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FAQ 003376 EN

31 July 2019

# According to which formula is the elastic critical buckling load for the torsional buckling Ncr,T calculated in RF-/STEEL EC3?

The elastic critical buckling load for torsional buckling Ncr,T is calculated as follows:

${\mathrm N}_{\mathrm{cr},\mathrm T}\;=\frac1{{\mathrm i}_{\mathrm M}^2}\;\cdot\;\left(\frac{\mathrm\pi^2\;\cdot\;\mathrm E\;\cdot\;{\mathrm I}_{\mathrm w}}{{\mathrm L}_{\mathrm T}^2}\;+\;\mathrm G\;\cdot\;{\mathrm I}_{\mathrm t}\right)$

${\mathrm i}_{\mathrm M}\;=\;\sqrt{{\mathrm i}_{\mathrm u}^2\;+\;{\mathrm i}_{\mathrm v}^2\;+\;{\mathrm u}_{\mathrm M}^2\;+\;{\mathrm v}_{\mathrm M}^2}$

with

 E Modulus of elasticity Shear modulus Iw Warping resistance It Torsion moment of inertia iu, iv Pricipial radius of gyration um, vm Shear center coordinates in the principal axis system LT Torsional buckling critical length