#### Further Information

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• ### I have used the RF-/DYNAM Pro add-on module to generate the governing result combinations of seismic loads. What is the next way to perform a design of the individual components?

FAQ 003598 EN

With the Equivalent Loads and Forced Vibrations add-on modules, you can create result combinations that contain the governing combinations of seismic loads. To perform a design with them, they have to be combined further on the basis of the extraordinary combination. This combination is defined, for example, in EN 1990 Art. 6.4.3.4:

${\mathrm E}_{\mathrm d}\;=\;\underset{}{\sum_{}^{}\;{\mathrm G}_{\mathrm k,\mathrm j}\;+\;\mathrm P\;+\;{\mathrm A}_{\mathrm{Ed}}\;+\;}\overset{}{\underset{}{\sum{\mathrm\psi}_{2,\mathrm i}\;{\mathrm Q}_{\mathrm k,\mathrm i}}}$

This accidental combination has to be defined manually in RFEM. Make sure that (for a direction combination with the 100/30% rule), both created result combinations from RF-/DYNAM Pro have to be added with the "Or" condition. A combination like this is displayed in Figure 02.

This accidental combination can then be used for further design. It is possible to evaluate the governing internal forces as well as to import and calculate this combination in the design modules.
• ### Is it possible to create or generate load combinations for the 1st Order Theory and the 2nd Order Theory (including imperfections) in RFEM in parallel?

FAQ 003347 EN

Yes, it is possible. It works.

If the automatic combinatorics is activated in RFEM or RSTAB, e.g. for the design situation "ULS", the load combinations are set automatically according to the 2nd Order Theory.

Thus, it is possible to get a list of load combinations based on the defined load cases, which are calculated according to the 2nd Order Theory. The consideration of imperfection load cases can also be activated.

If some other load combinations have to be generated according to the 1st order theory (without imperfections) in addition to the existing load combinations calculated according to the 2nd Order Theory incl. imperfection, it is possible to create another combination rule for this. In this additional combination the design situation "ULS" can also be selected by now. However, you can now select the calculation type "1st Order Theory" and deselect the imperfections.

As a result, load combinations according to the 2nd Order Theory incl. imperfection (blue marking in the graphic below) and load combinations according to the 1st Order Theory without imperfection (red selection in the graphic below) are now obtained.

This approach can be used, if structural analysis according to the 2nd Order Theory (incl. imperfection) has to be performed on a part of the structure and on individual structural components, e.g. according to the equivalent member method or model column method.

Optionally, it is also possible to control the numbering of the individual CO groups in the "Combination Rule" tab in advance. Thus, for example, a group can start with CO 100, and the second group with CO 200. As a result of this, the user can improve the clarity or allocation of the COs.

• ### Why is not possible to select alternative or simultaneously acting load cases in the 'Combination Expressions' tab?

FAQ 003259 EN

The option "Individually/Simultaneously Acting Load Cases" is not available for every standard.

In case of selecting e.g. 'EN 1990' standard in the general data of the model, this option is available in the 'Combination Expressions' tab.

On the other hand, this option is (currently) not available if selecting e.g. 'ASCE 7-16'.

• ### How can I consider the partial safety factor γQ,T in the automatic load combinatorics with 1.0 in compliance with DIN EN 1992‑1‑1/NA: Chapter NCI 2.3.1.2 (3) or DIN EN 1990/NA Chapter NDP A.1.3.1 (4)? The value γQ,T = 1.5 is used by default.

FAQ 003164 EN

To apply this in the program, it is necessary to copy the "Temperature" load case (see Figure 01). All loads contained in the load case will be copied as well. One of the load cases is used for the ultimate limit state (ULS) load combinations, the other one for the serviceability limit state (SLS). The loading in the load case for ULS is now multiplied by 1.0/1.5 = 0.667 (see Figure 02).

In order to ensure that both load cases do not occur simultaneously, but only for the specific design situation, the exceptions are determined in the respective combination expressions. For ULS, it is quite simple to define the dead load case in the way that it is not combined with the temperature load case for SLS (see Figure 03). SLS applies exactly the other way around, that is, the load case of dead load is not combined with the temperature for ULS (see Figure 04). In this case, the "Differently for each combination expression" option must be activated.

The desired load combinatorics is then obtained (see Figure 05).

• ### How can I generate load combinations automatically in an existing file retroactively?

FAQ 003083 EN

For this, open the "General Data" dialog box of the present model. Right-click the model description in the Data navigator.

Figure 01 - Opening General Data via Shortcut Menu of File

As an alternative, you can open the "General Data" dialog box via the "Edit" menu.

In the "General Data" dialog box, you can first select the standard according to which the combinatorics is to be performed, or whether to create load combinations (CO) or result combinations (RC).

If CO or RC are already available in the existing file, a query appears asking whether the program should delete or keep the existing combinations.

• ### What is the meaning of the abbreviations of the design situations in the "Combination Expressions" tab?

FAQ 002943 EN

ULS:

Ultimate limit state

SLS:

Serviceability limit state

EQU:

Design of the structural safety; Loss of structural security of the structural system or one of its parts, for example By tilting, floating or lifting

STR:

Failure of structural system or parts due to exceeding of material strength, excessive deformations, reaching kinematic state or unstable position

GEO:

Extensive deformations or failure of the soil

• ### When generating wind loads, some external pressure coefficients have a value of 0. What is the reason for this?

FAQ 002924 EN

For duopitch roofs with a roof iclination of > 5 °, the roof areas F, G, H, I and J have to be separately classified according to the windward and leeward side. For the wind direction of 0 ° (wind in longitudinal direction), positive as well as negative aerodynamic coefficients have to be taken into account for roof inclinations of up to 45 °.
For these cases, this results in a total of 4 possible wind combinations, depending on the building side (see Figure 1).
For the wind direction of 90 ° (wind on gable side), however, there are no positive external pressure coefficients for a roof inclination of > 15 °. For a building with a roof inclination of 45 ° you would receive 10 possible wind load cases (0 ° = 4 * 2, 90 ° = 1 * 2).

LC w+:

Only positive (pressure) aerodynamic coefficients per roof area are used.

LC w-:

Only negative (suction) aerodynamic coefficients per roof area are used.

LC w-/+:

Negative (suction) aerodynamic coefficients for the windward side and positive (pressure) coefficients for the leeward side of the roof are used.

LC w+/-:

Positive (pressure) aerodynamic coefficients for the windward side and negative (suction) coefficients for the leeward side of the roof are used.

If there are, for example, only negative coefficients for a load position, then only negative loads are applied to the roof surface. Consequently, there is no pressure -> therefore these values are set to 0. A load case, which thus contains only values with the size 0, could also be deselected during the generation.

For example, this is always possible, as already described, for the LC w + with a wind direction of 90 ° (gable-sided wind) and a roof inclination of > 15 °.
• ### Where is the damage consequence class defined in RX wood?

FAQ 002879 EN

The damage sequence class can be set in the RF Combi module. In the coefficients the desired setting can be made (see picture).
• ### For a design, I need the load combinations from 1.00 * G + 1.50 * Q. How can I generate it automatically?

FAQ 002753 EN

You will find this option in the settings for the combination rules.

There, the hook can be set at "Favourable permanent action".
This generates combinations of 1.35 * G + 1.50 * Q on the one hand. On the other hand you get the same combinations with 1.00 * G + 1.50 * Q.

These can then be used in the additional modules for further proof.
• ### For the foundation design, I need the results (support reactions) of a design situation for 'static equilibrium'. How do I get them?

FAQ 002691 EN

You can generate the required load combinations for the design situation Static Equilibrium (EQU) according to EN 1990 in RFEM or RSTAB.

If you activate the option to create combinations automatically, there are four design situations (ULS, S Ch, S Fr, and S Qp) are available. However, you can create a new additional combination expression and specify a design situation for this (for example, EQU according to EN 1990).

With this specification, you obtain additional load and result combinations for the 'static equilibrium' design situation, which you can then use for the design in RF‑/FOUNDATION Pro.

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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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