Aluminium Design and Construction John Dwight

In determining A zp , an appropriate level of thermal control should be
assumed for weld X. When a member contains just two welds, both
may count as if welded under strict control, provided equation (6.7) is
satisfied and both are single-pass.
6.5.11 RD method, summary
The procedures described in Sections 6.5.4–6.5.10 are summarized below.
They enable the area and extent of the nominal HAZ (Section 6.5.2) to
be found at any given cross-section in a member, adjacent to a MIGwelded
joint.
1. Decide on the weld size w, or the modified value w1 in the case of a
small weld (Section 6.5.5), or estimate w from the plate thickness.
2. Decide on the effective level of thermal control (normal or strict)
(Section 6.2 and 6.5.10).
3. Decide whether the joint is category 1 (long straight) or category 2
(attachment weld), see Section 6.5.1.
4. Category 1 joint containing a single MIG weld. Figure 6.11 shows
assumed shape of nominal HAZ, defined by parameter s. Section
6.5.6 explains how to find s, using Table 6.2.
5. Category 1 joint containing two or more MIG welds. Obtain s as in 4
for each weld treated on its own, and then proceed as in Figure 6.15.
(Section 6.5.8).
6. Category 2 joint. Base the nominal HAZ on a value of s which is 25%
higher than that for a category 1 joint having the same weld section
geometry. See Section 6.5.9.
6.6 APPLICATION OF HAZ DATA TO DESIGN
6.6.1 Design of members
Some members are welded in such a way as to cause total softening at
a particular cross-section, as for example at the end connection of a
tubular member in a welded truss, or where transverse stiffeners are
welded to an I-beam. In such cases, the resistance of the cross-section
is simply found by making a conventional calculation, but using the
appropriate limiting stress (kzp) in place of the parent value (p).
Such a calculation would be pessimistic if applied to cross-sections
that are only partially softened, as it would leave the non-softened
material understressed. Instead, the accepted practice for these is to
take an effective section, in which HAZ softening is allowed for by notionally
removing some of the area locally around each weld. The resistance is
then based on the effective section, instead of the actual one, assuming
it to be entirely composed of full strength (unsoftened) material.
Copyright 1999 by Taylor & Francis Group. All Rights Reserved.