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Steel Designers' Manual - 6th Edition (2003)
704 Welds and design for welding
times the leg length. When a fillet weld terminates at the end or edge of a plate it
should be returned continuously round the corner for a distance of twice the leg
length.
Intermittent fillet welds are laid in short lengths with gaps between. They should
not be used in fatigue situations or where capillary action could lead to the formation
of rust pockets. The effective length of each run within a length is calculated in
accordance with the general requirements for fillet welds.
24.5.3 Spacing limitations
The longitudinal spacing between effective lengths of weld along any edge of an
element should not exceed 300 mm or 16t for compression elements, where t is the
thickness of the thinner part joined.
24.6 Methods of analysis of weld groups
24.6.1 Introduction
Any weld group may be required to resist an applied load acting through the centroid
of the group either in or out of plane producing shear or tension respectively.
The load may also be applied eccentrically producing in addition bending tension
or torsional shear. Examples are given in Fig. 24.12.
24.6.2 Weld groups loaded in shear
British and Australian practice is to distribute the torsional shear due to eccentricity
elastically in proportion to the distance of each element of the weld from the
centroid of the group. This is referred to as the polar inertia method.
In some countries, notably Canada and in some cases the USA, the instantaneous
centre method, referred to in Chapter 23 for bolt groups, is also used for weld
groups.
The polar inertia method
Consider the four-sided weld group shown in Fig. 24.13(a). Assume the throat
thickness is unity.
b
I
a b
3 2 Ê ˆ
xx = + 2
12 Ë 2¯
2