Eurocode standard: EN 1993-1-1

Section: 5.5

Cross-sections are classified in different classes (1, 2, 3, and 4). The classes are used to define how the cross-section capacity is limited due to local buckling.

Class 1 cross-section are the "strongest" section and class 4 cross-sections are those which local buckling will occur before yield stress is reached for one ore more parts of the section. For class 4 sections, the effective section should be calculated according to EN 1993-1-5 section 4.4.

Table 5.2 in EN 1993-1-1 is used to determine the cross-section class. The width/thickness of the parts of the section is used to determine the class. See one example below.

Example

Determine cross-section class of tubular section with diameter 100mm, thickness 10mm and with material S235.