Steel Designers Manual - TheBestFriend.org

This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007
To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/
Steel Designers' Manual - 6th Edition (2003)
686 Welds and design for welding
24.1.2 Stiffness
Welded construction allows a designer to introduce stiffness and strength where
required, in the most discreet and/or the most structurally efficient manner. The
transfer of load and the stiffness can, with welding, be introduced in a gradual
continuous manner, instead of in step changes through bolted pieces.
24.1.3 Weight, volume and size
Bolting requires the use of lap joints, which add weight to a structure. For example,
the use of site welds, instead of bolted joints, to join plate girders to crossheads saved
about 50 tonnes of connection plates, bolts, and nuts in the construction of the new
Thelwall Viaduct.
In addition to savings in weight, the use of welded joints provides more usable
volume in a typical building. Bolted joints reduce usable volume significantly
because current legislation and fire engineering can demand that the fireproofing
coatings that must be applied give a minimum thickness over every protruding nut
and bolt head.
24.1.4 Durability and corrosion resistance
Total life cycle costing, including the costs of maintenance, is becoming increasingly
important in all structures. For one aspect of this, the durability, the corrosion of
structural steelwork can be retarded by three means – controlling the surrounding
environment, effective coating systems, and the use of steels (and weld metals) with
improved inherent corrosion resistance. Coating systems, however effective they are
on plate surfaces, can only with great difficulty prevent corrosion in all the crevices
of bolted joints, but the clean lines of welded structures allow the full effectiveness
of modern coatings to be demonstrated. The use of corrosion resistant (weathering)
steels (from BS EN 10155: 1993 1 ) imparts long life, and although they can be used
in bolted connections, they perform poorly in crevices and thus they work far better
in welded solutions.
24.2 Ensuring weld quality and properties by the use of standards
The flow of information required for the successful design, fabrication, and inspection
of welded buildings is shown schematically in Fig. 24.1.
Designers are responsible for the selection of joint type, weld size, weld properties,
and required quality. The choice of welding process, the details of the edge
preparation suitable for the process, and the achievement of the desired quality are
the responsibility of the steelwork contractor. A comprehensive series of standards
has been developed and harmonized across Europe to ensure that the performance