Equations 6.52 and 6.53 of SS EN 1993-1-1:2005 are to be used to calculate the non-dimensional slenderness parameter, λT, to be used for torsional and torsional-flexural buckling checks. The SS 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 SS EN 1993-1-1:2005). Therefore, the NCCI document SN001a-EN-EU: Critical axial load for torsional and flexural torsional buckling modes provides methods to calculate the Ncr,T,F and Ncr,T factors and hence will to be included in this implementation of the Singaporean NA.
The program will only consider Channel Sections and Tee- sections while working out the critical torsional and Flexural Torsional buckling loads as per Cl 126.96.36.199.
The critical axial load for torsional buckling is
iz||=||the radius of gyration about the Y-Y (weak
axis) and Z-Z (strong axis) respectively|
The critical axial load for torsional-flexural buckling
is evaluated as:
For details on these equations, refer to the NCCI document