QUESTION: (2015) Clause 13.13.2.2 of S16-14 waives the base metal capacity requirement for fillet welds except where over-matched electrodes are used. This suggests that the rated strength of the over-matched electrode should be used to calculate the weld resistance but W59-13 requires that matching electrode strength to be used in this situation. What should I do?
ANSWER: Until these standards reconcile, they can be satisfied if the matching electrode strength (smaller) is used in this situation.
QUESTION: (SPRING2013) How is the strength reduction factor for multi-orientation fillet welds, Mw, applied? Please show an example.
ANSWER: In the weld configuration shown in Figure 1, 8-millimetre fillet welds are used, Xu = 490 MPa and the plate is G40.21 350W steel. Note that the farside plate is thicker.
In accordance with CSA S16-09 Clause 13.13.2.2:
Vr = 0.67 ɸw Aw Xu (1.00 + 0.50 sin1.5 θ) Mw
where:θ = angle of axis of weld segment with respect to the line of action of the applied force
Mw = strength reduction factor for multi-orientation fillet welds
a) Weld segment at θ = 60o:
Orientation of the weld segment under consideration: θ1 = 60o
Orientation of the weld segment in the joint that is nearest to 90o: θ2 = θ1 = 60o
Orientation of the weld segment in the joint that is nearest to 90o: θ2 = 60o
c) Weld group resistance:Vr = 2 x 0.67 x 0.67 x 8 x 100 x 0.707 x 0.490 (1.00 + 0.50 sin1.5 0o) 0.895
+ 0.67 x 0.67 x 8 x 120 x 0.707 x 0.490 (1.00 + 0.50 sin1.5 60o) 1.00
= 2 x 111 + 209 = 431 kNFor matching electrodes, the base metal resistance need not be checked
Figure 1: Strength Reduction for Multi-Orientation Fillet Welds
QUESTION: (FALL2012) When designing fillet welds in shear, is it necessary to check the base metal resistance at the fusion face?
ANSWER: In accordance with S16-01, the shear resistance of fillet welds is taken as the lesser of: (a) the weld metal resistance given as a function of the ultimate strength of the electrode, Xu , and the effective throat area, Aw and (b) the base metal resistance given as a function of its tensile strength, Fu , and the fusion face area, Am. Unless over-matched electrodes are used the base metal resistance does not govern the design of longitudinally loaded joints. However, when the weld orientation approaches the transversely loaded case the base metal resistance governs due to the significantly larger weld metal resistance.
In S16-09, it is no longer necessary to check the base metal strength at the fusion face when matching electrodes are used (Clause 13.13.2.2). Research studies conducted at the University of Alberta have demonstrated that the base metal resistance determined using the virgin strength of the base metal does not represent the shear resistance. The researchers pointed to the fact that the properties of the base metal at the fusion face are influenced by intermixing of the weld and base metals. Unless over-matched electrodes are used, base metal resistance at the fusion face need not be checked, regardless of weld orientation.For a list of matching electrodes for CSA G40.21 steels, see Table 4 in S16-09.