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Frequently Asked Questions (FAQ)
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AnswerThe reason is that there is no stability analysis for unsymmetrical, open cross-sections according to EN 1999-1-1 when the compressive normal forces and the bending moments are effective.You can neglect the bending moments in Details in the Stability tab by selecting a filter. Then, the flexural buckling design is performed without moments. However, this is under your own responsibility. An alternative is to use a stability check according to the second-order analysis, which would be possible by means of the RF-/FE-LTB add-on module.
If you need to define different types of lateral intermediate supports, you need 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.
AnswerThis kind of result may occur if the limit internal forces of the cross-section can not be determined. In most cases, the problem consist in a wrongly defined cross-section or in the selection of an unsupported cross-section. Please check if you have selected a cross-section allowable for the aluminum structure in the add-on module. These include rolled cross-sections and parametric thin-walled cross-sections.The cross-section HK 120/40/5/5/5/5 shown in Figure 01 is not an allowable cross-section because it has been selected from the range of solid cross-sections (concrete components).
In this case, you have to change the cross-section to TO 120/40/5/5/5/5.When designing in the RF-/ALUMINUM, please note that it is necessary to select a material which also involves thicknesses used for the cross-sections. A material that is only allowed up to t=3 mm can not be used for a cross-section with t=5 mm.
AnswerBy default, the computation kernel of the cross-section program SHAPE‑THIN is used in the RF‑/ALUMINUM add‑on module to determine the stresses of the effective cross-section in an iterative procedure. This method is precise as all corners and edges of the cross-section are covered, but can be very time-consuming in the case of compound cross-sections.As an alternative, it is possible to determine the effective cross-section by using the simplified analytical method (see Figure 01), which is significantly faster. In the case of using this approach, the corners, roundings, and others, are neglected and then compensated by a factor. No iterative calculation is performed. Therefore, the effective cross-section values might be higher than with the SHAPE‑THIN calculation.In such a case, it is recommended to carry out the calculation using the analytical method and then to only design the governing structural component with the governing load combination by using the SHAPE‑THIN solution.
With the COM interface, you can access most operating elements as well as results of the following programs or add-on modules:
- RF-/STEEL EC3
- RF-/TIMBER Pro
- RF-/DYNAM Pro
Unfortunately not. Intermediate supports and nodal supports have to be set manually. The default configuration for effective lengths is 1,0*member length and for set of members, one nodal support with definition u_y' and phi_x' is defined on each side of the set of member.To speed up the process of defining nodal supports, you can pick more nodes in one step by using the highlighted function in the attached picture.
In the general data, the sets of members must be selected first in order to be able to design them for the corresponding limit states (see Figure 1). Then, you can enter different specifications for the serviceability limit state design in the serviceability data (see Figure 2).
AnswerIn the printout report selection, you can find filter options, for example, to display only the maximum design by member in the table. These filters considerably reduce the extent. The filter options are also available directly in the module.
AnswerThe DUENQ cross-section consists of several non-contiguous partial cross-sections, so that in DUENQ it is calculated according to the theory of stiffening systems. DUENQ also gives a hint before the calculation. The dimensioning of such cross sections is not possible in add-on modules such as RF / STEEL EC3, RF / ALUMINUM etc.In most cases, however, the cross-sectional parts should be connected to each other. The FAQ describes how this connection can be modeled.
AnswerAll effective length factors are preset to 1.0 by default. There is no calculation of the factors based on the model.
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