Aluminium Design and Construction John Dwight

where p a =limiting stress for unwelded parent metal, and k z1 = softening
factor (Section 6.4.1).
For the non-heat-treatable alloys it is found from:
p f =0.5(f oo +f uo ) (11.18b)
where f oo and f uo are the proof and ultimate of the parent metal in the
annealed condition. Values of p f thus obtained are listed in Table 5.4.
The width of failure plane h should normally be based on the nominal
weld size (Figure 11.7), ignoring any penetration into the preparation
at a butt or at the root of a fillet, unless this has been clearly specified.
As before, the factor � is a function of the angle � between the line
of action of the transmitted force and the assumed failure plane (Figure
11.8 b). It may be read from Figure 11.9 or calculated from equation
(11.16). For a weld under longitudinal loading, we again have �=0 and
�=0.58.
11.3.6 Welded joints carrying axial moment
A welded joint required to transmit moment about its longitudinal axis
should be of one or other of the forms shown in Figure 11.10: (a) containing
two parallel welds; or (b) full penetration butt-weld.
With (a), the two welds in the joint are effectively subjected to equal
and opposite transverse forces as shown, and can be designed accordingly.
With (b), the basic requirement to be satisfied at any position along the
weld is that:
(11.19)
where M – =moment transmitted per unit length of weld when factored
loading acts on the structure, M – c =calculated moment resistance per unit
length of weld, and � m =material factor.
Here M – c should be taken as the lesser of two values determined as
follows, corresponding to an elastic stress pattern:
Figure 11.10 Welded joints transmitting axial moment.
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