Aluminium Design and Construction John Dwight

When the method of surface preparation does not follow the standard
procedure, should be based on tests, which may be carried out in
accordance with BS.4604: Part 1. The resulting -value may be lower or
higher than 0.33, depending on the procedure used.
11.2.7 Serviceability factor
British Standard BS.8118 is confusing as to the value to be used for the
serviceability factor � s in equation (11.8). When the slip-factor is taken
as 0.33, based on the standard surface preparation, alternative values
� s =1.2 and 1.33 are given and it is not clear which to use when. On the
other hand, when is found from tests, BS.8118 permits � s =1.1. An
appropriate value would lie in the range 1.1–1.2. The value of 1.33
seems too high.
11.3 WELDED JOINTS
11.3.1 General description
In this section, we consider the static strength (ultimate limit state) of
aluminium welds made by the MIG or TIG process. There are two
essential differences from steel: firstly, the weld metal is often much
weaker than the parent metal; and, secondly, failure may occur in the
heat-affected zone (HAZ) rather than in the weld itself. The weld metal
can be stronger or weaker than the HAZ material, depending on the
parent/filler combination. It tends to be less ductile and better joint
ductility is obtained when failure occurs in the HAZ. Refer to Chapter
6 for data on HAZ softening.
The various action-effects that a weld may be required to transmit,
possibly occuring in combination, are as follows (Figure 11.4):
(a) transverse force acting perpendicular to the axis of the weld;
(b) longitudinal force acting parallel to the weld axis;
(c) axial moment acting about the weld axis.
Figure 11.4 Action-effects at a weld.
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