RAM Frame calculates the lateral torsional buckling capacity based on the Draft Amendments to BS5950 Structural Use of Steelwork in Building. Part 1:1990, Dated April 20^th 1998. In these proposed amendments the calculation of an equivalent uniform moment factor (mLT) has superceded the calculation of the slenderness factor n and the old equivalent uniform moment factor (m). The calculated value of mLT is provided on all detail output. Any section in which the lateral torsional buckling capacity is larger than the section bending capacity (without LTB) is designed without considering lateral torsional buckling.

For all sections of class 3 the capacity of the section is considered to be the compression flange section modulus multiplied by the design yield strength.

CHS and double angles subject to high shear (Fv > 0.6Pv) will be assigned a small nominal capacity. The shear area required to determine the plastic modulus of the web of an unsymmetrical I-section, when subject to high shear, does not include the thickness of the flanges.