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Frequently Asked Questions (FAQ)
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AnswerFor volumes, we do not provide any internal forces in the program. The conversion of the Spannnugnen in internal forces would be very complex, since not only mx, my and mz would be present, but also the parts of the drill, mxy, myz, mxz also lateral forces and normal forces. With volume one limits oneself usually on a direct voltage evaluation. If you still need internal forces, you have the option to apply the internal forces of the volume to a rod. For this purpose the result bar was implemented in the program.
AnswerRF- / STEEL EC3 measures cross-sections of cross-section class 4 using the effective width method according to EN 1993-1-5. The existing voltage is taken into account.
You have probably carried out the design in RF‑/TIMBER Pro according to DIN 1052:2008 and used a cut-to-grain angle of less than 3° (see Figure 01). According to Section 10.4.1 (1) of DIN 1052, such a cut-to-grain angle does not need to be considered. If you switch the design to the current DIN EN 1995 (see Figure 02), the design will also be carried out for the angle of less than 3°.
Furthermore, the module allows you to analyze transversal tension stress in the apex etc., according to the Section 6.4.3 ff. of the Eurocode. This procedure is explained in detail in the webinar.
AnswerNo stresses are calculated for orthotropic surfaces: The different stiffness coefficients would cause "blurred" results because they refer to an average value of the thickness. These stresses do not correspond to the orthotropy model.It is recommended to use the add-on module RF-LAMINATE here .
AnswerFor the surfaces type of stiffness "glass" no voltage is displayed in RFEM. The reason for this is that this stiffness type is only a placeholder for the add-on RF-glass module. This means that for the glass more inputs such. As layers, node bearings, edge bars and inputs to the load duration are necessary. These entries can be made in the add-on module RF-GLAS. The stresses, workloads and deformations per layer can also be evaluated in the add-on module (see Figures 1 and 2).
AnswerIf you want to see the results of the edges of a surface, then you can view the results of the line by right-clicking.
If a staff is on the line, you must hide it first. The easiest way is probably to see all the bars in the Show Navigator> Disable model data.
AnswerIn Window 1.12 "Parameters - Members" and Window 1.13 "Parameters - Sets of Members," you can define the cross-sectional areas for tension designs according to EN 1993‑1‑1 (see figure).
Why do I get no stresses on the top or bottom side of a member loaded with temperature (heating on the top side) if the member has no elastic foundation? Or more specifically, why does the upward curved member (due to heating on the top side) have tension stress on the bottom side if the member has elastic foundation? There must be compression stress on the bottom side.
The topic can be easily illustrated on a single-span beam. For this, three structural systems are described below. These models are documented in the attached file.
Statically determined system (no foundation), dT = 80 ° on the top side
The member is curved upwards, but is free of stress in itself.
Like System 1, but with an additional member elastic foundation. The member elastic foundation is entered without a possible failure (nonlinearity).
If you would display the stresses sigma_x of the member for System 2a, you obtain compression on the top side of the member and tension on the bottom side of the member (see Figure 01).
Due to the curvature of the member and the existing member elastic foundation, the contact force p-z occurs, which should prevent the member curvature upwards (see Figure 02).
These contact forces p-z (Figure 02) are caused by the member curvature due to the temperature and the applied member elastic foundation. The illustrated contact forces can be replaced by the member load opposed to the curvature. This is shown in System 2b in the example file.
The member elastic foundation is removed and a variable member load is entered in the Z-direction.
When comparing the results (for example, deformations u-z) on both System 2a and System 2b, you obtain the results with the same value (see Figure 03).
Moreover, you can also display the stresses sigma_x for both System 2a and System 2b. These have also the same value (see Figure 04).
System 3 should only document the stresses due to the temperature difference on a statically determined system (without foundation).
The results documented in the "single-span beam" example can also be transferred to the surfaces with elastic foundations.
In concrete design, the design situations can be defined as characteristic with direct load, characteristic with forced deformation, frequently and quasi-constantly.
You can view the verifications required according to the standard for the respective dimensioning initiatives in the detail settings of the add-on module (see Figure 1).
If proofs are now activated in tab sheet 1.6 under suitability for use that do not correspond to the design situation, a hint will appear after the calculation.
In this case it is recommended to define the necessary design situations or to remove the proofs to be calculated in register 1.6.
According to EN1992-1-1, section 9.3.1, a minimum reinforcement to ensure a ductile component behavior is to be inserted in the main tension direction of the plate. By default, in RF-CONCRETE Surfaces the option "Reinforcement option with main traction in the considered element" is selected. This now means that for each element, the greatest tensile force is sought for each reinforcement direction and for the top plate (-z) and bottom plate (+ z). If the greatest tensile force was found for the single element, the minimum reinforcement is applied there. If, for example, the minimum reinforcement is only arranged in the main direction of tension for biaxially tensioned plates, this can be specifically controlled by the user. To do this, open the dialog "Settings of the minimum reinforcement with ductile component behavior". If you select "Define", you can specifically set in which direction and on which side of the component the minimum reinforcement is to be arranged.
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