CEMP-E
TI 809-26
1 March 2000
with a phi of 0.75. There is no need to check the stress in the base metal along the base of the plug or
slot. Plug and slot welds may be designed only for shear forces along the base of the hole or slot, not for
shear along the walls of the hole or slot.
(15) With shear stress in any type weld, the Code requires a check of the base metal in shear,
limiting the base metal stress to 0.60 times the minimum specified yield strength of the base metal, with
a phi of 0.75. This check is applied to the thickness of the material, not the weld/steel interface, to verify
that the steel has the capacity to carry the load delivered to or from the weld. This is especially
applicable to situations using fillet welds on opposite sides of thin beam and girder webs.
c. Minimum Weld Size. Minimum weld sizes are incorporated into both the AWS D1.1 and AISC
codes. AWS D1.1 Table 5.8, provides minimum fillet weld sizes, and Table 3.4 provides minimum
prequalified PJP groove weld sizes. The basis of these tables is the need to slow the cooling rate when
welding on thicker materials. Small welds provide little heat input to the thick base metal, which acts as
an efficient heat sink, and therefore the weld region cools very rapidly. The rapid cooling creates a hard,
martensitic heat-affected zone (HAZ), with potentially high levels of trapped hydrogen, with a higher risk
of cracking. Larger welds are made with higher welding heat input, therefore reducing the cooling rate,
and reduce the risk of HAZ cracking to acceptable levels. AISC Table J2.3 provides minimum fillet weld
sizes similar to AWS D1.1 Table 5.8, but does not provide weld size reductions based upon the use of
low hydrogen electrodes or preheat.
d. Maximum Fillet Weld Size. A maximum fillet weld size is established for lap joints where a fillet
weld is placed along the edge of a part. The maximum fillet weld size that should be specified, when the
part is 6 mm (1/4 in.) or more in thickness, is 2 mm (1/16 in.) less than the thickness of the part. This is
to protect the edge of the part from melting under the arc, making it difficult to verify adequate leg size
and throat. For lap joints where the part receiving the fillet weld along its edge is less than 6 mm (1/4 in.)
in thickness, the specified fillet weld size may equal the thickness of the part. See AWS D1.1 Section
2.4.5.
e. Available Design Aids. Design aids for welded connections, in the form of tables and software, are
available. See Appendix B, Bibliography.
f. Weld Access Holes. Weld access holes provide access for welding equipment to reach the weld
region, reducing the interference from the member itself. They also provide access for weld cleaning and
inspection. Access holes also serve to separate weld shrinkage stresses when fully welded joints are
made in both the member web and flange, as an example. Typically, weld access holes are provided in
beam and girder webs when splicing flanges, or when making welded flange connections in beam-to-
column joints, but may also be used in other joints where interferences exist. See AWS D1.1 Section
5.17, and AISC LRFD Specification Section J1.6 for minimum access types, dimensions, and quality.
When weld access holes are used in heavy sections or high-seismic applications, special provisions
regarding surface quality and inspection apply.
g. Reentrant Corners. Reentrant corners are internal cuts in members. Typical reentrant corners in
buildings are found at openings for piping and ductwork in beam webs. Reentrant corners must be
smooth, with no notches, with a minimum radius of 25 mm (1 in.). Grinding of reentrant corners and
tangency is not required. Beam copes and weld access holes are treated separately by the code. See
AWS D1.1 Section 5.16.
h. Heavy Section Joint Provisions. Under the AISC LRFD Specification, special material, welding and
quality requirements apply for applications using ASTM Group 4 and 5 shapes, and for built-up sections
5-6
Previous Page
