;-\;{\mathrm h}_1}{{\mathrm b}_{\mathrm{ges}}}\right)\;=\;\arctan\left(\frac{6,000\;-\;4,000}{12,000}\right)\;=\;9,46^\circ$

${\mathrm b}_1\;=\;\tan\left(\mathrm\alpha\right)\;\cdot\;{\mathrm h}_1\;=\;\tan\left(9,46^\circ\right)\;\cdot\;4,000\;=\;0,667\;\mathrm m$

${\mathrm l}_1\;=\;\sqrt{{\mathrm b}_1^2\;+\;{\mathrm h}_1^2}\;=\;\sqrt{0,667^2\;+\;4,000^2}\;=\;4,055\;\mathrm m$

${\mathrm l}_2\;=\;\cos\left(\mathrm\alpha\right)\;\cdot\;{\mathrm h}_2\;=\;\cos\left(9,46^\circ\right)\;\cdot\;6,000\;=\;5,918\;\mathrm m$

${\mathrm A} _ {\mathrm R}\; =\frac {\; {\mathrm b} _1\;\cdot\; {\mathrm h} _1} 2\; =\;\frac {\; 0.667\;\cdot\; 4,000} 2\; =\; 1.335\;\mathrm m ^ 2$ (remaining area marked in red in Figure 4)

${\mathrm l}_{\mathrm{ges}}\;=\;\sqrt{{\mathrm b}_{\mathrm{ges}}^2\;+\;\left({\mathrm h}_2\;-\;{\mathrm h}_1\right)^2}\;=\;\sqrt{12,000^2\;+\;\left(6,000\;-\;4,000\right)^2}\;=\;12,166\;\mathrm m$

${\mathrm q} _ {\mathrm c}\; =\:\frac {\mathrm q\;\cdot\; {\mathrm A} _ {\mathrm R}} {{\mathrm l} _ {\mathrm {ges}}}\; =\;\frac {1.00\;\cdot\; 1.333} {12.166}\; =\; 0.110\;\mathrm {kN}/\mathrm m$ (constant load component on loaded member)

${\mathrm q} _2\; =\: {\mathrm q} _ {\mathrm c}\; +\; {\mathrm l} _1\;\cdot\;\mathrm q\; =\;\: 0.110\; +\; 4.055\;\cdot\; 1,000\; =\; 4.165\;\mathrm {kN}/\mathrm m$ (member load node 2)

${\mathrm q} _5\; =\: {\mathrm q} _ {\mathrm c}\; +\; {\mathrm l} _2\;\cdot\;\mathrm q\; =\;\: 0.110\; +\; 5.918\;\cdot\; 1,000\; =\; 6.028\;\mathrm {kN}/\mathrm m$ (member load node 5)

q4 = qc = 0.110 kN/m (member load node 4)

• ### A rigid member should only be able to absorb tensile forces or only compressive forces. What are the options for considering these nonlinearities in the calculation?

There are two options for defining the failure:

1. Assignment of member nonlinearity
For the member types "Beam" and "Rigid", you can define a member nonlinearity for each member. You can find the corresponding option in the "Settings" tab (see Figure 01).

2. Assignment of nonlinear member hinges
Alternatively, you can define a member end hinge with failure criterion for the member. For the desired degree of freedom, you can assign the hinge condition with nonlinearity accordingly (see Figure 02).
• ### Does a user-defined layer composition in RF-LAMINATE need to be shared separately with other users along with the RFEM model file or is this information stored directly in the RFEM file?

The material file needs to be saved separately within RF-LAMINATE and then shared with another user if they would like to access the user-defined compositions or custom layups. The additional user will then need to open the .jyr file that was shared within RF-LAMINATE directly.

• ### How can I define a single moment in the middle of a surface?

A single moment must act on a node within the program. Accordingly, you have to model a node at the corresponding location and define the single moment there.

If the node is modeled correctly, it is automatically integrated into the surface by default. This can be checked in the "Edit Surface" dialog box, "Integrated" tab, see Figure.

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#### First Steps

We provide hints and tips to help you get started with the main programs RFEM and RSTAB.

#### Wind Simulation & Wind Load Generation

With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.

The generated wind loads acting on these objects can be imported to RFEM or RSTAB.

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