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Frequently Asked Questions (FAQ)
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In RFEM and RSTAB, the simplified design from , Chapter 2.2.3, have been implemented for the automatic load combinations. This means that, strictly speaking, the structures concerning the final deformation may only be analyzed, in which the materials with identical creep behavior occur since the creep deformations are considered in a simplified way on the load side. If the structure is a combined structure made of timber with different creep behavior or in combination with steel, the final deformations must be determined according to  Amendment to 2.2.3 as follows:
"(4) If the structure consists of members or components having different creep behaviour, the long-term deformation due to the quasi-permanent combination of actions should be calculated using final mean values of the appropriate moduli of elasticity, shear moduli and slip moduli, according to 126.96.36.199(1). The final deformation ufin is then calculated by the superposition of the instantaneous deformation due to the difference of the characteristic and quasi-permanent combinations of actions with the long-term deformation."
However, this requires the superposition of the results from different load combinations, which cannot be implemented automatically in RFEM and RSTAB. If the different creep behavior should be taken into account, it is necessary to create the load combinations manually, and reduce the stiffness according to the creep coefficient. The procedure is described on an example of a timber-concrete composite floor presented on the Info Day 2017. Below this FAQ, you can find the link for this video.
AnswerThis function cannot be assessed or determined at the basic program level. This issue can be fixed at the level of the add-on modules, such as RF‑STEEL EC3 or RF‑DEFORM. The second module is generic and can be used for any member. More information can be found at: https://www.dlubal.com/en-US/products/rfem-and-rstab-add-on-modules/others/rf-deform .
AnswerNo, this option is not available. Nodal deformations are always displayed in relation to the global coordinate system, regardless of whether the structure input has been set by means of a user-defined coordinate system.If necessary, the output of the local member or surface deformation results can help.
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).
First, open the result diagram of a member, line support, section or line. Then select the desired internal forces and deformations.
Finally, right-click the navigator and select Save Check Boxes State.
Use Refresh Check Boxes State (this button is now available) to cancel your settings.
AnswerIt is correct that the rib members defined in the model are not taken into account when calculating the realistic deformations in cracked state.
However, you can solve this problem if you do not model the downstand beams as rib members, but replace them with a surface model. Thus, the entire slab can be modeled as a surface structure and designed with RF‑CONCRETE NL in RF‑CONCRETE Surfaces.
I superimpose two of the load cases into one result combination by using the 'Or' criterion. The results graphic of the result combination, however, shows deformations smaller than the two contained load cases.
Furthermore, I get a positive as well as a negative maximum value for the RC, despite the fact that the individual load cases yield positive deformation values.
In the result combination, RSTAB superimposes the (orthogonal) components u-x, u-y und u-z of the individual load cases and creates the total deformation u. According to the definition of the coordinate system, the orthogonal components of the load cases can be positive or negative. Therefore, it is only a display issue, because the deformations u shown in the graphic are not definitively specified in terms of their direction.
The determination of the RC extreme values yields two values: maximum and minimum. The geometric addition of the minimum and maximum value yields the correct deformation value of the result combination. The results table shows the correct value.
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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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