#### Further Information

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• ### Is it possible to somehow verify the bending moment from the integration of contact stresses determined in RF-/FOUNDATION Pro?

New FAQ 004225 EN-US

A detour in RFEM is possible.

The soil pressure from which the bending moment is determined for the design by means of integration can be applied as an "external load" in an RFEM equivalent model.

Compression Distribution in RF-/FOUNDATION Pro

This compressive stress can be applied to a replacement system in RFEM as a "Free Surface Load".

In this case, the equivalent system is a rigid surface. The size of the surface depends on the position of the design section set in RF-/FOUNDATION Pro. In this case, we set "in column center".

With this equivalent system, it is possible to recalculate the "moment from compression stress distribution" determined in RF-/FOUNDATION Pro.

You can download the example described above using the link below and open it in RFEM 5.

• ### What is the meaning of 'Shear Failure in Glued Contact Surface' in the details of the RF-LAMINATE add-on module?

New FAQ 004206 EN-US

In the case of cross laminated timber panels not glued to the narrow sides and a wall-like structural behaviour, the torsion stress in the glued joints is often decisive. This design is performed according to the explanations in the literature reference below according to the following equation.

$\eta_x=\frac{\tau_{tor,x}}{f_{v,tor}}+\frac{\tau_x+\tau_{xz}}{f_R}=\frac{\displaystyle\frac{3\ast n_{xy}}{b(n-1)}}{f_{v,tor}}+\frac{{\displaystyle\frac{\frac{\partial n_x}{\partial x}}{n-1}}+\tau_{xz}}{f_R}\leq1$

Values:
• b board width
• n number of board layers
• nxy shear in pane plane
• $\frac{\partial n_x}{\partial x}$ shear of board layers
• $\tau_{xz}$ shear in thickness direction
• fR rolling shear strength
• fv,tor torsion shear resistance
For the y-direction, the design is analogous but with the values for the y-direction.
• ### When calculating a curved surface in RF-GLASS, I get a message indicating that the surface has more than 4 boundary curves and thus no layered FE mesh can be used. How can I avoid this message?

New FAQ 004174 EN-US

The same requirements apply for a layered FE mesh as for a contact solid (see the links below this FAQ). If the requirements are not met, the layered FE mesh must be deactivated in the layer layout details (see Figure 02).
• ### How can a downstand beam be retroactively modeled under an existing floor so that only vertical compression forces are transferred?

FAQ 003569 EN-US

In this case, the slab should rest on the downstand beam without any bond (see Figure 1).

First, assign the member type 'Beam' to the downstand beam because the rib is not effective here due to the missing joint.

To implement the non-linearity 'Only Transfer of Compression Forces in Z-Direction', you can use the 'Line Release' function. In this case, all forces and moments must be activated, that is, released, within the 'New Line Release Type' dialog box. Moreover, for uz, the non-linearity "Fixed if vz Is Positive" must be set, see Figure 2.

The line of the member within the corresponding area should be selected as a line to be released, and the corresponding surface like a released object.

• ### During the plausibility check, I receive the error message saying that the surface opposite to the contact surface cannot be localized. How can I fix it?

FAQ 003519 EN-US

When modeling a contact solid, it must be noted, among other things, that the two contact surfaces must be arranged in parallel and designed identically.

In Figure 1, a contact solid with existing contact between the top and bottom surface should be created. The top contact surface is divided into two surfaces F2 and F3 and thus does not correspond to the bottom contact surface F1. Therefore, the error message shown in Figure 2 is displayed. It is necessary to define two contact volumes in this case. The contact solids can be created, for example, by the function "Create Solid with Contact." To do this, select the contact surfaces and open the corresponding function in the shortcut menu; alternatively, it is possible to create the contact solid manually. Watch the FAQ explanatory video to see both procedures.

• ### In compliance with DIN 1054, the allowable soil pressure "Sigma_all" has been entered for the soil contact stress analysis. RF‑FOUNDATION Pro requires a "characteristic value" to be entered. How are both approaches of DIN 1054 and EN 1997‑1 compatible?

FAQ 003457 EN-US

This discrepancy is often caused by changing DIN 1054 to EN 1997.

In the "old" DIN 1054, the design was performed by using the characteristic values on the action side and the allowable stress on the resistance side. The actions were used without partial factors and compared with certain allowable stress. In this case, the "eta" resistance was completely included in the allowable stress.

In the predecessor module of RF‑FOUNDATION Pro, which performed the calculations according to DIN 1054, there was a special tab "Ground Failure Analysis (Service Loads)" for this purpose.

In the Eurocode, the ground failure design is performed in a different way.
Here, a partial factor is applied to the action and the resistance side. Thus, the loading is increased by the factor of 1.35 or 1.5, and the resistance is reduced by the factor of 1.4.

With regard to the "old standard," the "eta" resistance is completely included in the "allowable stress sigma_all."

Under the Downloads link below, you can find a model file for RFEM or RSTAB, which clarifies the problem in RF‑/FOUNDATION or RF‑/FOUNDATION Pro. Here, the design has not been performed by using the user-defined entry of the soil pressure, but using the allowable stresses from the standard case tables. There should be the same soil with approximately the same foundation dimensions resulting or the Eurocode and for the old standard.

The following assumptions for the foundation have been made in both add-on modules:
• Cohesive soil
• Pure silt - UL
• Stiff consistency
• Embedment depth of the foundation t = 4.92 ft
When using the all. soil resistance according to DIN EN 1997‑1 from the standard case tables, the factor of 1.4 is already included. The base values Sigma‑R,d(B) of the soil resistance also differ by the factor of 1.4 compared to the allowable soil pressure "sigma_all" (DIN 1054).

Results of the comparison:

Ground failure design according to DIN 1054 in RF‑/FOUNDATION (old):

Ground failure design according to EN 1997‑1 in RF‑/FOUNDATION Pro:

In spite of different input values, the results from DIN 1054 and EN 1997‑1 are comparable.

If you want to recalculate the foundation in RF‑/FOUNDATION Pro, which has already been designed with RF‑/FOUNDATION (old), you would have to apply twice the soil pressure Sigma_R,k:

Sigma_R,k (input in RF‑/FOUNDATION Pro) = 1.40 (partial factor for ground failure) x 1.35 (resistance on the load side in the example) x Sigma_all (from RF‑/FOUNDATION (old)).

In the attached file, this has been done in CA2 in both add‑on modules. In this case, the allowable soil pressure has been entered as 4,595 kip/ft² in RF‑/FOUNDATION. In RF‑/FOUNDATION Pro, 8,688 kip/ft² has been entered.

• ### Which material model should be assigned to a contact solid made of timber?

FAQ 003401 EN-US

For the solid type 'Material', the material model 'Orthotropic Elastic/Plastic 3D' has to be assigned for timber (Figure 1).

Since the solid object type 'Contact' is considered as a member within the program, it generally requires an isotropic material model (Figure 2).

• ### During the calculation in RF‑/FOUNDATION Pro, I receive an error message saying that the foundation dimension is less than twice the eccentricity. Why? And what can I do?

FAQ 003350 EN-US

In the case of a ground failure analysis or soil contact stress analysis, the "equivalent surface" is determined in RF‑/FOUNDATION Pro in order to calculate the soil contact stress.

If the foundation dimension is smaller than twice the load eccentricity "e," the "equivalent surface" or the "effective foundation" cannot be determined. In this case, you receive the corresponding error message.

In most cases, the problem is that a user has entered too small dimensions of the foundation plate.

To remedy the problem, you can manually set greater dimensions. Or select the "Dimensioning" feature.

• ### How can I display the contact stresses on a contact solid?

New FAQ 003307 EN-US

The result values described in RFEM as "Contact Stresses" are by definition reserved for surfaces with surface supports (see RFEM Manual).

Instead, contact solids can be evaluated like standard solid elements. According to the definition of the contact solid axis system, it is thus possible to display the stresses in the contact direction as well.

Please note that for the evaluation of contact solid, the option "Remove Contact Solid from Display" must be deactivated in the Display navigator (see Figure 2).

• ### How can I apply the standard case tables for the soil contact stress analysis in RF‑/FOUNDATION Pro?

FAQ 003299 EN-US

First, set 'DIN' as National Annex.

Thus, the 'For standard case acc. to DIN EN 1997‑1, A6.10' option becomes available (see Figure 01).

You can set here whether there is the 'cohesive' or 'non-cohesive' soil. In 'Details', you can then enter further settings for the standard case tables, such as the values for allowable soil pressure (see Figure 02).

It is not possible to modify the values in the standard case table.

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#### First Steps

We provide hints and tips to help you get started with the main programs RFEM and RSTAB.

#### 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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