За полноѕидни I носачи препорачана должина на стандарден елемент е 1,25 од h.
Standard member: 1.5 * h
Hollow section: 2 * h
[h] ... maximal cross section height
From version 21:
default length of both open and hollow sections modeled by shell elements is decreased to 1.25 × cross-section height
The only difference is for linear buckling and stiffness analyses where the length of the condensed element is 0.5 × cross-section height. The reason is to keep the buckling mode shapes in the internal plates of the connection rather than in members.
https://www.ideastatica.com/support-center/analysis-model-improvements-in-idea-statica-version-21-0
example if stiffener is added