3 Buckling Capacity of Other Structures

3.1 Struts, pillars and cross ties

3.1.1 Buckling utilisation factor

The buckling utilisation factor, η, for axially compressed struts, pillars and cross ties is to be taken as:

where:

σ_av : Average axial compressive stress in the member, in N/mm².

σ_E : Minimum elastic compressive buckling stress, in N/mm², according to [3.1.2] to [3.1.4].

R_{eH_S} : Specified minimum yield stress of the considered member, in N/mm². For built up members, the lowest specified minimum yield stress is to be used.

3.1.2 Elastic column buckling stress

The elastic compressive column buckling stress, σ_EC, in N/mm² of members subject to axial compression is to be taken as:

where:

I : Net moment of inertia about the weakest axis of the cross section, in cm⁴.

A : Net cross sectional area of the member, in cm².

A pillar end may be considered fixed when brackets of adequate size are fitted. Such brackets are to be supported by structural members with greater bending stiffness than the pillar.

3.1.3 Elastic torsional buckling stress

The elastic torsional buckling stress, σ_ET, in N/mm², with respect to axial compression of members is to be taken as:

where:

I_sv : Net St. Venant’s moment of inertia, in cm⁴, see Table 7 for examples of cross sections.

c_warp : Warping constant, in cm⁶, see Table 7 for examples of cross sections.

: Length of the member, in m as defined in [3.1.2].

y₀ : Transverse position of shear centre relative to the cross sectional centroid, in cm, see Table 7 for examples of cross sections.

z₀ : Vertical position of shear centre relative to the cross sectional centroid, in cm, see Table 7 for examples of cross sections.

A : Net cross sectional area, in cm², as defined in [3.1.2]

I_y : Net moment of inertia about y axis, in cm⁴.

I_z : Net moment of inertia about z axis, in cm⁴.

3.1.4 Elastic torsional/column buckling stress

For cross sections where the centroid and the shear centre do not coincide, the interaction between the torsional and column buckling mode is to be examined. The elastic torsional/column buckling stress, σ_ETF, with respect to axial compression is to be taken as:

where:

y₀ : Transverse position of shear centre relative to the cross sectional centroid, in cm, as defined in [3.1.3].

z0 : Vertical position of shear centre relative to the cross sectional centroid, in cm, as defined in [3.1.3].

A : Net cross sectional area, in cm², as defined in [3.1.2].

I_pol : Net polar moment of inertia about the shear centre of cross section, in cm⁴ as defined in [3.1.3].

σ_EC : Elastic column compressive buckling stress, as defined in [3.1.2].

σ_ET : Elastic torsional buckling stress, as defined in [3.1.3].

3.2 Corrugated bulkhead

3.2.1 The buckling utilisation factor of flange and web of corrugation of corrugated bulkheads is based on the combination of in plane stresses and shear stress.