C 474 combinations of welds fillet welds deposited

C-4.7.4 Combinations of Welds. Fillet welds deposited over groove welds do not directly increase the effective
throat of the joint; therefore the strength of the joint may not be taken as the algebraic sum of the strength of the groove
weld and the strength of the fillet.
C-4.7.5 Butt, Corner, and T-Joint Surface Contouring. Reinforcing and contouring fillet welds serve a useful
purpose in T- and corner joints, and in butt joints joining parts of unequal width or thickness. They provide a fillet which
reduces the severity of the stress concentration that would exist at the ninety degree geometric change in section.
C-4.7.6 Weld Access Holes. Weld access holes are not required nor even desirable for every application. However it
is important to recognize that any transverse joint in the flange of wide flange, H and similar cross sections made without
the use of a weld access hole cannot be considered as a prequalified CJP groove welded joint. This is true, because
prequalified CJP groove welded joints are limited to the cases of plain plate elements to plain plate elements shown in
Figure 5.1. The decision to use prequalified CJP joints or to use non-prequalified joints without access holes depends
upon consideration of several factors which include but may not be limited to the following:
(1) The size of the members being joined.
(2) Whether the joint is a shop or field weld, that is, whether the parts may be positioned for welding so that overhead
welding may be avoided and reinforcing fillets may be readily deposited at the location of peak stress concentrations.
(3) The variation in the restraint to weld shrinkage and the distribution of applied stress along the length of transverse
joint due to geometry of parts being joined.
For example, the high restraint due to the column web in the region of the column flange centerline as compared to lower
restraint away from the centerline causes welding residual stresses and applied stresses to peak sharply in the difficult-to-
weld region at the middle of beam flange.
(5) Whether, in the case of geometry that affords more uniform restraint without a “hard spot” along the length of the
joint, the probability of increased number of small internal weld metal discontinuities, but without the large discontinuity
of the weld access hole, might provide a higher strength joint. For example, tests of end plate moment connections
(Murray 1996) have shown that joints between beam ends and end plates made without weld access holes, but with unre-
paired discontinuities in the region of the web to flange junction provide higher strength than similar connections made
using access holes but with fewer internal discontinuities.
Research, thought and ingenuity are being directed toward improved details for welding of beam-to-column moment
connections. Alternative joint design and details to provide the strength and suitability for service should be considered
where they are applicable. Engineering judgment is required.