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Frequently Asked Questions (FAQ)
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A result of the column design with RF‑CONCRETE Columns is the provided reinforcement. This is displayed in Table 4.1 and illustrated in the graphics below and in the table on the right.
You can use the "Edit Reinforcement" button to change the provided reinforcement, if necessary. Click the button to open the "Edit Longitudinal Reinforcement" dialog box (see the image). It includes the table for the "Position of Reinforcement Bars." Here you can delete rows by selecting the row that contains the member to be removed and then clicking the button below.
Subsequently, it is necessary to recalculate the design for the modified reinforcement layout.
The described procedure is shown in the explanatory video.
Yes, the RF‑PUNCH Pro add-on module allows for defining the desired longitudinal reinforcement in the "1.5 Punching Nodes" window, see the image.
If you want to consider the minimum moments when calculating the reinforcement for columns, you can also activate this in the add-on module as described in FAQ 004371.
If I do not specify any basic reinforcement in RF‑CONCRETE Surfaces, I obtain the value X as an additionally required reinforcement. If I enter this value X as the provided basic reinforcement, I correctly do not get any additional required reinforcement.
However, if I enter a lower value than the determined required total reinforcement as the basic reinforcement, the additionally required reinforcement is increased in such a way that the originally required reinforcement content is exceeded. Why?
Please check the concrete covers of the basic reinforcement and the additional reinforcement. In this case, a higher concrete cover is probably defined for the additional reinforcement than for the basic reinforcement.
If the existing basic reinforcement is so small that the additional reinforcement is required, but a lower effective depth is available due to the higher concrete cover, the program must adjust the reinforcement content accordingly, that is, increase it.
Therefore, the concrete covers in the "Reinforcement Layout" tab in Window 1.4 "Reinforcement" have to be considered, see the image.
The automatic increase of the reinforcement for the SLS is based on the assumption of a lever arm, as it is also used for the ULS design. However, increasing the lever arm may change it. This occurs especially if the required reinforcement is applied with a different diameter than for the ULS, or is placed in a different position.
At the end of the calculation, however, the add-on module performs another design with the automatically designed reinforcement. In this design, the actual position of the reinforcement is considered. This can usually lead to a slight exceeding.
Since the ratio is set to one decimal place according to the default setting, the exceeding may have a more dramatic effect than it is. In the add-on module, you can also set two decimal places under "Settings" → "Units and Decimal Places..."
The minimum of the entered shear reinforcement can be controlled by two settings:
- Window 1.4 - Reinforcement Ratios - Minimum Shear Reinforcement Ratio
- Window 1.4 - depending on the standard, for example, for DIN EN 1992-1-1 - Minimum Shear Reinforcement
Please note that the minimum shear reinforcement according to DIN EN 1992‑1‑1 refers to the width-height ratio of the entire slab. Since RF‑CONCRETE Surfaces is suitable for any surfaces and the individual FE elements are designed, this ratio must be determined and entered manually.
AnswerIf there are several similar beams or ribs in the model, you can use the functions "Save Provided Reinforcement as Template" and "Load Reinforcement from Template." It is recommended to design the beams together in one case. You can save the modified reinforcement from one downstand beam and then load it for the other beams.
The descriptions of the reinforcement in the Results navigator are defined as follows:
As,-z (top) :
- Upper longitudinal reinforcement, that is, all longitudinal reinforcement that is above the centroidal axis of the cross-section, see Image 01
As,+z (bottom) :
- Bottom longitudinal reinforcement, that is, all longitudinal reinforcement that is below the centroidal axis of the cross-section
- Total longitudinal reinforcement of the cross-section that is required due to torsion
As,-z (top) + As,T/2 :
- Upper longitudinal reinforcement (see above) plus half of the required longitudinal reinforcement from torsion
As,+z (bottom) + As,T/2 :
- Bottom longitudinal reinforcement (see above) plus half of the required longitudinal reinforcement from torsion
- Stirrup reinforcement from torsion
- Always single-leg, that means: reinforcement content from one leg on one stirrup member
- Resulting from the theoretical assumption of a spiral stirrup reinforcement
- Stirrup reinforcement from shear force
- Two-, three-, or four-leg, that means: reinforcement content from one leg on two, three, or four stirrup members
- Setting the number of legs under stirrup parameters, Window "1.6 Reinforcement", "Stirrups" tab, see Image 02
2*asw,T,stirrup + asw,V,stirrup :
- Total stirrup reinforcement from torsion and shear force
- In this case, two-leg for torsion, therefore Factor 2 before asw,T,stirrup, shear reinforcement according to the setting from Image 02
AnswerIn terms of the consideration of creep and shrinkage, the program concept is as follows: Creep and shrinkage are only considered in RF‑CONCRETE Members if there is a curvature and if the cross-section is cracked. The explanation of this can be found in the manual, see Chapter 188.8.131.52.The concept for determining the longitudinal stiffness is designed for curved components. In the case of pure axial loading, the program is not able to determine the exact deformation in connection with the creep and shrinkage according to the current concept.
While Member 1 is an upstand beam, Member 2 is a downstand beam. This results in a compression axial force for Member 1, and a tensile force for Member 2.
For the concrete design, a compressed cross-section is more favorable than a tensioned cross-section. For comparison purposes, here are the axial forces of the members:
Now, if you deactivate the axial forces for the design in RF‑CONCRETE Members, the result is a required reinforcement that is affine to the moment distribution:
With this setting, you are on the safe side for Member 1, but on the unsafe side for Member 2.
In this case, you should pay attention to the following steps:
- In Window 2.3 "Required Reinforcement by Point," select the "In Grid Points" option, see Image 01.
- Export the results using the "File" menu → "Export Tables," see Image 02.
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Wind Simulation & Wind Load Generation
With the stand -alone program RWIND Simulation, you can simulate wind flows around simple or complex structures 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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