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• Which explicit method is used in the RF-DYNAM Pro - Nonlinear Time History add-on module?

FAQ 002376 EN Add-on Modules RF-DYNAM Pro - Nonlinear Time History

Answer

The RF-DYNAM Pro - Nonlinear Time History offers, in addition to the implicit NEWMARK method of mean acceleration, also an explicit method. In the manual of this add-on module, it is mentioned that this is a solver which uses the central difference method.

It should be noted that not the "original" version of the central difference method is used here, but a modified form. The modified form is characterized by the fact that it is simply not a central difference when applying the speed difference. The following two equations show the applied speed and acceleration differences.

Speed: (no central difference)
${\dot{\mathrm x}}_{\mathrm n+\frac12}=\frac{{\mathrm x}_{\mathrm n+1}-{\mathrm x}_\mathrm n}{{\mathrm{Δt}}_{\mathrm n+{\displaystyle\frac12}}}$

Acceleration: (central difference)
${\ddot{\mathrm x}}_\mathrm n=\frac{{\dot{\mathrm x}}_{\mathrm n+{\displaystyle\frac12}}-{\dot{\mathrm x}}_{\mathrm n-\frac12}}{{\mathrm{Δt}}_\mathrm n}$

This approach leads to a faster convergence since it responds "faster" to changes in loading or structure (nonlinearities).
• For wall ends and wall corners, no soil contact stresses are deducted in RF-PUNCH pro, even though the type "Foundation" has been set. It is also nowhere possible to define that the soil contact stresses should be deducted. Why does this happen?

FAQ 002375 EN Add-on Modules RF-PUNCH Pro RFEM 2D RFEM

Answer

If you perform a punching shear design for a wall corner or a wall end at a floor slab or foundation plate, this entry is not necessary.

Since the punching load is determined at a wall corner or a wall end from the shear forces in the control perimeter when performing the punching shear design, the ratio of the surface load is missing anyway within the control perimeter (up to the load application). Therefore, this entry is also not necessary in the 1.5 dialog box.

If you, however, perform the punching shear design for a single column at a foundation plate with the punching load from the normal force of this column, you can enter the "Deductible Surface Load" at the end of the dialog box "1.5 Nodes of Punching Shear - Node of Punching Shear - Details" which allows to determine ΔVEd.
• I have modelled a precast slab as "orthotropic surface". Can I use these surfaces also in reinforced concrete design?

FAQ 002374 EN Add-on Modules RF-CONCRETE RF-CONCRETE NL

Answer

Yes, you can use "orthotropic surfaces" for the reinforced concrete design in RF-CONCRETE Surfaces.

If you only would like to carry out serviceability limit state designs, you do not have to define additional settings in RF-CONCRETE Surfaces concerning the surface type.

You need the RF-CONCRETE NL add-on module to perform the serviceability limit state designs. Select in the "serviceability limit state" tab (in the dialog box "1.1 General Data") the design method "Nonlinear...". See Figure 01.

You can then change the surface type to "Constant" in the dialog box "1.3 Surfaces" so that the serviceability limit state design is also possible here. See Figure 02.
• Can you give me a hint where to activate the design for limiting a gaping joint according to DIN 1054: 2010-12 A 6.6.5 in the FOUNDATION Pro add-on module?

FAQ 002365 EN Add-on Modules FOUNDATION Pro RF-FOUNDATION Pro

Answer

First, select the National Annex "DIN" in the "1.1 General Data" window. Then, open the [Details...]. A dialog box opens where you can find the design for limiting the gaping joint which is described as "Highly eccentric loading in the core". See Figure 01.
• Is is correct, that you have to enter the allowable soil pressure as the characteristic value in input form 1.1 General Data in FOUNDATION Pro? Is the design value determined automatically?

FAQ 002357 EN Add-on Modules RF-FOUNDATION Pro FOUNDATION Pro

Answer

Yes, this is correct.

The characteristic value of soil pressure is entered in input form 1.1 General Data. See Figure 01.

The design value is:
${\mathrm\sigma}_\mathrm{Rd}\;=\;{\mathrm\sigma}_\mathrm{Rk}\;/\;\;{\mathrm\gamma}_{\mathrm R;\mathrm v}$

The estimated partial factor for spread foundations can be found in the parameters of the national annex you selected for the design. See Figure 02.
• In the add-on module RF-CONCRETE Surfaces, is it possible to limit crack widths due to internal restraint and with customized fct,eff?

FAQ 002355 EN Add-on Modules RF-CONCRETE

Answer

To determine the minimum reinforcement from restraint (drain of hydration heat) in RF-CONCRETE, you have to select at least one load case or CO for design in the "Serviceability Limit State" register of the 1.1 General Data input form. The analytical method of check for the serviceability limit state is activated by default in this tab. See Figure 01.
After activating the checks in the serviceability limit state, you can now adjust their settings in input form 1.3 Surfaces. Switch to the Limit of Crack Widths tab in input form 1.3. On the right side, you'll find the "Minimum Reinforcement for Effects Due to Restraint". Once the box "Crack formation in the first 28 days" has been selected, the factor for controlling fct,eff,As,min can be entered. See Figure 02.
• How can I enter concrete covers of individual reinforcement layouts independently when designing reinforced concrete surfaces?

FAQ 002294 EN Add-on Modules RF-CONCRETE 2D RF-CONCRETE NL RF-CONCRETE Deflect

Answer

It is only possible to enter concrete covers of individual reinforcement layouts independently if no serviceability limit state design is performed.

As soon as you have selected a load for the serviceability limit state design in Table 1.1 in RF-CONCRETE Surfaces, the reinforcement layouts will be coupled together.

• Calculating a result combination in STEEL EC3 or Aluminium takes a very long time. What might be the cause and how can I improve the performance?

FAQ 002290 EN Add-on Modules RF-STEEL EC3 STEEL EC3 ALUMINUM RF-ALUMINUM

Answer

Cross-sections of the type "General" might cause this long-lasting analysis in STEEL EC3 and Aluminium.

You find them in Table 1.3 Cross-Sections. For these cross-sections, it is necessary to calculate the stresses for the cross-section classification with SHAPE-THIN in the background. The result combination (RC) for the design may contain many load combinations (CO). This could lead to the fact that the SHAPE-THIN analysis will be performed very often and might take a very long time. However, there is a workaround. With the option displayed in the second figure, the enveloping internal forces of the RC are used, and each CO included in the RC cannot be calculated. This may be more conservative, however, it is faster because not every CO requires a SHAPE-THIN analysis, only the envelope.

• I was just about to perform the punching shear design in RF-PUNCH Pro and assign shear rails of HALFEN for the design, but when I click on the button [HDB...], only a warning appears. What am I doing wrong?

FAQ 002282 EN Add-on Modules RF-PUNCH Pro

Answer

Check if the design software Punching Shear Reinforcement HDB from HALFEN has been successfully installed and also registered. The best way to test it is to start the design software HDB without using RF-PUNCH Pro, either from the Windows start menu or from the desktop shortcut.

If starting the program has been successful, you can use the interface of RF-PUNCH Pro to HDB for further processing.

• How can I design a slab with downstand beams in RF-CONCRETE NL? I would like to know the deformations in state II; however, this does not seem to work with the entered rib members. Is there an alternative for entering this?

FAQ 002277 EN Add-on Modules RF-CONCRETE RF-CONCRETE NL

Answer

It is right that the rib members defined in the structure are not considered when calculating realistic deformations in state II. However, you can solve this issue by displaying the downstand beams not as rib member but by replacing them as surface model. Thus, the complete slab can be displayed as plate structure and designed with RF-CONCRETE NL in RF-CONCRETE Surfaces.

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