Page 147 - Handbook of Structural Steel Connection Design and Details

Design of Connections for Axial, Moment, and Shear Forces

132 Chapter Two

The portion of the shear force induced in the doubler plate by the
moment connection flange force F is H. For the doubler to be in equi-
f
librium under the forces H, vertical shear forces V Hd/w must exist.
The welds of the doubler at its four edges develop the shear strength of
the doubler. Let the shear force R from the weak axis connection be
applied to the face of the doubler at or near its horizontal center as
shown in Fig. 2.35. If it is required that all of the shear R can be car-
ried by one vertical section a-a of Fig. 2.35, that is, 1.0 0.6 F t d
y d
R, where t is the doubler thickness and F is the yield strength of
d y
the doubler (and the column), then the free-body diagram of Fig. 2.35 is
possible. In this figure, all of the shear force R is delivered to the side
of the doubler where it is opposite in direction to the shear delivered by
the moment connection, thereby avoiding over-stressing the other side
where the two shears would add. Since the doubler and its welds are
capable of carrying V or R alone, they are capable of carrying their
difference. The same argument applies to the top and bottom edges of
the doubler. Also, the same argument holds if the moment and/or weak
axis shear reverse(s). The validity of this approach is based on the lower
bound theorem of limit analysis.

2.3.2.2 Associated shear connections—Beam 1. The specified shear for the
web connection is R 163 kips, which is the shear capacity of the
W21 62 (A36) beam. The connection is a shear plate with two erec-
tion holes for erection bolts. The shear plate is shop welded to the column
flange and field welded to the beam web. The limit states are plate
gross shear, weld strength, and beam web strength.
1
Plate gross shear. Try a plate / 18
2
R 0.5 18 0.9 0.6 36 175 kips > 163 kips, ok
gv
Plate net shear need not be checked here because it is not a valid limit
state.
Weld-to-column flange. This weld sees shear only. Thus
163
D 5 5 3.25 ; use / FW
1
2 3 18 3 1.392 4
Weld-to-beam web. This weld sees the shear plus a small couple. Using
AISC 13th Edition Manual Table 8-8, l 18, kl 4.25, k 0.24, x
0.04, xl 0.72, al 4.28, a 0.24, c 2.71, and
163
D 5 5 4.46
0.75 3 2.71 3 18
5
Thus a / fillet weld is satisfactory.
16

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