#### Further Information

In addition to our technical support (e.g. via chat), you’ll find resources on our website that may help you with your design using Dlubal Software.

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• ### How to enter a covering of a bucket foundation up to 10 cm below the top edge of the bucket in RF-/FOUNDATION Pro?

New FAQ 004297 EN

This is possible in RF-/FOUNDATION Pro by defining the soil profile.

In the input dialog box '1.1 General Data', you can find the button that opens the dialog box for defining the soil profile.

In the 'Soil Profile' dialog box, you can then set the PGL altitude and PGL'.

Important:
The altitude after soil change must not be higher than the altitude of the original profile.
For a bucket foundation, PGL or PGL' refers to the upper edge of the bucket.

• ### What happens if I activate the "Soil failure" function in RF-SOILIN?

New FAQ 004261 EN

The zero coefficient of structural soil strength can be used for better convergence of deeper excavations or small loading. Damaged soil have no structural soil strength. Therefore, it better picture damaged subsoil in the upper layers with this function. The possible entry for the depth of the soil failure is from 0.0 m to 1.0 m.
• ### According to which approaches is the lap length design performed in RF-/FOUNDATION Pro? And can I deactivate this check?

New FAQ 004259 EN

The check of the lap length is performed according to DIN EN 1992-1-1 clause 8.7.3 or clause 10.9.6.3 for block and bucket foundations with profiled bucket surface.

The design can be optionally deactivated using the [Details ...] button.

You can find an example of the calculation of the lap length for the bucket foundation in the RF-/FOUNDATION Pro manual, which you can download using the following link or open with the module started by pressing the [F1] key.

• ### According to which theoretical approaches are the forces and moments analyzed in the bucket foundations with rough inner sides and the reinforcement layout carried out in RF-/FOUND Pro?

FAQ 004222 EN

The theoretical approaches for this can be found in 'Fritz Leonhardt, Lectures on Concrete Structures, Third Part, Third Edition'.

Special attention must be paid to Chapter 16.3 'Single Foundations for Columns'.
• ### 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

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.

• ### Does the program check the lap length of the vertical stirrups of a block foundation with smooth bucket sides?

FAQ 003446 EN

The design of a block foundation as well as a bucket foundation with smooth bucket sides is performed by analyzing the horizontal components Ho and Hu.

In this case, the restraining moment at the column base is converted into a horizontal component on the upper side (Ho) and on the bottom side (Hu).

For block and bucket foundations with smooth bucket sides, no vertical component is calculated to be used for the design of anchorage.

See Figure 01 and Figure 02.

A different situation is with block and bucket foundations with rough bucket sides. In this case, you can activate the design of the lap length of bucket reinforcement in Details.

• ### For the settlement calculation with the RF-SOILIN add-on module, the weight gamma and the specific gravity gamma, sat are interrogated for a certain soil. What do I need the value gamma, sat for, and how does it fit into the calculation?

FAQ 003422 EN

The value $\gamma,_{sat}$ corresponds to the weight of the saturated soil and can be adjusted, if necessary, in the material parameter settings. If there is groundwater in a layer, the weight of the saturated soil $\gamma,_{sat}$ is automatically reduced from this layer by the weight of groundwater (10kN/m³). Above this layer, the stresses are calculated with the specific weight of the soil.
• ### Can I only apply an impact load to the bucket instead of the entire foundation?

FAQ 003352 EN

First, the impact load if defined as a load case in RFEM or RSTAB. This load case is then considered in a load or result combination, for which the support forces are determined.

In the design, RF‑/FOUNDATION Pro always uses the support forces from RFEM or RSTAB. This applies for all designs and cannot be controlled separately.

It is only possible to completely deactivate a certain support force for the designs.

If you do not want to consider a load for geotechnical designs, for example, because the foundation is otherwise constructively stabilized with regard to the impact load, it is possible to deactivate the load in the setting shown in the figure.

However, if it is necessary to consider the impact load for bending design (for example, design of bucket walls), you should copy the design case and include the impact load again.

The foundation evaluation would then be performed using two design cases in the module.

• ### How can I change the Standard / National Annex set for the design in add-on modules?

FAQ 003312 EN

You can usually set the standard and the National Annex in the top right corner of an add‑on module (see Figure 01). In most cases, it is also possible to display the factors of the National Annex and edit them, if necessary (see Figure 02).
• ### How can I apply the standard case tables for the soil contact stress analysis in RF‑/FOUNDATION Pro?

FAQ 003299 EN

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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