Page 162 - 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 147

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The nominal erection set back a / in. For calculations, to account
2
3
for underrun, use a / in. Try a seat 6 in long (c 6). In order to
4
use Table 10-6 from the AISC Manual of Steel Construction, the
required bearing length, N, must first be determined. Note that N is
not the horizontal angle leg length less a, but rather it cannot exceed
this value. The bearing length for an unstiffened seat starts at the
end on the beam and spreads from this point, because the toe of the
angle leg tends to deflect away from the bottom flange of the beam.
The bearing length cannot be less than k and can be written in a gen-
eral way as

R 2 R 1 R 2 R 3 R 2 R 5
N 5 maxe , , ,kf
R 2 R 4 R 6
where R through R are defined in the AISC Manual of Steel Construction
1 6
pp. 9–48, and are tabulated in Table 9-4. For the W14 22,
R 1 5 21.1, R 2 5 11.5, R 3 5 23.1, R 4 5 2.86, R 5 5 20.4, R 6 5 3.82

Thus
33 2 21.1 33 2 23.1 33 2 20.4
N 5 maxe , or ,0.735f
11.5 2.86 3.82
5 max51.04, 3.46 or 3.30, 0.7356 5 3.46 or 3.30

Therefore, N is either 3.46 or 3.30 depending on whether N/d 0.2
or N/d > 0.2, respectively. With d 13.7, 3.46/13.7 0.253, and
3.30/13.7 0.241. Since clearly N/d > 0.2, N 3.30 in.
It was stated earlier that (N a) cannot exceed the horizontal angle
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1
3
leg. Using a / / / , N a 3.30 0.75 4.05, which estab-
2
4
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lishes a required horizontal leg equal to at least 4 in.
The AISC Manual of Steel Construction Table 10-6 does not include
1
required bearing lengths greater than 3 / in. However, extrapolating
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beyond the table, it would seem that a 1-in angle would be an appro-
priate choice. Since there is no L6 4 1 available, use a 6 6 1.
The extra length of the horizontal leg is irrelevant. Table 10-6 indicates
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that a / fillet weld of the seat vertical leg (the 6-in leg) to the column
16
web is satisfactory (40.9 kips). Consider this to be a preliminary design,
which needs to be checked.
The design strength of the seat angle critical section is
ct 2
R 5 F y
b
4e
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