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Frequently Asked Questions (FAQ)
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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).
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).
AnswerNo, this is unfortunately not possible.The intermediate values from the calculation (e.g. statical height d applied for the shear check) are only available for the selected FE node or grid point when opening the 'Design Details' dialog box. However not for all FE mesh nodes of the designed surfaces.Therefore, these intermediate values cannot be used for a graphic display on the model, but only in tabular form in the design details.
AnswerIn this case, the Calculation Method and the type of the 2D position are important.When using the analytical method (RF-CONCRETE Deflect), it is possible to perform a calculation in 2D positions. When using the nonlinear method (RF-CONCRETE NL), the calculation for 2D XY (uZ/φX/φY) is not possible. In the nonlinear calculation, shrinkage is represented internally as strain load, which is not possible in this type of 2D position due to the limited degrees of freedom.Convert 2D to 3D PositionIn the general data, it is possible to simply convert a 2D position into a 3D position. For the supports, all degrees of freedom not contained in the 2D position are fixed when converting to a 3D position (see the video).
Yes, it is because the CONCRETE module of RSTAB 8 also includes the nonlinear reinforced concrete design. Thus, you can activate the 'Nonlinear Analysis (State II)' in the 'Ultimate Limit State' tab.
In the detail settings for the nonlinear design, you can select the 'General Design Method for Members in Axial Compression acc. to Second Order Theory'.
It is important that you define the imperfections in RSTAB and apply load curves (CO) according to the second-order analysis for the design, no result combinations (RC)!
Note on RFEM 5:
In RFEM 5, the same procedure is possible in RF-CONCRETE Members. However, the add-on module RF-CONCRETE NL in RFEM is required for the non-linear reinforced concrete design.
AnswerDifferences resulting from the determination of the deformation in the cracked state can have different causes. The following points should be checked for deviations:
Is the same calculation method applied?
RF-CONCRETE Deflect uses an analytical analysis approach according to EN 1992-1-1 7.4.3.RF-CONCRETE NL uses a physically nonlinear analysis approach.More detailed information about the calculation methods can be found, for example, in the RF-CONCRETE Surfaces Guide in Chapter 2.7 and 2.8.
Is the same initial structure available?
The results of the linear calculation provide the best tool for consideration if the underlying system should be taken for equivalent. The linearly determined deformation of the underlying combination should be approximately equal. Any possible differences in the linear deformation may be increased in the cracked state in connection with the deformation analysis.
Are the same effects taken into account?
When performing a comparison, make sure that the same effects as for example creep and shrinkage are taken into account (Figure 02).
Are the same input values available?
Furthermore, it should be checked in connection with the deformation analysis if the same input values are available. In this case, it is necessary to pay particular attention to whether the applied reinforcement (Figure 03) and the lever arm or concrete cover are the same.
If not having found the cause after the fundamental examination, please contact our hot line.
Yes, it is possible.You can do this by selecting the checkbox next to 'Use Required Reinforcement for Design of Serviceability' in the input dialog box '1.4 Reinforcement', 'Longitudinal Reinforcement' tab.Thus, the module places the entire reinforcement required for the ultimate limit state design and/or serviceability limit state design in the reinforcement layout.The results output 'Additional Reinforcement' is omitted after designing in the results windows in the add-on module as well as in the printout report.The option "Use Required Reinforcement for Design of Serviceability" can be combined with the option 'Increase Required Longitudinal Reinforcement Automatically for Serviceability Limit State Design'.
The 'Design Details' button is only available or can be selected if the required reinforcement has been selected from the ultimate limit state (ULS).As soon as the governing reinforcement consisting of ULS and SLS or only the SLS is shown in the results tables, the "Design Details" button is grayed out.You can select the design details for the serviceability limit state in Tables 3.1 - 3.3.
When using the automatic arrangement of the reinforcement, make sure that, in addition to the basic reinforcement, additional reinforcement is applied, if applicable, for the serviceability limit state designs. The default setting in the add-on module is such that the required reinforcement from the ultimate limit state is also applied for the SLS.
You can select the reinforcement that is applied for the SLS in 'Additional Reinforcement for Serviceability State Design'. The Info button explains the individual options (Figure 02).
The reinforcement applied for the designs can be reproduced via the function 'Selected Reinforcement for SLS Check' (Figure 03).
AnswerThe RF-/JOINTS add-on module is divided into several joint groups. For this, see the following FAQ.Therefore, there is no straightforward answer to the special aspects of the design as in this FAQ.In contrast to the RF‑/TIMBER Pro add-on module described in the mentioned FAQ, however, it is obvious that the RF‑/JOINTS add-on modules cannot design EC2, even if manually changing the LDC, for example in the RF‑/JOINTS Timber - Steel to Timber add-on module (see Figure 01).Furthermore, this also applies to the add‑on modules RF‑GLASS and RF‑/CONCRETE NL.The reason for this is that there are stiffnesses exported in the program in the case of some joint groups of the RF‑/JOINTS add‑on module. For nonlinear calculations, the superposition with result combinations is not allowed. In the case of the second result combination mentioned above, there is the special feature that the superposition is no longer conservative, even in the case of simple structures. The design cannot be also performed correctly by manually changing the LDC.Nevertheless, if a result combination should be superimposed with constant and alternative additive, it is necessary to split EC2 in the attached file into load combinations as follows.
- RC2*=CO1 or CO2
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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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