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

Question

Accepted 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 Image 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 should also be evaluated accordingly after the transfer to RFEM/RSTAB.Thus, you should confirm the query appearing before SHAPE‑THIN shows an incorrectly modeled element (see Image 02).

Incorrect Torsion Calculation for Reversed Element Thickness

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