Joints - The Behaviour and Design of Steel Structures to EC3 - page 417

factor for plate resistance to yield and γ M 2 = 1.1 is the partial factor for fracture.
Equation 9.21 corresponds to an elastic analysis of the net section subjected to
uniform shear and tensile stresses.
For situations of eccentric loading such as in Figure 9.20d, the block-tearing
resistance is limited to

√

N Ed ≤ V eff ,2, Rd = 0.5 f u A nt /γ M 2 + f y / 3 A nv /γ M 0 , (9.22)

which corresponds to an elastic analysis of the net section subjected to a uniform
shear stress and a triangularly varying tensile stress.

9.8 Design of welds

9.8.1 Full penetration butt welds

Full penetration butt welds are so made that their thicknesses and widths are not
less than the corresponding lesser values for the elements joined. When the weld
metal is of higher strength than those of the elements joined (and this is usually
the case), the static capacity of the weld is greater than those of the elements
joined. Hence, the design is controlled by these elements, and there are no design
procedures required for the weld. EC3-1-8 [1] requires butt welds to have equal
orsuperiorpropertiestothoseoftheelementsjoined,sothatthedesignresistance
is taken as the weaker of the parts connected.
Partialpenetrationbuttweldshaveeffective(throat)thicknesseswhichareless
thanthoseoftheelementsjoined. EC3-1-8requirespartialpenetrationbuttwelds
to be designed as deep-penetration fillet welds.

9.8.2 Fillet welds

EachofthefilletweldsconnectingthetwoplatesshowninFigure9.21isoflength
L , and the throat thickness a of the weld is inclined at α = tan − 1 ( s 2 / s 1 ) . Each
weldtransfersalongitudinalshear V L andtransverseforcesorshears V Ty and V Tz
betweentheplates.Theaveragenormalandshearstresses σ w and τ w ontheweld
throat may be expressed in terms of the forces

σ w La = V Ty sin α + V Tz cos α (9.23)

τ w La = √ V Ty cos α − V Tz sin α 2 + V L

.

(9.24)

In addition to these stresses, there are local stresses in the weld arising from
bending effects, shear lag, and stress concentrations, together with longitudinal
normal stresses induced by compatibility between the weld and each plate.
It is customary to assume that the static strength of the weld is determined by
the average throat stresses σ w and τ w alone, and that the ultimate strength of the