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Frequently Asked Questions (FAQ)
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RF-CONCRETE Columns determines the equivalent moment M0e from the moment M02 at the column head and M01 at the column base according to EN 1992‑1‑1, 22.214.171.124 (2), and performs the design according to the model column method with this equivalent moment M0e.
Now, it may happen, for example, that a computationally larger required reinforcement area would result from the cross-section design with the moment M01 at the column head.
To ensure this, message 28) is displayed, according to which the user should perform a standard design with the internal forces according to the linear static analysis. To do this, simply open the RF‑CONCRETE Members add-on module and perform pure design of the internal forces according to the linear static analysis for the member designed in RF‑CONCRETE Columns.
AnswerThe Design According to Formula column lists the equations of the standard used to carry out the design.The abbreviations stand for the following designs:CS Cross-section designST Stability analysisSE Serviceability (SLS design)The numbers directly behind it are internal information.The lower table of the intermediate values shows the design formulas with the design conditions that are relevant for the selected design.
AnswerYes, it is possible to select the high-strength steel SAS 670 for nonlinear design in RF‑CONCRETE Members. In this way, you can perform stability analysis for columns, among other things.The steel can be selected in the Materials section of the add-on module (see Figure 01). Since DIN EN 1992‑1‑1 only allows fyk = 500 N/mm² by default, this limit must be adjusted when using SAS 670.In General Data, you can create a user-defined National Annex where the maximum value of yield strength is increased to fyk ≥ 670 N/mm² in Point 3.2 (see Figure 02).
The setting in Figure 01 only controls the effect on the design side. After activating this function, the buckling designs in the "Effective Lengths" window are deactivated. Thus, the lateral-torsional buckling analysis is only performed.
In order to calculate with the design values of stiffnesses, it is necessary to reduce them by the partial safety factor according to . For this, select the highlighted option in the calculation parameters (see Figure 02).
If using the automatic combinations for the standard EN 1990 + EN 1995, this setting is automatically activated in the combinations for ULS according to the second-order analysis. In the case of the combinations for SLS and the combinations generated according to the linear static analysis, this option is automatically deactivated. However, the combinations are only assigned automatically by using the method of analysis in the "Combination Expressions" tab (see Figure 03).
If you want to calculate the component stiffnesses with the 5% quantile value of the stiffness parameters divided by the partial safety factor, you have to additionally activate the "Modify stiffnesses" option in the calculation parameters and modify the stiffnesses manually.
AnswerPlease check if all sets of members selected for the design are straight sets of members. The equivalent member method is only applicable for straight sets of members with a uniform cross-section, so no taper is applicable, for example. In this case, use the preset General Method.
AnswerThe reason is that there is no stability analysis for unsymmetrical, open cross-sections according to EN 1999‑1‑1 if the compressive normal forces and bending moments are effective.You can neglect the bending moments in Details, the Stability tab, by selecting the corresponding filter. Then, the flexural buckling design is performed without moments. However, this is under your own responsibility. Another way is to check the stability according to the second-order analysis, which would be possible by using the RF‑/FE‑LTB add-on module.
AnswerCurrently, there is no option to perform a stability analysis in the RF‑CONCRETE Surfaces add-on module. However, you can use a result beam to perform a simplified design by means of the nominal curvature method in RF‑CONCRETE Columns.
AnswerThe design internal forces do not change because no load modification has been defined. The torsional stresses are calculated once with Gamma M1 1.0 and once with Gamma M1 according to the National Annex, so that the warning can appear twice. If the filter is increased once more in the following, another x-location (or loading from LC/CO/RC) can also become governing for the warning.
AnswerFor cross-section and stability analyses, Eurocode provides different partial safety factors. It is important to pay attention whether the stability analyses are performed by using the second-order analysis and applying imperfections as cross-section designs. In this case, it is necessary to reduce the resistance with γM1.
AnswerFor a vault-free cross-section, a proof of the complete system is recommended using theory II. Order - internal forces and local imperfections. The entry of the effective lengths and nodal bearings (with staff sets) can thus be omitted. However, please activate gamma_M1 for cross-section verification.
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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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