Aluminium Design and Construction John Dwight

(through the centroid) for ß S . For convenience, the neutral axis may
be based on the gross section when classifying the section. But when
subsequently calculating the section properties, an effective section
must be taken.
7.3.3 Slender internal elements under strain gradient
For a slender element under strain-gradient it is logical to assume that
the stress blocks comprising its effective section are unequal. The block
at edge 2 should be made wider than that at edge 1, thus reflecting the
asymmetry of the buckled form. In our method, the two block-widths
are found as follows (Figure 7.11).
=�
(a) Inclined flange element (1>�>0)
be1 1 +�t (7.11a)
be2 =(1.4-0.4�)be1 (7.11b)
where � 1 is found from equation (7.5), or Figure 7.6, still taking �=ß/�.
(b) Web element (�