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FAQ 003612 | For cross-section design of a flat steel, I obtain abnormally high shear stresses due to the torsion in the STEEL EC3 add-on module, which can be disproved by a simple manual calculation. What is the error?
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For cross-section design of a flat steel, I obtain abnormally high shear stresses due to the torsion in the STEEL EC3 add-on module, which can be disproved by a simple manual calculation. What is the error?Answer
Most likely, the error is in the selection of the cross-section:
For steel design, a thin-walled flat bar cross-section should be selected instead of a rectangular solid cross-section, see Figure 01.
The reason for the high shear stress of a solid cross-section is caused by the existing stress points of the cross-section or by the corresponding thickness of this stress point.
In the case of a thin-walled flat bar cross-section, there are four stress points at the corner points of the cross-section with the corresponding thickness t = 10 mm, see Figure 02.
Figure 02 - Stress Points of Flat Bar
For a solid cross-section, however, there is another stress point in the center, where the maximum of height h or width b is assumed as the thickness t for this cross-section type. In this case, the width b is 200 mm, see Figure 03.
Figure 03 - Stress Points of Solid Cross-Section
This results in a small torsional section modulus Wt and the correspondingly high shear stress.
The solution is, as described above, to select a flat bar in the main program.
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Dlubal FAQ Implausible Result Shear stress Torsion Frequently Asked Question FAQ about Dlubal Question and Answer about Dlubal
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General method for stability designs according to EN 1993-1-1 and buckling in the main bearing plane
In EN 1993-1-1, the General Method was introduced as a design format for stability designs, which can be used for planar systems with any boundary conditions and variable structural height.
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.
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