BS EN 1993-1-8:2005
EN 1993-1-8:2005 (E)
(2) smaller than 60° are also permitted. However, in such cases the weld should be considered to
be a partial penetration butt weld.
(3) For angles than l20° the resistance of fiUet welds should be determined by testing 111
accordance with EN 1990 Annex D: Design by testing.
(4) Fillet welds finishing at the ends or sides of parts should be returned continuously, full size, around the
corner tor a distance of at least twice the length of the weld, unless access or the configuration of
the joint renders this impracticable.
NOTE: 1n the case of intermittent welds this rule applies only to the last intermittent fillet weld at
corners.
(5) End returns should be indicated on the drawings.
(6) For eccentricity of single-sided fillet welds, see 4.12.
4.3.2.2 Intermittent fillet welds
(1) Intermittent fillet welds should not be used in corrosive conditions.
(2) In an intermittent fillet weld, the gaps (L I or L z ) between the ends of each length of \veld Lw should
fulfil the requirement in Figure 4.1.
(3) In an intermittent finet weld, the gap (LI or L 2) should be taken as the smaller of the distances between
the ends of the welds on opposite sides and the distance between the ends of the welds on the same
side.
(4) In any run of intermittent fi}]et weld there should always be a length of weld a1 each end of the part
connected.
(5) In a built-up member in which plates are connected by means of intermittent fillet welds, a continuous
fillet weld should be provided on each side of the plate for a length at each end equal to at least
three-quarters of the width of the narrower plate concerned Figure 4.1).
39
BS EN 1993-1-8:2005
EN 1993-1-8:2005 (E)
L,
~nbl.
I i
~,;;;;;;;;;====:;;;:;;;;;;=:::=:::=;;;;;;,;;;;;;;;;;::==I F,,,
I~
-:rtl
~t 1.....--
ljb
Ij~ ~ ~ I I
The smaller of Lwe 2:: 0,75 band
For build-up members in tension:
The smallest of L1 S; 16 t and and 200 mm
For build-up members in compression or shear:
The smallest of :5 12 t and 12 t1 and 0,25 b and 200mm
Figure 4.1: Intermittent fillet welds
4.3.3 Fillet welds all round
(I) Fillet welds all round, comprising fillet welds in circular or elongated holes, may be used only to
transmit shear or to prevent the buckling or separation of lapped parts.
(2) The diameter of a circular hole, or width of an elongated hole, for a fillet weld all round should not be
less than four times the thickness of the part containing it.
(3) The ends of elongated holes should be semi-circular, except for those ends which extend to the edge of
the part concerned,
(4) The centre to centre spacing of fillet welds all round should not exceed the value necessary to prevent
local buckling, see Table 3.3.
4.3.4 Butt welds
( I) A full penetration butt \veld is defined as a weld that has complete penetration and fusion of weld and
parent metal throughout the thickness of the joint.
40
BS EN 1993-1-8:2005
EN 1993-1-8:2005 (E)
(2) A partia1 penetration butt weld is defined as a we1d that has joint penetration which is less than the ful1
thickness of the parent material.
(3) Intermittent butt welds should not be used.
For eccentricity in single-sided partial penetration butt \velds, see 4.12.
4.3.5 Plug welds
(l) Plug welds may be used:
to transmit shear,
to prevent the buckling or separation of lapped parts, and
to inter-connect the components of built-up members
but should not be used to resist externally applied tension.
(2) The diameter of a circular hole, or width of an elongated hole, for a plug weld should be at least 8 111m
more than the thickness of the part containing it.
(3) The ends of elongated holes should either be semi-circular or else should have corners which are
rounded to a radius of not less than the thickness of the part containing the slol, except for those ends
which extend to the edge of the part concerned.
(4) The thickness of a plug weld in parent material up to 16 1ml1 thick should be equal to the thickness of
the parent material. The thickness of a plug weld in parent material over 16 mm thick shou1d be at
least half the thickness of the parent material and not less than 16 mm.
The centre 10 centre spacing of welds should not exceed the value necessary to prevent local
buckling, see Table 3.3.
4.3.6 Flare groove welds
(I) For solid bars the design effective throat thickness of flare groove welds, when fitted flush to the
surface of the solid section of the bars, is defined in 4.2. The definition of the design throat
thickness of flare groove welds in rectangular hollow sections is given in 7.3.1(7).
Figure 4.2: Effective throat thickness of flare groove welds in solid sections
4.4 Welds with packings
(1) In the case of welds with packing, the packing should be trimmed flush with the edge of the part that is
10 be welded.
(2) Where two parts connected by welding are separated by packing having a thickness less than the leg
length of weld necessary to transmit the force, the required leg length should be increased by the
thickness of the packing.
41
BS EN 1993-1-8:2005
EN 1993-1-8:2005 (E)
(3) Where two parts connected by welding are separated by packing having a thickness equal to, or
greater than, the leg length of weld necessary to transmit the force, each of the parts should be
connected to the packing by a weld capable of transmitting the design force.
4.5 Design resistance of a fillet weld
4.5.1 Length of welds
(1) ~ The effective length of a fillet weld leif @l] should be taken as the length over which the fillet is
fuJl-size. This maybe taken as the overall length of the weld reduced by twice the effective throat
thickness a. Provided that the weJd is full size throughout its length including starts and terminations,
no reduction in effective length need be made for either the start or the termination of the weld.
(2) A Rllet \veld with an effective length less than 30 mm or less than 6 times its throat thickness,
whichever is larger, should not be designed to carry load.
4.5.2 Effective throat thickness
(1) The effective throat thickness , a, of a fillet weld should be taken as the height of the largest triangle
(with equal or unequal legs) that can be inscribed within the fusion faces and the weld surface,
measured perpendicular to the outer side of this triangle, see Figure 4.3.
(2) The effective throat thickness of a fillet weld should not be less than 3 mm.
(3) In determining the design resistance of a deep penetration fillet weld, account may be taken of its
additional throat thickness, see Figure 4.4, provided that preliminary tests show that the required
penetration can consistently be achieved.
J
[
Figure 4.3: Throat thickness of a fillet weld
Figure 4.4: Throat thickness of a deep penetration fillet weld
4.5.3 Design Resistance of fillet welds
4.5.301 General
(1) The design resistance of a fillet weld should be determined using either the Directional method given
in 4.5.3.2 or the Simplified method given in 4.5.3.3.
42
BS EN 1993-1-8:2005
EN 1993-1-8:2005 (E)
4.5.3.2 Directional method
(1) In this method, the forces transmitted by a unit length of weld are resolved into components parallel
and transverse to the longitudinal axis of the weld and normal and transverse to the plane of its throat.
(2) The design throat area should be taken as = La
(3) The location of the design throat area should be assumed to be concentrated in the root.
(4) A uniform distribution of stress is assumed on the throat section of the weld, leading to the normal
stresses and shear stresses shown in Figure 4.5, as follows:
(T..L is the normal stress perpendicular to the throat
(TIl is the normal stress parallel to the axis of the weld
T..L is the shear stress (in the plane of the throat) perpendicular to the axis of the weld
Til is the shear stress (in the plane of the throat) parallel to the axis of the weld.
Figure 4.5: Stresses on the throat section of a fillet weld
(5) The normal stress (TIl parallel to the axis is not considered when verifying the design resistance of the
weld.
(6) The design resistance of the fillet weld will be sufficient if the following are both satisfied:
... (4.1)
where:
f~ is the nominal ultimate tensile strength of the weaker part joined;
fJw is the appropriate correlation factor taken trom Table 4.1.
(7) Welds between parts with different material strength grades should be designed using the properties of
the material with the lower strength grade.
43
