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Answer
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:
I_{z} or I_{y}:second moment of area in relation to the axis z or y S_{z} or S_{y}: first moment of area in relation to the axis z or y t*: effective element thickness for shear transfer A*:
surface area based on effective shear thickness t*
The effective element thickness for shear transfer t* has a significant influence on the shear area. Therefore, the defined effective element thickness for shear transfer t* (Figure 1) of the elements should be checked.

Answer
With the FE mesh refinement, it is also possible to create an aligned FE mesh in the program. Thus, the automatic FE mesh generator can be controlled to a certain extent. However, it is not possible to use it for setting of a specified mesh geometry. 
Answer
In the 'c/tParts and Effective CrossSection' tab of the 'Calculation Parameters' dialog box, you can define settings for the automatic creation of c/tParts.
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/tPart. Stiffeners (longitudinal ribs, slopes (lips), or bulges, etc.) are not recognized by the program during the automatic generation of the c/tParts. The c/tParts have to be adjusted manually. The changes can be made in Table '1.7 CrossSection Parts for Classification' or in the 'Edit c/tPart' dialog box.
The check box with the reference to Element is 'significant' controls whether a curved element is considered as a c/tPart. 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. Arcs are normally 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 connecting line (start/end node) to element length is higher than the specified value. 
Answer
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.

Answer
RSTAB is a pure framework program and only determines internal forces, deformations, and support reactions.
Stresses are variable depending of the crosssection and are calculated on the stress points of a crosssection. This stress determination is performed in the RF/STEEL Addon Module by calculating existing stresses and comparing them with the limit stresses. 
Answer
This kind of result may occur if the limit internal forces of the crosssection can not be determined. In most cases, the problem consist in a wrongly defined crosssection or in the selection of an unsupported crosssection. Please check if you have selected a crosssection allowable for the aluminum structure in the addon module. These include rolled crosssections and parametric thinwalled crosssections.The crosssection HK 120/40/5/5/5/5 shown in Figure 01 is not an allowable crosssection because it has been selected from the range of solid crosssections (concrete components).
In this case, you have to change the crosssection 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 crosssections. A material that is only allowed up to t=3 mm can not be used for a crosssection with t=5 mm. 
Answer
The crosssection class is defined according to EN 199311 and EN 199911 by the maximum width/width ratio c/t or b/t of the crosssection parts subjected to compression. EN 199311 or EN 199911 only list different straight c/t or b/t parts. Therefore, a classification and a determination of the effective widths is not carried out for curved c/t or b/t sections.

Answer
This behavior is caused by the detail settings in the RF/STEEL addon module. The results of result combinations can be used in many different ways.
To use the same maximum internal forces for stress analysis, the settings should be made according to Figure 01.However, this setting is very conservative because not all maximum internal forces can occur at the same time. 
Answer
By default, the compute core of the crosssection program SHAPETHIN is used in the RF/ALUMINUM addon module to determine the stresses of the effective crosssection in an iterative procedure. This method is precise because all vertices and edges of the crosssection are considered, but can be very timeconsuming for complex sections.Alternatively, it is possible to determine the effective crosssection by means of a simplified analytical method (see Figure 01) that runs much faster. Using that approach, corners, roundings, etc. are neglected and subsequently compensated by a factor. No iterative calculation is performed. Therefore, the effective crosssection values may be higher than with the SHAPETHIN calculation.In such a case, it is recommended to carry out the calculation with the analytical method and then to design only the governing structural component with the governing load combination by means of the SHAPETHIN solution. 
Answer
The RF / ELPL addon module is designed only for the elasticplastic design of steel crosssections. As a result, you can only calculate materials from the "Steel" category in the addon module.
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