Aluminium Design and Construction John Dwight

Figure 9.18 Axial load with biaxial moment.
combination of P and M being considered.The relevant checks (E–G)
are given below (refer to Table 9.5). P, M and M – and the sign convention
are the same as in Section 9.7.4.
Check E: Localized failure of the cross-section
(9.23)
where: P c =value found as in Section 9.3 based on p a
M cx , M cy =resistance of cross-section to bending about xx and yy,
reduced to allow for shear.
Check F: General yielding along the length
where: P c =value found as in Section 9.4 based on p o
M cx , M cy =as for check A, but with no reduction for shear.
Check G: Overall buckling
(9.24)
(9.25)
where: M – cpx =permissible value of M– acting about Gx taken as the lower
of the values given by (9.20) and (9.21)
M – cpy =permissible value of M– acting about Gy given by (9.20).
The above interaction formulae may also be applied to a skew-symmetric
section, if x and y are changed to u, v.
9.7.7 Alternative treatment (P+biaxial M)
The checks E and F sometimes prove unduly pessimistic, in which case
better economy may be obtained by using alternative procedures as follows:
Copyright 1999 by Taylor & Francis Group. All Rights Reserved.