D5.B.5.7 Clause 6.3.1.4 - Slenderness for torsional and torsional-flexural buckling
Equations 6.52 and 6.53 of BS EN 1993-1-1:2005 are to be used to calculate the non-dimensional slenderness λT, to be used for torsional and torsional-flexural buckling checks. BS EN 1993-1-1:2005 does not provide equations to calculate the elastic critical loads Ncr,T,F and Ncr,T (refer 6.3.14 of BS EN 1993-1-1:2005).
The NCCI document "SN001a-EN-EU: Critical axial load for torsional and flexural torsional buckling modes" provides methods to calculate the Ncr,TF and Ncr,T factors. Therefore, the program uses these methods to evaluate the elastic critical loads for the UK NA.