Page 64 - Handbook of Structural Steel Connection Design and Details

Design of Connections for Axial, Moment, and Shear Forces

Design of Connections for Axial, Moment, and Shear Forces 49

3. Gusset-to-beam: The loads are 627 kips shear and 168 kips axial.
The length of the gusset is 52.25 in. The 1-in snip can be ignored with
negligible effect on the stress.
a. Gusset stresses:
627
f 5 5 16.3 ksi , 1.0 3 0.6 3 36 5 21.6 ksi, ok
v
0.75 3 51.25
168
5 5 4.37 ksi , 0.9 3 36 5 32.4 ksi, ok
f a
0.75 3 51.25
b. Weld of gusset to beam bottom flange: The resultant force per inch
of weld is

0.75
2
2
f 5 216.3 1 4.37 3 5 6.33 kips in
r
2
To account for the directional strength increase on fillet welds
4.37
21
5 tan a b 5 15.08
16.3
1.5 1.5
5 1.0 1 0.5 sin 5 1.0 1 0.5 sin s15d 5 1.07
The required weld size is
6.33
D 5 3 1.25 5 5.31
1.392 3 1.07
which indicates that a 3/8-in fillet weld is required. The factor 1.25
is a ductility factor from the work of Richard (1986) as modified by
Hewitt and Thornton (2004). Even though the stress in this weld
is calculated as being uniform, it is well known that there will be
local peak stresses, especially in the area where the brace-to-gusset
connection comes close to the gusset-to-beam weld. An indication
of high stress in this area is also indicated by the Whitmore sec-
tion cutting into the beam web. Also, as discussed later, frame
action will give rise to distortional forces that modify the force dis-
tribution given by the UFM.
c. Checks on the beam web: The 627-kip shear is passed into the
beam through the gusset-to-beam weld. All of this load is ulti-
mately distributed over the full cross-section of the W14 82, 411
kips passes to the right, and 216 kips are transferred across the
column. The length of web required to transmit 627 kips of shear
is l , where 627 1.0 .6 50 .510 l . Thus
web web
627
l web 5 5 41.0 in
1.0 3 0.6 3 50 3 0.51

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