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Frequently Asked Questions (FAQ)
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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".
To implement this in the program, you have 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 Load Combinations for Ultimate Limit State (ULS), the other one for the serviceability limit state (SLS). The load in the load case for ULS is now multiplied by 1.0/1.5 = 0.667 (see Figure 02).
In order that the two load cases do not occur simultaneously, but only for the specific design situation, exceptions are determined in the respective combination rules. For ULS, it is quite simple to define the self-weight load case such that it is not combined with the Temperature User-Defined Case for SLS (see Figure 03). For SLS exactly the other way round, so load case dead weight not with temperature for ULS (see picture 04). The "Differently for each combination expression" check must be activated.
The desired load combinatorics is obtained subsequently (see Figure 05).
To do this, open the “General Data” dialog box of the current model. Right-click the model description in the Data navigator.Figure 01 - Opening the General Data by Using the Shortcut Menu of the FileAlternatively, you can open the “General Data” dialog box with the “Edit” menu.In the “General Data” dialog box, you can first select the standard according to which the combinatorics is to be carried out, or if load combinations (CO) or result combinations (RC) should be created.If CO or RC are already available in the existing file, a query appears asking if the program should delete or keep the existing combinations.
Ultimate limit stateSLS:
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 liftingSTR:
Failure of structural system or parts due to exceeding of material strength, excessive deformations, reaching kinematic state or unstable positionGEO:Extensive deformations or failure of the soil
AnswerFor 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 °.
AnswerThe damage sequence class can be set in the RF Combi module. In the coefficients the desired setting can be made (see picture).
AnswerYou 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.
AnswerYou can also generate the load combinations of RSTAB or RFEM required for the design of the structural security (EQU) according to EN 1990.If you activate the automatic combinator, four design situations (UL, G Ch, G Ha, and G Qs) are initially available. However, you can create a new additional combination expression by specifying a designitution for it (that is, for example, EQU according to EN 1990).With this specification, you receive additional load and result combinations for the "Situational Safety" design situation, which you can then use for the design in RF- / FOUNDATION Pro.
You can find the corresponding setting in Program Options in the 'Program' tab (see the figure): unselect the 'Combination description according to action category' option in order to display load case numbers for LCs.
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