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Frequently Asked Questions (FAQ)
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Error 108) appears if the stress analysis cannot be performed because the design situation preset for the design has not been defined.
By default, RF‑CONCRETE Surfaces requires a load or a load case from the "characteristic design situation" for the stress analysis of the reinforcing steel. If it has not been defined, the design is not performed and the corresponding error message is displayed.
To avoid this, select a "characteristic load" in the "Serviceability Limit State" tab of Window "1.1 General Data." See the video.
As an alternative, you can change the detailed settings for the serviceability limit state design, so that the stress analysis is performed with a quasi-permanent load, for example. However, this change of the default setting or standard specifications is at the discretion of the user.
AnswerIn the case of the combinations according to the general Eurocode without considering a national annex, the design situation in the serviceability limit state - quasi-permanent must be considered as in Figure 01. Here, it becomes clear that due to the last term, the variable loads are considered as unequal to 0 due to Ψ0,i, even in the case of Ψ2,1 = 0.
The selection in the "Limit of Crack Widths" tab of Window "1.3 Surfaces" has a direct impact on the kc factor for the analytical calculation of the minimum reinforcement As,min for effects due to restraint according to Equation (7.1) of DIN EN 1992‑1‑1, 7.3.2.If selecting the "pure tension restraint," the value kc = 1.0 applies in Equation (7.1). In the case of the approach of "bending Restraint," the add-on module sets the kc factor strictly to 0.4.If you select "Depending on the defined load," the program interpolates the element of the kc value by the element depending on the stress distribution in the cross-section using the defined load.This results in a constant distribution of the minimum reinforcement due to restraint being determined for the respective reinforcement direction of the surface when selecting "pure tension restraint" or "bending restraint." If you select "Depending on the defined load," there will be no constant distribution of the minimum reinforcement due to restraint.The program behavior described above is the same in RF‑CONCRETE Members and RF‑CONCRETE Surfaces (in RFEM 5), and is also applied to the CONCRETE add-on module (in RSTAB 8).
AnswerPlease deactivate the "indirect calculation" using the limit diameter "lim ds" or the member spacing "lim sl."The calculation of crack widths smaller than 0.20 mm is only possible by using the direct calculation according to EN 1992‑1‑1, 7.3.4.
Whether you see the selection in the Results navigator or not depends on the settings for the serviceability limit state design.In the settings for the serviceability limit state design, you can find the "Increase the required longitudinal reinforcement automatically for serviceability limit state design" option.Figure 01 - Settings for Analytical Method of Serviceability Limit State Design in RF-CONCRETE SurfacesIf activating the automatic increase of the longitudinal reinforcement, the "Limit State" entry is only available in the Results navigator.
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 result tables, the "Design Details" button is grayed out.You can select the design details for the serviceability limit state in Table 3.1 - Table 3.3.
AnswerThe deduction of the precamber in the serviceability limit state design is actually not regulated in steel structures. After numerous customer requests, we have adopted this in accordance with the TIMBER or CONCRETE add-on module. However, according to the standard specification, this value should only be considered in the quasi-permanent design combination.This does not apply to the characteristic and frequent design situation. Thus, as soon as the design situation in the add-on module is adjusted accordingly (see figure), the applied precamber is also subtracted from the resulting deformation.
When checking the deformation value, for example, as a result of the deformation analysis in STEEL EC3, it is necessary to subtract nodal deformations from the total deformation shown in RSTAB (see Figure 01): the deformation value in the centre of the member represents the total deformation of the component (the deformation of nodes plus the deformation of the component).
If the deformation is set as relative to the 'undeformed system' in Details of the serviceability limit state design in the add-on module (see Figure 02), the maximum deformation including nodal deformations (the deformation value displayed in RFEM/RSTAB) is used.
In order to calculate the deformations in cracked state in RF‑CONCRETE Surfaces, it is necessary to select at least one load case or combination in the "Serviceability Limit State" tab in Window "1.1 General Data" (see Figure 01).
In the lower part of the window, specify whether the method of check should be "Analytical" or "Nonlinear."
- If "Analytical..." is selected, it is necessary to activate the "Deflection with RF‑CONCRETE Deflect" option in the detailed settings (see Figure 02).
- If "Nonlinear..." is selected, the design of deformations can also be found under the detailed settings. The "deformation" is activated here by default (see Figure 03).
This depends on the selected settings in the navigator: for the ultimate limit state and the serviceability limit state design, it is possible to select the "limit state" in the Results navigator, whose required reinforcement is to be displayed.
The following settings are possible (see the figure):
- ULS / SLS governing (the envelope of "ULS/SLS")
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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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