Aluminium Design and Construction John Dwight

Figure 11.6 Fillet welded joint under eccentric load.
length of the joint. Components P – 1 and P– 2 are then combined vectorially
to produce P – , and hence the required components P – t (transverse) and
P – 1 (longitudinal).
11.3.4 Calculated resistance, weld-metal failure
The calculated resistance P – c per unit length of weld to either transverse
or longitudinal loading on its own (Figure 11.4(a), (b)), based on weldmetal
failure, may be found from:
P – c =kagpw where: pw =limiting stress for weld metal,
g=weld throat dimension,
a=factor governed by weld geometry,
k=1.0 for butts or 0.85 for fillets.
(11.15)
The limiting stress p w depends on the choice of filler, and Table 11.6
lists the p w -values given by BS.8118. If the filler alloy is not known at
the design stage, the lowest listed value of p w should be taken for the
parent alloy concerned, corresponding to the weakest filler. When a
stronger filler is used, there may be a greater risk of cracking and hence
a need for tighter control in fabrication. This might for example apply
when a 5183 filler (Al-Mg) is used for joining 6082 plates, with a 15%
strength increase compared to one of the more tolerant 4xxx–type fillers
(Al-Si). For a weld between dissimilar parent metals, the lower of the
listed values for p w should be taken.
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