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Frequently Asked Questions (FAQ)
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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.
There are several ways to find the non-designable locations.
- If the location is selected by clicking the table row in the add-on module, it is indicated by an arrow in the graphic of the main program (see Figure 01). You can adjust the view by moving the add-on module window to the second screen, if necesary. Furthermore, there is the "Jump to Graphic to Change View" button available in the add-on module.
- If the add-on module window is closed, you can use the search function by clicking the menu Edit → "Find via Number." In this case, you can enter the FE node number noted previously.
- If you activate the results of the add-on module in the work window of RFEM and select the result display using "Values on Surfaces," you can select the "Notes Only" result option. The numbered notes are then displayed in the list at the bottom left of the screen.
Yes, it is possible, for example, if a file (calculated in version 5.23.01) is opened in an older version (such as 5.20.01).
The add-on modules for reinforced concrete structures have no backward compatibility. This means that the module entries must be deleted, depending on the version change.
For instance, this may be necessary if there is a function or a feature contained in the latest program version, which was not yet available in the older version. To avoid compatibility problems, the entries in the add-on modules are removed.
In the example, the file from version 5.23.01 is opened in version 5.20.01. In this case, the entries from RF‑CONCRETE Surfaces will be lost. If you open it in the version 5.17.01, for example, the entries from RF‑CONCRETE Members is also lost.
To avoid the problem, it is recommended to conclude a service contract and use the current version of RFEM.
AnswerThe fire resistance design is based on the temperature course from Annex A EN 1992‑1‑2.The initial values for temperature courses cannot be adjusted in the add-on modules (RF‑/CONCRETE Members and RF‑/CONCRETE Columns). The temperature curves according to Annex A EN 1992‑1‑2 are based on the following assumptions:
- The specific heat of concrete corresponds to the specifications according to EN 1992‑1‑2, 3.2.2.
- The moisture is 1.5%. For moistures greater than 1.5%, the specified temperatures are on the safe side.
- The thermal conductivity of concrete is the lower limit value mentioned in EN 1992‑1‑2, 3.3.3.
- The emissivity value of the concrete surface is 0.7.
- The convective heat-transmission coefficient is 25 W/m²K.
AnswerIn the printout report selection, you can add the intermediate results of the add-on module in the Reinforcement tab.
AnswerYes, it is possible to adjust the parameters of a national annex. For this, it is first necessary to create a new user-defined national annex. The newly created annex is based on the original annex selected previously.Once the annex has been created, you can change the parameters. It is also possible to adjust the description of the national annex.The user-defined attachment is marked with "*".
AnswerSuch a feature for increasing the load up to the failure does not exist with regard to the design of reinforced concrete structures.As an alternative, you can proceed as follows:Create a separate load case or load combination for each load increment. This can be done by using load factors, for example.Then, select the individual load cases or combinations in the add-on module.After performing the calculation to the point "Provided Reinforcement" for the first time, you can adjust and save the existing reinforcement proposed by the add-on module.Finally, you can carry out the nonlinear analysis on the basis of the defined reinforcement.The existing safety or the available utilization can be evaluated graphically after the successful calculation.
In the design modules of RFEM or RSTAB, you can define "Provided Basic Reinforcement" and perform a nonlinear calculation in the ultimate limit state for this reinforcement.
As a result, you obtain the utilization ratio from the nonlinear calculation assuming the provided longitudinal reinforcement.
The nonlinear calculation is already included in the CONCRETE add-on module for RSTAB. In RFEM, the RF‑CONCRETE NL add-on module is required.
AnswerThe partial safety factors for reinforced concrete design can be edited in Window 1.6 "Reinforcement" in the corresponding tab for the selected National Annex (for example, DIN EN 1992‑1‑1).If required, you can also reset these values to the default value.In a similar way, this also applies to the add-on modules RF‑CONCRETE Surfaces and RF‑/CONCRETE Columns.
The RF‑CONCRETE Columns add-on module allows you to define a "creep-producing permanent load." You can find the corresponding tab in Window "1.1 General Data."
The reason for the entry is that RF‑CONCRETE Columns can apply this "creep-producing permanent load" for the automatic determination of the effective creep ratio according to EN 1992‑1‑1, 5.8.4.
In contrast, there is no explicit input option for this creep-producing permanent load in RF‑CONCRETE Members. In RF‑CONCRETE Members, the stability analysis of reinforced concrete columns by means of nonlinear design does not automatically reduce the effective creep ratio. You can find the background to the effective creep ratio applied in RF‑CONCRETE Members in Chapter 2.4.6 of the RF-CONCRETE Members manual.
The same applies to the CONCRETE Columns or CONCRETE add-on modules for RSTAB.
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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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