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Frequently Asked Questions (FAQ)
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Yes, it makes because this affects the stiffness of the entire system.
When entering a level-floor downstand beam as a ‘Rib’, you will add the stiffness of the defined rectangular cross-section to the area of the line.
For the result beam, however, you have only to define the integration width. The entered rectangular cross-section does not influence the stiffness of the entire system but is only applied as a design cross-section in the add-on modules (e.g. RF-CONCRETE Members).
AnswerA non-designable situation like this is displayed if the shear resistance without shear reinforcement VRd,c is arithmetically smaller than zero.A VRd,c value of less than zero is caused by large tensile axial forces. In this context, the cross-section is completely under tension or completely cracked, and no shear force resistance can be created.For coated cross-sections with planned shear reinforcement, the following situation results:In RF-CONCRETE Surfaces, if VRd,c < 0, no further shear check is performed, and message 13) is displayed. This approach is conservative.In this context, there was a request (194) for the interpretation of the standard, which allows the truss model to be used even with a completely cracked cross-section.If a shear reinforcement is designed as planned, the message about the non-designable situation in the program can be ignored. In this case, it should be ensured that VEd is smaller than VRd,max and VRd,s.
You can connect a rib member to a line on two surfaces with different thicknesses.
To determine the stiffness or internal forces, the eccentricity of the rectangular cross-section is determined using the mean value of both connected surfaces in RFEM.
For designing in RF-CONCRETE Members, the add-on module determines its cross-section, which is displayed in the input dialog box ‘1.4 Ribs’ of the add-on module.
By clicking the ‘i’ button (see Figure 02), it is possible to open an info dialog box for the generated rib cross-section, where all cross-section properties applied for the design in the module, like the position of the shear center and centroid, etc., can be viewed.
If the ‘Effective Width’ is adjusted in the ‘1.4 Ribs’ dialog box (e.g. to 0.50 m) this has influences on the cross-section applied in RF-CONCRETE Members and its cross-section properties.
However, this does not influence the stiffness or the determination of internal forces in the 3D model in RFEM.
The selection in the '1.3 Surfaces' input dialog box within the 'Limitation of Crack Widths' tab has a direct influence on the kc factor for the analytical calculation of the minimum reinforcement As,min for absorbing effects due to restraint according to Equation (7.1), DIN EN 1992-1- 1, 7.3.2.If 'Centrical Restraint' is selected, a kc value = 1.0 is applied in equation (7.1). When applying 'Bending Restraint', the module sets the kc factor strictly to 0.4.If ‘Depending on Defined Load’ is selected, the program interpolates the kc value element by element depending on the stress distribution in the cross-section using the defined load.This results in a constant distribution of the minimum reinforcement from restraint being determined for the respective reinforcement direction of the surface when ‘Centrical Restraint’ or ‘Bending restraint’ is selected. If you select 'Depending on Defined Load', no constant distribution of the minimum reinforcement is resulting from restraint.The program behavior described above is identical in RF-CONCRETE Members and RF-CONCRETE Surfaces (in RFEM 5) and also applies to the CONCRETE add-on module (in RSTAB 8).
If the calculation of the longitudinal reinforcement according to the standard is activated, the required reinforcement content is taken into account when displaying the required reinforcement.See the following graphic with the distribution of the required reinforcement without the minimum longitudinal reinforcement according to the standard:Figure 01 - Distribution of Required Reinforcement Without Minimum Longitudinal Reinforcement According to StandardAnd in comparison, the distribution of As,erf,-z(top) with the minimum longitudinal reinforcement according to the standard:Figure 02 - Distribution of Required Reinforcement Incl. Minimum Longitudinal Reinforcement According to StandardIn the result window '2.4 Required Reinforcement by x-Location', you can see which reinforcement is required at each x-location of the designed member. If the minimum longitudinal reinforcement according to the standard becomes relevant, this is indicated by the message No. 26) or 27).At locations where the minimum longitudinal reinforcement is not critical, only the statically required longitudinal reinforcement is displayed. Messages No. 26) and 27) are missing in this case.
AnswerYes, for the nonlinear calculation in RF-CONCRETE Members, it is possible to select the high-strength steel SAS 670 for the design. In this way, you can perform stability analysis for columns, among other things.The steel can be selected in the Materials section of the 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 the 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).
AnswerPlease deactivate the 'Indirect Calculation' by means of the steelbar diameter 'limit ds' or the steelbar distance 'lim sl'.The calculation of crack widths smaller than 0.20 mm is only possible via the direct calculation according to EN 1992-1-1, 7.3.4.
Whether or not you see the selection in the Results navigator depends on the settings for the serviceability limit state design.In the settings for the serviceability limit state design, you can find the option 'Increase Required Longitudinal Reinforcement Automatically for Serviceability Limit State Design'.Only if the automatic increase of the longitudinal reinforcement has been activated is the 'Limit States' entry available in the Results navigator.
Please select only members with a reinforced concrete cross-section in the input dialog box 1.6 for the design. If selecting members made of steel (e.g.), you will get the corresponding error message.Figure 01 - Message No. 2379 - Invalid Material DataIn case you select 'All Members', the members with a steel reinforcement area are automatically removed from the design.
AnswerYes, you can also use the RF-CONCRETE Surfaces add-on module to design bidirectional ribbed plates, ribbed floors, or hollow core slabs. The design is possible for the ultimate limit state.
The plates can be created as orthotropic surfaces in RFEM (see Figure 01).
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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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