Lateral torsional buckling

The factor used for lateral buckling k_crit will be used in the analysis if the lateral torsional buckling is taken into consideration. This factor is calculated in accordance with chapter 6.3.3. of EN 1995-1-1:

The relative slenderness for bending is calculated using this formula

where is:	*λ_rel,m*	Relative slenderness for bending
	*f_m,k*	Characteristic bending strength
	σ_m,crit	Critical bending stress

The critical bending stress is calculated using formula

where is:	*E_0,05*	Fifth percentile value of modulus of elasticity
	*G_0,05*	Fifth percentile value of shear modulus
	*I_z*	Second moment of area about the weak axis z
	*I_tor*	Torsional moment of inertia
	*l_ef*	Effective length
	*W_y*	Section modulus about axis y

The critical bending stress for softwood with solid rectangular cross-section is calulated in accordance with (6.32)

where is:	*σ_m,crit*	Critical bending stress
	b	Width of the member
	h	Depth of the member
	*l_ef*	Effective length
	*E_0,05*	Fifth percentile value of modulus of elasticity

The factor used for lateral buckling k_crit is equal to 1.0 for λ_rel,m ≤ 0,75. Following formula is used for the range 0,75 < λ_rel,m ≤ 1,4

Following formula is used for λ_rel,m > 1,4

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