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• ### How is the support spring calculated for a wall?

The support spring is determined from the modulus of elasticity (E), the cross-sectional area of the wall (A) and the height of the wall (H) as follows:

Since the display of the spring for the linear meter is displayed, the unit kN/m² results, see Figure.

• ### What should be considered when using a failure of columns under tension in the RF‑/DYNAM Pro - Equivalent Loads add-on module?

In order to consider the failure of certain members when using RF‑/DYNAM Pro - Equivalent Loads, proceed as follows:

1) Deactivating the corresponding members for the eigenvalue determination within the corresponding load case, see Image 01 (add-on module, tab Natural Vibration Cases, Calculation Parameters) and Image 02 (main program, Calculation Parameters, Deactivate and select).

2) Determining dynamic load cases from RF‑/DYNAM Pro by using the calculation, then deactivating the corresponding member in the main program within the global calculation parameters of the dynamic load cases, see Image 03.

• ### How can I teach the program to automatically increase the longitudinal reinforcement when calculating the deflection of slabs in order to meet the preset deflection?

The automatic increment of a reinforcement for the deformation analysis is not possible. As soon as the deformation calculation is based on the stiffness determination, it is not constructive to develop an algorithm that, for example, increases the reinforcement at the point of the maximum deformation. Such a procedure would not result in the deformation being reduced.

Therefore, the reinforcement must be increased manually.

• ### I calculate the deformations at time 0 and at time infinite. The deformations at the time infinite seem plausible to me. The deformations at time 0 seem significantly smaller and therefore implausible. What is the reason?

Please check if the structure tears due to pure load. It is possible that the increase in deformations is mainly caused by creep and shrinkage, which are not active at time 0. In the nonlinear calculation, shrinkage is considered as a strain load, which can cause additional stresses.
• ### A rigid member should only be able to absorb tensile forces or only compressive forces. What are the options for considering these nonlinearities in the calculation?

There are two options for defining the failure:

1. Assignment of member nonlinearity
For the member types "Beam" and "Rigid", you can define a member nonlinearity for each member. You can find the corresponding option in the "Settings" tab (see Figure 01).

2. Assignment of nonlinear member hinges
Alternatively, you can define a member end hinge with failure criterion for the member. For the desired degree of freedom, you can assign the hinge condition with nonlinearity accordingly (see Figure 02).
• ### Does a user-defined layer composition in RF-LAMINATE need to be shared separately with other users along with the RFEM model file or is this information stored directly in the RFEM file?

The material file needs to be saved separately within RF-LAMINATE and then shared with another user if they would like to access the user-defined compositions or custom layups. The additional user will then need to open the .jyr file that was shared within RF-LAMINATE directly.

• ### In a 3D model consisting of three identical floors, I applied a unit load of 1 kN/m² to the top slab to determine the spring stiffness of the supports for 2D modeling of the slabs from normal forces and deformations of the columns. Despite the deactivation of the self-weight of the structure, there is a redistribution of the column normal forces by storey. Is it possible to deactivate this effect?

This effect is most likely caused by the bending, torsional and shear stiffness of the slabs and can be avoided by modifying the stiffnesses mentioned.

To modify stiffnesses, go to the "Modify Stiffness" tab in the "Edit Surface" dialog box, see Figure.

• ### For the directions and forces, there are four options under the "Grouped" selection box to smooth the internal forces. Which grouping should I select here?

The "Grouped" determination of internal forces is divided into four subcommands.

1. u with my,mxy,vy,ny,nxy
2. v with mx,mxy,vx,nx,nxy
3. u with mx,mxy,vx,nx,nxy
4. v with my,mxy,vy,ny,nxy

The effect of these commands is explained using a simple example.

Structure:

• Plate as a deep beam
• Span 9 m
• Beam height 1.5 m
• Concentrated load 20 kN in the middle of the span
• FE mesh size 10 cm
Image 01 shows the maximum and the minimum internal forces at the load application point unsmoothed. Obviously, these internal forces are singular results. You can find detailed information about singularities in Technical Article 001503.

In order to completely include at least two FE elements for each side of the load introduction using the average region, an average region of 50/50 cm is defined (Image 02).

The following table shows the change of smoothing separately for each grouping. For this, the drawn upper region of the load application is only considered. Grouping 0 stands for the unsmoothed internal forces in this case.

01234
nx 74.9 kN/m74.9 kN/m47.2 kN/m51.8 kN/m74.9 kN/m
ny109.0 kN/m26.5 kN/m109.0 kN/m109.0 kN/m5.8 kN/m
nxy75.1 kN/m30.7 kN/m15.8 kN/m30.7 kN/m15.8 kN/m

The table shows that a combination of Grouping 1 and Grouping 2 as well as Grouping 3 and Grouping 4 is always reasonable in relation to the axial forces.

Image 03 shows the averaged internal forces for Groups 1/2 and 3/4 together.

The following values are used for the combinations:

1/23/41/2 and 3/4
nx47.2 kN/m51.8 kN/m47.1 kN/m
ny26.5 kN/m  5.8 kN/m 5.3 kN/m
nxy12.9 kN/m12.9 kN/m12.9 kN/m

As already mentioned, the combinations 1/2 and 3/4 use the minimum average internal forces of the respective grouping. The shear force nxy is calculated from the forces in the normal direction and is therefore already displayed as "smeared shear force" for the combination 1/2 and 3/4.

Conclusion

For a material with pronounced stiffness and strength directions, such as reinforced concrete or cross-laminated timber, the orientation of the strengths is relevant for the selection of the correct grouping. In the combination of group 1/2, the internal forces are smoothed in the longitudinal direction of the structural component, in group 3/4 in the transverse direction. If the structural component is oriented in the longitudinal direction as shown in Figure 4, the smoothing in the longitudinal direction is therefore recommended. However, the type of load application and the governing design are also important here. All groupings can be used for an isotropic material as well as for a governing shear force design.
• ### Are the Dlubal Software programs suitable for the analysis and design of hydraulic steel structures?

Hydraulic steel structures, such as sluices, locks and lock chambers, roller water gates, sliding and sector gates, weir flaps, drum gates, flood protection gates, ship lifts, canal bridges, are highly sophisticated structures. RFEM provides the possibility for structural design as well as static and dynamic analysis of such complex structures with surface and solid elements.

#### Available Programs and Add-on Modules

• RFEM is the main program where structures, materials, and actions are defined. Planar and spatial plate, slab, shell, and member structures are possible.
• RF‑STEEL allows you to perform general stress analysis.

#### Other Add-on Modules for Steel Structures

For the analysis and design, the add-on modules for concrete structures are also available.

#### Data Exchange and BIM

Various interfaces allow for efficient work in exchange with other project participants. In this way, you can also cooperate smoothly in BIM processes.

#### Dynamic Analysis

If it is necessary to perform seismic analysis or vibration designs, the RF‑/DYNAM Pro add-on modules provide special tools for determining natural frequencies and mode shapes, an analysis of forced vibrations, a generation of equivalent loads, or for a nonlinear time history analysis.

If you have any question about the Dlubal Software programs, please do not hesitate to contact our sales department.

• ### How do I display the nodal displacements graphically?

To display the nodal displacements graphically, the setting "Nodal Displacement" in the Display Tab under Results - Deformations - Members - Nodal Displacements must be activated.

Under the Results tab, turn on Global Deformations. Then the nodes can then be highlighted and isolated by using the "Views By Selected Objects" for a better view of the nodes and displacements.

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If not, contact us via our free e-mail, chat, or forum support, or send us your question via the online form.

#### 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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