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Steel Designers' Manual - 6th Edition (2003)
696 Welds and design for welding
Full-penetration butt welds are best made with one of several types of weld
backing, some of which are shown in Fig. 24.6. The backing allows the welder to use
sufficient heat to ensure penetration through the full thickness of the members
being joined. Backing can often be provided by an adjacent member, especially in
corner welds.
H
(a) (b)
(c)
(d)
Fig. 24.6 Full penetration in butt welds is best achieved with root backing such as with
closely fitting steel strips attached by fillet welds at the back (a), or within the
groove (b), by a copper bar (c), or by ceramic tiles (d) and (e).
24.3.4 Consultation with fabricators
Even though steelwork contractors hold designers to be responsible for many
welding problems, welding staff are reluctant (and often not qualified professionally)
to recommend improvements. On the other hand, designers cannot be expected
to be familiar with all welding innovations, nor the capabilities of individual welding
shops and their personnel. The best way to ensure efficient welding details is for
designers to initiate genuine dialogue with fabricators and to consider suggestions
for alternative approaches to welding.
24.3.5 Summary of recommendations
The items discussed above can be summarized as follows:
• minimum number of welds and fewest different weld types
• minimum cost welds (i.e. fillets rather than butts)
• full penetration welds only where the following show them to be essential:
(a) partial penetration throat area is insufficient to support the stresses,
(b) for a one-sided weld the loading might open the root of the weld,