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FAQ 004597 | When selecting the elements for a stiffener of a stiffened panel, I get a message saying that at least one of the selected elements is a null element. What should I do?
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Question
When selecting the elements for a stiffener of a stiffened panel, I get a message saying that at least one of the selected elements is a null element. What should I do?Answer
Stiffeners may only contain the elements with a thickness t > 0 mm. If you select null elements (thickness t = 0 mm), the message shown in Figure 01 appears. It is necessary to replace the null elements by the elements with a thickness t > 0 mm.
Figure 01 - Error Message "At least one of the selected elements is a null element."
The stiffener shown in Figure 2 includes Element 8 and Element 3. However, Element 3 has a thickness t = 0 mm, so the message in Figure 01 is displayed. For Element 3, define a thickness t > 0 mm. As an alternative, you can delete Element 3 and connect Element 8 directly to the panel. This is also shown in the video.
Keywords
Dlubal FAQ Longitudinally stiffened Longitudinal stiffener Stiffener Panel Sheet metal panel Null element Frequently Asked Question FAQ about Dlubal Question and Answer about Dlubal
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Manual adjustment of the buckling curve according to EN 1993-1-1
The RF-/STEEL EC3 add-on module automatically transfers the buckling line to be used for the flexural buckling analysis for a cross-section from the cross-section properties. In particular for general cross -sections, but also for special cases, the assignment of the buckling line can be adjusted manually in the module input.
SHAPE-THIN | Cold-Formed Sections
SHAPE-THIN determines the effective cross-sections according to EN 1993-1-3 and EN 1993-1-5 for cold-formed sections. You can optionally check the geometric conditions for the applicability of the standard specified in EN 1993‑1‑3, Section 5.2.
The effects of local plate buckling are considered according to the method of reduced widths and the possible buckling of stiffeners (instability) is considered for stiffened sections according to EN 1993-1-3, Section 5.5.
As an option, you can perform an iterative calculation to optimize the effective cross-section.
You can display the effective cross-sections graphically.
Read more about designing cold-formed sections with SHAPE-THIN and RF-/STEEL Cold-Formed Sections in this technical article: Design of a Thin-Walled, Cold-Formed C-Section According to EN 1993-1-3.
- When calculating a longitudinally stiffened panel, I get a message saying that the stiffener cannot be at the end of the panel. What should I do?
- When calculating a buckling panel, I get a message saying that some elements are connected to the panel, but they are not defined as stiffeners. What should I do?
- When calculating a stiffened panel, I get the message that the boundary c/t-zone of the panel is not supported. What should I do?
- When selecting the elements for a stiffener of a stiffened panel, I get a message saying that at least one of the selected elements is a null element. What should I do?
- During the calculation, I get a warning that some elements are connected to the buckling panel, but are not defined as stiffeners (Figure 1). What should I do?
- Why do I get high differences when designing a longitudinally stiffened buckling panel compared to the German and Austrian National Annexes?
- How can I perform the stability analysis for an edgewise supported flat steel, for example 100/5, in RF-/STEEL EC3? Although the cross-section is rotated by 90 ° in RFEM/RSTAB, it is displayed lying flat in RF-/STEEL EC3.
- How can I create a curved or curved section?
- How are the signs to be interpreted for the release results of the line release and line hinges?
- How are hot -dip galvanized components considered for fire protection in the Steel EC 3 add -on module?
