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Frequently Asked Questions (FAQ)
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AnswerIn the add-on module, the shear design is performed in the following sequence:1. VEd / VRd, c
2nd VEd / VRd, max
3. VEd / VRd, pIn the course of VEd / VRd, max, the inclination of the compression strut is determined and in the course of VEd / VRd, s, the reinforcement amount is determined iteratively.If VEd / VRd, max is not fulfilled in the design run, the subsequent design VEd / VRd, s is not performed and the design criterion VEd / VRd, c is displayed.
AnswerThe load from the form-finding load case (FF) is impressed 1.0-fold into the system. If you want to factor in the self-load in combination with combinatorics, you can additionally create a permanent load case for the self-load with a load of 0.35 times the load.
AnswerIt is difficult to enumerate one or particular reasons for the deviations. Basically, the design in RF-CONCRETE Columns is an analytical method, the nominal curvature method according to EN 1992-1-1 5.8.8. One advantage here is that it is a standardized method and that all intermediate values of the calculation are output in the add-on module.With the help of the intermediate values, you can search for the cause of a deviation between different design programs.If you can not find the cause, please contact our hotline. In this context, however, we need a printout including the input and intermediate values from the program used for the comparison.
AnswerThe surfaces output in RFEM are Smooth internal forces. The design in RF-CONCRETE Surfaces is based exclusively on the internal forces, which have been smoothed within a surface. Smoothing is not performed across the supported line. In this context, the shear force distribution shown in Figure 01 may occur.
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 under "Additional Reinforcement for Serviceability Limit State Design." The Info button explains the individual options (Figure 02).
The reinforcement applied for the designs can be reproduced with the function "Check applied for SLS design" (Figure 03).
AnswerThe situation can be caused by the following conditions:
- Reinforcement layers are virtually adjacent to each other in the centroidal axis of the surface
- A smaller rebar diameter has been selected
- The cross-section is completely drawn, which means that there is no neutral axis depth.
In this case, the smallest distance between the reinforcement layers is applied as a lever arm. If it is close to zero, the lever arm is also applied close to zero.
AnswerThe cause of such an effect could be free edges, which can deform almost infinitely during Form-Finding. A state of equilibrium is difficult to achieve.As a basis for Form-Finding, there should be no free edges on the membrane surface. Ropes must be arranged on the free edges of the membrane whose stiffness can be based, for example, on the folded or reinforced edge strips of the membrane.
AnswerYes, the problem might also be caused by RFEM. Previewing RFEM files in Windows Explorer may cause Explorer to react more slowly.For a possible solution, proceed as follows:Open the file ThmShellEx64.dll in C:\Program Files\Common Files\Dlubal, and rename it to BACKUP-ThmShellEx64.dll.
In case of working with 32Bit version, open the ThmShellEx.dll file in C:\Program Files (x86)\Common Files\Dlubal, and rename it to BACKUP-ThmShellEx.dll
Afterwards, a restart of the PC is required
AnswerIn case of significant deviations, the problem may be caused by the applied bending theory (Mindlin or Kirchhoff).See also Mindlin Krichhof FAQ
Currently, there is no option to perform a stability analysis in the RF-CONCRETE Surfaces add-on module. However, it may be possible to perform a simplified design by means of a result beam by means of the nominal curvature method in RF-CONCRETE Columns.
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