A : Gross cross-sectional area of member
Aeff : Effective area
Ncr : the elastic critical force for the relevant buckling mode
E : Modulus of Elastisity,
fy : Specified minimum yield stress of the type of steel being used,
K : Effective length factor
L: Laterally unbraced length of the member
Lcr : the buckling length in the buckling plane considered
i: Radius of gyration
Flexural Buckling Limit State
The buckling deformations (deflections) all lie in one of the principal planes of cross section. No twisting of the cross section occurs for flexural buckling.
The limit state of flexural buckling is applicable for axially loaded columns with, doubly symmetric sections such as bars, HSS and round HSS, and I-shapes and singly symmetric sections, such as T- and U-shapes. Flexural buckling is the simplest type of buckling.
There are two different equations depending on classification of cross sections. Eq. 6.47 is for class 1,2, and 3 and Eq. 6.48 is for class 4. The non-dimensional slenderness of flexural buckling is determined according to Eq. 6.50 and Eq. 6.51.
for Class 1,2 and 3 cross-sections
for Class 4 cross-sections
For the calculation of reduction factor, the imperfection factor should be determined depending on buckling curve according to Table 6.1. There are five different buckling curve in EN 1993-1-1 Figure 6.4. To select buckling curve of the cross section is determined according to Table 6.2.