FAQ 000418 EN

1 December 2017

Robert Vogl Calculation SHAPE-THIN

I have only defined one element. If I swap the long and short side (that is, the thickness becomes the length), the St. Venant torsion constant is, in my opinion, calculated incorrectly. [*T28672502*] [*T28672504*]

Answer

SHAPE-THIN is (as the program name suggests) a program for designing thin-walled cross-sections. Cross-section properties are determined according to the theory of thin-walled sections. Strictly speaking, this theory only applies if the width-to-length ratio is below approximately 1/10.

SHAPE-THIN determines the torsional constant according to the expression shown in Figure 01. The element thickness t* is included with the third power, explaining the differences for swapped thicknesses.

These It,St.Ven. results obtained with a very great element thickness are therefore useless and also should be evaluated accordingly after the transfer to RFEM/RSTAB.

Thus, you should confirm the query appearing before SHAPE-THIN shows a incorrectly modelled element (see Figure 02).

Keywords

torsion moment of inertia Saint Venant element thickness moment of torsional rigidity thin-walled cross-section theory cross-section properties

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Cross-Sections Thin-Walled
SHAPE-THIN 8.xx

Cross-Section Properties Software

Section properties, stress analysis, and plastic design of open and closed thin-walled cross-sections

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