Classifying Thin-Walled and Massive Cross-Sections
Tips & Tricks
For certain cross‑sections, it is difficult to say whether it is a thin‑walled or a massive section. If it’s not a clear-cut case, it might be helpful to look at the shear area.
The determination of the shear area of thin‑walled sections is described in the manual for RFEM (page 119) or RSTAB (page 55). For I‑sections with a thick web and slender, thin flanges, the shear area Ay can be greater than the cross‑sectional area.
For example, for a cantilever tapering in its width with the cross‑sections IS 300/40/25/20/0 (start) and IS 300/150/25/20/0 (end), a greater value is determined for the shear area than for the cross‑section area. Therefore, the determination of internal forces is no longer possible.
A massive ITS cross‑section might be the solution; the calculation of the shear area is based on the theory of Grasshof-Zuravski. If an IS cross‑section is absolutely necessary to perform an analysis according to EC 3, you can determine the shear area separately and adjust it manually.
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