2. Local buckling under normal stresses due to N or M

The local buckling referred to here is illustrated in [ C 2 551 , figure 35]. It occurs as a result of the normal stresses generated by the normal force N or the bending moment M in the walls making up the beam section. As with all shape instability problems, there is a critical stress above which buckling occurs. This critical stress depends on the wall width/thickness ratio b/t, which can be likened to slenderness.

EC 3-DAN provides slenderness criteria for classifying cross-sections (see [ C 2 550 – tables 13 to 17]). For Class 1, 2 and 3 cross-sections, the risk of local buckling does not govern the design, i.e. the critical buckling stress for these cross-sections is well above the material's...