#### Further Information

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• ### Is it possible to perform automatic live load reduction in RFEM or RSTAB per the ASCE, IBC, or NBCC?

Live load reduction is not considered automatically in RFEM. RFEM and RSTAB are general FEA and framework programs. The program does not understand what is a floor element vs wall element. Only a general plate element is defined. It is not possible for the program to determine the area of a floor for live load reduction.

A user must manually consider the reduction by modifying the live load magnitude directly in the load application.

• ### After dividing a column with intermediate nodes, the results in the RF‑/CONCRETE Columns add-on module are different from those before the division. What is the reason?

The reason for the different results is probably the settings of effective lengths for the stability analysis. According to the default setting, these are determined automatically in the RF‑/CONCRETE Columns add-on module. However, this method does not work for divided members, and thus no stability analysis is performed (a corresponding warning message appears).

If you have entered the effective lengths manually, this only applies to a single member. In order to perform a correct stability analysis of the column as an entire structural component, it is necessary to define it as a set of members.

• ### Why are there the intermediate results for some members exactly at the member end node in the result table of member internal forces?

New

FAQ 004343 EN

The result display of intermediate values is generally linked to the member division property. Also, member loads defined in sections in RFEM generate further intermediate results. For example, if a member load defined in sections is distributed from the member start to the member end, the intermediate results are obtained at the member end nodes.

• ### When displaying the result diagrams on a member (the "rib" type), there is the option to display the internal force VL. What is this value and how is it calculated?

The force VL is the longitudinal shear force between the top surface and the member. It is calculated as an integrated shear flow between the plate and the member at a particular point on the member.

For the simplified example provided here, the resulting cross-section values for the integration width of 10 cm are as follows:

• $I_y=\frac{b\times h^3}{12}=\frac{10 cm\times20 cm^3}{12}=6,666.67 cm^4$
• $S_y=h_1\times b\times((h-e_z)-\frac{h_2}2)=10 cm\times10 cm\times((20 cm-10 cm)-\frac{10 cm}2)=500 cm^3$
• $\tau=V_L=\frac{V_z\times S_y}{I_y\times b}=\frac{5.53 kN\times500 cm^3}{6,666.67 cm^4}=0.415 kN/cm=41.5 kN/m$
The integration width has been set to the total of 10 cm.

Values:
• Iy second moment of area
• Sy statical moment
• h1 height of the upper cross-section part
• h2 height of the lower cross-section part
• ez centroidal distance
• h total height
The values can be adjusted for a T-beam.
• ### How can I check the generated load combinations for different design situations in CRANEWAY?

In the CRANEWAY program, you can select the display of load combinations for the individual design situations in the middle of Window 1.5 Load Combinations.
• ### In RF-FOUNDATION Pro, I receive error message No. 30195. What can I do?

The error message indicates that no option was found to define the required reinforcement for the mats and rebars selected from you.
After clicking OK, you will automatically be redirected to Window 1.3. Here, please select additional mats and/or rebars and then perform the design again.
• ### In RF-CONCRETE Surfaces, I get non-designable situations with a note saying that the shear resistance cannot be checked (cross-section entirely cracked). What is the reason for this message?

A non-designable situation like this is displayed if the shear resistance without shear reinforcement VRd,c is arithmetically smaller than zero.

A VRd,c value of less than zero is caused by large tensile axial forces. In this context, the cross-section is completely under tension or completely cracked, and no shear force resistance can be created.

For coated cross-sections with planned shear reinforcement, the following situation results:
In RF-CONCRETE Surfaces, if VRd,c < 0, no further shear check is performed, and message 13) is displayed. This approach is conservative.

In this context, there was a request (194) for the interpretation of the standard, which allows the truss model to be used even with a completely cracked cross-section.

If a shear reinforcement is designed as planned, the message about the non-designable situation in the program can be ignored. In this case, it should be ensured that VEd is smaller than VRd,max and VRd,s.
• ### How to set in RF-LOAD-HISTORY whether to determine the deformations of the individual load steps separately in each load step or to add them?

New

FAQ 004317 EN

This setting can be made in the RF-LOAD-HISTORY add-on module under ‘Details’ → ‘Options’ → ‘Deformation Type’, see Figure 01.

The deformation type 'In Particular Load Step' displays the deformations of each individual load step separately, the deformation type 'On Undeformed Structure' shows the sum of all load steps.

• ### Are there any facade surfaces in RFEM for the transmission of wind loads to the main structure?

In RFEM, there are no special facade surfaces for distributing wind loads. However, you can create such a load distribution element without any influence on the resistance of the main structure using the standard tools of RFEM. To do this, proceed as follows:

1. Define the isotropic linear elastic "facade material" with the average stiffness of the adjacent elements of the main structure without the weight, thermal expansion property, and stiffness modification.

Figure 02 - Material of Facade Surfaces

2. In the facade areas, describe the surfaces made of the facade material with the "Orthotropic" stiffness type. To ensure that there is no opposed load at the surface corners transferred to the main structure, the thickness and torsional stiffness must be defined near to zero. We recommend to apply the average thickness of the adjacent elements of the main structure / 1,000 as the thickness, and to divide the related torsional stiffness k33 by the factor of 1,000 as well.

Figure 03 - Properties of Facade Surfaces

3. Define a line release between the facade surfaces and the main structure elements so that the forces perpendicular to the main structure elements can only be transferred. All other directions must be specified without any force.

Figure 04 - Possible Definition of Connection Between Facade Surfaces and Elements of Main Structure

4. To ensure that the surfaces with the line releases do not slip in the wall plane, it is necessary to apply the surface support to the facade surfaces in the plane degrees of freedom x and y.

Figure 05 - Support of Facade Surfaces

This option allows for the distribution of compression loads acting perpendicular to the facade surfaces as well as of wind pressures from the RWIND Simulation calculation to the main structure. In this case, it is necessary to use this modeling of the facade surface in connection with the linear method of analysis.

• ### When trying to calculate the design in RF-STEEL Surfaces, I receive Warning No. 1162 - Surface No. XX is of the type "Orthotropic" and cannot be designed. What does this Warning mean?

Orthotropic surfaces are non-linear and cannot be designed within the RF-STEEL Surfaces add-on module. It is possible to get a full stress analysis in RFEM for the orthotropic surfaces defined with the orthotropy type "constant thickness" and compared to limiting stresses manually. For all other orthotropy type, the program is not aware of the geometric properties for the surface at every FE mesh point which is needed to calculate stresses. An extensive and detailed FE model would need to be created. See FAQ 2468 for an example of this. Surface types need to be set to "standard" to be designed within the add-on module.

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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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