#### 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.

Receive information including news, useful tips, scheduled events, special offers, and vouchers on a regular basis.

• ### I would like to calculate results such as ordinates, static moments, stresses at a specific location of the cross-section. What should I do?

If the results are to be displayed at a specific location of the cross-section, the element must be divided at this location.

An element can be divided by right-clicking the element and selecting the "Split Element" function in the shortcut menu (Figure 1).

For example, if you want to determine the stress at a distance s = 32.5 mm from the start of element 1, you have to divide element 1 at this point. This is also shown in the video.

• ### How can I calculate stresses in SHAPE-THIN?

If you want to calculate the stresses in SHAPE-THIN, create at least one load case. A new load case can be created by:

• Input in table "2.1 Load Cases"

Furthermore, internal forces must be defined. Internal forces can be entered via:

• Menu "Insert" → "Loads" → "3.1 Internal Forces" → "Dialog Box"

• Input in table "3.1 Internal Forces"

• Import of internal forces from RSTAB or RFEM in Table "3.1 Internal Forces"

After the calculation, the stresses can be displayed graphically and in tables (Figure 01). This is also shown in the video.

• ### Is it possible to use a cross-section from SHAPE‑THIN 9 in older versions of RFEM or RSTAB?

Yes, it is.
The cross-section created in SHAPE‑THIN 9 (file extension *.du9) should be opened and saved as SHAPE‑THIN 8 cross-section (file extension *.du8) in SHAPE‑THIN 8.

In order to open the cross-section in SHAPE‑THIN&nbso;8, set the file type to "All Files."

Now, you can normally save this cross-section as a SHAPE‑THIN 8 cross-section, and also open it in the previous program versions.

• ### It is not possible to design a SHAPE‑THIN cross-section due to invalid symmetry. What is the cause and how can I fix it?

RF-/ALUMINUM checks the symmetry of general cross-sections and compares them with the SHAPE-THIN evaluation if activating the "Determine symmetry by module and compare with SHAPE‑THIN definition" check box (Figure 01).

If both methods provide different results, the corresponding error message appears (Figure 02).

Usually, there are small inaccuracies in the SHAPE‑THIN cross-section. Thus, the cross-section Sec‑1.du9 shown in Figure 03 is not absolutely symmetrical to the Z‑axis: The Z‑coordinates of Node 1 and Node 4 as well as Node 55 and Node 60 do not match in the second decimal place.

SHAPE‑THIN classifies the cross-section as asymmetrical, but RF‑/ALUMINUM as monosymmetric to the z‑axis, so the error message shown in Figure 02 appears.

The SHAPE‑THIN cross-section should be checked for symmetry. When modeling in SHAPE‑THIN, it is useful to only display one side of the cross-section and to create the other half by mirroring. This is also shown in the video.

• ### How does the calculation of the moments of inertia differ when the cross-section consists of several unconnected or connected partial cross-sections?

If the cross-section consists of several unconnected partial sections, the sum of the moments of inertia is calculated without the parallel axis theorem components. The cross-section shown in Figure 01 consists of two angle sections that are not connected to each other.

The individual angle sections have the following moments of inertia:

Iy,1,2 = 180.39 cm4 (referred to the centroidal axes y, z)

Iz,1,2 = 65.05 cm4 (referred to the centroidal axes y, z)

The moments of inertia of the entire cross-section result in:

Iy,1+2 = 2 ⋅ Iy,1,2 = 2 ⋅ 180.39 = 360.78 cm4 (referred to the centroidal axes y, z)

Iz,1+2 = 2 ⋅ Iz,1,2 = 2 ⋅ 65.05 = 130.11 cm4 (referred to the centroidal axes y, z)

If the cross-section consists of several connected partial sections, the sum of the moments of inertia is calculated with the parallel axis theorem components. The cross-section shown in Figure 02 consists of two connected angle sections.

The individual angle sections have the following cross-section properties:

A1,2 = 16.25 cm²

yS,0,1,2 = ±2.30 cm (referred to the zero point)

zS,0,1,2 = 3.07 cm (referred to the zero point)

Iy,1,2 = 180.39 cm4 (referred to the centroid axes y, z)

Iz,1,2 = 65.05 cm4 (referred to the centroid axes y, z)

The cross-section properties of the entire cross-section result in:

yS,0,1+2 = 0.00 cm (referred to the zero point)

zS,0,1+2 = 3.07 cm (referred to the zero point)

Iy,1+2 = 2 ⋅ Iy,1,2 + 2 ⋅ A1,2 ⋅ (zS,0,1,2 - zS,0,1+2

Iy,1+2 = 2 ⋅ 180.39 + 2 ⋅ 16.25 ⋅ (3.07 - 3.07)² = 360.78 cm4 (referred to the centroidal axes y, z)

Iz,1+2 = 2 ⋅ Iz,1,2 + 2 ⋅ A1,2 ⋅ (yS,0,1,2 - yS,0,1+2

Iz,1+2 = 2 ⋅ 65.05 + 2 ⋅ 16.25 ⋅ (2.30 - 0.00)² = 301.46 cm4 (referred to the centroidal axes y, z)

• ### How is it possible to consider the real cross-section geometry of member elements in RWIND Simulation?

The "Simulate and Generate Wind Loads" interface application allows you to exchange member, surface, and solid elements in RFEM, and member elements in RSTAB.

To avoid too fine mesh and thus too long calculation time, the program simulates all members with a rectangular cross-section by default. In this case, the size of the rectangular cross-section is selected in such a way that it barely includes the real cross-section geometry.

By deactivating the "Export optimized member topology" option, you can avoid this additional optimization of the model and allow consideration of the real cross-section geometry within the existing cross-section settings.

If the exact display of the cross-section geometry requires more than 1,000,000 elements, the interface automatically switches to the simplified rectangular cross-section display.

• ### SHAPE‑THIN calculates a very small shear area. Why?

The shear area is calculated as follows:

${\mathrm A}_{\mathrm y}\;=\;\frac{{\mathrm I}_{\mathrm z}^2}{\int_{\mathrm A^\ast}\left({\displaystyle\frac{{\mathrm S}_{\mathrm z}}{\mathrm t^\ast}}\right)^2\operatorname d\mathrm A^\ast}$

${\mathrm A}_{\mathrm z}\;=\;\frac{{\mathrm I}_{\mathrm y}^2}{\int_{\mathrm A^\ast}\left({\displaystyle\frac{{\mathrm S}_{\mathrm y}}{\mathrm t^\ast}}\right)^2\operatorname d\mathrm A^\ast}$

where

 Iz or Iy is the second moment of area in relation to the axis z or y, Sz or Sy is the first moment of area in relation to the axis z or y, t* is the effective element thickness for the shear transfer, A* is the surface area based on the effective shear thickness t*.

The effective element thickness for the shear transfer t* has a significant influence on the shear area. Therefore, the defined effective element thickness for the shear transfer t* (Figure 01) of the elements should be checked.

• ### My aim is to mesh a circular hole plate in a mapped way. Is such a meshing possible in RFEM?

Using the FE mesh refinement, it is possible to create an aligned FE mesh in the program. The automatic FE mesh generator can thus be controlled to a certain extent. However, it is not possible to set a specified mesh geometry.
• ### How is the automatic creation of c/t-parts carried out?

In the "c/t-Parts and Effective Cross-Section" tab of the "Calculation Parameters" dialog box, you can define the settings for the automatic creation of c/t-parts.
It is also possible to specify an angle from which a support should be created between two elements. In case that the angle for connection of elements is smaller, they are considered as an interconnected c/t-part. Stiffeners (longitudinal ribs, slopes (lips), or bulges, and so on) are not recognized by the program during the automatic generation of the c/t-parts. The c/t-parts have to be adjusted manually. You can make the changes in Table "1.7 Notional Flat Widths | EN 1993‑1‑3" or in the "Edit Notional Flat Width" dialog box.
The check box for Element is "significant" controls whether a curved element is considered as a c/t-part. If the length of the arc is larger than the diameter entered here, it cannot be neglected.
A corresponding error message appears before the calculation.
The option Element ist "straight" refers to curved elements. The arcs are usually excluded from the determination of the effective widths because the standards do not provide clear specifications. A curved element is assumed to be straight if the ratio of the connecting line (start/end node) to the element length is higher than the specified value.
• ### I need to define different types of lateral intermediate restrains for a single element in RF-/STEEL EC3. Is this possible?

If you need to define different types of lateral intermediate supports, it is necessary to divide the specific member. After that, you can create a set of member and with that done, you can easily define different types of intermediate supports along this set of member, or you can use different nodal supports in the nodes of the set of member.

1 - 10 of 16

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.

#### Your support is by far the best

“Thank you for the valuable information.

I would like to pay a compliment to your support team. I am always impressed how quickly and professionally the questions are answered. I have used a lot of software with a support contract in the field of structural analysis, but your support is by far the best. ”