Page 262 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

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CRITERIA FOR BUILDING DESIGN

5.42 CHAPTER FIVE

TABLE 5.6 Minimum Size of Fillet Welds
Material thickness of thinner Minimum size of fillet
part joined, in (mm) weld,* in (mm)
1
To / 4 (6) inclusive 1 / 8 (3)
1
1
Over / 4 (6) to / 2 (13) 3 / 16 (5)
Over / 2 (13) to / 4 (19) 1 / 4 (6)
1
3
3
Over / 4 (19) 5 / 16 (8)
*Leg dimension of fillet welds. Single-pass welds must be used.
Source: “Specification for Structural Steel Buildings,” American
Institute of Steel Construction, Chicago, Ill., 2005, with permission.
The minimum effective length of fillet welds designed on the basis of strength is four times the
nominal size. Otherwise, the weld size must be taken as no more than one-quarter of the effective
length of the weld. If longitudinal fillet welds are used alone in end connections of flat-bar tension
members, the length of each fillet weld must be not less than the perpendicular distance between them.
For end-loaded fillet welds with a length up to 100 times the leg dimension, the effective length
may be taken as the actual length. When the length of an end-loaded fillet weld exceeds 100 times
the weld size, the effective length is determined by multiplying the actual length by the reduction
factor β:
 L 
β= 1.2 − .002 ≤1.0 (5.140)
0
 w 
where L = actual length of end-loaded weld, in (mm), and w = weld leg size, in (mm). When the
length of the weld exceeds 300 times the leg size, the value of β is taken as 0.60.
Intermittent fillet welds may be used to transfer calculated stress when the required strength is
less than that for a continuous fillet weld of the smallest permitted size, and also to join components
of built-up members. The effective length of any segment of intermittent fillet welding should be not
1
less than four times the weld size, with a minimum of 1 / 2 in (38 mm).
In lap joints, the lap must be at least five times the thickness of the thinner part joined, but not
less than 1 in (25 mm). Lap joints joining plates or bars subjected to axial stress that utilize trans-
verse fillet welds only must be fillet welded along the end of both lapped parts, except where the
deflection of the lapped parts is restrained to prevent opening of the joint under maximum loading.
Fillet welds may be stopped short or extend to the ends or sides of parts, or may be arranged in
a box configuration, subject to the following limits for fillet weld terminations given by the AISC
Specification:

For lap joints in which one connected part extends beyond an edge of another connected part that is subject
to calculated tensile stress, fillet welds shall terminate not less than the size of the weld from that edge.
For connections where flexibility of the outstanding elements is required, when end returns are used, the
length of the return shall not exceed four times the nominal size of the weld nor half the width of the part.
Fillet welds joining transverse stiffeners to plate girder webs shall end not less than four times nor
more than six times the thickness of the web from the web toe of the web-to-flange welds, except where
the ends of stiffeners are welded to the flange.
Fillet welds that occur on opposite sides of a common plane, shall be interrupted at the corner com-
mon to both welds.

Where not otherwise limited, it is considered good practice to terminate fillet welds one weld size
from the edge of the connection element, to minimize notches in the base metal.
Fillet welds may be used along the periphery of holes or slots to transmit shear in lap joints, to
prevent buckling or separation of lapped parts, and to join components of built-up members. Such
fillet welds are not considered plug or slot welds. Plug welds and slot welds may also be used for

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