#### Further Information

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• ### How can you perform a factorized combinatorics of the self-load in connection with form-finding?

New FAQ 003459 EN

The load from the form-finding load case (FF) is impressed 1.0-fold into the system. If you want to factor in the self-load in combination with combinatorics, you can additionally create a permanent load case for the self-load with a load of 0.35 times the load.
• ### What does superposition mean according to the SRSS rule in the dynamic analysis??

New FAQ 003413 EN

In the Settings, you can define how results from different mode shapes of the structure are combined. The modal combination is the first step of the dynamic combinations. The modal responses can be combined with the Square Root of the Sum of Squares (SRSS) or the Complete Quadratic Combination (CQC). Both of these quadratic combinations can be applied in the standard form or modified as an equivalent linear combination. The standard form of the SRSS rule combines maximum results and the algebraic signs are lost; the combination expression is as follows:

${\mathrm E}_{\mathrm{SRSS}}\;=\;\sqrt{\mathrm E2\;1\;+\;\mathrm E2\;2\;+\;\dots\;+\;\mathrm E\;2}$

In the RFEM add-on module RF-DYNAM Pro, a modified form of the SRSS rule is available to determine the corresponding results, such as the corresponding internal forces. In relation to the standard form of the SRSS rule, the corresponding internal forces are usually much smaller. Furthermore, the corresponding signs are correct in relation to the governing internal force. The SRSS rule is used as an equivalent linear combination:

${\mathrm E}_{\mathrm{SRSS}}\;=\overset{\mathrm p}{\underset{\mathrm i=1}{\sum{\mathrm f}_{\mathrm i}}}{\mathrm E}_{\mathrm i}$

with:

$f_i=\frac{E_i}{\sqrt{{\displaystyle\sum_{i=1}^p}E_j^2}}$

If this formula is applied, the results are consistent.
• ### Why do several seemingly identical load combinations occur when combining automatically?

New FAQ 003359 EN

The automatically created load combinations result exclusively from the definition of combination expressions. Thus, it may happen that two load combinations are created according to different combination expressions, but contain the same load cases with the same factors.

However, the load combinations only seem to be the same, because the information saved in the load combination is different. Thus, the load combinations are assigned to the underlying combination expression and can subsequently be selected, for example, when combined in the design.
Consequently, it is necessary to define a unique combination expression for each load combination, so these seemingly identical load combinations are not combined.

• ### For my result evaluation, I only need the extreme values of the vertical support forces with the corresponding horizontal forces from a result combination for several support nodes. Can this be set in the program?

New FAQ 003358 EN

The graphical output always displays the extreme values of all support reactions. Thus, the largest and smallest values across all combination possibilities. The individual support forces cannot be combined in this way, because they usually occur in different load situations.
However, the table shows the extreme values with the corresponding results. In addition, column H shows the corresponding load combination or the corresponding load cases by default.
If you only need the extreme values of PZ with the corresponding horizontal forces, you can use the filter function of the results table according to the graphic.

• ### 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?

New 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.

• ### I have generated the earthquake loads manually. How can I combine them according to the superposition rules of the standard?

New FAQ 003346 EN

If you have defined load cases with earthquake loads and can not combine them with the RF-/DYNAM Pro add-on module, you should not apply the automatic combinatorics for this. The following steps describe how to define the manual combinatorics:

• Depending on whether you want to use the SRSS or CQC rule, you may have to activate it in the general data (only necessary in the case of the CQC rule). For the CQC rule, you have to activate additional parameters; this can be set in the load cases.

• Create one result combination per direction. Add all load cases where you have defined earthquake actions in this direction. The type of superposition can then be defined in the calculation parameters.
• Next, the directions are superimposed in further result combinations. For this purpose, the Eurocode 8, for example, specifies the 100/30% rule. To do this, add "and"  to the result combinations of the individual directions and change the factors to 1.0 for the dominant direction and 0.3 for the other directions. It is necessary to create always one result combination for each direction.

• Finally, another result combination is created, which can then be used for the design. In this table, the earthquake loads are superimposed with the permanent and the imposed loads (creation of the unusual combination). Please note that the result combinations for earthquakes must be added with "or".

• ### Is it possible to renumber load cases, load combinations, and result combinations?

New FAQ 003345 EN

To access this function, select Tools - Renumber - Move. This is shown in the attached video.

• ### What is the best way for displaying the related internal forces of the maximum results as result combinations in the printout report?

New FAQ 003343 EN

In RFEM or RSTAB, it is possible easily read the related support reactions/internal forces in a result combination in the tables. This is automatically preset.

Provided that they should be displayed in the printout report, it is necessary to activate the extreme values in the related tables. You can do this in the selection.

In this example, the extreme values were only activated for the support force Pz, which means that the respective maximum support forces in Z-direction are displayed with the related support reaction of the other directions.

If you want a graphical display, you have to print the graphic of the displayed load cases or load combinations in the printout report.

• ### Why do I get different design results for a load combination (CO) and a result combination (RC) in STEEL EC3 despite the same internal forces?

New FAQ 003313 EN

The difference between a design with RC and CO lies mainly in the moment distribution applied for the calculation of the elastic critical moment Mcr. For a load combination (CO), it is possible to apply explicitly the moment distribution for the existing load position. However, the result combination (RC) can only analyze the enveloping of the moment distributions. Then, the more unfavorable distribution (Max or Min) is applied. As a consequence, unfavorable values result for the critical load factor.

###### Summary:
The internal forces applied for the design can be the same in LC and RC, but the moment distribution in the result combination is applied more unfavorably to determine the critical branch value. Thus, the RC provides a higher utilization for the design with STEEL EC3.

• ### After running a time history analysis, I'm not able to see all results on surfaces. Is there a possibility to show them?

New FAQ 003282 EN

In the results of the module RF-/DYNAM Pro only "Basic Internal Forces" and "Basic Stresses" on surfaces are provided. But with the option to export the results in a result combination, you have the possibility to display all results after a time history analysis.

Simply use the option to create a result combination in the add-on module as shown in Figure 1 and show the results of this in the graphic. All results, such as "Design Internal Forces" or "Stresses" are available.

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