Cross-Section Classification According to EN 1999-1-1

Cross-Section Classification According to EN 1999-1-1

 

The classification of cross-sections is intended to determine the limits of resistance and rotational capacity due to local buckling of cross-section parts. In EN 1999‑1‑1, 6.1.4.2 (1), four classes are defined.

 

• Class 1 cross-sections are those that can form a plastic hinge with the rotation capacity required for plastic analysis without reduction of the resistance.
• Class 2 cross-sections are those that can develop plastic moment resistance, but have limited rotation capacity because of local buckling.
• Class 3 cross-sections are those in which the calculated stress in the extreme compression fiber of the aluminum member can reach its proof strength, but local buckling is liable to prevent development of the full plastic moment resistance.
• Class 4 cross-sections are those in which local buckling will occur before the attainment of proof stress in one or more parts of the cross-section.

Basic Types of Cross-Section Parts

A cross-section's classification depends on the width/thickness ratio b/t of its parts subjected to compression. According to EN 1999-1-1 [1], 6.1.4.2 (6), thin-walled parts are classified into the following basic types.

• flat outstand parts
• flat internal parts
• curved internal parts

These parts can be unreinforced, or reinforced by longitudinal stiffening ribs, edge lips, or bulbs (Image 1).

 

 

 

https://www.dlubal.com/en/support-and-learning/support/knowledge-base/001673

Cross-Section Classification According to EN 1999-1-1