CSA S16:19, Design of steel structures, has introduced changes to the factored shear resistance of fillet welds.
In both the current edition, S16:19, and the previous one, S16-14, the shear resistance of a concentrically loaded weld segment is given in Clause 18.104.22.168:
If we incorporate the strength enhancement factor and the reduction factor for multi-orientation welds, the expression becomes:
and θ is the angle of the weld segment axis with respect to the line of force. For example, θ = 0o for a longitudinal weld and 90o for a transverse weld. As shown in Figure 1, a transverse weld has a strength that is 1.5 times greater than a longitudinal weld:
Strength Enhancement Factor
S16:19 has clarified that the strength enhancement factor does not apply to single-sided welds. Welded connections featuring double-sided and single-sided welds are shown in Figure 2.
Double-Sided and Single-Sided Welds
The reduction factor for multi-orientation fillet welds appearing in Equation 4 (above) has a value of Mw = 1.0 for joints with a single weld orientation. For multi-orientation weld groups, its value was given by the following expression in S16-14:
where θ1 is the orientation of the weld under consideration, and θ2 is the orientation of the weld segment in the joint that is nearest to 90o. This is illustrated for the weld group in Figure 3. For the transverse weld, θ1 = θ2 = 60o, Mw = 1.0; and for the two longitudinal segments, θ1 = 0o, θ2 = 60o, Mw = 0.895.
Multi-Orientation Weld Group
In CSA S16:19, Mw has been simplified as follows:
Referring again to Figure 3, for the transverse weld and longitudinal welds, Mw = 1.0 and Mw = 0.85, respectively.
Figure 4 shows a comparison between the resistances calculated using S16-14 and S16:19, for a concentrically loaded C-shaped weld group with k = 0.4, incorporating both the strength enhancement factor and the reduction factor for multi-orientation welds, Mw. The resistance given by S16:19 is significantly smaller for this example, especially for a load angle of about θ = 45o.
Shear Resistance of a Multi-Orientation Weld Group