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Frequently Asked Questions (FAQ)
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AnswerThe cause is the active partial reliability factor γM. After deactivation, the results are identical.
The shear stiffness was probably not considered in the manual calculation or it was assumed as infinite. In RFEM/RSTAB, this is taken into account according to reality by default, so that the deformation is more unfavorable than in the manual calculation, which only includes the deformation component from bending.
The shear stiffness can be deactivated under the global calculation parameters (menu "Calculation" → "Calculation Parameters"), see the figure.
The reference system can be changed both in the graphical display in the Project Navigator (see Figure 01) or in the tabular results in the add-on module (Figure 02).
Figure 03 shows the different deformations of a structural system. On both sides, Construction Stages 2 to 4 are displayed from top to bottom, referring to the undeformed system (initial state) on the left and to the respective construction stage on the right.
AnswerWhen calculating according to Theory III. Order, the membrane stiffness or the axial stiffness is also considered with regard to pure bending stress. For theory I and II. Order, only the bending stiffness is taken into account for pure bending stress.
In RF‑CONCRETE Members, the deformation in the cracked state is determined by using a coefficient "ζ" (according to EN 1992‑1‑1, 7.4.3). For this simplified method, the coefficient ζ is only determined once per member. The linear deformation is upscaled according to the governing location in the member.
In this context, it is possible to determine different coefficients ζ for the individual members. When scaling the linear deformation, jumps occur between the individual members.
To avoid this effect, it is recommended to use sets of members.
First, check if the "design of deformation" has been activated in the settings for the calculation of the SLS designs.
Furthermore, check whether a load for the "quasi-permanent" design situation has been specified in the "Serviceability" tab of Window 1.1. By default, the calculation of deformations in RF‑CONCRETE Surfaces (with RF‑CONCRETE Deflect or RF‑CONCRETE NL) requires a quasi-permanent load.
Simply use the deformations for the result evaluation. Since the deformations are very small, increase the number of decimal places for the display of the deformation in the first step.
If you display the deformation in global Y for the wall pillar and increase the display factor, you can clearly see how the wall is bent. The support reaction counteracts as restraint of this deformation.
If you define a line support directly on the slab edge, the flexibility of the wall surface is not applicable.
There are three options you can choose from.
Undeformed system: The deformation is related to the initial structure.
Displaced parallel surface: This option is recommended for an elastic support of the surface. The deformation uz,local is related to a virtual reference surface displaced parallely to the undeformed structual system. The displacement vector of the reference surface is as long as the minimal nodal deformation within the surface.
Displaced user-defined reference plane: If the supports of a surface deform very differently, an inclined reference plane for the designed deformation uz,local can be defined. This plane must be defined by three points of the undeformed system. The program determines the deformation of the three definition points, places the reference plane through these displaced points, and then calculates the local deformation uz,local.
Regarding the analytical calculation of SLS, you should note that the calculation is based on a provided or applied reinforcement for SLS.
The provided reinforcement can result, for example, from the ultimate limit state design, the defined basic reinforcement, or the automatically determined required reinforcement for SLS. The reinforcement applied to the SLS design can be displayed graphically.
If there are too small or no reinforcement results from ULS or the basic reinforcement in some areas and no required reinforcement is determined for SLS at the same time, the serviceability limit state design is performed without or with too small reinforcement. In this context, very high results may occur during the deformation, for example. Also, there may be poor convergence.
It is necessary to ensure that there is a reinforcement in each area of the structural system. For this, you can apply a basic reinforcement or a minimum reinforcement, for example.
AnswerFor building construction, there are no specific limit values specified in the standards for the serviceability limit state design. Therefore, the limit values should be agreed with your client and, if necessary, with the respective authority. Nevertheless, there are various recommendations in technical literature, which we have also adopted as the default values.
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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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